Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/05/17
Area Forecast Discussion
National Weather Service Bismarck ND
928 PM CDT Thu May 4 2017
.UPDATE...
Issued at 925 PM CDT Thu May 4 2017
Other than to increase cloud cover over central North Dakota per
satellite trends through 02 UTC, no other changes were required
with this update.
UPDATE Issued at 643 PM CDT Thu May 4 2017
No change other than to blend to observed trends through 23 UTC.
&&
.SHORT TERM...(This evening through Friday)
Issued at 219 PM CDT Thu May 4 2017
Warm and dry in the short term period.
Upper level ridging over the northern plains will bring a warm day
to western and central North Dakota on Friday. Will likely see a
little more in the way of high thin clouds spilling over the
ridge. About the only other concern will be fire weather. Utilized
a blend of the Latest with the new HRRR Friday dewpoints to get
minimum humidities Friday afternoon. Models are showing a weak
backdoor front pushing into our northeast CWA, with higher
dewpoints ahead of this boundary. Thus a little higher dewpoints
than forecast last night over the Turtle Mountains area. And in
general across the CWA, min RH values just a tad higher than
forecast last night. Winds are still forecast to be light on
Friday so no fire weather issues are expected. Due to the dry air
in place we did lean toward the cooler guidance tonight and bumped
temperatures up a degree or two above our given guidance for
Friday.
.LONG TERM...(Friday night through Thursday)
Issued at 219 PM CDT Thu May 4 2017
Sharp upper level ridge remains over the region through the
weekend. As the ridge axis move across the state, south to
southwest flow will begin to influence our weather late in the
weekend and early next week. Main forecast concern over the
weekend will be fire weather issues. Southeast flow increases
Saturday and Sunday but this should also bring increasing moisture
into the region. Will need to monitor but at this time it looks
like the increased moisture will help offset the increased winds
and alleviating any fire weather issues.
Thunderstorm chances re-enter the forecast late Sunday afternoon
in the far west, but moreso Sunday evening across the west. We
remain a little unsettled Monday and Tuesday with deterministic
models not showing a lot of consistency with the evolution of a
blocking pattern by mid to late week. Our consensus forecast cools
temperatures into the 60s with only minimal precipitation chances
Wednesday and Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 925 PM CDT Thu May 4 2017
VFR conditions are forecast through the 00 UTC TAF cycle across
western and central ND.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AYD
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...AYD
Area Forecast Discussion
National Weather Service Green Bay WI
1043 PM CDT Thu May 4 2017
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Friday
Issued at 222 PM CDT Thu May 4 2017
The latest rap analysis and satellite/radar imagery show a weak
shortwave passing over the central Upper Peninsula to southwest
Wisconsin early this afternoon. Scattered showers are developing
within the mid-level moisture channel ahead of the shortwave from
Wausaukee to Clintonville, and should push towards the highway 41
corridor by 21-22z. Scattered cu behind this line of broken showers
extends west into Minnesota, but should diminish by sunset. The
next disturbance due to arrive late Friday afternoon is currently
over northern Manitoba. Forecast concerns mainly revolve around
precip trends into this evening and precip chances on Friday
afternoon.
Tonight...The weak shortwave trough will exit to the east by early
this evening, with a few showers lingering over or just north and
west of the Fox Valley by 01z or 02z. Should then see clearing
skies for the rest of the night, with brisk northeast to north winds
developing over eastern WI by late in the evening. Closer to the
surface ridge axis positioned over northwest WI, could see patchy
ground fog develop over Vilas county and adjacent nearby areas.
Tweaked low temps up a skosh over eastern WI due to the breezy north
winds.
Friday...Relatively quiet conditions will begin the morning, and
should see winds over eastern WI gradually diminish as a weak
surface ridge axis pushes southeast across the area. Should see
ample sunshine through early afternoon before clouds start dropping
in from the north ahead of a potent shortwave. Though lacking
moisture, this shortwave will bring in good forcing and steep mid-
level lapse rates to far northern WI, which makes me think that
precip associated with the wave could out-perform the model blends.
The higher res models are more ambitious with precip, and think this
is the way to go. Will leave a mention of isolated thunder in the
forecast also. With an inverted V sounding in the boundary layer,
the beefier showers and any thunderstorms could produce gusty winds
up to 40 mph. Raised highs a bit over central and north-central WI
based on model forecasted 925mb and good mixing.
.LONG TERM...Friday Night Through Thursday
Issued at 222 PM CDT Thu May 4 2017
Focus begins with the chance for showers and a few isolated
thunderstorms Friday evening, then as high pressure settles in for
the weekend the focus shifts to winds, relative humidity, and
temperatures.
A rather weak surface cold front will be passing across the area
Friday evening. This is coupled with potent 500mb vorticity
maximum and the left front quadrant of the upper level jet. Would
expect enough lift present to produce scattered showers and
perhaps a few thunderstorms. Models indicate some instability
with total totals around 50 and mid- level lapse rates ranging
from 6.5 to 7.5 J/kg. There is very limited CAPE and moisture,
but with surface to 6km shear of about 55 to 65 knots would not be
surprised to see some stronger gusts in any showers or
thunderstorms that do form. Any activity should diminish and exit
the southern forecast area by around midnight.
Saturday through Monday...models are in good agreement that
surface high pressure will build in from the north as a mid-level
ridge sets up across the Plains. North winds will be gusty on
Saturday due to the pressure gradient between a strong low
pressure system to the east and the building high over Wisconsin.
This will likely lead to a period of Marine headlines. This also
aids in fire weather concerns. Dry air will certainly accompany
this setup with daytime relative humidity ranging from about 20 to
30 percent in north- central Wisconsin, and 30 to 35 percent in
central Wisconsin and the Fox Valley. Finally, temperatures are
expected to fall near or a bit below freezing Sunday and Monday
morning, leading to the potential for frost or a freeze in parts
of the forecast area, primarily north.
Next week...models mostly agree on developing a chance of showers
ahead of a surface warm front moving north sometime Tuesday. From
here models diverge on how to handle the energy circulating around
the 500mb low located northeast of the Great Lakes, with
some solutions showing a piece of this energy retrograding and
interacting with another system trying to move into the southern
Plains. Hard to determine any details at this point and continued
with a blended model solution which features a few chances for
showers here and there during the middle of next week.
Temperatures in the long term period will be a bit below normal
through the weekend (highs in the 50s, lows in the upper 20s and
lower 30s) and will moderate to around average next week (highs
in the 60s, lows in the 40s).
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1043 PM CDT Thu May 4 2017
A line of showers that was across the area during the late
afternoon/early evening died off as they moved southeast.
An area of mid level clouds moved into the area tonight but
coverage has continued to decrease with time. VFR conditions
should prevail throughout the night, with the possible exception
of some fog across the far north late tonight.
A mid level short wave and a surface low will move southeast
toward Wisconsin, bringing some showers to the area by late
Friday afternoon. Showers should continue to move slowly to the
southeast, spreading across the rest of the area during the night.
Expect mostly VFR and MVFR conditions with scattered showers late
Friday afternoon through 06Z Saturday.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......KLB
AVIATION.......MG
Area Forecast Discussion
National Weather Service Grand Rapids MI
1113 PM EDT Thu May 4 2017
LATEST UPDATE...
Update/Marine
.SYNOPSIS...
Issued at 330 PM EDT Thu May 4 2017
A slow moving storm system moving through the Ohio Valley Region
will continue to support widespread rainfall across far southwest
and south central lower Michigan. The rainfall will slowly move east
out of the region early Friday. Skies are expected to slowly clear
from west to east on Saturday. The cool conditions will continue
through the weekend. Frosty conditions are possible Saturday night
and possible freezing conditions Sunday night.
&&
.UPDATE...
Issued at 1115 PM EDT Thu May 4 2017
The area of rain has largely moved. So the question is does it
move back into our area? There is some suggestion that it may well
do that during the mid morning hours of Friday as the upper low
over Tennessee lifts northeast and starts to merge with then
northern stream wave. Even so the HRRR, RAP and NAM now have the
precipitation area will shift northeast back into our extreme
southern sections prior to sunrise but then it goes away. So I cut
back on the pop significantly and lowered the QPF significantly.
For the most part consider the rain event over.
&&
.SHORT TERM...(Tonight through Friday)
Issued at 330 PM EDT Thu May 4 2017
The well developed, closed, deep tropospheric cyclone centered over
the mid-Mississippi Valley has staged impressive moisture transport
into the southern Great Lakes region. The widespread rainfall is
locked into a deep region of system-relative deformation across
southeast Michigan back into central Illinois. The moisture supply
conveyor along the 300K isentropic surface, currently pinching in on
the deformation axis over south-central Lower Michigan, is projected
to roll northeast along the deformation zone. This will allow the
rain canopy to wander eastward through the evening hours. The
deformation axis is expected to maintain integrity in the 296-304K
layer over the southeast sections of the forecast area (mainly
affecting areas south and east of Lansing) through early Friday. To
the west, substantially drying is expected, allowing for clearing
across the northwest counties and substantial thinning around Grand
Rapids. Temperatures will remain below average with the anomalously
cool airmass overhead.
.LONG TERM...(Friday night through Thursday)
Issued at 330 PM EDT Thu May 4 2017
A compact shortwave topping the long wave ridge over central Canada
is projected to get caught up in the height fall region to the north
of the ejecting Ohio Valley closed low circulation late Friday. This
wave will aid in coaxing the upper low westward over the Lower
Peninsula on Saturday. Current guidance suggests the best chances
for rainfall with the shortwave will remain west of the area Friday
night. As the low wobbles west on Saturday, clouds are expected to
thicken, but the rain should remain over eastern Lower Michigan.
Skies are expected to clear by Saturday night. The combination of the
resident cool airmass and good outgoing radiative forcing will set
the stage for a chilly night. Lows will be cold enough to support
some frost formation. The colder night appears to be Sunday night,
as even drier air filters in allowing for ideal radiative cooling
conditions. Lows could dip to around freezing across most locations.
The overall pattern is expected to become more unsettled once again
during the early portions of next week. The upper low over the
eastern CONUS is expected to undergo areal expansion via downstream
amplification as a significant blocking pattern continues to
solidify over the entire Northern Hemisphere. The net result will be
the introduction of diurnally driven light shower chances and below
average temperatures through the balance of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 744 PM EDT Thu May 4 2017
The issue tonight will be what happens to the rain area south and
east of Grand Rapids. There is little question there is enough dry
air to keep the rain from building back in. There is some
question as to if the rain is now ending at BTL and AZO but JXN
should for the most part have rain until around 18z on Friday.
There is a second shortwave that rotates through the area early
Friday that should redevelop the rain as far west as AZO but this
is not a sure thing. I wrote the TAFs with the idea the rain would
move back in. If this does not happen, more than likely MKG, GRR,
AZO and BTL would all be VFR by 12z. JXN should be IFR, mostly
due to low ceiling.
&&
.MARINE...
Issued at 1114 PM EDT Thu May 4 2017
The latest data suggests we may need gales in our Saturday
forecast. I coordinated with the CHI office and decided we would
wait till the next shift of the day shift to make a decide if and
when to upgrade to gales.
&&
.HYDROLOGY...
Issued at 330 PM EDT Thu May 4 2017
The heaviest rainfall is confined to the far southeastern sections of
the forecast area. Given the recent substantial rainfall was in the
Maple basin - feeding the Grand - not much change is expected in
that portion of the basin. This rainfall is only expected to
influence the headwater region of the Grand near Jackson in the near
future.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from 5 AM Friday to 2 AM EDT Saturday for
LMZ844>849.
&&
$$
UPDATE...WDM
SYNOPSIS...Mann
SHORT TERM...Mann
LONG TERM...Mann
AVIATION...WDM
HYDROLOGY...Mann
MARINE...WDM
Area Forecast Discussion
National Weather Service Wilmington NC
1009 PM EDT Thu May 4 2017
.SYNOPSIS...
A complex storm system will affect the forecast area tonight
through the 1st part of this weekend. Strong to possibly severe
thunderstorms will occur tonight thru midday Friday. Breezy to
windy conditions will overtake the forecast area tonight thru
Friday night followed by a slow diminishing thru Sat night.
Cooler temperatures, dropping below normal, will work into the
area Fri night thru the weekend. High pressure will follow late
Sunday through early next week with dry conditions, lighter
winds and temperatures rebounding back to near normal.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 930 PM Thursday...All updates have been sent out regarding
the Tor Watch thru 3 am due to the convective band having become
a bit more active than anticipated. The vertical extent of these
isolated storms along this band are limited as indicated by
the quantity and density of the lightning. Fortunately where you
have this lightning, you have the increased potential for severe
convection from this active cell given the amount of individual
cells racing north within this band.
The RAP and HRRR indicate the convective band behind this
initial one, will eventually "catch up" and coalesce with it
well after midnight. And eventually this band will work it`s
way across the FA before finally exiting by mid to late
Fri daytime morning. Thus this secondary band, may be more
active with lightning due to better vertical development. The
hodograph will be favorable for Tor activity but after daybreak
Fri, winds become more unidirectional thru the atm column along
with hier speeds when compared to current soundings. Thus, the
severe looks more like damaging wind gusts but still the
isolated tornado.
Previous thinking.............................................
As of 3 PM Thursday...Very active weather expected through the
period. Easterly flow has been veering and will continue to do so as
low pressure rapidly deepens over TN/KY and a secondary low forms
over GA this evening. The already strong wind fields will further
strengthen and increase moisture advection into the area. Rain will
spread into western zones this evening and the coast a few hours
thereafter (though it may be as late as 09z according to some
guidance like the WRF and even the HRRR lately). Just ahead of or
even coincident with the arrival of the rain will be the arrival of
a 50kt low level jet at 925mb. Even shallow convection may thus have
the chance of producing gusts to that speed-and most convection will
be of modest depth due to weak instability. It is the latter that
SPC sites for capping today`s SWODY1 at MRGL. Hodographs also show
the greatest shear within the lowest km, so there is also a small
but nonzero tornado threat, likely right along the front where the
sharp wind shift leads to some helicity.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
As of 3 PM Thursday...Large H5 low over eastern TN/western NC will
lift into PA by Saturday morning and the eastern Great Lakes region
by Saturday night. Large cyclonic surface flow will persist across
the Carolinas in the wake of this system. Although the highest
precipitable water values will become displaced off the NC/SC coast
by the onset of the short term there is still enough moisture for
periods of clouds and a couple rounds of showers. Below normal
temperatures are expected through the period as well (typically we
have high temperatures around 80/lower 80s and lows in the mid to
upper 50s this time of year). Otherwise, breezy conditions are
expected to continue Saturday given strong low level wind field in
place and mixing potential during the day.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 3 PM Thursday...Unseasonably cool and dry weather will
mark the late weekend to early next week time period, as air
of Canadian origin is pulled into the Carolinas by a large
upper low lifting northward into the Great Lakes and SE Canada.
Deep and dry W-WNW flow aloft and downslope wind flow in the
low levels will make for a comfortable feel with no trace of
mugginess the first half of the week at least, with daytime
highs in the 70s and lows in the 50s. No mentionable POP values
planned for the extended period although by Thursday we should
begin to see in influx of column moisture into the region on
WSW-NW trajectories with temperatures reaching normal readings
for this time of May.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 00Z...VFR/MVFR conditions this evening from sporadic
shallow convection will worsen by and after midnight to
MVFR/IFR. This will persist thru the pre-dawn hrs thru roughly
15z before the last band of convection finally moves
downstream.
Initially this evening, looking at isolated moderate showers in
SE to SSE low to mid level flow moving onshore and inland.
Later this evening, a narrow convective band from Kershaw to
Hilton Head Island and south of the Atl Waters. The band is
moving east at 20 mph but the individual cells are racing
northward up to 40 mph. This band will translate across the
inland terminals late this evening and across the coastal terms
by and after midnight. Models indicate this lead band will
weaken as it pushes across. HRRR and the RAP models to a
degree, indicate the next narrow convective band behind this
lead band, will become the stronger and more dominate as it
pushes across the area roughly between 07Z and 14Z Fri. Have
highlighted the possibility of 45 kt convective wind gusts.
By midday Fri, only isolated -shra will be left across the
region.
Besides the strong to possibly severe convection, the area
terminals will see strong synoptic scale winds thruout this
period. Initially SE 10 to 20 kt with g25+ kt veering to SSE to
SSW 15 to 25 kt with g30+ kt during the pre-dawn hrs thru late
Fri morning. From midday Fri thru the end of the 24 hr issuance
period, SW 15 to 25 kt with g30+ kt.
Extended outlook...Mainly VFR thru the weekend and into early
next week. Brief MVFR ceilings possible late Fri night into
Saturday morning.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 10 PM Thursday...Highlighted the severe threat with
waterspouts the main threat thru 3 am Fri, ie. Tornado Watch.
The isolated/discrete cells displaying lightning within this
convective band are the ones to stay away from late this evening
into the overnight. The lack of lightning thruout this band has
actually made it somewhat easier to locate potential severe
tstorms with waterspouts, which do exhibit lightning. However,
the next convective band/round late in the pre-dawn Fri hrs thru
midday Fri will have more vertical development and increased
lightning. These later storms will have the potential to produce
severe wind gusts across the marine environment with a
waterspout as a secondary possibility. Have continued the wind
trends from the previous update with little tweaking at best
given the Gale Warning has already been issued. Significant seas
may need to be tweaked slightly hier Fri if winds stay active
longer above 30 kt sustained. Peak seas will occur with mainly
locally produced short period wind waves.
Previous thinking.............................................
As of 3 PM Thursday...With a 50kt jet progged to bear down upon
the waters overnight and to collaborate with neighbors have
raise a Gale Warning. The prefrontal flow regime will last until
about 18Z at which time there will be a sharp veer and a
decrease in wind speeds. The decrease will only be adequate for
us to lower the Gale Warning to a Small Craft advisory...well
beyond the near term period.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 3 PM Thursday...Strong south-southwest winds will continue
across the coastal waters Friday night. The flow will only veer
slightly to the west-southwest into Saturday but will remain gusty
through Saturday night. Offshore flow will open up a range of seas
from the coast to the 20nm waters given a fetch limited trajectory.
Regardless, still enough of a fetch to generate steep waves off the
more exposed Cape Fear marine zones. Will likely need to follow-up
the Gale Warning with a Small Craft Advisory through Saturday
night.
LONG TERM /SUNDAY THROUGH MONDAY/...
As of 3 PM Wednesday...A very manageable marine period as
offshore flow of moderate strength endures mainly 15 KT or less,
as a low pulls well north of the waters and high pressure builds
in from the northwest. As a result, inshore seas will remain
suppressed, but a little higher offshore as fetch length is
increased. The air column will remain dry this period and no
TSTMS or marine rain showers are expected and no marine fog to
contend with. Seas of 3 feet or less expected much of the
extended period but up to 4 feet offshore on Sunday as seas
still recover from a departing storm system.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Gale Warning until 6 PM EDT Friday for AMZ250-252-254-256.
&&
$$
SYNOPSIS...DCH
NEAR TERM...DCH/MBB
SHORT TERM...SRP
LONG TERM...MJC
AVIATION...DCH
Area Forecast Discussion
National Weather Service Melbourne FL
906 PM EDT Thu May 4 2017
.UPDATE...
Initial round of convection in association with the east and west
coast sea breeze merger will continue pushing offshore and further
into the Atlantic. Looking upstream toward the Gulf, little
convection is noted on radar mosaic and satellite, suggesting rain
chances will remain quite low through at least the first half of
the night.
Guidance, including the HRRR and local WRF models, suggest that
additional convection will fire again over the eastern Gulf, most
likely in association with a shortwave rounding the larger scale
trough centered near Tennessee. There still remains some question
whether the air mass, both over the eastern Gulf, and over the
peninsula, will recover enough for convection/storms to redevelop
overnight. For this forecast cycle, will indicate increasing
chances for showers and a few storms during the pre-dawn hours,
initially along the I-4 corridor and then spreading south Friday
morning.
Overnight lows will be a few degrees either side of 70.
&&
.AVIATION...
Initial round of convection pushing into the Atlantic, leaving
behind VFR conditions that will continue through the early morning
hours on Friday. Expect showers and a few storms to redevelop over
the eastern Gulf and push over the central peninsula beginning a
few hours before sunrise, producing local tempo MVFR conditions.
Front will move through Friday morning and lead to gusty winds out
of the west through the afternoon.
&&
.MARINE...
Initial round of thunderstorms pushing off the coast will continue
to move further east into the Atlantic this evening. A secondary
round of showers and storms are expected to form and push offshore
beginning during the pre-dawn hours Friday.
Increasing south winds out ahead of a late season front will lead
to choppy seas and steadily deteriorating conditions overnight.
Expect winds to transition to the southwest and then west by
Friday afternoon around 20 knots and gusty. Seas steadily
building, especially the further offshore one travels due to the
increasing offshore flow.
&&
.FIRE WEATHER...
Saturday-Sunday...Min RH values nearing the mid to upper 30s and
breezy westerly winds Saturday will make for a more sensitive fire
weather day across the region. Lower RH values will be possible into
Sunday afternoon, mainly across the interior, but winds are forecast
to be somewhat lighter.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 67 78 55 77 / 50 30 10 0
MCO 69 79 58 79 / 50 40 10 10
MLB 71 82 59 80 / 30 60 10 10
VRB 72 83 59 80 / 60 60 10 10
LEE 68 77 58 77 / 60 20 10 10
SFB 68 80 57 79 / 50 30 10 10
ORL 70 79 59 78 / 50 40 10 10
FPR 72 84 59 82 / 60 60 10 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory for winds from 4 AM Friday to 8 AM EDT
Saturday for Flagler Beach to Volusia-Brevard County Line 0-
20 nm-Sebastian Inlet to Jupiter Inlet 0-20 nm-Volusia-
Brevard County Line to Sebastian Inlet 0-20 nm.
Small Craft Advisory from 4 AM Friday to 8 AM EDT Saturday for
Flagler Beach to Volusia-Brevard County Line 20-60 nm-
Sebastian Inlet to Jupiter Inlet 20-60 nm-Volusia-Brevard
County Line to Sebastian Inlet 20-60 nm.
&&
$$
Ulrich/Kelly/Combs
Area Forecast Discussion
National Weather Service Raleigh NC
1005 PM EDT Thu May 4 2017
.SYNOPSIS...
A strong low pressure system will move through the Ohio Valley
overnight, while the associated cold front moves through the region.
An upper level trough will remain across the area through the
weekend.
&&
.NEAR TERM /through tonight/...
As of 1005 PM Thursday...
Elevated risk of severe cells producing tornadoes and damaging winds
remains tonight, mainly S and E of the Triangle, although the
Triangle itself isn`t out of the woods. The latest surface analysis
shows the warm frontal zone just NW of the CWA with uniform SE flow
to its SE. 00z upper air analyses show well the strong veering
profile with southeasterly 25 kt winds at 925 mb, shifting to SW at
50 kts at 500 mb. Latest KRAX VAD wind profile already shows 0-1 km
helicity of 153 m2/s2 with a long looping hodograph that should
become more pronounced over the next few hours as the wind field
strengthens through the column. Numerous high res models continue to
support strong rotating convective cells across our south and east
from late evening through much of the overnight hours, including the
SPC SSEO which focuses a high probability of high updraft helicity
over 25 m2/s2 over our SE at 06z-09z, similar in area and timing to
the hourly max updraft fields from the NSSL WRF and the HRRR/RAP,
the latter of which shows 0-3 km helicity over 600 m2/s2 at FAY at
08z. The RAP also depicts a small mid level jet streak of 60 kts
just east of a vorticity max over southern SC (seen as a subtle
feature in GOES-16 water vapor channels), and this speed max is
expected to track northward through central NC overnight. Despite
these favorable kinematics, the limited potential for instability
remains a challenge, with projections of just a few hundred J/kg of
CAPE at best overnight, a result of deep warm air east of the large
mid level low over W TN into N MS/AL, although the RAP projects our
far SE achieving 500 J/kg of MLCAPE by 06z. Have made minor
adjustments to the forecast timing and to add the severe risk to SE
sections. Lows 63 to 69. -GIH
Previous discussion from 215 pm: Overview: A potent upper level low
and attendant surface low will progress eastward through the TN
valley into the central Appalachians through tonight. An associated
cold front will approach the mountains from the west this evening
and progress eastward into the Carolinas late tonight. A warm front
will lift northward into central NC late this afternoon and evening,
in advance of the cold front.
Precip: Expect chances for convection to increase from during the
day as rich low-level moisture advects into central NC from the SE
(Atlantic) amidst diffluent flow aloft and shortwave energy /DPVA/
ejecting northeastward over the Carolinas in strengthening SW flow
aloft. Expect isold/sct showers to develop in the SE Coastal Plain
by early/mid afternoon in assoc/w diurnal destabilization and
sufficient forcing aloft. Precipitation chances will increase over
western portions of the state by mid/late afternoon as rich 925-850
mb moisture advects into upstate SC/western NC amidst strengthening
forcing throughout the column. Precip chances will increase to ~100%
across central NC overnight as a strong S/SE LLJ advects rich
Atlantic /Gulf Stream/ moisture beneath modest (6.0-6.5 C/km) mid-
level lapse rates (resulting in marginal/moderate nocturnal
destabilization) as deep-layer ascent strengthens from the west.
Temps: Challenging temperature forecast. Mid/upper level cloud cover
will increase from SW-NE during the day, resulting in mostly cloudy
to overcast conditions by mid/late afternoon in the western
Piedmont. If precipitation develops in the NW piedmont prior to the
arrival of a higher theta-e airmass from the west, a weak CAD wedge
may develop in the Foothills/far NW Piedmont. Stronger insolation
/less cloud cover/ and southeasterly flow will result in the warmest
temperatures this afternoon in the Coastal Plain. Expect highs
ranging from near 80F in the far SE Coastal Plain to the lower 70s
in the far NW Piedmont.
Severe Threat: A large MCS developed over the Deep South/GOMEX last
night and has progressed into FL/GA as of 15Z this morning, though
it has been rapidly decaying over the past 6 hours. An expansive,
long-lived wake low has been present on the western periphery of the
decaying MCS, with numerous reports of 40-60 mph winds over AL/GA
and extreme western NC/eastern TN as of 15Z. Model guidance did a
poor job in forecasting the aforementioned convective system
overnight. As a result, uncertainty has increased w/regard to the
severe weather potential (timing/mode/coverage), and severe weather
cannot be ruled out late this aft/eve through Friday morning.
Nocturnal destabilization still appears likely given that rich low-
level moisture will not depend upon a southerly LLJ emanating from
the GOMEX. Indeed, observational trends already show rich low-level
moisture /mid 60s dewpoints/ advecting inland from the Atlantic into
the Carolinas. With the above in mind, the threat for severe weather
(coverage-wise) appears to have decreased. However, given the
thermodynamic/kinematic environment and high likelihood of convection
later today into tonight, the most likely scenario (at this time)
appears to be a potential for isolated supercells capable of
producing a few tornadoes. -Vincent
&&
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 305 PM Thursday...
Ongoing convective band/QLCS associated with the strong southerly
warm conveyor feed(effective lead front)will exit the coastal plain
counties/I-95 corridor between 12 to 15z, marking the end of the
locally damaging winds and isolated tornado threat across central
NC.
Once this convective band moves offshore, it should be mostly dry
for the remainder of the day with only isolated/slight chance of
showers as the upper low moves jogs slowly eastward, de-amplifying
into an open wave trough as it finally swings east through the area
through overnight. Under a mixture of clouds and sun(cloudier in the
west in proximity to the upper low),highs Friday will range from
mid/upper 60s NW to mid 70s east. Trailing sfc cold front, marking
the leading edge of the cooler air will move east through the area
during the late afternoon early evening. Much cooler Friday night
with overnight lows in the mid/upper 40s NW to lower 50s east.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 305 PM EDT Thursday...
On the heels of lead upper low/wave lifting out of the area, another
potent upper wave will dive south, reinforcing the upper trough over
the region. Isolated to scattered showers will be possible over the
area Saturday afternoon/evening owing to strengthening DCVA as the
cold core(H5~ -23 to 26 C) rotates east through the region.
Otherwise, it will remain dry with a prolong period of cooler
weather(~10 degrees below normal) underneath the negative H5
anomalies(-2 to -3 SD) over the Mid-Atlantic region. Highs in the
mid 60s north lower 70s south. Lows in the lower 40s north to
mid/upper 40s south.
By mid to late week, there is increasing model spread and decreasing
forecaster confidence in the evolution of the omega block across the
CONUS. Given the blocky pattern, will favor a slower eastward
progression of the omega block, with the potential for the upper
low to wobble/gyrate over the NE US and Mid-Atlantic regions through
late next week. As such, under the continued influence of the upper
low/trough, temperatures are expected to remain at or below normal
with the potential for disturbances in the deep NW flow aloft to
bring scattered rain chances to the area Wednesday and into
Thursday.
&&
.AVIATION /00Z FRIDAY THROUGH WEDNESDAY/...
As of 630 PM Thursday...
24-Hour TAF period: Expect periods of adverse aviation conditions as
thunderstorms move into the region overnight. Expect rain showers to
move into the region first, under generally south-southeasterly flow
while the system itself slowly progresses slowly eastward. Expect
the cold front to move through Friday morning (after 10Z in the west
to around 16Z in the east), with conditions improving, storms
exiting the area from west to east and winds becoming more
southwesterly, albeit still strong and gusty.
Timing is still a bit uncertain with regard to when the strongest
storms will impact any given terminal, but the latest high
resolution models show the best chances at KINT and KGSO between 04Z
and 08Z, at KRDU and KFAY between 07Z and 12Z, and at KRWI between
09Z and 13Z Friday. Rain showers and isolated thunderstorms may
impact the terminals prior to the arrival of the intense storms.
Winds have become light over the past couple of hours, but expect
them to pick up again overnight to around 10 kts or so with gusts of
20-25 kts possible. With the aforementioned strongest storms, winds
could also become quite strong (around 20-25 kts) with gusts of 35-
40 kts. -KC
Looking ahead: MVFR showers will remain possible Friday aft/eve as
an upper level trough progresses over the region in the wake of the
cold front Friday morning. Showers and MVFR conditions may re-
develop again Saturday aft/eve as the upper trough over the eastern
US amplifies in response to additional shortwave energy digging SE
through the OH valley. VFR conditions are anticipated Sun/Mon as the
upper trough lifts NE away from the region. -Vincent
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...SEC
NEAR TERM...Hartfield/Vincent
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...KC/Vincent