Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/20/24
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
859 PM EST Fri Jan 19 2024
.SYNOPSIS...
An upper level low pressure system pushes off the coast this
evening, with scattered to numerous showers gradually ending
tonight. A very cold airmass moves in tonight through the
weekend. A moderating trend in temperatures begins Monday,
with warm and unsettled weather by the middle of next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 900 PM EST Friday...
Evening obs and radar indicate most of the snow has dissipated
or moved offshore. Therefore, the last of the remaining winter
weather advisories on the MD Eastern Shore have been cancelled.
Otherwise, analysis continues to show low pressure system moving
well offshore of the Mid-Atlantic coast with strong high
pressure (~1040 mb) over the Midwest states. Aloft, a strong
shortwave (that provided the synoptic forcing for the earlier
snowfall) is also now offshore. With ongoing cold advection,
temps have fallen across the area (especially over central and
srn portions of the FA), with temps as of 830 PM generally in
the low-mid 30s. A few upper 20s are also starting to show up in
areas away from the water.
Overnight, most of the area should be mainly clear with just
some passing stratoCU. It will remain cloudier over the MD/VA
Eastern Shore where cloud streamers will continue to funnel off
of the (relatively) warmer Chesapeake Bay in NW flow. Speaking
of the winds, NW winds will remain gusty through the night with
gusts 20-30mph (and locally higher over the coast and the
eastern shore). Lows tonight drop into the teens across the far
west with low-mid 20s elsewhere. Wind chill values fall into
the teens most areas with a few spots in the piedmont as low as
5-10F. This could lead to a few slick spots in areas that
received snowfall today, with some refreezing possible.
Another thing to note is CAMs continue to suggest one of the
aforementioned bay-effect streamers could produce some snowfall
over Northampton and Accomack counties in VA and Worcester
county in MD overnight into the morning or early aftn hrs of
Sat. There is a small chance ones of these bands also sneaks
southward into coastal portions of Hampton Roads. HRRR/RAP/NAM
soundings show steep low- level lapse rates and a nearly
saturated (but very shallow) layer just above the sfc. In fact,
this layer is almost solely confined to the DGZ in the HRRR and
RAP which suggests a high- ratio snow. Otherwise, the sounding
profiles are quite dry and this remains the biggest limitation
to any snow. Either way, can`t rule out a light accumulation if
one of these bands sets up for a time tonight through Sat. PoPs
are 30% for SN in a narrow stripe over the eastern shore w/ a
20% buffer surrounding it.
Otherwise, partly sunny W to mostly cloudy E Saturday. Blustery
and cold with strong NW winds and highs upper 20s/around 30F N
to the mid 30s SE. Wind chills remain in the teens to lower 20s
CWA- wide.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 400 PM EST Friday...
Winds will let up to some extent Saturday night inland (but
likely do not go completely calm given the sfc high still W of
the Appalachians) , but will remain gusty on the Eastern Shore
and immediately near the coast. Very cold Saturday night with
lows 10-15F well inland, and in the upper teens to lower 20s at
the immediate coast. Wind chill values will end up in the single
digits above zero for most, locally close to zero well inland.
High pressure settles over the region Sunday, allowing winds to
let up through the day. Mainly sunny with highs still cold,
with highs in the mid- upper 30s. Lows Sunday night drop into
the teens again for most with the clear skies and light winds
allowing for good radiational cooling. Highs will moderate into
the 40s Monday under mostly sunny skies.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 400 PM EST Friday...
High pressure slides offshore Monday night into Tuesday with a
significant warmup commencing. Lows Monday night will be
seasonally cool (in the mid 20s to lower 30s), with highs
moderating into the 50s Tuesday. Clouds will likely increase
Tuesday due to WAA aloft, but temperatures will become much
warmer and remain that way through the rest of the extended
period. Lows Tuesday night with lows in the mid 30s to lower
40s, followed by highs in the lower 50s N to mid 60s S on
Wednesday, and upper 50s-upper 60s/around 70F Thursday-Friday.
Minimal PoPs for light rain arrive Wednesday with PoPs increasing
to high chc to likely Thursday-Friday as the flow aloft becomes
SW (allowing deep- layered moisture to increase). The primary
sfc low pressure system is forecast to stay W of the
Appalachians, but with a sfc boundary expected in the vicinity
of the local area, it remains unsettled and mostly cloudy on
average Wed-Fri.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
As of 800 PM EST Friday...
Light snow over the MD Eastern Shore (mainly E of SBY as of
00z/20) continues to diminish and/or move offshore. Current
trend in the obs at SBY suggest the IFR CIGs and vsby are mostly
a thing of the past. Will carry a one hr TEMPO of IFR
CIGS with MVFR CIGs then likely prevailing for at least the
next few hrs. Elsewhere, BKN- OVC cloud deck (w/ bases ~5k ft
AGL) is pushing through far SE VA and NE NC w/ perhaps a very
brief rain/snow mix. Kept any mention of this out of the TAFs
given the very brief period (generally next hr or so). Dry for
most tonight with FEW- SCT CU. Additionally, a gusty NW wind
will continue tonight and on Saturday (in addition to SCT- BKN
CU Saturday aftn/evening) as high pressure builds into the
region. While not likely to impact any of our local TAF sites,
there could be also be a bay streamer with some snow across the
VA Eastern Shore late tonight-early Sat morning which could
bring localized IFR conditions.
VFR with less wind on Sunday and Monday. Increasing clouds are
expected by Tuesday as high pressure moves offshore, with a chc
for rain by Tue night/Wed.
&&
.MARINE...
As of 340 PM EST Friday...
Low pressure continues to move NE out to sea this afternoon into
tonight. As it does, CAA increases behind it as an arctic airmass
moves in with a tightening pressure gradient between the low moving
offshore and a strong (~1040mb+) high pressure building in. Winds
continue to increase to 25-30 kt with gusts 35-40 kt this afternoon
and linger into Sun morning with a lull to 20-25 kt with gusts ~30
kt Sat morning into Sat afternoon before a second surge Sat
evening/night. The surge Sat evening appears to be the stronger
surge with wind probs around 100% for gusts to 34 kt across the N
coastal waters. As such, Gale Warnings have been extended until 10
AM Sun across the Chesapeake Bay and coastal waters (except 7 AM Sun
for the NC coastal waters) and until 7 AM Sun for the Currituck
Sound. Additionally, a Gale Warning has been issued for the Lower
James until 7 AM Sunday. SCAs remain in effect for the rest of the
rivers into Sun afternoon for winds 15-25 kt with gusts to 30 kt.
Will not a few gusts to 35 kt are occuring this afternoon over the
York and Upper James River with an SMW in effect due to low
confidence in 3 hours of frequent 35 kt gusts. A similar situation
may unfold Sat evening with SMWs possible due to a shorter duration
surge and lower confidence. High pressure moves into the area Sun
night before moving offshore early next week with winds becoming
light and likely remaining sub-SCA criteria through next week.
Additionally, with very cold temperatures and gusty NW winds, light
freezing spray is possible Sat with higher confidence Sat night into
Sun morning.
Waves and seas were generally 2-4 ft this afternoon. Waves and seas
build to 4-5 ft and 4-7 ft respectively tonight into Sun before
subsiding below 5 ft Sun evening/night.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Gale Warning until 10 AM EST Sunday for ANZ630>632-634-650-652-
654-656.
Gale Warning until 7 AM EST Sunday for ANZ633-638-658.
Small Craft Advisory until 1 PM EST Sunday for ANZ635>637.
&&
$$
SYNOPSIS...LKB/SW
NEAR TERM...LKB/SW
SHORT TERM...LKB
LONG TERM...AM/LKB
AVIATION...LKB/SW
MARINE...ERI/RMM
Area Forecast Discussion
National Weather Service Wilmington NC
1013 PM EST Fri Jan 19 2024
.SYNOPSIS...
Dry conditions but very cold temperatures will prevail this
weekend as strong Canadian high pressure builds across the
Carolinas. The high will migrate overhead Mon then shift
offshore by midweek allowing mild subtropical air to spread
across the area Wed through Fri along with a threat for
showers.
&&
.UPDATE...
Minor updates to the hrly dewpoints for the rest of the night
into daylight Sat, drier air infiltrating the FA quicker than
expected. Based this on latest and upstream obs and trends and
some HRRR guidance. Kept gustiness in the winds til midnight,
then held them 5 to 10 mph thru the pre-dawn Sat hrs. Should see
a rather close range of min temps across the FA, with low to
mid 20s west of I-95 to the mid and upper 20s as one moves east
to the immediate coast. Wind chill readings in the mid to upper
teens to occur during the pre-dawn Sat hrs, occurring by 3am
west of I-95, and spreading eastward and reaching the immediate
coast prior to daybreak Sat. Sat imagery and near term models
indicate clear skies for the FA thru the night.
SCA to continue into the pre-dawn Sat hrs followed by a
temporary lull in the CAA surge which should allow winds to
temporarily diminish-some, below SCA thresholds. With lack of a
fetch, seas will be dominated by short period wind driven waves.
&&
.NEAR TERM /THROUGH SATURDAY/...
Behind today`s cold front, cold/dry advection will continue
to ramp up through the remainder of the day and persist through
Saturday. Low-level stratocumulus clouds across the area this
afternoon will dissipate this evening as low-level moisture
scours out, insolation ceases, and subsidence strengthens aloft.
Gusty northwest winds will also relax this evening and tonight,
but winds around 5-10 kts will continue to usher remarkably
cold and dry air into the region. This will make for a very
chilly weekend with well-below normal temperatures on tap.
With cold advection in play through tonight, expect today`s
mild high temps in the upper 50s to near 60F to fall into the
mid-20s by late tonight. Wind chills in the teens to low 20s can
be expected around sunrise tomorrow morning. On Saturday, 850mb
temps look to bottom out around -12C, and with model soundings
supporting mixing up to that level, this supports highs staying
in the 30s just about everywhere. With winds around 10 kts and
gusts around 15 kts, wind chills during the day may not get
above the freezing mark.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
The coldest airmass of the winter season so far should arrive
Saturday night. 850 mb temps bottom out near -14C during the
day Saturday then rebound some Saturday night. Cold advection
coupled with the 10 mph winds expected to continue through the
night should keep low-level thermal profiles steep and well-
mixed. This is not unusual during strong cold advection
scenarios and historically has resulted in temperatures
remaining along the high end of model guidance. With this in
mind, I`ve raised Saturday night`s forecast lows slightly to
19-20 degrees along the coast and to 16-19 degrees inland. This
will still be the coldest of the season so far and near the NBM
guidance numbers. Forecast minimum wind chills in the 7-11
degree range are just above local Wind Chill Advisory criteria.
(5 deg F)
The high will move across the Ohio Valley Sunday, shifting winds
to the north. Weak January sunshine working on the cold air
should only push temps to around 40 degrees. The high will move
across the Appalachians Sunday night, settling across Virginia
and the Carolinas with winds becoming calm after sunset. This
sets the stage for an impressive night of radiational cooling
and my forecast lows Sunday night are among the low edge of
guidance with upper teens inland and 20 to lower 20s along the
coast. Local soil type differences will come into play and
normally-cold microclimates will see temps plunge much colder
than the nearby cities.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
The Canadian high will exit the North Carolina coast Monday,
shifting winds to a more easterly direction by late in the day.
Strengthening southeasterly flow Tuesday into Wednesday will
bring subtropical air back across the Carolinas with
temperatures and dewpoints quickly rebounding to, and then
above normal. All this moisture riding back over the retreating
cold airmass should result in plenty of low and mid clouds with
shower chances developing Tuesday night into Wednesday.
Upper level ridging centered over the Bahamas should intensify
during the second half of the week, steering shortwaves in the
main jetstream flow to our west and north around the periphery
of the ridge. With this in mind, I can`t find a reason to
increase shower chances substantially from the prior forecast,
still 20-40 percent each day Wednesday through Friday. The
bigger story will likely be the mild temperatures developing:
inland highs should rise into the 70s beginning Wednesday.
One final item of concern: dewpoints appear they will rise
into the 60s on light to moderate south winds. This fits the
pattern for dense sea fog which could develop beginning
Wednesday. Given the predicted wind direction, coastal cities
including Myrtle Beach could run significantly cooler and
foggier than inland locations.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR. SKC to prevail across all terminals this period, except
leftover Cu/SC may affect the coastal terminals early this
evening prior to moving off the coast. Drier and much colder
air to continue to plow across the local terminals thruout this
24 hr period. Winds will be the storyline this 24 hr period.
CAA combined with a tightened sfc pg will result in gusty NW
winds, g20+ kt at times, thru 05Z Sat. NW winds 10 kt or less
thereafter. NW-NNW winds pick back up in gustiness after 14Z
Sat.
Extended Outlook...VFR expected through most of the period.
Well-below normal temps this weekend, with teens likely
both Sat and Sun nights. High pressure will move overhead and
offshore early next week, resulting in MVFR cigs and vis
possibly becoming a concern from Tue onward as moist onshore
flow commences.
&&
.MARINE...
Through Saturday...Breezy offshore flow will dominate the
period as strong arctic high pressure builds across the
country. Elevated winds and seas will subside somewhat tonight,
with SCA conditions now expected to end by late tonight. Waves
will be primarily driven by northwesterly wind waves with 1-2 ft
southeasterly swells at 8 sec also contributing. On Saturday,
winds around 15-20 kts continue while seas fall into the 2-3 ft
range, mainly due to wind waves. The next chance for SCA
conditions returns with wind gusts over 25 kts during Saturday
night.
Saturday night through Wednesday...Canadian high pressure
centered west of the Appalachians will push the coldest airmass
of the winter season across the area Saturday night into Sunday.
Gusty northwest winds will likely bring Small Craft Advisory
conditions Saturday night into early Sunday morning before wind
speeds diminish during the day Sunday. The short offshore fetch
will limit wave heights to no higher than 4 feet even out at 20
miles distance from shore, but wave periods will be short.
Perhaps even more adverse will be air temperatures in the 20s
coupled with 15-25 kt winds which will drop wind chills down
into the 10-15 degree range.
Winds directions will veer northeasterly Sunday night as the
center of the high makes it to the Mid Atlantic coast. A rapid
modification in air temperatures should occur Monday into
Tuesday as subtropical air sweeps in from the southeast. By late
Wednesday the increase in moisture riding across cold nearshore
water could result in sea fog development which may worsen
later in the week.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until 4 AM EST Saturday for AMZ250-252-
254-256.
&&
$$
SYNOPSIS...DCH
UPDATE...DCH
NEAR TERM...ABW
SHORT TERM...TRA
LONG TERM...TRA
AVIATION...DCH
MARINE...TRA/ABW
===Extended Forecast Discussion===
Moving into the final week of January, the forecast teleconnection
pattern looks to feature a +AO/+NAO/+EPO/+PNA pattern. The MJO is
forecast to take an orbit through phases 4/5/6 before going into the
neutral circle on the RMM plots. Taken together, this will result
in a milder than normal pattern for the eastern US. Signal analysis
from early January points to a signal crossing in the 1/27-29 time
frame with maybe a rain to snow scenario here. A second weaker
signal may cross in the 1/30-1/31 time frame. A stronger signal
crossing looks likely in the 2/3 to 2/5 time frame which will have
to be watched closely. After about 2/7-2/9, it appears the MJO may
re-emerge in the phase 7/8/1 area and a return to colder conditions
may develop. However, there are some things that suggest that
return of a colder pattern could end up holding off until around
Valentine`s Day.
&&
.Aviation...(00Z TAF Issuance)
Issued at 640 PM EST Fri Jan 19 2024
Impacts/Confidence:
- Medium Confidence in MVFR ceilings tonight/tomorrow
- Low-Medium Confidence in flurries/light snow at LEX later tonight
- High Confidence in NW winds gradually relaxing tonight into
tomorrow
Discussion...At this hour, there is a messy-looking stratus field
across the region which is bringing borderline MVFR/VFR ceilings to
SDF, BWG, and LEX, while HNB has had more clearing so far this
evening. Later tonight, it is expected that clouds will try to build
in along the western flank of the current stratus deck as a mid-
level disturbance approaches the region from the NW. However,
upstream observations have not been as widespread with cloud cover
as models are anticipating, so have trended more optimistically with
CIGs tonight, especially at HNB and BWG. Would not be surprised to
see all forecast sites vary several times between VFR/MVFR CIGs
overnight tonight, and overall confidence in categories is medium.
Winds will gradually become less gusty overnight tonight, though a
steady 8-12 kt NW wind is expected to continue through Saturday
morning. As the disturbance approaches from the NW, it may be able
to interact with enough low-level moisture to produce a few light
snow showers, especially at LEX.
During the daytime hours on Saturday, would expect a broken MVFR
stratus deck atop the boundary layer gradually dissipating in the
afternoon and evening hours. Recent model trends have been more
optimistic, though past experience suggests that it will be
difficult to mix out the low-level moisture.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Wind Chill Advisory until 10 AM EST /9 AM CST/ Sunday for
KYZ023>043-045>049-053>057-061>067-070>078-081-082.
IN...Wind Chill Advisory until 10 AM EST /9 AM CST/ Sunday for
INZ076>079-083-084-089>092.
&&
$$
Update...CSG
Short Term...ALL
Long Term...MJ
Aviation...CSG
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
912 PM CST Fri Jan 19 2024
.UPDATE...
Issued at 912 PM CST Fri Jan 19 2024
Main forecast concerns continue to be with redevelopment of
heavier lake effect snow in northwest IN overnight, dangerously
cold wind chills across parts of northern IL, and light
snow/flurries ending overnight outside of the lake effect snow
band. No changes made to current headlines for the winter storm
warning for Porter county, and the wind chill advisory for
northern IL west and southwest of Chicago.
Evening vapor imagery and upper air analysis depicts a mid-level
short wave tracking east-southeast across northern IL. Radar
continues to indicate an area of light snow/flurries generally
east of the I-39 corridor associated with this wave. Visibilities
were currently observed in the 3-5+ mile range with generally
trace amounts to a tenth or two of accumulation. This light snow
will continue to diminish to just a few scattered flurries from
west to east across northeast IL through midnight. Temperatures in
the single digits will dip below zero west of the Fox River
Valley and I- 55 corridor overnight, and just above zero in
Chicago and northwest IN. Blustery west-northwest winds gusting
around 20 mph will send wind chills to -20 to -25 overnight again
from the Fox Valley and I- 55 west, and into the -10 to -15 degree
range farther east. Current wind chill advisory continues to
highlight the areas most likely to see chills -20 and lower.
Farther to the east, a combination of light snow associated with
the short wave disturbance and some lake effect component will
persist into the overnight hours. The intense primary LES single-
band which had brought 6 or more inches to far northeast Porter
county earlier this morning had shifted east into north-central IN
and southwest lower MI since midday, remains focused into the
Benton Harbor, Elkhart and Goshen areas at mid-evening. High-res
guidance continues to forecast a westward retreat of this band
overnight however, with CAMs in decent agreement in bringing the
potential for heavy lake effect snow back into Porter county after
midnight (perhaps after 2 am), and recent HRRR runs even clip
parts of eastern Lake county later tonight. This would support
another round of intense (2 inch per hour rates possible) lake
effect snow for those areas into early Saturday morning. Already
seeing evidence in radar imagery over central Lake Michigan of
this westward drift, increasing confidence in snow redeveloping
into at least Porter county, where current Winter Storm Warning
headline will be maintained for the expectation of additional
heavy snow with localized whiteout conditions and accumulations.
Depending on residence time of the snow band, headline could
potentially need to be lengthened a few hours into Saturday
morning, before backing low-level winds and gradually lowering
inversion heights shift the band back east of the cwa and allow it
to weaken.
Made some minor tweaks to hourly temp/dew point trends into the
overnight hours as well decreasing sky cover a little faster
especially across north central IL. Otherwise, going forecast and
headlines appear to be in good shape into Saturday morning with no
other significant changes made at this time.
Ratzer
&&
.SHORT TERM...
Issued at 302 PM CST Fri Jan 19 2024
Through Sunday...
Key Messages:
- Intense lake effect band of heavy snow with white out conditions
expected to shift back westward into La Porte and portions of
Porter County Indiana late tonight.
- Bitterly cold temperatures and wind chills expected through
Sunday morning.
Extreme lake induced instability (lake to 850 delta T`s and
equilibrium levels exceeding 20C and 12,000 ft, respectively)
continues to drive very intense snow squalls and embedded
mesovortices focused along a lingering land breeze convergence
zone along the eastern end of Lake Michigan. The focus for these
intense lake effect snow squalls has shifted east of the LOT
forecast area early this afternoon, leaving only some lingering
light snow showers across northeastern Porter County. This is
expected to change later this evening and overnight, however, as
the land breeze convergence zone retrogrades back westward in
response to the next surface trough shifting down the lake.
Accordingly, the expectation is for these intense lake effect snow
bands to begin to shift back into La Porte and at least into
northeastern sections of Porter County IN for a few hour period
overnight. While it remains somewhat unclear how far west into
Porter County these intense squalls will reach, the threat for
2+" per hour rates and temporary white out conditions within the
heavier squalls prompted us to issue another Winter Storm Warning
for Porter County for the overnight period tonight (10pm through
6am). Some of this activity could persist into Saturday morning,
just beyond the current warning period. However, the focus for the
most intense snow is expected to wane shortly after daybreak.
For the remainder of the area outside the lake effect, some
occasional flurries and light snow showers can be expected late
this afternoon and evening as the next upstream disturbance
continues to shift across the area. Any additional accumulations
away from the lake effect with this activity will be minimal (a
coating at best). Otherwise, the main story will be the cold
tonight through Sunday. A Wind Chill Advisory continues tonight
for the western half of the WFO LOT CWA (roughly along and west of
the Fox Valley), where winds chills in excess of 20 below are
expected later tonight.
Following a cold and breezy day on Saturday, a stout 1040 mb
arctic high shifting south-southeastward across IL will set the
stage for a very cold night across the area. Currently looks
likely (80%+ chance) that overnight low temperatures will fall
down to -15 to -10 along and west of the Fox Valley, and from near
zero to -10 to -5 elsewhere. Fortunately wind speeds will become
light, but any remaining light breeze will push wind chills back
down into the teens to 20s below zero into early Sunday morning.
Cold conditions continue during the day on Sunday, with high
temperatures expected to remain in the teens.
KJB
&&
.LONG TERM...
Issued at 308 PM CST Fri Jan 19 2024
Sunday night through Friday...
Key messages:
- Increasing potential for another round of precipitation
(including freezing rain) late Monday into Tuesday.
- Temperatures moderate back into the 30s next week.
- Hydrologic concerns will continue along area rivers due to the
lingering ice jam threat.
Following another very cold weekend, a larger scale pattern shift
is expected to set the stage for moderating temperatures for next
week. This pattern shift is expected to onset late Sunday into
Sunday night following the eastward departure of the progressive
arctic high. Following its passage, southerly low-level flow will
drive a steady feed of a warmer and increasingly moist airmass
northward into the area Sunday night and on Monday. Accordingly,
temperatures are expected to warm into the 20s Sunday night, then
likely climb up into the lower 30s during the day on Monday.
A longwave upper-level trough, whose axis will roughly remain
centered over the Rocky Mountains/Great Plains regions, will help
funnel a handful of disturbances out across the central CONUS next
week. Model and ensemble forecast guidance are in good agreement
that a more robust impulse will eject northeastward from this long
wave trough out across the Midwest into the Lower Great Lakes
region Monday into Tuesday. This impulse is expected to drive a
good slug of moisture (and increased precipitation chances) into
our area Monday into Tuesday. The primary weather concern with
this precipitation will be determining its predominant type.
Current indications are that the airmass above the near surface
layer will gradually warm above freezing across much, if not all,
of the area as surface temperatures hover near freezing. This of
course increases the concern for some periods of freezing rain
(possibly mixed with snow and sleet at times north) with the
initial stages of precipitation Monday into Monday night,
especially since the ground will remain subfreezing following this
weekend`s cold spell. How long this freezing rain threat persists
into Tuesday remains unclear at this time. While this remains in
question, it does appear increasingly likely (80%) that some
freezing rain threat will exist for a period on Monday as the
precipitation onsets. The expectation is then that a continued
steady feed of moisture and warmer air from the south will favor a
gradual change over to primarily rain from south to north with
time into Tuesday. Given the continued uncertainties this far out
with timing of changing P-Types, we opted to keep it simple and
just mention a wintry mix of rain and freezing rain, with some
snow and sleet potential across far northern IL Monday into Monday
night.
Following this impulse it appears that we could have a period of
quieter weather around midweek, but with additional impulses
likely to eject out of the long wave trough west of the area, we
will have to keep an eye out for additional precipitation chances
later in the week. Expect temperatures during the latter part of
the period to primarily be in the mid to upper 30s as we work on
a gradual melt of our snowpack.
Hydrologic concerns will persist through the period, especially
along area rivers as the ice jam threat continues. We will also
have to keep an eye on the melting potential of our snowpack next
week, as a rapid melt could result in a significant increase in
runoff and an increased flooding threat. Fortunately, however, at
this time it appears the melting may occur more gradually through
the week as the threat for very warm temperatures and high dew
points looks to largely remain south of the area. Nevertheless,
with the large amount of ice now on the rivers, this is something
we will have to keep a close eye on for the next couple of weeks.
KJB
&&
.AVIATION...
For the 00Z TAFs...
Forecast concerns for the terminals...
* Light snow showers/flurries through midnight tonight
* Lake effect snow band pivots back into portions of northwest
Indiana overnight
An upper-level disturbance continues to pivot through northern
Illinois this evening which will allow periods of light snow
showers and flurries through midnight. While recent radar trends
and observations have shown the snow showers to be weakening, I
have decided to maintain the TEMPOs for MVFR visibility reductions
in the off chance showers redevelop as the disturbance pushes
through. Regardless, little to no accumulation is expected with
these snow showers/flurries and they will fully come to an end
after 06z tonight.
However, the intense lake effect band, currently near the
Indiana-Michigan line, is forecast to pivot back into portions of
northwestern Indiana late tonight into Saturday morning. The
majority of guidance continues to favor the band remaining east of
GYY but there are some members that bring it rather close. Given
that confidence on the band reaching GYY is low I have decided to
maintain the dry forecast after the aforementioned
showers/flurries through tonight but will keep a close eye on it.
Though, areas under the lake effect band can expect snow rates
upwards of 2 inches per hour resulting in very low visibilities
and quick snow accumulations totaling 4 to 6 inches in spots.
Otherwise, expect the lake effect snow to taper Saturday morning
leaving the area with gradually decreasing cloud cover and light
west-northwest winds around 10 kts. Though, some 1500 to 2000
clouds may linger through Saturday afternoon.
Yack
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Chill Advisory...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ019-ILZ020-ILZ021-ILZ032-ILZ039 until 9 AM
Saturday.
IN...Winter Storm Warning...INZ002 until 6 AM Saturday.
LM...Small Craft Advisory...IL nearshore waters until noon Saturday.
Small Craft Advisory...IN nearshore waters until 9 PM Saturday.
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