-- Discussion containing changed information from previous version are highlighted. --
978
FXUS61 KBGM 201804
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
204 PM EDT Tue Aug 20 2024

.SYNOPSIS...
Cool and breezy conditions are expected this afternoon into
Wednesday with scattered lake effect rain showers this afternoon
and isolated thunderstorms Wednesday afternoon. Quieter and
warmer conditions are expected for the second half of the week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
1230 pm Update...
Radars show scattered showers forming downwind of Lake Ontario
mainly around Onondaga County to the highlands northeast of BGM.
Around this area, there were more isolated showers or sprinkles
with little if anything in northeast PA. The low-level flow was
northwesterly around 320 to 330 degrees and with Lake Ontario
surface water temperatures around 22C we are seeing lake
effect/enhanced rain showers develop with the days heating.
There was an upper level low over southwest Quebec with some
synoptic moisture wrappring around it as well into central NY.
Unseasonable low 850 mb temperatures were advecting southeast
across NY and PA with 850 mb temperatures down to +4C this
afternoon leading to an 18C differential with the Lake Ontario
temperatures. So we have scattered lake effect rain showers
mainly in central NY downwind of Lake Ontario with sprinkles
elsewhere. Made some adjustments to previous forecasts mainly
for POPs based on current radar data.

915 AM Update...
For this update, tweaked POPs for lake enhanced rain showers
based on current radar trends. Only minor changes needed.
Upper Level low was dropping southward from southern Quebec and
will combine with low-level northwest flow across Lake Ontario
to produce scattered rain showers and sprinkles downwind into
central NY and northeast PA.

603 AM update...
Still seeing some very light echoes dropping north to south from
either Lake Ontario or the Finger Lakes or both in the form of
very light rain or drizzle. No significant changes made to the
forecast at this time.

333 AM update...

Main concerns in the near term are centered around the lake
effect clouds and light rain showers on and off today, followed
by additional chances for lake effect showers tonight and
through the day Wednesday, along with afternoon weak
thunderstorms with potentially some graupel or small hail.

Cold core upper level low currently situated over southern
Quebec this morning with a steady flow of cool Canadian air
advecting south on the back side of the low over southern
Ontario and and eastern Great Lakes. This air mass dropping in
from the north has a relatively deep layer of dry air aloft, but
has been able to tap into the warm waters of Lake Ontario to
generate low level lake effect clouds south of the lake. 850mb
temperatures around +2 to +3 deg C, combined with lake sfc temps
around 21 deg C will continue to be sufficient for inland lake
effect moisture in the form of clouds and light rain showers
today into tomorrow.

It will definitely feel more like fall today with highs in the
60s, plenty of strato-cumulus clouds, and brisk N/NW winds
gusting to 20 mph. Some breaks in the clouds this afternoon
should induce only a weak amount of low level
instability...enough to regenerate the low clouds and keep the
light rain showers going. Model soundings are hinting at a mid
level capping inversion that, if simulated correctly, will keep
a decent lid on any widespread precipitation, at least today.

The chances for rain increase tonight as the upper low over
southern Quebec drops S into northern NY. The favorable
position of this upper level feature, combined with a
compression of the boundary layer and most of the moisture in
the low levels being concentrated in the lowest 10kft will allow
the chances for rain showers to increase (up to 40-60 pct
chance) late tonight and early Wed morning...mainly over the
Finger Lakes and adjacent areas of the southern tier of NY.

The potential for scattered showers in addition to weak
thunderstorms continues through the day Wednesday as the upper
low tracks east into VT/NH. A deeper and more moist air mass
will be entrained into the system by Wed afternoon , and when
combined with the large scale forcing and the cold temperatures
aloft/steep lapse rates, the threat for thunderstorms increases.
The storms should be relatively low- topped...up to 20kft or
so, but given the wet-bulb zero height around 6000 ft, it should
not take much to generate small graupel or hail and
subsequently a few lightning strikes. The most favorable time
for TS will be in the afternoon when the boundary layer will be
the most unstable. Sfc based CAPE values 100-300 J/kg are
possible. The convection is expected to subside around or just
after sunset. Daytime high temperatures on Wed should be only
into the lower to mid 60s once again, with breezy NW winds 10 to
20 mph.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
A broad upper level low will continue to slowly move northeast
across New England Wednesday night and Thursday. However, west
to northwest flow will continue to bring in some clouds and
sprinkles or light showers to portions of central New York.
Coverage decreases with the low now departing. As is typically
the case, the NBM is likely way to fast with clearing on
Thursday. A very chilly airmass should continue to be present
under the upper level low with morning temperatures near 50 and
highs struggling to 70 for most of the area.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
High pressure then builds into the area Thursday night. With clear
skies, light winds and residual moisture fog could develop and
become widespread toward sunrise Friday. Temperatures start a
warming trend going from near 50 well into the 70`s. Our region then
ends up on the front end of an omega block late this week into early
next week. A few ensemble members try to sneak a disturbance from
the north into the region at some point early next week. However,
the majority of members are dry at this point each day. An overall
warming trend should continue with humidity starting to edge upward
as the airmass moving in is more seasonable. Still highs in the
low to mid 80`s with lows around 60.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Conditions were mainly VFR across all terminal sites with mainly
BKN celluar cumulus and a few rain showers. There is a chance
that at KSYR, KITH and BGM that a shower could drop ceilings to
MVFR this afternoon. Then into this evening, conditions should
remain VFR for the most part with MVFR ceilings coming in later
tonight as an upper level low drops southward.

Winds will be northwest around 8 to 13 knots gusting between 15
and 20 knots through the day this afternoon...before subsiding
below 5 kt after 00Z this evening.

.Outlook...
Wednesday night...Mainly VFR with intermittent MVFR cigs.
Afternoon showers and isolated weak thunderstorms are possible
with small hail or graupel not out of the question.

Thursday through Sunday...Mainly VFR with high pressure over
the region.
-- End Changed Discussion --

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

&&

$$

SYNOPSIS...BJT/DJN
NEAR TERM...BJT/DJN
SHORT TERM...MWG
LONG TERM...MWG
AVIATION...DJN