000
FXUS61 KBGM 170835
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
435 AM EDT Sun Oct 17 2021

.SYNOPSIS...
Cooler weather will persist for the next few days. Lake effect
rain showers will be persistent across the NY Thruway corridor
much of today, tonight, and into Monday. A rumble of thunder
can`t be ruled out as well. Elsewhere, showers will be more
scattered in nature with significant dry periods. Warmer and
drier weather looks to return by Tuesday, as highs reach back
into the 60s.

&&

.NEAR TERM /THROUGH MONDAY/...
430 AM Update...
A high-amplitude, negatively-tilted trough over eastern Canada
and the northeastern U.S. will keep cyclonic flow in place
across our area through the next couple of days, while west to
northwest winds persist at the surface. This will lead to
periods of lake effect showers modulated by the passage of
relatively weak shortwave disturbances rotating through the mean
trough.

While the heaviest and most persistent showers will be focused
along the Mohawk Valley, or near and north of the Thruway/I-90,
more widely scattered showers will also drift across the rest of
the area, particularly this afternoon as one of the shortwaves
drifts through, aided as well by diurnal heating and weak
instability.

A few thunderstorms will also be possible relatively close to
Lake Ontario as lake temps in the mid-60s yield lake-induced
CAPE over 1000 J/Kg this afternoon. The effects of the lake on
low level lapse rates thus, overall instability, will diminish
the further inland you go, as temps on land will top out in the
upper-50s. Best shot at thunder will be over northern Onondaga/
Madison, and western Oneida Counties.

We may see a lull in activity even across the Thruway late this
afternoon and evening in the wake of the shortwave disturbance,
but PVA will increase again during the early evening hours, with
precip chances increasing again over the northern counties ahead
of a stronger shortwave disturbance and associated surface
trough. Surface/low-level winds will veer more to the northwest
behind the trough, allowing lake effect bands to shift further
south of I-90 early Monday morning, eventually spreading into
parts of NE PA. Showers will gradually diminish in intensity
through the afternoon.

Overall precip amounts will be light for most -- however, where
the rain is most persistent (near/north of the Thruway) precip
amounts will rack up. Total rainfall from this morning through
Monday afternoon may range from 1 to 1.50 inches over parts of
Onondaga County. Some showers may be moderate to briefly heavy
at times today and again early Monday, and localized minor
flooding can`t be ruled out, especially as some parts of
Onondaga County picked up over 2 inches with the earlier
rainfall. Any flooding will likely be of the nuisance variety,
e.g., urban and poor drainage (possibly impacted by leaf-
clogging).

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
325 AM Update

A few lingering lake effect rain showers possible for the first half
of Monday night. There will be a northwest flow, so the best chance
to see scattered showers will be across the favored upslope areas of
the Susquehanna region & western Catskills of Central NY. High pressure
slowly builds in from the west overnight, helping to dissipate any
lingering showers before daybreak. Clouds also gradually decrease
overnight, becoming mostly clear across our western zones. Seasonably
cool, with overnight lows in the mid-30s to lower 40s in most areas.

The rest of the short term period will feature very pleasant fall
weather as a ridge of high pressure moves over the region. The slow
moving upper level low will still be near far northern New England
on Tuesday, but will eject east by Wednesday. Overall, our weather
should feature plenty of sun and clear skies this period, with a
return to seasonably mild temperatures. Slightly breezy northwest
winds 8-15 mph Tuesday decrease under 10 mph by Wednesday. Highs
both days will be in the mid to upper 60s, with overnight lows in
the 40s both Wednesday and Thursday night.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
325 AM Update

The weather pattern will turn a bit more active in the extended
period. Latest deterministic and ensemble guidance, including the
NBM is speeding up the arrival time of the next system on Thursday.
Whereas before it looked like we may have stayed dry for much
of the area on Thursday...that is now beginning to change.
Current data suggests rain showers move in from the west
sometime Thursday morning and overspread most of the forecast
area Thursday afternoon. For now, stuck close to the NBM, which
gave higher end chance PoPs for the afternoon...so there is
still some potential guidance changes course and slows this
system down again. Exact timing remains to be seen. The upper
ridge out ahead of the system is not very high amplitude...so am
not surprised by the slightly faster timing from the latest
model guidance. Chance to low end likely PoPs continue Thursday
night for rain showers as the low pressure system slides across
the area. With the faster overall timing, guidance is now
starting to lower PoPs on Friday...now only looking at slight
chance to low end chance for some rain showers under partly
sunny skies. Temperatures still above average on Thursday (well
into the 60s for highs)then falling about 10 degrees (back to
near average) on Friday, behind the cold front.

There is then uncertainty in the forecast for next weekend; but
overall there looks to be a broad, longwave trough over the
Northeast during this timeframe. 00z GFS is much stronger and colder
with this upper level trough than the 00z ECMWF...with the 00z
Canadian being in between the other two models. For now, stuck very
close to the blended ensemble guidance (NBM) considering the uncertainty.
This gave slight chance to low end chances for a few showers under
partly sunny skies. Temperatures would be seasonably cool, with
lows in the upper 30s to lower 40s and highs in the 50s. Again,
if the GFS solution pans out it could be a colder...but at this
time this seems to be an outlier solution.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
VFR conditions prevail over most areas, through ceilings are
still expected to drop to MVFR levels over most NY terminals.
While some patchy and shallow ground fog is likely to develop
in sheltered areas region-wide, WNW winds look to remain stay
strong enough to keep this out of most terminals.

Expect off-and-on rain showers downwind of Lake Ontario pretty
much throughout the period, with the focus favoring SYR
overnight, but moving back into RME during the day Sunday. Lake
Ontario temps in the mid-60s will result in stronger afternoon
instability over and immediately downwind of the lake, and will
carry VCTS for a few hours at SYR.

With mixing, ceilings will improve to VFR again during the day,
but should also mix-down some gusts around 20 knots.

Outlook...

Sunday night...Chance of showers, mainly for the NY terminals;
intermittent restrictions possible.

Monday...Chance of showers, mainly RME and SYR, and associated
restrictions. Otherwise, mainly VFR.

Tuesday through Thursday...Mainly VFR.

&&

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

&&

$$
SYNOPSIS...MPH
NEAR TERM...MPH
SHORT TERM...MJM
LONG TERM...MJM
AVIATION...MPH/MWG

NWS BGM Office Area Forecast Discussion

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