183
FXUS61 KBGM 180757
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
357 AM EDT Sun Aug 18 2024

.SYNOPSIS...
An upper level system brings showers and thunderstorms today,
with risks for locally heavy rainfall and perhaps gusty winds in
the strongest cells. Showers and a chance of thunder will
linger into Monday, in time pressing mainly east of Interstate
81. Drier and cooler conditions will arrive Tuesday, with fair
weather persisting for much of the week ahead.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
355 AM Update...
Main concern today will be the potential for locally heavy
rainfall in showers and thunderstorms that redevelop this
afternoon through early evening. Also, a few of the strongest
cells could turn severe in Northeast Pennsylvania and bordering
counties of New York.

Small clusters of showers lost their lightning upon reaching
our Central Twin Tiers zones as well as Pike-Sullivan-Delaware
counties given nocturnal timing. Cells in Central Pennsylvania
continue to have lightning, and we will monitor their progress
this morning.

However, primary attention will turn to renewed diurnally-
driven convection later today, especially afternoon-early
evening. Axis of instability will initially enhance along or
just west of the I-81 corridor, then shift slowly east with
time. Axis of instability will be situated along an amorphous
shallow stationary front roughly up the Wyoming Valley and
Poconos to Catskills. This setup can sometimes lead to trouble,
due to a shallow layer of southeast flow with slight veering
just above it. The Storm Prediction Center thus has brought in a
marginal risk for severe thunderstorms across Northeast PA to
the eastern Southern Tier and Catskills counties. HREF modeling
and model soundings indicate 0-1km helicity values of 50-100
m2/s2. Though amount of heating is in question today because of
cloud cover, the shallow shear and low Lifting Condensation
Level (LCL) environment supports at least a small potential for
severe cells, and indeed SPC also indicates a 2 percent risk
for isolated tornadoes within 25 miles of a point. Our region
will also reside in the left exit region of an upper jet aloft,
which will provide forced ascent as an extra nudge to any
diurnal heating from below.

The bigger overall risk for the area, however, will continue to
be potential for locally heavy rainfall. This is especially the
case for locations that have already had recent rains. Meso-
beta element vectors, that is cloud layer velocity vector minus
low level jet vector, become very short late today east of I-81,
suggesting potential of training or backbuilding of cells. Add
to this Precipitable Water (Pwat) values of 1.50-1.75 inches,
and locations that get either multiple cells or a slow moving
axis of rain could exceed what the ground can handle which would
allow water to quickly run off. The Flood Watch was expanded to
include all of Northeast Pennsylvania, as well as the Southern
Tier to Sullivan County in New York, through this evening. These
areas have somewhat better potential for localized flash
flooding, but even counties outside the Watch could have
isolated excessive rainfall. If potential and confidence
increase farther north, the Watch could still be expanded.
Monitor the forecast for updates.

After this evening, activity will press east and/or wane with
loss of heating. However, the upper low pressure system
ultimately driving our current unsettled pattern will only
slowly edge east on Monday. This will trudge a cold front across
the region Monday, with a final round of showers and chance of
thunderstorms. Rain amounts will tend to be less than today, yet
much of the area will also be even more sensitive to additional
rainfall, and thus isolated excessive rain still cannot be ruled
out though mainly east of Interstate 81. Behind the front,
cooler air will start to advect in during the afternoon, sending
temperatures all the way down into upper 40s-mid 50s by dawn
Tuesday.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
310 AM Update:

A cold front will help push remaining showers through the region
Monday night. The best chances will be east of I-81, especially over
the Catskills. Some instability will support thunderstorms during
the late evening as well. While some lingering showers may remain
Tuesday morning, most of the region will be rain-free as cool, dry
fills in behind the front. Some spotty showers cannot be ruled out
over north-central NY as wraparound moisture from this stacked low
will try to nudge its way into the region. That will be the case for
Tuesday night as well.

Temperatures will fall into the upper 40s to mid 50s Monday night.
Tuesday will be noticeably cooler as temperatures will only climb
into the 60s, though some valley locations may just reach 70.
Tuesday night will be chilly as well as most will be in the 40s.
With mostly clear skies over the region, temps were slightly reduced
below guidance.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
310 AM Update:

Moisture from this pesky low pressure system will once again make an
effort to push in from the north. Because of this, there may be some
spotty showers on Wednesday as well. Since instability will be
lacking, thunderstorms are not expected. Eventually, a ridge of high
pressure will win out and gift us with an extended period of quieter
weather. The next chance for rain won`t be until later this weekend,
and even then, that is questionable. The long term will be pleasant
with highs in the 70s and lows in the 50s. Temperatures due trend
warmer throughout the week, so 80s return just in time for the
weekend.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
MVFR to fuel alternate required ceilings will persist the
remainder of the night through morning from moist southeast
flow. As ceilings attempt to lift in afternoon, there will also
be heating-driven development of showers and thunderstorms.
Thunder chances are too iffy at this time to specifically include
in TAFs for KELM-KITH, but farther east there is more
confidence thus TEMPO CB groups have been introduced KSYR-KBGM-
KAVP-KRME. In the wake of showers-thunder, expect MVFR to fuel
alternate ceilings to redevelop in the evening, with potential
for IFR.

.Outlook...

Late Sunday Night into Monday morning...Likely fuel alternate
required to IFR ceilings.

Monday midday through evening...Scattered showers and thunderstorms
with resultant occasional restrictions.

Tuesday through Thursday...Mainly VFR as high pressure gradually
builds across the region.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch through this evening for PAZ038>040-043-044-047-
     048-072.
NY...Flood Watch through this evening for NYZ022-024-055-056-062.

&&

$$

SYNOPSIS...MDP
NEAR TERM...MDP
SHORT TERM...BTL
LONG TERM...BTL
AVIATION...MDP