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399
FXUS61 KBGM 271632
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1232 PM EDT Mon May 27 2024

.SYNOPSIS...
A strong system will bring locally heavy rain and a chance for
thunderstorms today. A few storms may become severe this
afternoon and evening. Additional scattered showers will linger
through midweek, with drier conditions expected towards the end
of the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
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1200 PM Update...

Rain has moved into the western portion of the CWA over the past
hour. Persistent clouds here this morning did not allow any
instability to develop so thunderstorms are not forming here.
Thunderstorms have begun to pop off south of Bradford county,
and we expect storms to develop along and east of this area as
clearing this morning has allowed most of the CIN to dissipate
and CAPE values climb to 500-1000 j/kg. Very strong low level
winds will continue the tornado threat, especially from the
Southern Tier and south. Current storms are moving quickly to
the NNE at around 45-50kts so if we can get any of these storms
to organize, they should produce severe winds, hail or even spin
up a tornado. This first batch of storms should push through
the area by 6pm. Another period of showers and storms is
expected to develop and move into the western portion of the CWA
by 4pm, moving to the east. CAPE and shear remain high enough
for the severe threat to remain into the evening hours. A third
group of showers and storms will push through from west to east
tonight, but severe weather is not expected here.

Flooding concerns remain for NEPA and the Catskills as high
PWATs from SE flow off the Atlantic will fuel heavy rain
development over the region. Multiple periods of rain today
could drop 2-3 inches from Sullivan county south into NEPA, but
flooding will depend on how fast this rain falls and if a
location is impacted by multiple waves. The current setup does
not give great confidence in specifics of the flooding threat,
but the ingredients are there for some of our flashier areas to
see some impacts.


945 AM Update...

We have been able to see some clearing east of the Finger Lakes
this morning, allowing surface CAPE to climb to around 500 j/kg.
It looks like we will be a couple more hours of partial
clearing, which will help drive CAPE values up to 1000 j/kg.
This is looking a little higher than originally thought, given
we did not expect the clearing to hang around this long. This
instability, combined with very high shear and helicity, will
continue the severe weather chances across the area late this
morning into the late afternoon hours. CAM guidance shows a
couple different shots of severe weather chances, with the first
line moving through during the late morning/early afternoon
hours, followed by another line of thunderstorms in the late
afternoon, and concluding with a third weaker line pushing
through in the evening hours. Tornado threat continues to be
highest along and south of the NY border during the first
severe window as surface winds will be out of the SE, with mid-
level winds out of the SW. As the afternoon progresses, surface
winds veer to the S, reducing tornado chances but not
eliminating them. Flooding concerns remain, especially across
the Catskills and Poconos as we will see several rounds of
thunderstorms with the chance of producing heavy rain.
Confidence in this is still not high enough for a flood watch at
this time given the progressive nature of the storms and the
high flash flood guidance thresholds over the area.

4 AM Update...

Several rounds of showers and thunderstorms will impact the
region today. Big question will be the amount of destabilization
that can occur before the main shortwave arrives this afternoon.
On-going convection across the Ohio Valley this morning will
continue pushing E-NE through the morning and reaches our
forecast area by late morning/early this afternoon. At this
time, it looks like we will be in a strong shear, but limited
instability environment. CAPE values will top out at 500 - 1000
J/kg, with the higher end of that threshold only expected if
some clearing is able to occur later this morning. 0-1 km shear
is quite strong at about 40 knots and plenty of helicity will
exist as EHI approaches a value of 2 across NE PA this afternoon.
Although instability is expected to be low, the high low level
shear values are a concern, as this can lead to an isolated
tornado or two from a relatively low-topped thunderstorm or even
convective shower. SPC has expanded the slight risk across most
of our forecast area, however the greatest tornado threat will
remain across NE PA, where low level shear will be maximized.

Other than the severe thunderstorm threat, there is also a
concern for flash flooding. A flood watch was considered, but
confidence is still too low at this time and after discussing
with surrounding weather forecast offices, the decision was made
to hold of on a watch for now. Localized heavy rainfall, over 3"
will be possible, but this will be dependent on the amount of
training and back building that will be able to occur. We will
continue to highlight this threat in the HWO.

Finally, the thunderstorms and heavy rain threat will push east
of the area during the evening hours. Conditions will be quiet
overnight, however the break won`t last too long. Upper trough
swings in overhead on Tuesday and more showers and thunderstorms
are likely to develop during the late morning to early
afternoon. These storms will be less potent than today, and not
expecting much in the way of impacts on Tuesday.
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&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
1020 AM Update...
Forecast was completed earlier than usual due to operations
being focused on event-at-hand. Little change from what was
already discussed below, other than to linger rain chances
longer Tuesday evening for Central NY.

Previous discussion...
A shortwave embedded in the long wave upper trough overhead
will be moving away from the area Tuesday night, and shower or
thunderstorm activity across CNY will taper off. Lows Tuesday
night range from the upper 40s to the mid 50s. Another shortwave
will dive southeastward toward the area Wednesday enhancing the
cooler, northwest flow over the region. High temperatures will
mainly be in the 60s with the Wyoming Valley perhaps squeaking
out 70 degrees. There is some uncertainty with regards to the
shower coverage this day with the main lobe of energy with the
shortwave looking to pass by to the south. This would limit
showers over CNY Wednesday but lead to a higher chance over NE
PA. PoPs were lowered some from NBM across CNY to reflect this
idea. This disturbance is expected to push off to the east
Wednesday night and drier, colder air filters in dropping low
temperatures into the 40s. Some of the highest elevations are
expected to dip back into the low 40s.

Yet another shortwave looks to drop south out of Canada on
Thursday, but with the drier air in place and this feature
projected to pass by to our south and west, any showers look
isolated in nature. It will remain cool with highs again
generally in the 60s and overnight lows falling back well into
the 40s.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
1020 AM Update...
Forecast was completed earlier than usual due to operations
being focused on event-at-hand. Little change from what was
already discussed below for what appears to be a mainly dry
period with temperatures trending from slightly below average
initially to near average over the weekend.

Previous discussion...
Surface high pressure builds in from the west on Friday and the
long wave upper trough finally moves off the coast by the start
of the weekend. Ridging builds in at the upper levels and as a
result, a pretty nice weekend looks to be in store with largely
dry conditions. High temperatures will be on the rise going from
the 60s to near 70 degrees on Friday to the mid and upper 70s
by the time Sunday rolls around.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
A potent system pushes through the region today bring heavy
showers and thunderstorms as well as gusty winds. IFR
conditions will be possible at times during heavy rain and
thunderstorms with the heaviest storms likely occurring this
afternoon. Confidence is still low on the exact timing and
intensity of thunderstorms this afternoon, but have added Tempo
groups to each site when the window of heaviest storms is
expected. Showers and thunderstorms will come to an end this evening,
but restrictions will be possible in lingering stratus and fog
overnight.

Outlook...

Tuesday through Wednesday...Occasional restrictions likely from
multiple batches of showers and thunderstorms.

Thursday and Friday...Mainly VFR.

&&

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

&&

$$

SYNOPSIS...MPK
NEAR TERM...JTC/MPK
SHORT TERM...DK/MDP
LONG TERM...DK/MDP
AVIATION...MPK