000
FXUS61 KBGM 190745
AFDBGM

AREA FORECAST DISCUSSION
National Weather Service Binghamton NY
345 AM EDT Fri Apr 19 2019

.SYNOPSIS...
A large slow moving low pressure system will move from the
Tennessee Valley through the Ohio Valley and Mid-Atlantic
region today and Saturday, bringing periods of heavy rain and
thunderstorms to most of the area. On and off rain showers with
mild temperatures expected through the first half of next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
4 am update...
Main concern in the near term remains focused on the potential for
thunderstorms producing heavy downpours which may lead to a threat
for flash flooding across ne PA and south-central NY this afternoon
through tonight.

A Flash Flood Watch remains in effect for all of ne PA and
northward into the central srn tier of NY and the wrn
Catskills...this afternoon through early Saturday morning.

Large scale synoptic pattern forecast several days now is still
relatively unchanged with a large cutoff upper low near TN/MO/AR
this morning moving slowly to the e/ne today and into the the
Ohio Valley tonight/Saturday morning and eventually into the
Mid-Atlantic region Sat evening. The main concern with this
system is still centered around the large slug of moisture
expected to advect north ahead of the low along the East Coast
into ern PA and central NY later today and tonight...producing
the potential for heavy rain within showers and thunderstorms.
The combination of wet antecedent ground conditions and elevated
rainfall rates could lead to flooding issues...and this threat
remains about the same.

Weather conditions this morning will likely remain quiet across
the forecast area with some light rain showers or drizzle
popping up before noon within an increasingly moist southerly
flow. However, the environment will become unstable south and
east of the main surface boundary situated roughly from
n-central PA into the Adirondacks...and remain relatively stable
north and west of this boundary. There is expected to be two
areas of heavy rain when the entire system is said and done. One
area will be along and west of this boundary...triggered by the
strong upper level forcing and sufficient moisture and layer
lifting up and over the front. Could see 1-2 inches over areas
of wrn NY into the Finger Lakes. The rain back to the west will
likely fall during an extended 12 to 18 hr period...which will
limit the potential for any widespread flooding. The main area
of heavy precip we are concerned about is east of the
front...where the Flash Flood Watch is in effect. This area will
be of concern due to 1-2 inches or locally more, occurring
during a short 2-4 hr period late this afternoon or this
evening. There may be two waves of convection as well...one this
afternoon and another one late evening and into the early
overnight hours. Will likely more concerned with the second
wave...potentially centered on the Poconos and srn Catskills
when the deep moisture arrives.

There is still some uncertainty with respect to placement of the
heavy rain bands...which is typical with warm season convection
associated with a large slow moving low pressure system. So, be
mindful of the weather situation if you have outdoor activities
planned later today and tonight.

The upper low will move slowly into the wrn Mid-Atlantic region
on Saturday with a wedge of dry air directly ahead of the
system...which will allow for noticeable drying and potentially
clearing of sky conditions Saturday afternoon. Linger rain
showers in the morning will trend toward quiet weather later in
the day and temperatures warming into the upper 60s and lower
70s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
An upper level low pressure system will be located across the
region during this timeframe. With the cold pool of air aloft,
lapse rates will steep. Moisture will be limited. However, the
steep lapse rates should provide enough instability for some
scattered showers throughout this period. Lows look to be in the
40`s for most locations with highs in the 60`s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Monday through Tuesday night: The upper level low pressure system
will head offshore. However, a cold front looks to move into our
area on Tuesday. Moisture and lift ahead of the cold front Tuesday
should be enough for another round of scattered showers. The new 00z
ECMWF and GFS are both slower with the approach with the cold front
leading to a dry window Tuesday morning and enough warm air
advection to get highs to around 70. We have trended highs a bit
above ensemble and blended guidance to account for this with most
locations in the 60`s to 70 for highs on Tuesday. Temperatures
Monday and Monday night should range from lows in the 40`s and highs
in the 60`s.

Wednesday through Thursday: The previously mentioned cold front
moves southeast of the region with the potential for a cooler but
drier airmass to move in. Even though the forecast is mainly dry,
some ensemble members do linger shower chances through Thursday. So
trends will have to be watched over the upcoming days. The cooler
airmass looks to knock highs down to around 60 with lows in the
40`s.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Primarily VFR conditions expected early this morning with
mainly mid level clouds. The exception to this is at KAVP/KBGM,
where moist southerly flow will bring MVFR/Alternate Required
ceilings into the terminals between 12Z-14Z. These restrictions
will continue through the day with showers and brief MVFR
conditions likely after 21Z. Convective showers between 21Z-
01Z...with an increase in coverage and intensity likely after
01Z...so added TEMPO grp with mention of TS at all terminals.

Low level wind shear for all terminals early this morning with
southwest winds around 50 knots at 2K feet. Surface winds will
be southerly around 10 knots with occasional gusts around 20
knots through the day...subsiding to less than 10 kt late
afternoon and evening.

Outlook...

Late tonight through Saturday...Restrictions likely with rain
and possible thunderstorms.

Sunday...Restrictions likely in CNY and maybe AVP.

Monday/Tuesday...Restrictions possible in rain showers.

&&

.HYDROLOGY...
4 am update...
Minimal changes made to the forecast with the latest rainfall
guidance still suggesting around 1 inch from Steuben county into
the Finger Lakes through the entire storm event...and an
enhanced area of 1-2...possibly up to 3 inches across ne PA into
the western Catskills and central srn tier of NY with most of
that rain falling late this afternoon through tonight over a
short period of time. Confidence in heavy rain and possible
flooding is much lower across western basins as compared to our
eastern zones.

Focus still remains centered on the threat of heavy rain...most
likely in the form of heavy downpours in a short period of
time...across the Upper Susquehanna headwaters, and most of the
Upper Delaware basin...including the portion of ne PA which
received 2-3 inches earlier in the week.

Nuisance drainage and flash flooding will also need to be
monitored closely, especially since the bulk of this event will
be occurring at night when the threats are harder to see.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Flash Flood Watch from this afternoon through Saturday morning
     for PAZ038>040-043-044-047-048-072.
NY...Flash Flood Watch from this afternoon through Saturday morning
     for NYZ024-044>046-055>057-062.

&&

$$
SYNOPSIS...BJT
NEAR TERM...BJT
SHORT TERM...MWG
LONG TERM...MWG
AVIATION...BJT/RRM
HYDROLOGY...BJT/JAB

NWS BGM Office Area Forecast Discussion

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