Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Binghamton New York
1057 am EDT Wednesday Apr 23 2014

Synopsis...
light rain showers will slowly diminish today as cold and dry air
moves into the region. Winds will be quite gusty across central
New York and northeast Pennsylvania through Thursday afternoon as
the pressure will be tight over the region. High pressure will
then take control of the region Thursday night which will result
in the winds to become light again. The next chance for rain will
be Friday night when the next storm system approaches.

&&

Near term /through tonight/...
1100 am EDT update...
the upper level short wave has now moved to the east of the County Warning Area and
northwest flow aloft will continue across the area through tomorrow
afternoon. A secondary push of colder and drier air has started to
move into the region this morning... and as a result the lingering
rain showers are slowly diminishing across the County Warning Area. Expect the dry
air to continue to advect into the region through the period.

At the surface... the upper level attendant surface low is currently located
over Maine and a surface high pressure is located over the Great Lakes
region. The surface low will be very slow to move off to the east and
a surface high pressure will try to build in from the west today. This
combination will result in the mslp tightening over the region
which will create gusty winds. The winds will continue to blow
through the night. Dew points will slowly decrease throughout the
day and fall into the low to middle 20s by late tonight. Critical fire
weather conditions are not expected today even though we will have
gusty winds because it will take a while for the true dry air to
move in.

Tonight... winds are expected to still be breezy as the mslp will
still keep tight and due to cold air advection the 850mb temperatures will fall to near -6
c. The dry air will result in skies becoming clear across central
New York and northeast PA by early evening. The mentioned above combination
will allow temperatures to become quite chilly falling into the low 30s
to middle 20s.

&&

Short term /Thursday through Thursday night/...
415 am EDT update...
main concern is for gusty winds and very low humidity levels
Thursday afternoon. See fire weather section of the afd /near
bottom/ for further details specific to fire weather...including
the Fire Weather Watch issued for portions of the Poconos-western
Catskills.

Though high pressure will be building in Thursday...a tight
pressure gradient will still exist between the surface ridge over
the Ontario peninsula-western NY/PA...and the deepening low
offshore of Nova Scotia. Subsidence inversion due to building high
will be getting established...resulting sunshine and very dry air
mixing down with the gusty winds of pressure gradient.

Model guidance is already quite low with dewpoints...yet in this
kind of situation models typically struggle with mixing down
enough of the dry air. Thus I went even lower than
guidance...reaching into the low to middle teens dewpoints for
majority of area /upper teens towards Finger Lakes region/. With
high temperatures generally in the 50s to near 60...this yields
relative humidity bottoming out into the middle teens to middle 20s
percent range. Definitely a static electricity kind of day if
walking on carpet.

As for the northwest winds...they will be highest towards the
western Catskills and Poconos...with sustained reaching 20-25 miles per hour and
gusts to 35 miles per hour. Even further west...frequent gusts 20-30 miles per hour can
be expected Thursday afternoon.

Winds will decouple quickly Thursday evening as surface ridge
moves in. The initially clear sky will help quickly drop
temperatures to lows of upper 20s to middle 30s. High thin clouds
will start spreading in overnight well ahead of next front...but
not before a good period of radiational cooling.

&&

Long term /Friday through Tuesday/...
415 EDT am update...
model consensus continues to slow arrival of occluded front
Friday...connected well upstream to a surface low in the northern
Great Lakes 12z Friday. Band of showers will sweep west to east
mainly in the afternoon hours with little consequence. No
instability aloft...thus no thunder potential...and rain amounts
on the light side...perhaps only a tenth of an inch or so.

Main surface low will traverse across eastern Great Lakes
Saturday...pushed by a wave rounding the broad upper trough. This
should yield some showers...and I sided with wpc guidance for
probability of precipitation in chance to likely range...highest north. Secondary front
with a better push of cold air advection should push temperatures
to below climatology Saturday night into Sunday.

Models exhibit uncertainty on what to do with the broad upper
trough early next week...with European model (ecmwf) orienting a very negatively
tilted axis mainly over northern New England...versus the GFS with
a large stacked cutoff low encompassing more of the northeast. The
European model (ecmwf) solution would allow more moderation in temperatures yet
also potential rain from baroclinic zone. GFS only slight gradual
moderation in temperatures yet also mainly dry as we get into
upper ridging between the northeast cutoff low...and another large
one in the Midwest. Given the uncertainty...I went lower than wpc
guidance by only introducing slight to low chance probability of precipitation at this
time...along with gradual moderation in temperatures.

&&

Aviation /15z Wednesday through Sunday/...
645 am update...

IFR ceilings in New York except Elm at this time will continue until 14 or 15z. MVFR
until 19 or 20z in New York. Avp will bounce between VFR and MVFR
until 16z. Ceilings scatter around 00z. VFR tonight.

Winds will be west to northwest at 10 to 15 kts with higher gusts
to start...then northwest increasing to sustained at 15 to 20 kts
with gusts to 25 to 30 kts during the day. This evening winds
dropping to 10 kts still out of the northwest. Avp may gust all night to
20.

Outlook...

Thursday-Friday morning...VFR.

Friday aftn-sun... restrictions possible in rain showers.

&&

Fire weather...
415 am EDT update...
heads up...critical conditions to be approached or even
exceeded Thursday...especially in portions of the Poconos to
western Catskills. First...it will be cooler today with scattered
showers. While gusty winds are expected...minimum relative
humidity will be in the upper 30s to 40s percent range.
However...a very dry air mass moving in Thursday will allow humidity
levels to plummet into the middle teens to low 20s percent range by
Thursday afternoon with continued gusty northwest winds. Some
areas got localized wetting rains from our most recent system that
just came through Tuesday...but most only received very light
amounts. Also...showers today will be spotty...so fuels may be
quite vulnerable to quickly drying out Thursday given the forecast
weather conditions. A Fire Weather Watch has been issued for
portions of the Poconos in northeast PA...and the western
Catskills in New York...where critical fire weather conditions should be
breached. Outside of the watch area...relative humidity values
will easily get into critical levels but winds will be more
borderline so confidence is not high enough yet for watch. Monitor
forecast for updates including possible watch expansions or
warning issuances.

&&

Bgm watches/warnings/advisories...
PA...Fire Weather Watch from Thursday morning through Thursday
evening for paz040-044-047-048-072.
New York...Fire Weather Watch from Thursday morning through Thursday
evening for nyz057-062.

&&

$$
Synopsis...kah
near term...kah
short term...mdp
long term...mdp
aviation...tac
fire weather...mdp