FXUS61 KBGM 260703

Area Forecast Discussion
National Weather Service Binghamton NY
303 AM EDT Wed Sep 26 2018

A cold frontal boundary will move through the region tomorrow
with another round of showers and a few thunderstorms. High
pressure will then build southeast into the region on Thursday
and Friday.


800 pm update...
No major changes made to the forecast. Still expecting very
isolated rain showers through tonight and a batch of more
extensive rain Wed morning with the cold front passage in the
afternoon with a line of showers and storms. Increased nw winds
along/just behind the front late Wed afternoon/evening slightly.
Remainder of the forecast is on track at this time.

Previous discussion...

Temperatures will stay steady or slowly rise through upper 50s
to lower 60s with skies remaining mostly cloudy with a strong
LLJ and southerly flow. Mesoscale modeling from the RAP/HRRR
maintains a slight chance of showers throughout most of the
night with our region in the warm sector. More concentrated
showers may begin to clip the Thruway corridor and Finger Lakes
by sunrise as a cold front draws closer to the region.


Larger scale models
show an upper level trough axis moving east into the Great Lakes
region during the day. The trough will press up against a
persistent upper level high pressure off the southeast U.S coast
Wednesday. This will lead to an acceleration of the upper level
jet streak from the mid Mississippi Valley northeast through
the upper Ohio Valley, eastern Great Lakes and eastern Canada.
In response to this, a cold front will push east into the
eastern Great Lakes region to eastern Ohio Valley Wednesday
morning. A strong southerly low- level jet develops in response
the movement of the surface front east and the ageostrophic
response from the upper level jet dynamics. The winds at 850 mb
reach up to 35-40 knots from the southwest across central NY and
northeast Pa Wednesday. This will transport moisture northward
and lead to 0-1 km shear values of 25 knots or better between
15z and 21z in central NY and northeast Pa. The higher winds
aloft lead to 0-6 km shear values of 45 to 50 knots which is
more than ample for organized severe storms Wednesday. The CAPE
will be limited as the NAM and GFS both are underwhelming with
mixed layer values generally less than 1000 J/kg. CAPEs are
projected to be highest in our northern counties. Even with
limited CAPE this is a fairly strongly forced event and concur
with SPC slight risk given the strong low-level wind fields.

The other concern for Wednesday is the potential for localized
flash flooding in a few of our high risk counties where flash
flood guidance is less than 1 inch per hour. Too early for a
flash flood watch given the localized nature of the storms and
given the fast moving nature of storms Wednesday. Hence, a
period of training would be needed to increase flash flood
concerns and we can't pinpoint where that's going to occur

CAMs models show a line of storms moving into the Finger Lakes
around 15z and moving southeast clearing the Poconos/Catskills
between 21z and 00z. Will continue to mention potential for
severe thunderstorms and localized flash flooding in HWO.

After this front passes by, a high pressure will build across NY
and Pa by Thursday morning. Given the expected rainfall,
clearing skies and light winds we expect patchy dense fog mainly
in our valleys Thursday morning. The rest of Thursday will be
fair close to seasonable.

Another wave will ride up the cold front that will move through
the region Wednesday and lead to a chance for a few light
showers or sprinkles on Friday mainly in south central NY and
northeast Pa.



300 AM UPDATE...Old frontal boundary to the south may generate a
few showers on Friday over the southern zones, meanwhile a cold
front racing through the Great Lakes will push through on
Saturday also generating a few showers,especially over the NY
counties. Behind the front, a large and cool high pressure area
will build in and keep dry weather over the area into Monday. On
Tuesday, yet another front moves into the area with another
chance for showers.

Made some adjustments to the grids to align to the latest
guidance and model timing. In general no major changes at this
update. Previous discussion below.

Model uncertainty grows for the weekend into Monday with several
waves moving into the northeast and middle Atlantic through the
period. Models vary on timing and extent of these waves and
potential for light precipitation. So used the superblend and
have slight chance to chance POPs for a few showers through this
period. Temperatures will average close to normal to slightly
above normal.


Ceilings through the TAF period will be predominantly MVFR with
occasional IFR possible. Ceilings will likely be rather steady
or fall some through the rest of the overnight. Conditions will
be near or just exceeding the criteria for LLWS at all TAF
sites over the next 6-12 hrs except at KAVP. Winds will increase
from the south and southwest to around 15 knots during the late
morning with gusts over 20 knots. Showers also will begin
moving into the area with timing anywhere from around 14z at
KSYR to around 18Z at KAVP, this may still need to be adjusted
by a couple of hours with future updates. Added in a tempo group
for tsra at all sites as the front/squall line move through,
mainly between 17-21z this afternoon...except 20-23z KAVP. Any
t'storms could bring brief IFR conditions along with gusty and
erratic winds.

Winds will gradually shift to more westerly then northwesterly
in the afternoon as the cold frontal passage. Expect a return to
mainly VFR conditions after 27/00z as clouds begin to scatter
out and high pressure builds into the area.


Wednesday night...Ceilings lifting during the evening then
patchy valley fog with restrictions around sunrise Thursday.

Thursday...Improving to VFR early, then VFR. Winds under 10

Thursday night and Friday...More restrictions possible with
showers at KAVP and KBGM. Some possibility the showers reach
KITH, KELM, KSYR and KRME for a time in the morning. Winds
generally 10 knots or less.

Saturday and Sunday...VFR conditions expected. Winds generally
10 knots or less.




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