Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 291720

Area Forecast Discussion
National Weather Service Buffalo NY
120 PM EDT Wed Mar 29 2017

High pressure north of the region will move east tonight while a
low pressure system over the Mississippi Valley draws moisture
northward toward the New York on Thursday. Chances for rain
will increase over far Western New York Thursday afternoon, with
precipitation spreading across all of Western and Central New
York Thursday night. This complex system may bring some thunder
to far Western New York while a brief period of snow will be
possible east of Lake Ontario. The system will change to all
rain by Friday and move east of the region for the weekend.


High pressure to the north of the state is providing the area
with northerly flow. A thin layer of moisture has morphed from
stratus along and north of Lake Ontario to clearing while inland
areas have experienced a flat cumulus field. Expect this to
dissipate later this afternoon with clearing over much of the
region by sunset.

Tonight...high pressure settles across the region with mostly
clear skies and light winds resulting in decent radiational
cooling conditions. Low temperatures will drop below freezing
for most locations, with the coldest readings in the mid 20s in
the North Country.

Friday...increasing clouds from west to east will be the main
feature for much of the day as moisture streams northeastward
in a warm advective pattern. However, models continue to
struggle with the depth of the moisture with the operational NAM
and GFS differing toward the onset of precipitation. Ensemble
data of course is somewhere in between. There will be a
tightening baroclinic boundary moving in and this will help
moisten up the atmosphere, but at this time cannot fine tune the
rain start time in terms of rain starting in the early
afternoon, late afternoon, or early evening for at least Western
NY. Will therefore continue with a increasing probability of
rain with time, starting out as sprinkles due to the initial dry
air near the surface.



Increasing isentropic ascent and strong northward moisture transport
Thursday night will overcome in-place dry air across the area from
southwest to northeast. Thus, a steady increase in precipitation
with the steadiest/most widespread precipitation arriving during the
late evening/overnight hours and continuing through at least Friday
morning. Model soundings do not suggest steep enough lapse rates
aloft, so without significant elevated CAPE, will continue to keep
the mention of thunder out of the forecast.

For the most part precipitation type should not be an issue, with
most expected to fall as rain as a lack of true cold air helping to
sufficiently warm boundary layer temperatures. However, the
expectation could be across the North country as marginal thermal
profiles could allow for a brief period of mixed precipitation late
Thursday night/early Friday morning.

The complex system responsible for the all of the unsettled weather
will push to our east by Friday night. While the bulk of the
associated lift and mid level moisture will be removed, there will
still be the chance for some leftover showers, especially along and
east of the axis of the surface trough, which will be aligned over
the Genesee Valley for the first half of the night. Some of the
lingering precipitation could change to a wintry mix late.


There is high confidence that this will be a relatively mild a progressive ridge will make its way across the eastern
half of the country. This ridge will also keep the bulk of the
period rainfree. The tranquil weather will come to an end though by
Monday night and the next southern stream system will
lift northeast out of the Lower Mississippi Valley. The details...

A storm system exiting off the East Coast will support some leftover
nuisance showers across the region Saturday morning. In its wake...
expansive high pressure centered over Hudson Bay will build south
across the Lower Great Lakes Saturday afternoon through Monday. This
will promote fair dry weather. While high temperatures will
generally be in the 40s on Saturday...the mercury will climb into
the 50s for Sunday and Monday.

Monday night and Tuesday...low pressure over the Lower Mississippi
Valley is forecast to push north towards the Lower Great Lakes. Most
of the ensemble members of the GEFS along with the operational
ECMWF track the broad low to our west within a negatively tilted
trough...which will once again set up a scenario where we experience
another round of rain.


VFR conditions are expected through Thursday. High pressure
will be north of Lake Ontario with light northerly flow today.
There is a stratus deck over Lake Ontario and eastern Lake
Ontario, but CIGS are near 5000`. This will not make much
progress to the south today, and it should start to mix out in
the dry airmass later this afternoon. Winds will shift to the
east overnight and Thursday. Eventually higher clouds will move
into the region, with slowly lowering cigs during Thursday

Thursday night into Saturday...MVFR/IFR with rain showers.
Sunday and Monday...VFR.


Winds will turn easterly by Thursday and southeasterly Friday
as our next storm system passes south of the Great Lakes. Winds
will approach 15-20 knots but higher waves should remain in
Canadian waters. Winds should be out of the northwest following
the passage of the low for the weekend.





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