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Area forecast discussion 
National Weather Service Buffalo New York
714 am EST Thursday Mar 5 2015

Synopsis...
Arctic air will surge across the region today bringing a return to
very cold temperatures along with a Few Lake effect snow showers
southeast of Lake Ontario. Tonight should be the coldest night of
the coming week as temperatures will gradually moderate towards
normal through the weekend with readings potentially climbing above
average next week.

&&

Near term /through tonight/...
it will be a cloudy start to the day for much of western and
north-central New York this morning as the area remains covered by
middle/high clouds courtesy of a large area of divergence aloft
associated with aa very strong 200kt upper level jet currently
streaming across New York state. These clouds should diminish from
west to east today as the jet slides off to the east...though we may
some diurnal strato-cumulus form this afternoon as an upper level trough
axis approaches the area...with associated DPVA providing enough
lift to squeeze some limited cloud cover out of what little
lingering moisture there is to work with. Temperatures will change
little today as ongoing cold advection will offset much of the
diabatic heating...leading to highs that will barely creep into the
middle teens.

High pressure will bringing clear skies and diminishing winds
tonight with the only exception being southeast of Lake Ontario
where lake effect cloud cover is expected to linger through a good
portion of the night. The light winds and largely clear skies
coupled with the very cold and dry air overhead will promote strong
radiational cooling with readings plunging into the single digits
either side of zero...with areas near the lakes staying above zero
while areas inland will likely drop below zero. The light evening
breeze should diminish almost entirely as high pressure shifts
overhead tonight and while winds chills will certainly will run
close to advisory levels...they should stay just a hair above the
-15 threshold thanks to the slackening winds overnight.

&&

Short term /Friday through Sunday/...
Arctic high pressure will extend across the forecast area Friday
providing dry weather and a good amount of cold sunshine through
partly cloudy skies with temperatures struggling to reach into the
upper teens. Clouds will increase from the west later in the day
ahead of a surface trough pushing across the central Great Lakes.

Models show this surface trough with associated synoptic moisture
and support from a 850mb shortwave trough aloft will cross the lower
Great Lakes early Saturday morning into afternoon. 00z GFS is a bit
faster than 00z European model (ecmwf) which holds back the arrival of snow until
Saturday afternoon. Moisture will be limited to just a few
hundredths quantitative precipitation forecast but within an Arctic airmass a coating to an inch of
fluffy dendrites could accumulate with highest probabilities focused
across the North County. The southwest flow ahead of the surface
trough axis will help boost temperatures toward 30 degrees Saturday.

On the heels of saturdays trough passage a weak clipper is forecast
to quickly cross the Great Lakes. This clipper looks to feature a
bit more moisture and better upper level support that the previous
surface trough. A 500mb shortwave trough and embedded vorticity maximum
should bring a higher probability of widespread snow with likely
probability of precipitation featured Saturday night. The 00z European model (ecmwf) is now better aligned
with the GFS which supports the increase in probability of precipitation. The snow and cloud
cover and missing direct pathway to Arctic air will keep overnight
temperatures Saturday much warmer than the previous two nights. Lows only
falling into the teens across the North County and lower 20s
elsewhere. Chances of lingering snow showers Sunday as the clipper
departs across New England. Yet another weak system will be working
across the upper lakes behind this clipper with weak warm advection
supporting highs pushing toward the freezing mark.

&&

Long term /Sunday night through Wednesday/...
one last surface trough and supporting 500mb shortwave is forecast
to cross the lower Great Lakes Sunday into Monday with a chance of
some more light snow showers. This shortwave looks to finally kick
the Great Lakes trough off the East Coast. Warming aloft as a
progressive zonal 500mb flow takes shape into next week will help
boost temperatures back toward normal on Monday then finally into at
least the 40s Tuesday and Wednesday with some 00z guidance even
suggesting a chance at 50 across portions of western New York.
Both days should remain dry as a system moves through the southeast
and middle Atlantic...with a second northern stream system moving
through central Quebec leaving weak high pressure between across the
lower Great Lakes.

Looking a little farther ahead...model guidance diverges on how long
the warming trend will last. The 00z European model (ecmwf) keeps a progressive zonal
within the polar jet across southeast Canada for the second half of
next week with a southern stream cut off low developing over Baja California.
This would keep temperatures near to above normal for the rest of
the week. The 00z GFS looks to have flip-flopped with the 12z European model (ecmwf)
with a broad trough across southeast Canada and the Great Lakes for
the second half of next week which would suggest a return to below
normal temperatures. Stay tuned.

&&

Aviation /12z Thursday through Monday/...
VFR conditions will persist across western and north-central New
York through the forecast period with the exception of southeast of
Lake Ontario where occasional periods of MVFR will be possible
through the day in light lake effect snow showers. In addition...an
approaching upper level trough may result in the development of some
diurnal stratocu this afternoon with scattered-broken ceilings around 2500 feet
possible. This cloud cover should diminish tonight as high pressure
moves overhead.

Outlook...
Friday...VFR.
Friday night...mainly VFR with a chance of snow showers late.
Saturday...MVFR/IFR with snow showers likely.
Sunday and Monday...mainly VFR with a chance of snow showers.
Tuesday...VFR.

&&

Marine...
gusty northwest winds of 15-20kts behind an Arctic front will keep
Small Craft Advisory conditions in place on Lake Ontario this
morning before dropping off by late morning as high pressure builds
across the region. Brisk southwest flow will develop on the lakes on
Friday as the high shifts to the east ahead of another clipper that
will cross the area this weekend.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory until 10 am EST this morning for loz042-
043.

&&

$$

Synopsis...wood
near term...wood
short term...Smith
long term...Hitchcock/Smith
aviation...wood
marine...wood

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