Area Forecast Discussion
Issued by NWS Buffalo, NY

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622
FXUS61 KBUF 210655
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
255 AM EDT Tue Mar 21 2017

.SYNOPSIS...
A weak front will cross the region overnight and early Tuesday...
bringing little more than some clouds and spotty light showers.
A secondary arctic front will then push across the region Tuesday
evening along with some scattered flurries and snow showers...with
much colder weather and very limited lake effect snow showers then
following for later Tuesday night and Wednesday. Temperatures will
then rebound markedly Thursday and Friday as much warmer air works
its way back into our region...with wetter conditions also arriving
in time for Friday and Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Through the rest of the night and the early morning hours of
Tuesday...an initial weak cold front will slowly cross our region
from west to east. As this boundary is accompanied by only very
weak forcing and limited moisture...it will continue to generate
little more than some light rain showers or sprinkles as it crosses
our region...with some limited snow showers/flurries possibly mixing
in with these across portions of the Finger Lakes and North Country.
Expect the best chances for any precip to lie across the North
Country and Saint Lawrence Valley very late tonight and early Tuesday
morning when a passing weak mid level shortwave will provide a
little more in the way of support...however even there PoPs will
only reach the low-end chance range. Otherwise expect a cloudy
and relatively mild (by late March standards) overnight and early
morning period across our region...with overnight lows ranging
in the lower to mid 30s.

As we progress through the day on Tuesday...weak surface-based ridging
and much drier air will build in behind the departing initial front...
which will result in sunshine increasing from west to east from about
mid morning onward. While this improvement will be somewhat muted across
the North Country owing to the later departure of the front from that
region...areas further west should see a good deal of sunshine develop
by midday or early afternoon. While weak cold air advection will be in
place with 850 mb temps falling to between -2C and -4C...this will be
offset by the influence of the strong March sun and improving mixing...
which will help temperatures to climb higher than experienced on Monday.
Expect afternoon highs to reach into the lower to mid 40s across the
North Country and to the mid 40s to lower 50s south of Lake Ontario...
with the warmest overall readings found across the Genesee Valley and
portions of the Finger Lakes.

Tuesday night...a sharp secondary arctic front will quickly slide
southward across our region. With moisture also looking to be rather
limited along this boundary...it will be hard pressed to generate
much more than some scattered snow and rain showers across the North
Country and Finger Lakes regions...with just some scattered flurries
affecting areas further to the south and west. Following the passage
of the arctic front...a north-northwesterly flow of much colder air will
quickly flood southward across our region overnight. This will send
temperatures plummeting back to well below average levels...with
overnight lows dipping to between 10 and 15 across the North Country
and to the mid teens to lower 20s south of Lake Ontario. The incoming
colder airmass will also help to generate a lake response southeast
of the lakes...though this should be rather muted given the short
fetch...a relatively low cap and the relatively dry nature of the
arctic-sourced air...all of which should keep any snow showers rather
light and scattered in nature...with only minor accumulations of less
than an inch expected.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
On Wednesday some limited lake effect clouds and mostly
flurries will will be found on a cold northwest flow. Expect
areas southeast of Lake Erie to remain dry, non-accumulating
scattered flurries southeast of Lake Ontario into the Finger
Lakes region mainly during morning hours. The low cap,
relatively dry air, and springtime insolation should preclude
any lasting accumulation.

Surface high pressure will move directly overhead Wednesday night
and result in clear skies under the strong subsidence. This
will lead to excellent radiational cooling and thus a very cold
night. The mercury should drop to within a few degrees of 10 for
a large portion of western New York, with single digit readings
likely across the North Country, locally toward the 0 mark in
well sheltered locations. Single digits are also expected in
inland areas of the Southern Tier.

The high will shift to the mid Atlantic coast on Thursday, but will
still maintain dry weather with mostly sunny skies. Afternoon
temperatures are expected to climb through the 30s to near 40 over
the western counties, while it will be a little chillier east of
Lake Ontario with max temps close to the freezing mark.

On Thursday night a broad upper level ridge over the Mississippi
Valley will push east to the Ohio Valley and Great Lakes. Ahead of
this feature, a tightening baroclinic zone will become established
from Wisconsin and Lower Michigan to Lake Erie. The associated
isentropic lift along this elevated boundary will generate some
showers, possibly reaching far Western NY late. Any light pcpn will
fall as a mix of light rain or wet snow showers. Given the strength
of the warm advection, temps after midnight should actually start to
rise and climb back above freezing for counties near Lake Erie.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Model guidance remains in generally good agreement on the general
pattern during the long term period, however our region will be near
a sharpening frontal boundary which will lead to uncertainty in our
temperatures forecasts during the period. Despite differences in the
position of the boundary, there remains high confidence that it will
be a wet pattern in the Friday through Sunday timeframe.

Model consensus places a cut-off 500 mb low near Nebraska on Friday
with an associated warm frontal boundary forecast to extend
northeast of this system toward our region. This front will lift
into the area on Friday and will likely stall somewhere just north
of Lake Ontario. Showers will accompany the frontal passage, which
may start off as a brief period of snow at the onset. By Friday
night, thermal profiles will likely be warm enough to support rain
showers which will be most prevalent across northern portions of
the cwa which will be closest to the front. South of the front
should be mainly dry, with above normal low temperatures in the 40s.

On Saturday high pressure across Ontario will expand southward
toward the Lower Great Lakes while the closed low moves slowly east
to near Missouri. This will push the frontal boundary a bit south,
with temperatures eventually cooling enough for some snow across
northern portions late Saturday. Temperatures along the NY/PA border
will be much warmer, with forecast highs still in the upper 50s
while the North Country should be much cooler with highs in the
lower 40s. This is significantly cooler than the previous
forecast for some areas.

Expect the front to meander as it weakens Saturday night and Sunday.
It will continue to be a moist pattern, with a high likelihood of
precipitation. Some thermal profiles in BUFKIT indicate a potenial
for sleet or freezing rain, and this is plausible given the shallow
cold air.  This said, it is not climatologically favored for late
March so for now will keep the forecast rain or snow, keeping in
mind there is a small potential for other forms of precipitation.
Forecast temperatures reflect the expected position of the frontal
boundary, but again keep in mind these may change with future model
runs.

The weakening upper level disturbance should finally reach the mid-
Atlantic coast by Monday which should finally lead to a drier
pattern heading into next week. There may be some lingering showers
on Monday, with seasonable highs in the 40s.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
A weak initial cold front will cross the region between late tonight
and early Tuesday morning...with just some spotty light rain and snow
showers or sprinkles/flurries marking its passage. Otherwise flight
conditions will be dry and primarily VFR...with just a period of MVFR
possible along and immediately behind the front.

In the wake of this initial boundary...weak surface-based ridging and
much drier air will build across the area during the day on Tuesday.
This will bring increasing amounts of sunshine and improvement to
VFR from west to east.

A trailing secondary arctic front will then cross the region Tuesday
night and bring some additional scattered snow and rain showers to
the Finger Lakes and North Country...with a north-northwesterly flow
of much colder air in its wake helping to generate some scattered
light snow showers and flurries southeast of the lakes. Expect the
potential for brief reductions to MVFR/IFR within any snow showers...
with general high-end MVFR to lower-end VFR conditions otherwise
prevailing.

Outlook...
Wednesday...Scattered snow showers/flurries and associated MVFR
southeast of the lakes dissipating...otherwise VFR.
Thursday...VFR.
Friday...Deterioration to MVFR/IFR with mixed rain and snow
developing...then changing over to all rain.
Saturday...MVFR/IFR with rain likely.

&&

.MARINE...
Relatively tranquil conditions will prevail on the lakes overnight
as a weak trough of low pressure crosses the region. West-
northwesterly winds will freshen by Tuesday afternoon as cold
air begins to filter in behind the trough. Winds will continue
to strengthen Tuesday night as much stronger arctic front
crosses the lakes, with Small Craft Advisories likely needed
Tuesday night into Wednesday. Expect winds and waves to diminish
thereafter as a large area of high pressure shifts across the
region, with southwesterly winds developing towards the end of
the week as the high moves off the East Coast and return flow
develops across the region.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...JJR
NEAR TERM...JJR
SHORT TERM...APFFEL/RSH
LONG TERM...APFFEL
AVIATION...JJR
MARINE...SMITH/WOOD



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