NWS Area Forecast Discussion

FXUS61 KBUF 071438

Area Forecast Discussion
National Weather Service Buffalo NY
1038 AM EDT Fri May 7 2021

A slow moving upper level disturbance will bring a period of cold
rain to Western New York today, with the rain slowly moving east
into the Genesee Valley and Finger Lakes this afternoon, and the
eastern Lake Ontario region tonight through Saturday morning.
Otherwise, below average temperatures will persist through the
weekend and into next week.


A stagnant closed upper level low over James Bay will extend a
trough southward while a shortwave rounds its base, sharpening the
trough axis. This system, and associated rain will very slowly
spread eastward across the region through this afternoon. By this
evening, the main swath of rain will slowly move into the eastern
Lake Ontario region, with rain tapering off to light showers or
drizzle across Western New York.

The steady rain will continue most of the night east of Rochester.
Most of the night will be precipitation-free across Western New
York, but there may be a some showers as the shortwave drops across
the eastern Great Lakes tonight. 850mb temperatures of around -2c
are just cold enough to support some wet snowflakes across higher
terrain tonight. Then on Saturday the steady rain east of Lake
Ontario will taper off to showers, with a continued risk of a few
showers across Western New York due to steep mid-level lapse rates
underneath the upper trough. Very limited surface based instability,
but an isolated thunderstorm cannot be ruled out.

Storm total rainfall amounts through Saturday will average around a
half inch at most locations, with between a half inch and an inch
expected east of Lake Ontario.

Otherwise, cool temperatures will continue today with highs in the
mid 40s across the rainy areas in the west and low to mid 50s in the
eastern half where the steady rain will hold off until late in the
day. Temperatures will drop into the 30s tonight. Expect mostly
cloudy skies will limit radiational cooling, but if there is any
prolonged clearing then frost could be a concern. Slightly warmer
Saturday with highs in the upper 40s to mid 50s.


Saturday night a ribbon of drier air passes across our region,
ending showers and allowing for clearing skies. Weak surface high
pressure nearby will promote light winds and with a cold airmass
aloft, areas of frost are likely for a good portion of our region
and near freezing temperatures across the yet-to-begin frost-freeze
program counties of Cattaraugus and Allegany.

Sunday, Mother`s Day, will start cold albeit with plenty of warm
sunshine. A warm front stretched across the Corn Belt States will
push towards central Pennsylvania through the day. While this front
will remain south of our region, moisture will advect northward with
isentropic lift rain reaching the Southern Tier through the
afternoon hours. Within a zonal flow aloft, the northern edge of
this precipitation will be slow to push northward...not reaching
areas such as Buffalo and Rochester until the mid to late evening
hours. As a surface low tracks south of our region Sunday night rain
showers will taper off from west to east.

On Monday a sharp and cold upper level trough will dive towards our
region. A few showers or a rumble of thunder will be possible along
the leading edge of this feature.


Another push of much colder air aloft will start this period as a
cold upper level trough with 850 hPa temperatures -3 to -7C drops
across our region. This feature will bring cloudy skies, and a few
showers to areas east of Lake Ontario Monday night through Tuesday.
Highs on Tuesday could be as much as 15 degrees below normal.

Brisk northwest winds Tuesday will diminish Tuesday Night and
Wednesday as the upper level trough pushes east of our region.

Dry conditions Tuesday Night through Wednesday Night...and
frost/freeze conditions will again be a concern. By this time our
entire region will be within the frost freeze program.

Another storm system from the west may reach our area Thursday, with
chances for rain showers...and possibly a rumble of thunder as we
begin to warm back closer to normal.


An upper level trough will move slowly east across the region today,
with widespread rain across Western NY in the morning, reaching the
western Finger Lakes by early afternoon, and the eastern Lake
Ontario region by evening. In addition to rainfall, winds will shift
to the north, with cigs lowering to MVFR and eventually IFR
following the steadier rainfall and with the wind shift.

Tonight the steady rain will focus east of Lake Ontario with
widespread IFR conditions. Plenty of low level moisture will be
left behind the main area of rain, with areas of MVFR/IFR CIGS
in low stratus along with scattered light showers and some
drizzle. Fog is possible at KJHW where clouds may briefly
break up a bit this evening.


Saturday...Rain east of Lake Ontario, scattered showers elsewhere.
Areas of MVFR/IFR in the morning improving to VFR/MVFR in the
Sunday...VFR to MVFR with a slight chance for showers.
Sunday Night and Monday...VFR/MVFR with a chance for rain showers.
Monday Night and Tuesday...VFR. Mainly dry.


An upper level disturbance will pass across the eastern Great Lakes
through tonight. Since this system is rooted more aloft than at
the surface, expect waves to remain under small craft
thresholds. There will be a brief period of moderate north to
northeast winds that will create choppy conditions on Lake Erie
and the west end of Lake Ontario into this afternoon.





NEAR TERM...Apffel/EAJ/Hitchcock/TMA
LONG TERM...Thomas

NWS BUF Office Area Forecast Discussion