Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 232029

Area Forecast Discussion
National Weather Service Buffalo NY
429 PM EDT Tue May 23 2017

A weak ridge of high pressure will provide for mostly dry conditions
tonight, with air temperatures not as cool. An impulse tomorrow may
bring a few early showers to the So. Tier, and later in the day an
isolated shower or thunderstorm to the North Country. A deep upper
level low will spread rain across the region Wednesday night through
early Friday.


A weak ridge will continue to provide partly to mostly sunny skies
into early this evening. Diurnal cumulus fields inland from the
stable lake shadows will slowly dissipate going into the early
evening as the boundary layer begins to cool, only to be replaced by
a modest increase in mid/high clouds as moisture spreads northward
from PA.

The bulk of tonight will remain dry. However attention will be upon
the SE shortwave which should reach WNY by late tonight. This
feature, combined with increasing atmospheric moisture will bring a
chance for a rain shower late tonight early Friday across the So.
Tier, with slight chances spreading northward across WNY during the
morning. Later in the day this shortwave, combined with minor
afternoon instability of 500 J/KG of CAPE will bring a chance for a
shower or thunderstorm to blossom in the peak heating.

As the upper level low dips through the lower Mississippi Valley
tomorrow it will send additional moisture northward, with a small
chance for the leading edge of a broad area of rain reaching the So.
Tier by the end of the afternoon tomorrow.

Tonight clouds will begin to increase, which will limit the cooling
tonight. Overnight lows within a southeast wind will range from the
upper 40s to mid 50s. Tomorrow southeast winds across WNY will bring
mid to upper 70s, while a light east wind across the north country
within a similar airmass will promote highs in the low to mid 70s.


The deep closed low over the middle Mississippi Valley Wednesday
evening will track slowly across the Central Appalachians Thursday
to the Gulf of Maine by Friday afternoon. A complex surface low
occlusion over the Ohio Valley Wednesday night will lift northeast
as secondary development takes place from the Mid Atlantic to the
New England coast by Friday. Despite some model differences in
track/placement of these feature there is agreement that the
Wednesday night into Thursday night time frame will be a wet one.
Plenty of deep layer moisture and forcing in the front flank of the
of the system will generate a solid period of soaking rain, with
most areas receiving a general half inch to an inch of rainfall.
While forcing with the incoming system is impressive, instability is
not. Therefore, thunder chances remain rather subdued.

Precipitation will transition to showers Thursday night into Friday,
as the low moves overhead and past the forecast area, though
scattered to numerous showers should linger thorugh much of the day
on Friday, thanks to continued troughing across the area, coupled
with wrap-around moisture. Shortwave ridging moving into the region
in the wake of the departing low pressure system Friday night should
put an end to the showers.

This will be a cool period as plenty of cloud cover and rainy
conditions will help to suppress temperatures with highs both
Thursday and Friday likely not getting out of the 60s, with lows in
the 50s during the nights.


Upper level ridging crossing the region should result in generally
dry conditions on Saturday, though moisture moving through the top
of the low-amplitude ridge just might generate a shower or two, so
have low slight chance pops in place for now. A northern stream wave
diving across the upper Midwest and Great Lakes out of Canada will
bring the next likely round of showers to the forecast area on

The location and timing of the various vorticity maxima
rotating around the upper low, in addition to additional upper level
energy moving thorugh the longwave trough that will be re-
established across the east will determine the specific timing of
rounds of showers as we move into next week, and it is too far out
to pinpoint these kinds of details. However, given aforementioned
longwave troughing becoming re-established across the Great Lakes
and Northeast, suffice it to say that the coming week will trend
towards the cool and showery.


VFR flight conditions will predominate tonight through Wednesday.
Diurnal cumulus inland from the stabilizing influence of the lakes
will dissipate this evening, only to be replaced by a modest
increase in high clouds streaming north out of PA. A few impulses
advancing northward ahead of a deepening cut off low pressure will
bring moisture northward, with a chance for a few light showers
crossing the Southern Tier late tonight and early tomorrow. Will
place a VCSH within the KJHW TAF for now. Within this moisture CIGS
may lower to MVFR across KJHW. Otherwise VFR flight conditions
should prevail.


Wednesday night...VFR/MVFR with rain developing.
Thursday...VFR/MVFR within rain. Some IFR conditions late across
the So. Tier.
Friday...IFR to VFR with a chance of showers.
Saturday...Mainly VFR.
Sunday...MVFR/VFR in likely showers.


High pressure will maintain light winds and minimal wave action
tonight. Tomorrow winds will become southeasterly across Lake Erie,
and easterly across Lake Ontario. Winds may near small craft
criteria on the western waters of Lake Ontario, but for now will
keep both winds and waves just below thresholds.

Thursday easterly winds will become a bit stronger as a storm system
tracks towards the lower lakes. This flow may generate slightly
higher waves on the western waters of Lake Ontario with small craft
advisories possible.





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