Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 240221

Area Forecast Discussion
National Weather Service Buffalo NY
1021 PM EDT TUE AUG 23 2016

High pressure will slowly drift east and off the Mid Atlantic
coastline through midweek. This feature will provide our region with
fair and dry weather through midweek, with a developing
southwesterly flow of warmer air helping to drive temperatures back
to above normal. A weak cold front will then cross the region
Thursday with a few rounds of scattered showers and thunderstorms
before fair weather returns in time for the weekend.


Clear skies dominate most of the area late this evening with just a
few patches of mid level clouds that are in the process of
dissipating in the presence of ongoing subsidence and drying with
high pressure surface and aloft. Clear skies will continue to be the
rule overnight.

Overnight and Wednesday surface high pressure will slowly drift east
to the Mid Atlantic coastline. This feature will maintain fair and
dry weather across our region. Lows tonight will then drop back into
the lower 60s on the lake plains, with mid 50s in the cooler
Southern Tier valleys and Lewis County. Radiational cooling combined
with warm river water temperatures will again support typical river
valley fog across the western Southern Tier in the upper Allegheny
and upper Genesee drainages.

Wednesday will be another mostly sunny day across the region with a
few diurnal cumulus and some mid level clouds approaching western NY
very late in the day. As high pressure slides further off the coast
increasing southwesterly return flow will allow a steady increase of
heat and humidity. 850 mb temperatures will surge to around
+17/+18C, bringing high temperatures in the upper 80s to around 90
on the lake plains, and mid 80s elsewhere. The southwest wind will
keep the Lake Erie shore a little cooler, and the gradient flow will
be weak enough to allow a lake breeze circulation to develop along
the Lake Ontario shore with locally cooler temps within a few miles
of the lake.


After a quiet first half of the week, unsettled weather will return
to Western and North-Central New York starting Wednesday night.
Models are continuing to come into better agreement on a vortmax,
currently visible on wv imagery over Arizona, lifting across the
Great Plains and to the Upper Great Lakes by Wednesday. While the
core of this system and bulk of the resultant convection looks to
pass to our north across Ontario province Wednesday night, the
attendant 500mb trough should clip our area, and this along with
ongoing theta-e advection should be enough to keep a chance of
showers and thunderstorms in the forecast.

Aforementioned theta-e advection will strengthen across the forecast
area on Thursday as warm and sticky GOMEX air flowing around the
periphery of the sub-tropical ridge parked over the Southeastern
U.S. makes its way across the Lower Great Lakes. The arrival of this
hot and humid air will set the stage for more widespread showers and
thunderstorms Thursday afternoon into Thursday evening, with pieces
of shortwave energy ejecting out of the Midwest acting as additional
triggers to convection, in addition to the usual array of lakebreeze
and local convergence boundaries. Given the very moist nature of this
airmass, featuring pwats approaching 2.0 inches, localized heavy
downpours will be a threat. This slug of moisture is currently
progged to pass through the area Thursday night into Friday morning,
with pops diminishing Friday morning as a cold front pushes through,
ushering in cooler and much drier air for the weekend...

Regarding temperatures, with the arrival of the previously discussed
GOMEX airmass, we will see the return of sultry, sticky nights to
the region Wednesday and Thursday night, with lows ranging from the
upper 60s to the lower 70s, with warmest areas along the lake plains
and the urban areas. Thursday will be the warmest day of the period,
with highs climbing into the upper 80s, before the arrival of cooler
and drier air from Canada brings more pleasant highs in the upper
70s to lower 80s on Friday.


Overall, the weekend looks to be relatively quiet as a broad surface
high centered over the Upper Great Lakes slides across the region
and then moves into New England by late Sunday. The only hiccup,
increasing moisture and southerly flow across the region ahead of
the next approaching storm system which brings a chance of a few
showers and thunderstorms late in the day Sunday and into Monday.
Otherwise, the weekend looks spectacular, especially Saturday where
highs will peak in the upper 70s to low 80s with low relative
humidity levels. On Sunday, it will be several degrees warmer with
highs in the low to mid 80s, but humidity levels will tick up a bit
making it feel a little bit uncomfortable but not unbearable.
Monday, as a weak shortwave passes by to the north of the Lower
Great Lakes its associated cold front is forecast to slowly sag
southward across the region and then stall across OH/PA. Look for a
chance of a few showers and thunderstorms on Monday but mainly
across the Southern Tier and Finger Lakes to Central New York.
Otherwise, right now temperature wise the rest of this period looks
mild with above normal highs with no sign of fall weather at all.


High pressure drifting off the Mid Atlantic coast will keep mainly
clear skies and VFR for most areas tonight. Some typical river
valley fog will form across the western Southern Tier with local IFR
from 06Z-12Z. This fog should remain in the valleys and not impact
the hilltop KJHW airfield.

On Wednesday any valley fog will burn off by mid morning, leaving
VFR to prevail with just a few sct diurnal cumulus inland from the
lakes and some increase in mid level clouds late in the day across
Western NY.

Thursday...VFR with scattered showers and thunderstorms
becoming more numerous Thursday night...when some MVFR will also
become possible.
Friday thru Sunday...Mainly VFR.


High pressure will drift from Maryland off the Mid Atlantic
coastline through midweek...while maintaining light to modest winds
and lower waves. The gradient flow will be light enough to allow for
local lake breezes to develop again Wednesday afternoon, with winds
becoming onshore and waves building to up to 2 feet locally.

Thursday and Thursday night a cold front will ease its way across the
Lower Lakes. This feature will bring some showers and thunderstorms
to the region...with freshening southwesterlies out in advance of the
front veering to westerly following its passage Thursday night...
then gradually diminishing on Friday as high pressure builds into
the region. Depending upon how much winds and waves increase...small
craft advisories may eventually be needed for some areas Thursday
and Thursday night.





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