Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 260301

Area Forecast Discussion
National Weather Service Buffalo NY
1101 PM EDT Tue Jul 25 2017

High pressure centered over the Upper Great Lakes this evening
will drift across our forecast area tonight and Wednesday. This
will bring much improved weather to the bulk of the region while
keeping temperatures a few degrees below normal. A slow moving
cold front will then produce some showers and thunderstorms over
the region late Wednesday night and Thursday.


A wealth of low level moisture over the region early this
evening will continue to thin out and clear from the north and
west as we proceed through the overnight. This will lead to
mainly clear starlit skies over the western counties...although
the clearing trend may not be quite as pronounced for the
Eastern Lake Ontario region.

Given the wet antecedent conditions of the ground and slow late
day is likely that much of western New York will
experience some fog and/or the development of some low stratus
late tonight. This will be accompanied by relatively cool
conditions as the mercury will drop into the 50s regionwide. In
fact...some the southern tier valleys could experience
temperatures in the upper 40s by daybreak.

On Wednesday...the same area of high pressure that helped to
clear our skies will be exiting across New England. This will
support a nice day across our region with partly to mostly sunny
skies helping to boost our temperatures back up through the 70s.
Parts of western New York...especially the warmer valleys...
could make it back to 80.


Low level anticyclone will build east-southeast through the Great
Lakes region under building heights Wednesday. No real sensible
weather concerns as we start the period Wednesday, other than some
possible patchy Southern Tier river valley fog early Wednesday with
a stable/dry airmass in place. Developing warm air advection along
with ample sunshine will allow afternoon temperatures to recover
into the mid to upper 70s, perhaps a bit warmer for interior

Wednesday night and Thursday...models seem to be having a difficult
time with precipitation/convection on boundaries during this time.
There should be some convection Wednesday evening north of Lake
Ontario co-located with a weak surface trough.  With moisture
streaming north toward the boundary, there is a chance that some
convection may form along decaying/remnant lake breeze convergent
regions in the evening/overnight, which sometimes occurs in a warm
advective environment, but but bulk of potential convection should
remain north of Lake Ontario and/or into the Eastern Lake Ontario

For Thursday, the NAM and its variants seem to want to either bring
a boundary through early Thu AM or keep WNY completely dry through
Thu.  The Canadian leans toward the AM side.  Meanwhile, the GFS
follows more typical afternoon lake breeze forced convection with an
afternoon trough passage.  Forecast confidence for Wed eve and Thu
is rather low, so will in general continue with past forecasts
noting the highest threat for measurable precipitation on Thu.

By Friday, a north or northeast flow should be in place with upper
level forcing focused toward the OH Valley/PA.  This should keep the
bulk of precipitation and associated convection south of the region.
There is the chance of lake breeze initiated convection, so will
leave in a chance of showers in the afternoon, but confidence for
overall forecast for Fri is low until models hone in on overall
atmospheric pattern.


Picture perfect weekend weather on tap for all of western NY and the
North Country. On Saturday a splitting trough will move east of the
forecast area, with the southern portion settling over Virginia and
North Carolina while the northern portion exits through the Canadian
maritimes. The result for us will be a pool of cooler air aloft
advecting across the region in the wake of this trough passage. 850
mb temperatures around +8/+9C with a northerly wind picking up lake
moisture and upsloping will allow for cloudiness to linger through
Saturday morning, before diurnal mixing helps break clouds in a
cumulus field for the afternoon. High temps Saturday will be
slightly below normal in the mid 70s with low humidity. Ridging
builds into the region Sunday with warming 850 mb temps back into
the low teens C, which will push our afternoon highs back to near
normal with highs around 80. Sunday will feature more abundant
sunshine as high pressure builds overhead.

Model solutions diverge for the start of next week with differences
in the magnitude of a trough over easter Canada. A stronger trough
may force a weak cold frontal passage through the area with some
scattered showers and a very subtle few degrees cooler in
temperature to near normal. A weaker trough would keep the stretch
of dry weather going from the weekend right into the early next week
with slightly above normal temperatures.


High pressure will drift across western and north central New York
overnight. Dry air associated with this feature will continue to
thin out the cloud cover...although the clearing over the far
western counties will likely lead to some fog and areas of low
stratus (because of moist antecedent soil conditions). This should
lead to some IFR conditions across much of the Southern Tier and
possibly parts of the Finger Lakes region after 08z.

On Wednesday...while the area of high pressure will push east
across New will continue to support fair dry
weather. Any residual IFR conditions at daybreak will give way
to VFR weather regionwide by 14z.

Wednesday night...VFR.
Thursday...MVFR/VFR with showers and thunderstorms becoming
Friday through Sunday...Mainly VFR.


High pressure centered over the Upper Great Lakes at 23z will
continue to drift east across lakes Erie and Ontario tonight.
This feature has already allowed winds to subside across the all small craft advisories and related beach hazard
statements have been discontinued.

Light winds and negligible waves can thus be expected across the
Lower Great Lakes and their adjoining bodies of water tonight
through Wednesday.

While winds will freshen a little ahead of an approaching cold
front Wednesday night...winds and waves are forecast to remain
below small craft advisory criteria through Thursday. The only
concern will be an increasing risk for thunderstorms as we push
from late Wednesday night (Lake Ontario) into Thursday (all of
Lower Great Lakes region).





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