Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 241854

Area Forecast Discussion
National Weather Service Buffalo NY
254 PM EDT WED AUG 24 2016

High pressure will slowly drift east and off the Mid Atlantic coast
through tonight. This feature will provide our region with fair and
dry weather through this evening, with a southwesterly flow of
warmer air pushing 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.


Sprawling high pressure sliding off the Mid-Atlantic coast will
maintain tranquil conditions across the forecast area through this
evening. Temperatures will top out in the mid to upper 80s with a
few readings near 90 possible near the Genesee Valley.

Continued south to southwesterly winds overnight ahead of a
shortwave trough moving from Michigan northeastward to Ontario will
advect a more humid and unstable airmass into the region for
Thursday. Ongoing weak convection associated with the shortwave and
on the nose of a low-level moisture advection maxima will move
eastward across the forecast area overnight. This will bring a
chance of showers and a few rumbles of thunder across the forecast
area overnight, with best chances near the lower Great Lakes.
Overall keeping PoPs in the 30 to 40 range (with greater chances
farther north), with mainly scattered coverage expected. Subsidence
behind this leading shortwave will provide a relatively dry period
from mid morning to early afternoon Thursday, with some breaks of
sunshine possible. A trailing shortwave trough will approach the
region late Thursday afternoon into Thursday evening. Enhanced
moisture convergence and lift ahead of this trough, with
destabilizing airmass ahead of it during daytime heating, should
produce more widespread convective coverage across the region late
Thursday. Will maintain likely PoPs in the forecast as numerous
showers and thunderstorms are likely, but still not everybody will
pick up rainfall as is the nature of summertime convection. There is
a marginal chance for severe weather across the Southern Tier for
late in the day Thursday. Shear profiles will be marginally
favorable for severe weather as the secondary wave approaches, with
a convective complex likely evolving out of Ohio. The main question
for our forecast area will be how much instability can be built up
during the day (how much clearing can happen behind the initial
wave), and how much instability will linger into the evening hours
as the better forcing approaches.

With regard to temperatures, low temperatures overnight will remain
fairly warm with continued warm advection and moisture advection
keep lows in the upper 60s to low 70s and dew points rising into the
range as well. Thursday will be a more uncomfortable day temperature
and humidity wise, as 850 mb temperatures linger in the upper teens
C, resulting in highs in the mid to upper 80s, and dew points linger
in the upper 60s to near 70. Thursday afternoon may also be a bit
breezy with the subsidence behind the leading shortwave helping to
transport some higher gusts of 25 to 30 mph to surface across the
lake plains.


Unsettled weather will continue into Thursday night as a final slug
of higher theta-e air passes across the region in association with a
mid-level trough. This should trigger a final round of showers and
thunderstorms as the trough moves through. Although the airmass will
certainly be primed with plenty of moisture allowing for brief
periods of heavy rain, the flow regime aloft is progressive and not
conducive to training/back-building, and the concern for widespread
heavy rain is diminishing, and as a result have pulled mention from

After an unsettled start to the period Thursday night, the forecast
area will see a return to a quiet and dry regime moving into the
weekend as a cool front slides across the area Friday morning and an
amplifying upper level ridge moves overhead, ensuring plenty of
sunshine from Friday through Saturday night. Likewise, after
enduring another muggy night in the upper 60s/lower 70s Thursday
night, we will see temperatures in the upper 70s to lower 80s Friday
and Saturday. Drier air and clear skies will allow for cooler
temperatures Friday night, with lows in the upper 50s to lower
60s,while by Saturday night southerly flow returns, signaling the
return of increasingly warm and humid air to the region - reflected
in lows in the mid to upper 60s along the lake plains.


Persistent ridging based over the Southeastern states will provide
our forecast area with above normal temperatures and moderately high
humidity through this period. This will be accompanied by a little
unsettled weather...mainly Sunday night and Monday. The details...

Sunday should be the most uncomfortable day of this long term
period. A shortwave pushing across the Upper Mississippi Valley will
combine with the sub tropical ridge to our south to establish a deep
southerly flow across the Lower Great Lakes. Both the deterministic
GFS and ECMWF are suggesting that H85 temps will climb to as high as
20c over our region on Sunday...and that if it were well mixed...
would easily support afternoon highs close to 90F for the lake
plains and valleys. Given that we are on the backside of the thermal
solstice and have had a little rain the past week or so...will be
conservative with highs in the upper 80s for the favored warm areas.
These values could be nudged higher as the time period draws closer.

A pre frontal trough could cross our forecast area Sunday night
ahead of a more pronounced cool front that is expected to move
through during the day Monday. In both cases...the features could
touch off scattered showers and thunderstorms. The greatest chance
for this activity would come on Monday.

By Tuesday...the front is expected to be stalled to our south with
weak high pressure moving by to our north. While confidence with
this solution is relatively low from this vantage point...such a
scenario would keep at least slgt chc pops in place for the Southern
Tier and Finger Lakes regions. Max temps on Tuesday are forecast to
be in the lower 80s for most areas. Meanwhile...overnight lows
through the period will be in the low to mid 60s.


High pressure off the Mid-Atlantic coast will remain in place
through tonight. VFR conditions to prevail with just a few sct
diurnal cumulus inland from the lakes.

VFR conditions anticipated tonight with increasing mid level
cloudiness during the evening. However, a wave of low pressure
will push through the upper Great Lakes. This will bring showers
through the region early Thursday morning along with mainly MVFR
cigs, and possibly some IFR cigs across the higher terrain of the
Southern Tier including JHW.

On Thursday, cigs will slowly improve with more VFR/MVFR type cigs
likely into mid-day. Scattered showers and thunderstorms will
develop again Thursday late afternoon and evening producing some
localized/brief MVFR/IFR conditions in the stronger storms.


Friday thru Sunday...Mainly VFR.
Monday... Mainly VFR with a chance of showers and thunderstorms.


High pressure will drift from Maryland off the Mid Atlantic
coastline through tonight...while maintaining light to modest winds
and lower waves. The gradient flow will be light enough to allow for
local lake breezes to develop this 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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