Area Forecast Discussion
Issued by NWS Buffalo, NY

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908
FXUS61 KBUF 252143
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
543 PM EDT MON JUL 25 2016

.SYNOPSIS...
Any isolated showers and thunderstorms will end this evening as a
cold front crosses the region. This front will usher in another
period of fair and slightly less humid weather that will persist
through the midweek. Another, much weaker cold front will slide south
out of Canada Wednesday night into Thursday, bringing a slight chance
of showers and thunderstorms, however nothing that is expected to put
a dent in the current drought conditions.

&&

.NEAR TERM /THROUGH TUESDAY/...
The bulk of the more organized convection is moving into southeast
NY and the Mid Atlantic states early this evening. The cold front is
still poised just upstream however, and the airmass has quickly
recovered behind the morning and early afternoon rain with surface
temperatures jumping into the lower 80s and dewpoints in the lower
70s. This is yielding moderate instability, allowing the lake breeze
boundaries to become active. Storms have recently developed in a
narrow corridor from St. Catherine`s eastward across the Niagara
Frontier in response to instability and strong low level convergence
driven by the southwest flow off Lake Erie and northwest flow with
the approach of the cold front. This convection will hold together
for another hour or so before pushing southeast towards the western
Finger Lakes and falling apart with the cold frontal passage.

Elsewhere the rest of the area should stay mainly dry through this
evening with little in the way of low level forcing to support
additional convection. The one exception may be across the Saint
Lawrence Valley where scattered storms may develop with the cold
frontal passage early this evening.

While temperatures will cool slightly behind the front, upstream
dewpoints will remain in the lower 60s, and with clearing skies and
winds becoming light, we will see the potential for patchy fog across
lower lying areas, particularly those areas that see substantial
rainfall today. Temperatures will fall into the 60s overnight.

The upper level trough will complete its transition across the
forecast area overnight and will be replaced by low-amplitude upper
level ridging and surface high pressure across the Lower Great
Lakes. This should yield plenty of sunshine across the area with
highs in the low to mid 80s, with 70s along the lakeshores. With
slightly lower dewpoints in the upper 50s to lower 60s advecting in
behind the front, it should also feel nominally more comfortable
outside.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
There should not be much weather to contend with during this
period...as a low amplitude flow will be found along the length of
the Canadian border. While troughiness will characterize this
pattern over the Great Lakes region...a lack of baroclinicity and
low level forcing will mean that generally fair weather can be
anticipated. This despite the passage of a weak cold frontal
boundary. The day to day details...

High pressure centered over the Mid West will remain in control
across our forecast area Tuesday night. While light winds and clear
skies will encourage decent radiational cooling...we have not had a
fresh airmass change in a few days...so the mercury is only forecast
to drop into the mid 60s across the lake plains while 50s will be
found across much of the Srn Tier.

A cold frontal boundary over the Upper Great Lakes will then slowly
push south across Southern Ontario during the day Wednesday...while
high pressure over the Mid West will gradually lose control of our
weather in the process. Nevertheless...fair weather will persist
across the region with H85 temps in the upper teens C supporting
afternoon readings in the upper 80s to near 90 for the lake plains
and in the valleys.

We can anticipate a weak frontal passage Wednesday night...but with
little forcing...will only raise pops to slgt chc while increasing
cloud cover. Temperatures overnight will be a few degrees higher
than the night before...but with dew points holding steady near
60...it should not be overly uncomfortable.

The frontal boundary will stall and wash out over Pennsylvania on
Thursday...while a ribbon of moisture in its wake will settle over
our forecast area. The bulk...if not all...of the day will be rain
free...but the passage of a shortwave in the northwest flow will be
enough to warrant low chc pops for the afternoon and evening. Since
a northeast low level flow will be in place in the wake of the
front with little instability...will only use a slgt chc for tstorms.

The various guidance packages remain out of step with each other as
we push into Thursday night...as there is a `disagreement` as to
whether a wave will form along the west end of the aforementioned
frontal boundary. Will keep low chc pops in place for all but the
North Country. While there will be low confidence with these pops...
there is more certainty that clouds will remain in place...
especially over the western counties.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
This period has the potential to be rather unsettled...or at least
more disorderly than what we have become accustomed to the past
couple months. The good news is that this would lead to some needed
rainfall for the region...but the bad news is that it would
adversely impact some peoples plans for the weekend.

Troughiness found over the Great Lakes region is forecast by some of
the ECMWF/GFS based ensembles to amplify somewhat...and this would
encourage waviness along a stalled frontal boundary over the Mid
West to evolve into an actual sfc low. Will use a compromise of the
HPC and ECMWF solutions...which favors such a sfc low development.
This feature is forecast to slowly track northeast across the Lower
Great Lakes during the course of the weekend while generating
scattered showers and possible thunderstorms in the process. Given
the low confidence of this forecast...will keep chc pops in place.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
Isolated thunderstorms along a lake breeze convergence zone near
KIAG and KBUF will continue through 23Z before drifting southeast
and falling apart by around 00Z with the passage of a surface cold
front. Otherwise the rest of the area will remain largely dry with
any remaining areas of MVFR CIGS improving to VFR and scattering out
this evening.

Gusty SW winds late this afternoon will give way to light winds
behind the front tonight, and with skies clearing, we will likely see
the development of patchy fog across low lying areas, particularly in
the Southern Tier, that will potentially generate IFR/LIFR conditions
after 06Z. Fog may also affect KIAG late tonight/early Tuesday
morning. Fog should clear out after 12Z, giving way to widespread VFR
conditions on Tuesday.

Outlook...

Tuesday Night and Wednesday...Mainly VFR.
Thursday...Mainly VFR with a chance of showers and thunderstorms.
Friday and Saturday...VFR/MVFR with a chance of showers and
thunderstorms.

&&

.MARINE...
Gusty southwest winds will continue to be an issue this afternoon on
Lake Erie ahead of an approaching cold front, and small craft
advisories remain in effect. Winds will diminish rapidly behind the
cold front, however westerly flow to around 15 knots on Lake Ontario
will generate moderate chop on the eastern end of the lake Tuesday,
though conditions should remain sub-advisory. After that, high
pressure will build across the Lower Great Lakes, with winds and
waves remaining generally tranquil through the remainder of the week.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Beach Hazards Statement until 8 PM EDT this evening for NYZ010-
     085.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ020-
         040-041.

&&

$$

SYNOPSIS...HITCHCOCK/WOOD
NEAR TERM...HITCHCOCK/WOOD
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...HITCHCOCK/WOOD
MARINE...WOOD



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