Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 191312
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
912 AM EDT Wed Jul 19 2017

.SYNOPSIS...
While most areas will remain dry today...a weak frontal boundary
could generate some widely separated showers or thunderstorms during
the afternoon and evening. A higher chance for thunderstorms will
come Thursday afternoon. After a dry uneventful day on Friday...the
weekend will likely turn unsettled with showers and thunderstorms
becoming rather widespread.

&&

.NEAR TERM /THROUGH TONIGHT/...
A weak frontal boundary over southern Ontario this morning will
settle to the south across our forecast area later this afternoon
and evening. While there were a few isolated showers associated with
this feature over southern Ontario at 13z...the airmass is well
capped. This mornings KBUF sounding revealed a strong 2-3 deg C
subsidence inversion at 5k ft...and  this will effectively prevent
any true convection from occurring until the inversion gets eroded
after 18z.

As we push through the mid and late afternoon and the front makes
its way across Lake Ontario...the eroded cap will allow for some
spotty convection that will be generated as a result of weak
convergence along the front. Some enhanced lift will be found from
Niagara to Monroe counties in the vcnty of a lake breeze boundary.
Have thus raised pops to chc for some of these areas. Otherwise...
visible sat imagery shows a wealth of clouds moving in from southern
Ontario so have raised sky cover to go no more optimistic than
partly sunny. It will be warmer and more humid than yesterday (Mon)
as H85 temps in the mid teens will support afternoon highs in the
mid to upper 80s.

Whatever limited convection that does form this afternoon/evening
should quickly diminish this evening with the loss of heating and
the passage of the weak trough...with dry conditions then ensuing
for the balance of the night. With little in the way of an airmass
change...the upcoming night should be a warmer  with overnight lows
mostly ranging in the lower to mid 60s.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
A weak surface ridge will remain in place Thursday morning through
at least early afternoon, supporting dry weather across the region.
By late in the day a weak mid level shortwave will approach the
region, with this feature likely the remnants of an organized
complex of storms across the western Great Lakes early in the day.
This system will be moving out ahead of the better large scale
forcing and reservoir of strong instability over the Midwest, with a
steady weakening trend expected with eastern extent. There may be
just enough forcing and moisture when combined with local lake
breeze convergence to support a few widely scattered showers and
storms late Thursday afternoon through the first half of Thursday
night. By late Thursday night whatever remains of the system will
move south and east of the area, with any widely scattered showers
ending.

On Friday a push of somewhat drier and more stable air in the mid
levels will arrive in the wake of the weak wave, with the 00Z model
guidance more consistent now on the timing of this dry period. This
will support a decent amount of sunshine besides some diurnally
driven cumulus along and inland from the lake breeze boundaries. Dry
weather should remain in place Friday evening. By late Friday night
the next convectively augmented mid level shortwave will be moving
east across the central and southern Great Lakes. Increasing
moisture and large scale ascent will bring a west to east increase
in clouds overnight and may support a few showers or thunderstorms
toward Saturday morning across Western NY.

Temperatures will be quite warm through the period. Expect highs in
the mid 80s at lower elevations away from the lakeshores both
Thursday and Friday, with upper 70s to lower 80s across higher
terrain. Gradient onshore west to southwest winds will keep the
Buffalo and Watertown areas just a little cooler. Lows will be in
the mid to upper 60s on the lake plains and lower 60s in the cooler
Southern Tier valleys and Lewis County. Humidity will reach moderate
levels with dewpoints averaging mid 60s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
An unsettled pattern appears to be taking shape for the weekend into
early next week with several opportunities for more organized
showers and thunderstorms.

A zonal pattern will remain in place through the weekend with a
dominant, hot summer ridge across the southern 2/3 of the nation.
The southern edge of the westerlies will be found from the Great
Lakes to New England, with an east/west oriented frontal zone
forecast to stall across our region this weekend. Model guidance
continues to suggest several waves running west to east along this
frontal zone, with each bringing better forcing and moisture and
supporting better chances of more organized showers and
thunderstorms. It will remain quite warm and moderately humid
through the weekend.

By early next week the pattern will begin to amplify, with a trough
sharpening over the Great Lakes Monday and New England Tuesday. The
sharpening trough and associated surface cold front will continue to
support shower and thunderstorm chances through Monday, with cooler
and drier air arriving for Tuesday. Slightly above normal
temperatures through the weekend look to give way to slightly below
normal temperatures by early next week.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will be found across the region today...although
there will be a low chance for showers or thunderstorms near lake
Ontario after 18z.

Any convection that develops later this afternoon and evening will
then give way to clearing skies overnight. While VFR conditions will
be found across the majority of the region...IFR conditions in fog
and low stratus will be possible for portions of the Western
Southern Tier, including sites such as KJHW, KOLE and KELZ.

Outlook...
Thursday and Thursday night...Mainly VFR...with a chance of showers
and thunderstorms/attendant MVFR south of Lake Ontario.
Friday...Mainly VFR.
Saturday and Sunday...VFR/MVFR with a chance of showers and
thunderstorms.

&&

.MARINE...
Departing high pressure will maintain light to modest winds and
relatively minimal waves through most of today...with a passing
weak cool front only producing a few isolated to widely scattered
showers or thunderstorms this afternoon and early this evening.

While some additional rounds of scattered showers and storms will
then be possible Thursday/Thursday night and again over the weekend...
winds and waves are otherwise expected to remain at unremarkable
levels through Sunday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

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



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