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Area forecast discussion
National Weather Service Buffalo New York
436 am EDT sun Sep 22 2019

surface high pressure that brought a beautiful stretch of weather
the past few days will settle southward towards the Carolinas today.
A deep southwest flow around this surface high will make today mid
Summer-like with afternoon temperatures well into the 80s and a bit
of humidity. It will remain very warm tonight before a cold front
eases its way across our region tomorrow, bringing widespread rain
showers along with a stiff southwest breeze.


Near term /through Monday/...
surface high pressure this morning is now settling to the Carolinas,
while a low pressure near Hudson Bay is swinging a cold front across
the northern plains.

Around this broad surface high a southwest flow has brought a mild
start to Sunday...with the flow also advecting moisture northward.
This deepening moisture will eventually send precipitable waters to 1.75" or
greater later today and through early Monday.

Today will be The Pinnacle of this warm spell, with 850 hpa
temperatures of +15 to +17c that coupled with this southwest flow
will bring afternoon temperatures well into the 80s. These
temperatures will still be several degrees below daily records which
are: 89f at Buffalo (1965)...93f at Rochester (1895)...and 91f at
Watertown (1965).

The increase in moisture and heat today will begin to develop
instability. MUCAPE values potentially to around 500-700 j/kg may
bring a few spot showers along a weak warm thermal boundary...with
showers to the southeast of Lake Ontario and into Lewis County later
this afternoon. Otherwise the region will remain dry today.

A warm southwest wind will flow across our region tonight, keeping
overnight lows well above average. The last few hours of Summer will
remain in the 70s...with astronomical fall officially starting at
3:50 am Monday morning.

The upstream cold front will slowly edge eastward tonight, with the
front remaining to our west through the night. This will leave our
region mainly dry tonight, with perhaps a few showers entering far
wny late.

The cold front will swing across our region finally during the day
Monday. Widespread showers are expected...with precipitation amounts
outside thunderstorms generally a tenth or two of an inch or less.
Though high moisture content and deep warm cloud layer the strong
flow aloft (40 knot jet at 925 and 50 knots at 700 hpa) should keep
any storms moving.

Instability is not overly impressive with this system...with modest
instability over the Genesee river and Finger Lakes perhaps bringing
a few rumbles of thunder.

It will also be breezy to across the lake plain...windy tomorrow.
Steepening lapse rates in the lower levels will bring daytime mixing
layer heights to this low level jet at 925 that coupled with the tightening
pressure gradient with the cold front passage will yield gusts 30 to
40 mph mixing down to the surface.

Clusters of rain showers will shift across the County Warning Area through the
morning and early afternoon hours. Behind the cold front...and the
approach of the base of the upper level trough should begin to end
showers from west to east...though westerly breezy winds continue.


Short term /Monday night through Wednesday/...
a cold front will exit to the east of the area on Monday night with
a cyclonic flow and much colder air off the deck replacing it.
Temperatures at 850 hpa drop toward +4 to +6c, which should be cool
enough to get some lake response. Lake effect rain showers will
develop east and southeast of the lakes Monday night and last into
Tuesday. Showers will be most numerous and last the longest east of
Lake Ontario which will be closest to a closed 500 mb low which will
track across southern Quebec. Lingering lake effect clouds will keep
temperatures on the cool side Tuesday, with highs in the 60s.

Surface high pressure centered near Tennessee will ridge northward
into the region on Tuesday night. This high will drift off the
eastern Seaboard Wednesday, but will continue to provide dry weather
across the eastern Great Lakes. Following a chilly start,
temperatures will rise quickly on Wednesday with highs in the 70s.


Long term /Wednesday night through Saturday/...
a cold front will cross the eastern Great Lakes very late Wednesday
night and early Thursday, supporting a chance of a few showers and
increased cloud cover. The showers will end from west to east later
Thursday following the cold frontal passage. High pressure will then
build into the Ohio Valley and eastern Great Lakes Thursday night
and Friday, bringing a dry end to the week.

Temperatures will briefly cool off Thursday and Thursday night
behind the cold front, but will then quickly warm to above normal
Friday and Saturday as a strong ridge builds back into the eastern
United States. High temperatures may approach 80 again on Saturday
due to a warm southerly return flow when the high moves off the
mid-Atlantic coast.


Aviation /09z Sunday through Thursday/...
for the 06z tafs VFR flight conditions are widespread as clear skies
rule. The exception is valley fog...that is fluctuating between
IFR/MVFR at kjhw. As winds aloft increase in the next 6 hours we may
see this fog erode over the Airport...limiting the IFR visibility.

Today will feature VFR flight conditions as surface high pressure
settles towards the Carolinas. A deep southwest flow will bring a
breeze to the airports this afternoon...especially kiag/kbuf that
could have occasional gusts 25 to 30 knots.

Tonight a cold front will slowly ease its way eastward. Ahead of
this cold front a low level jet of 40 to 50 knots will bring some minimal low level wind shear
to wny. As surface winds increase tonight this low level wind shear will become less
of a factor.

Precipitation may hold off at all taf sites until after 12z Monday.


Monday...areas of MVFR with showers likely.

Tuesday...MVFR/VFR with scattered showers. Wednesday...VFR.

Wednesday night and Thursday...mainly VFR with a chance of showers.


a deep southwest flow will begin today between a surface high
pressure settling towards the Carolinas and an approaching front/mid
level trough. Winds on Lake Erie and the western end of Lake Ontario
will near small craft thresholds this afternoon...but it will not be
until tonight with the pressure gradient tightening with the
approaching cold front that winds will begin to increase into Small Craft Advisory
criteria. We will issue Small Craft Advisory for the lakes and Niagara River with
this package...with southwest winds peaking during the day Monday as
the cold front passes...and then veering to the west Monday evening.
This will maintain waves above 4 feet on lake's Erie and Ontario
through the night...with conditions not relaxing until during the
day Tuesday as winds and waves diminish.


Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory from 6 am to 8 PM EDT Monday for lez020.
Small Craft Advisory from 11 PM this evening to 11 am EDT
Tuesday for lez040-041.
Small Craft Advisory from 6 am to 8 PM EDT Monday for
Small Craft Advisory from 8 am Monday to 5 PM EDT Tuesday
for loz043-044.
Small Craft Advisory from 2 am Monday to 11 am EDT Tuesday
for loz042.
Small Craft Advisory from 5 am Monday to 2 PM EDT Tuesday
for loz045.



near term...Thomas

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