NWS Area Forecast Discussion

FXUS61 KBUF 170103

Area Forecast Discussion
National Weather Service Buffalo NY
903 PM EDT Mon Jul 16 2018

A cold front will advance across the area overnight tonight with
showers and thunderstorms ahead of it. Drier air and more
seasonable temperatures will follow this cold front for the
remainder of the week.


Showers and thunderstorms continue across the eastern Great Lakes
this evening. Multiple severe thunderstorm warnings and a flash
flood warning have been issued in the forecast area. A strong cold
front is stretched from western Ontario Province to Central Michigan
this evening. A plume of 1.75-2.0 inch PWATs stretches from the Ohio
Valley into Lake Ontario and the North Country. Heavy rain has been
present with showers and thunderstorms producing rainfall rates of 1-
2 in/hour. Unlike most days, where the loss of diurnal heating
causes updrafts to collapse, the very warm and humid airmass at the
surface will keep updrafts rooted in the boundary layer. Although 0-
6km shear is weak across the forecast area, some dry air and 35-
40kts in the mid-levels per the 00z BUF sounding will keep some
storms tilted and isolated damaging winds gusts are possible ahead
of the cold front tonight.

Showers and thunderstorms are likely across the dry ground in
Western and North-Central NY tonight so many will be happy to
wake up with a wet ground. Localized flash flooding is possible
mainly across the Southern Tier as storms train over the same
area. Radar estimates 2-4 inches across southeastern Allegany
County as of 8:30PM.

The front lags in passing the eastern fringe of the area Tuesday
morning, so showers and low end chances of thunder remain there
after sun up. Otherwise, rapidly drying conditions throughout
the column will yield a drastic improvement in conditions
through the day from west to east. Likewise, cold advection will
knock temperatures back several degrees. This will make heat
index values drop quite a bit more than temperatures, resulting
in fairly comfortable July conditions.


Tuesday night the mid level trough axis will cross Quebec and
eastern NY, reaching western New England by Wednesday morning. Deep
moisture will have been stripped away by the cold frontal passage,
so the mid level trough axis will cross the area dry. Northerly
upslope flow will bring a modest increase in cloud cover overnight,
mainly across the higher terrain south of the Thruway and east of
Lake Ontario. An incoming cooler and drier airmass will allow lows
to drop back into the mid to upper 50s on the lake plains of Western
NY, and lower 50s for the cooler Southern Tier valleys and east of
Lake Ontario.

High pressure will then build from the central Great Lakes Wednesday
to the eastern Great Lakes Thursday. This will bring another stretch
of dry weather and sunshine both days. Cooler 850mb temps around +9C
on Wednesday will support highs in the mid 70s in most locations,
and around 70 on the hills. Wednesday night will be quite cool with
lows in the mid 50s on the lake plains, and mid to upper 40s in the
cooler Southern Tier valleys and Lewis County. The airmass will
begin to modify on Thursday, with highs back into the lower 80s at
lower elevations and upper 70s for higher terrain.

Thursday night and Friday surface high pressure will drift off the
New England coast, with a mid level cutoff low and associated
surface low moving into the western Great Lakes. Clouds will slowly
increase from west to east later Thursday night and Friday as return
flow begins to advect moisture into the region. The GFS is on the
fast side of the guidance envelope in bringing rain chances into
Western NY by late afternoon. Continued to favor the slower
ECMWF/GEM guidance and kept a dry forecast through Friday evening. A
push of stronger warm advection ahead of the system will bring highs
back into the mid to upper 80s on Friday, with the warmest
temperatures on the lake plains of Western NY with an added boost
from southerly downslope flow.


Friday night and Saturday a mid level cutoff low and associated
surface low over the western Great Lakes will make only very slow
progress to the east across Michigan. A few widely scattered showers
or thunderstorms may reach Western NY later Friday night and
Saturday, with dry conditions prevailing east of Lake Ontario. A
better chance of rain will arrive Saturday night and Sunday as the
system advances east across Ohio and Lake Erie, with more favorable
forcing and moisture arriving. Model guidance also hints at some
moisture from a sub-tropical system advecting northward along the
eastern seaboard Sunday. Some of this moisture may get pulled back
into the system approaching from the west, although the model
consensus keeps the bulk of this along the east coast. The trough is
forecast to weaken in place by Monday, with a chance of a few more
showers or isolated thunderstorms. Given the convective nature of
all the rain chances this weekend, expect coverage of soaking rain
to be spotty, with only limited improvement of dry soil conditions.

Highs on Saturday will reach the mid 80s at lower elevations, with
upper 70s to lower 80s by Sunday with more cloud cover and shower
coverage. Lows will generally run in the mid to upper 60s on the
lake plains, and lower 60s across the interior along with moderate
humidity. Expect similar near average temperatures to persist
through early next week.


Showers and thunderstorms expected at the terminals tonight.
Heavy rain will result in IFR conditions at the terminals. Some
storms may be strong with gusts up to 40kts however confidence
is low it would reach the airfields. VFR/MVFR conditions
expected between showers and thunderstorms. A cold front will
move through the terminals from west to east Tuesday.

With the frontal passage, winds will rapid switch from SW to NW
on Tuesday, ushering in clear skies as drier air arrives in the
afternoon. The front will move through KIAG/KBUF early Tuesday
and KART by Tuesday afternoon.


Tuesday...VFR, except MVFR in showers and thunderstorms.
Wednesday through Friday...VFR.
Saturday...VFR, except MVFR in showers and thunderstorms.


Showers and thunderstorms will move from southwest to northeast
across the lakes tonight as a cold front approaches. SMW`s may
be warrented through the overnight.

The cold front will pass across the Eastern Great Lakes region
late tonight and early Tuesday, with west to northwest winds
freshening Tuesday and Tuesday night. This may bring wave
heights and wind speeds to advisory levels, especially on Lake
Ontario on Tuesday.





SHORT TERM...Hitchcock
LONG TERM...Hitchcock

NWS BUF Office Area Forecast Discussion