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-- Discussion containing changed information from previous version are highlighted. --
616
FXUS61 KPBZ 271027
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
627 AM EDT Tue Sep 27 2016

.SYNOPSIS...
High pressure will provide for dry conditions today. An upper low
will then return the chance for showers and seasonal temperatures
through the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
For the pre-dawn update, made only small tweaks to temperatures,
dewpoints, and sky based on the latest observations.

Surface high pressure will build overhead today. Some mixing will
continue with expected diurnal heating, which should allow for
dewpoints to further drop this afternoon as dry air aloft is
brought to the surface. With southwest flow continuing on the
periphery of the broad upper low over the northern Great lakes,
and some slight warming aloft, temperatures should be very close
to average today.

Wind should diminish with the loss of heating this evening, priming
the region for a good radiational cooling night. This may allow
for some locations to fall into the upper 30`s or low 40`s so long
as clouds associated with the upper low remain north of the
region.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
The Great Lakes upper low is forecast to dig southward across the
upper Ohio valley Wednesday, settling near KY/WV and cutting off
from the upper level pattern through at least Friday. As models
are coming into more consistent depictions, confidence in the
forecast of chance/scattered shower weather with sub- average
temperature is improving. Only minor changes were made to the PoP
and temperature forecast based on the latest blend of guidance
with likely probabilities carried over northwestern PA where a
southeasterly wind will support transport of deeper Atlantic
moisture inland. A period of heavier rain may be possible over
this area but with little rain reported over the region in the
last week, this is not significant enough to outline in the Hazardous
Weather Outlook, especially with some minor east- west
differences in the low position by late week.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Most of the models lift the stubborn upper low from the middle Ohio
Valley at the start of the period into the eastern Great Lakes by
12Z Sunday.  Details of individual waves rotating around the low
remain tricky at this distance, so kept PoPs fairly general, with a
slow decreasing trend through the weekend.  Expect Sunday night into
the first portion of next week to be dry as a flattening ridge
arrives.  Near-climatological temperatures will edge back above
normal by the end of the period with the departure of the upper low.
SuperBlend values were slightly knocked back early in the period,
but later numbers looked reasonable.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
Some low clouds and fog are lingering in some of the valleys east
of Pittsburgh this morning, although only DUJ is affected for now.
The clouds and fog will burn off by 15Z, with VFR conditions
continuing for the balance of the TAF period. Winds may gust to
between 15 and 20 knots out of the southwest during the afternoon.

.OUTLOOK /TUESDAY NIGHT THROUGH SATURDAY/...
Upper-level low pressure will settle into the Great Lakes region
through the week. Flight restrictions will be increasingly likely
beginning Wednesday.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.

&&

$$