-- Discussion containing changed information from previous version are highlighted. --
856
FXUS61 KPBZ 251715
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
115 PM EDT Mon Sep 25 2017

.SYNOPSIS...
High pressure will bring dry and warm weather through mid-week
before the passage of a cold front heralds a return to
seasonably-cool conditions.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper-level moisture on the outskirts of Maria (off the
Carolinas) will maintain a veil of occasional cirrus today as
the clouds continue to move nwd. Otherwise, the region will
remain in a generally-subsident ridging pattern, with strong
insolation leading to afternoon temp maxima approaching 90F
(given the pre-existing warm airmass evident in the 12Z PIT
RAOB). No rain is expected today given the dry air in the mid
levels of the atmosphere and a lack of lift.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
One weak jet streak that advected cirrus northward into our
area will peel off to the east by Tuesday. This will allow for
skies to clear yet again. Better insolation likely will be
offset by a fall off of about 1C in 850 mb temperatures and
loss of about 10 dam in 500 mb heights. Thus, highs will trend
toward the same numbers on Tuesday as Monday, which will
continue the trend of temperature above seasonal levels.

By Wednesday, the pattern looks set to finally start to break
down as an upper trough starts to shear off to the northeast as
it lifts through the Great Lakes. Moisture below the upper
levels is exceedingly modest with the diffuse H5 wave that moves
across the area largely beyond the diurnal maximum on
instability. Thus, while fairly impressive temperature falls
will be noted with the front, an utter dearth of moisture in the
column combined with forcing anywhere beyond the boundary layer
pushing well to the north of the area will mean what looks like
a largely dry frontal passage. Some slight chance PoPs were
added for the northern fringe of the area, but it would seem
most areas should remain dry through the frontal passage.

By Thursday, cyclonic flow and constant cold advection will have
dropped 850 mb temperatures roughly 10C from their levels
earlier in the week. As such, highs will be struggling to reach
70F even as dry weather continues. Fries

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Further changing of the pattern looks likely in the long term.
While post-frontal cyclonic flow will continue through the
remainder of the week, a much deeper upper level system will
arrive for the weekend. Substantial cooling seems likely with
this system in the mid-levels as it transits the Great Lakes and
heads into the northeastern CONUS. As a result, instability will
increase markedly and mid-level moisture will finally arrive.
Shower chances maximize with its passage on Saturday likewise.

Saturday`s system and increase in clouds will drop temperatures
back toward their coldest point of recent memory. Without much
in the way of sunshine and 850 mb temperatures dropping toward
+3 or +4C in the daytime, highs much beyond the mid 60s in the
lower elevations seem unrealistic. Even still, this will only be
a couple of degrees above normal for one day after a stretch of
above-normal days that will have been going on since September
13. Fries

&&

.AVIATION /17Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
High pressure will maintain light southeast wind and VFR
through the TAF period. In the early morning hours of Tuesday
morning some non-VFR visibility restrictions possible from
patchy morning fog.

.Outlook...
Restrictions are possible with cold fronts Wed night and Fri.
-- End Changed Discussion --

&&

.CLIMATE...
While we will not be quite as warm as over the weekend,
temperatures will still be 15 or more degrees above normal this
afternoon. Here are the local record high temperatures for
Monday:

PIT: 92 (1881, 1900)
ZZV: 94 (1908)
MGW: 93 (1930)
DUJ: 87 (2007)
HLG: 91 (1934)
PHD: 91 (2007)

&&

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

&&

$$