Area Forecast Discussion
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357
FXUS61 KPBZ 180710
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
310 AM EDT Mon Sep 18 2017

.SYNOPSIS...
High pressure centered over the region will bring a prolonged
period of dry weather, along with unseasonably warm temperatures
through the coming week.

&&

.NEAR TERM /THROUGH TODAY/...
High pressure will continue to hold sway through the morning
and into the daytime on Monday as a frontal boundary currently
straddling Indiana into Michigan inches eastward. This front is
set to run into a wall of high pressure and drier air aloft
concurrent with its upper forcing shearing off rapidly
northeastward toward Quebec. As this occurs, all convective
activity currently along the front should translate well north
of the area on Monday. Before that time, however, a clear
overnight with very weak boundary layer flow will transition
into a Monday with an increase in mid and high clouds as well
as the current boundary layer moisture resulting in fairly
pervasive cumulus development. However, with the surface trough
impinging upon the western fringe of the area, easterly flow
into the ridges will probably be weaker than in previous days.
This would seemingly result in a lower chance of showers in the
heat of the day in the terrain. Otherwise, continued elevated
dewpoints due to a lack of afternoon ventilation spurred by
cumulus development each and everyone one of the last couple
days will result in saturated valleys through morning. This
means a deja vu forecast for fog through sunrise.

Even with a decent bit of cloud cover, a warm air mass already
in place and at least some sun breaks through the day should
result in yet another above normal afternoon as highs jump
toward the lower 80s in most spots. Fries

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
With the upper level pattern favoring ridging in the east and
Jose moving closer to the coast, as well as deepening troughing
in the west, fairly high speed SW flow will exist through most
of the Midwest. One weak wave in the high speed flow will
attempt again to impinge upon the region late Tuesday into
Tuesday night. Again with this wave, shearing northward, a dry
column, and a lack of upper support driving eastward make adding
PoPs very difficult to do. PoPs for late Tuesday were adjusted
to just below mention for rainfall, however cloud expectations
were increased due to high projections of upper level moisture
as the wave approaches. Regardless, warm SW flow off the deck, a
humid boundary layer, and WAA will continue, thus well above
normal readings will be common. Fries

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A deepening upper trough in the west and retreating remnants of
Jose will allow for heights to go through the roof in the
eastern CONUS for the balance of the week. Low level flow looks
to finally lose some of its easterly component, which should rid
our area of the marine component and start to allow for more
ample insolation. Likewise, deep layer southwesterly flow above
the boundary layer should allow for 850 mb temperatures to
approach 18C from Friday into the weekend (and possible beyond).
This will allow for high temperatures to easily jump into no
less than the mid 80s even with the shorter daytime hours as
compared to mid-summer. That said, SuperBlend guidance is
utterly ridiculously cool, and all bias-corrected guidance is
taking several degrees of off explicit model/MOS output, hence
both were summarily dismissed as statistical rubbish. As a
result, the forecast was built entirely dry with very high
reliance on adiabatic mixing of 850 mb temperatures from model
guidance. This resulted in a continuation of far above normal
readings through the entirety of the long term. Fries

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
Deterioration to IFR is expected overnight in fog as crossover
temperatures are reached. Used persistence for most ports. A
return to VFR is expected within a couple of hours after sunrise
as the fog mixes out and dissipates. VFR is expected under upper
ridging for the rest of the TAF period, though a diurnal CU cig
and increasing mid/high clouds are expected.

.Outlook...
Patchy morning fog restrictions are possible through Thu with
ridging in place.

&&

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

&&

$$



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