PBZ issues Area Forecast Discussion (AFD) at Sep 18, 9:09 PM EDT715
FXUS61 KPBZ 190109
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
909 PM EDT Thu Sep 18 2025
.SYNOPSIS...
High pressure will maintain warm and mostly-dry weather into
the weekend. Rain chances return to the forecast next week,
though the chance for widespread wetting rain remains low.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
KEY MESSAGES:
- Dry weather continues
- Valley fog is possible tonight
---------------------------------------------------------------
High pressure will continue to maintain dry weather tonight.
Some limited increase in cloud cover is possible toward daybreak
ahead of an approaching, weakening cold front. Dry air has mixed
down through the day, with most locations reporting dew points
in the 40s to near 50. This should preclude fog for most
locations, though as temperatures cool, river valley steam fog
will be possible. Overnight lows are expected to be near
seasonable levels.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
KEY MESSAGES:
- Dry weather continues to end the work week
- A weak front brings slightly cooler temperatures
--------------------------------------------------------------
The set up on Friday will feature high pressure still in control
within developing northwest flow across the area. Friday night
will feature normal or just above normal temperatures again with
the potential of fog development, mainly in the river valleys.
Ensembles continue to show the high center positioned to the
north into the Great Lakes shifting southeast into the England
area. As this happens, a weak shortwave will drop into the Upper
OH Valley. This will bring some moisture to the region along
with a weak chance of precip over the northern WV counties. The
NBM is advertising a 20% to 40% probability of 0.01 or more with
this weak trough on Saturday.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
KEY MESSAGES:
- Still mostly dry and warmer than normal through the weekend
- Slight uptick in rain chances next week
- Temperatures remain above normal Monday through Wednesday,
albeit with a slight downward trend
------------------------------------------------------------------
The mentioned trough further infiltrates the region by Saturday
night into Sunday as additional moisture arrives into the
region. With a weak boundary in place, the winds begin to shift
to a more southern flow. This will ensure a better chance of
measurable precipitation. Thus, the NBM comes up with 40% to 60%
probs of 0.01 or more for Saturday night into Sunday. Sunday
morning will also stand the chance for some valley fog
developing, especially in river valleys.
Ensembles/cluster analysis continue to show a slower trend with
the progress of the next upstream trough, with the axis
progressing from the Upper Mississippi Valley to just the
Western/Central Great Lakes by Tuesday. Some solutions even
suggest the development of a cutoff upper low somewhere over the
eastern Plains. This trend, in turn, results in just a slow
increase to minimal PoPs, with slight chance values northwest of
Pittsburgh Sunday night/Monday, before eventually overspreading
the area Tuesday/Wednesday. QPF expectations are not high. The
NBM shows a 40-60 percent chance of 0.10" or more during the
72-hour period ending at 12Z Thursday. With increasing rainfall
deficits, we will need healthier precipitation totals to put a
better dent in the developing drought.
Overall, above-normal temperatures continue to be the
expectation through the middle of next week. Still, with the
slowly falling heights and increasing cloud cover potential, a
modest downward trend is the most likely scenario. The 25th-75th
percentile spreads do increase through this period, indicating
increasing uncertainty in the ultimate values. This is
reasonable given the range of potential solutions regarding the
speed/positioning of the upstream trough.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
VFR continues to be favored for the most part through tomorrow
morning, with few to no clouds as well as light and variable wind.
Warmer overnight lows will likely reduce valley fog development
compared to this morning.
A weak frontal boundary settles into western PA by 12Z Friday. While
no notable precipitation is expected with the boundary, enough low-
level moisture will accompany it to produce a stratocumulus layer at
FKL/DUJ. There is high confidence that cloud heights will be around
2000 feet, however there is only moderate confidence that skies will
be broken at these two sites. The boundary will also veer light wind
slightly to the north.
.OUTLOOK....
VFR is favored through Saturday with continued high pressure.
The approach of an upper-level trough may foster low-probability
rain/sprinkles Sunday and Monday, favoring locations northwest of
Pittsburgh. Those that observe any precipitation could see MVFR
ceilings, but VFR is likely to persist across most of the area.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Shallenberger
NEAR TERM...WM
SHORT TERM...Shallenberger
LONG TERM...Cermak/Shallenberger
AVIATION...CL/Lupo
Source:
PBZ issues Area Forecast Discussion (AFD) at Sep 18, 9:09 PM EDT---------------
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