863 FXUS61 KPBZ 182147 AFDPBZArea Forecast Discussion National Weather Service Pittsburgh PA 547 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.
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.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.
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.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.
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.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.
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.AVIATION /22Z THURSDAY THROUGH TUESDAY/... VFR continues to be favored for the most part over the next 24 hours, with few to no clouds and light northwest wind into the overnight hours. Warmer overnight lows should lead to a bit less valley fog than was seen 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 may accompany it to produce a stratocumulus layer at FKL/DUJ. Confidence in MVFR ceilings is only moderate at this time, and have introduced a scattered layer at 2000 feet at both sites for now. 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, but VFR is likely to persist.
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.PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None.
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SYNOPSIS...Shallenberger NEAR TERM...WM SHORT TERM...Shallenberger LONG TERM...Cermak/Shallenberger AVIATION...CL
NWS PBZ Office Area Forecast Discussion