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FXUS61 KPBZ 251341 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 941 AM EDT Thu Apr 25 2024

SYNOPSIS
Dry weather is expected through Friday as high pressure moves across the region. Shower chances return Friday night and Saturday with a warm front. Other than a slight chance of an afternoon shower or thunderstorm, mainly dry and much warmer weather is expected Sunday and Monday.

NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:

- Dry and warmer today under building high pressure

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The aforementioned freeze warnings and frost advisories have been cancelled with temperatures rising above freezing. Today's forecast is shaping up to be largely dependent on cloud cover.
In areas where clouds linger, cooler and slightly more saturated cognitions are favored, while clear areas will trend warmer and a bit drier. The forecast has been adjusted to reflect this.
Fire weather concerns are minimized with continued cloud cover and calm winds.

Previous Discussion

HRRR cloud product has been depicting this morning's stratocu layer well. The latest satellite imagery and recent model output indicates partial clearing of the stratocu will continue early this morning, especially across Ohio and far NW PA. The clearing should accelerate through the morning as surface high pressure builds across the Great Lakes and Upper Ohio Valley region, under a broad upper trough.

Otherwise, dry warmer weather is expected today under the building high, though highs are still expected to be around 5 degrees below average. Dew points are expected to drop with mixing this afternoon, though current RH projections are above 30 percent for all but NW PA. Wind is also expected to be light.

SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/
KEY MESSAGES:

- Dry and warmer through Friday - Showers and possible thunderstorms return Friday night into Saturday with a warm front

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High pressure will maintain dry weather tonight. Radiational cooling should be somewhat limited by warm advection aloft, despite coupling at the surface. Temperatures should be cold enough for some patchy frost in some locations north and west of Pittsburgh, though the patchy coverage precludes an advisory at this time.

The center of the surface high will shift east of the region on Friday, as upper ridging builds eastward across much of the Eastern CONUS. Rising 1000-500 mb heights, and warm advection, should drive temperatures back to or just above average for this time of the year.

The upper level ridge axis is expected to move just east of the region Friday night and Saturday, as warm, moist advection tracks across the Upper Ohio Valley region in SW flow aloft.
A surface warm front is also expected to lift NE across the region, with scattered to numerous showers moving across the region. A rumble of thunder is possible with limited instability across NW PA and eastern OH. The showers should taper off from SW-NE through the afternoon as the front lifts north of the region, and the upper support exits.

Generally dry weather is expected for most of the region Saturday night as a ridge becomes reestablished across the SE CONUS, and extends northward to the Upper Ohio Valley region. A few showers will still be possible across far NW PA as a weak vorticity max crosses on the northern periphery of the ridge. A noticeable warming of overnight lows is expected, with readings around 15 degrees above average by Saturday night.

LONG TERM /SUNDAY THROUGH WEDNESDAY/
KEY MESSAGES:

- Warm with minimal chances of afternoon thunderstorms Sunday and Monday - More widespread showers and possible thunderstorms with a Tuesday cold front -------------------------------------------------------------------

Model ensembles continue to indicate the strongest riding across the Upper Ohio Valley region Sunday and Monday. Sunday should be mainly dry under the ridge, with warm air aloft limiting convective potential. Still, an isolated afternoon storm or two is possible, mainly north of Pittsburgh, where another vort max moves across southern Ontario on the northern periphery of the ridge.

Similar conditions are expected Monday. The ridge axis is expected to shift slowly eastward later Monday, with slightly better chances for afternoon showers and thunderstorms late in the day as a shortwave trough and associated surface cold front begin to approach from the Midwest.

Showers are likely, along with a few thunderstorms, on Tuesday as the trough and cold front cross the region. The precipitation should end Tuesday night as the front exits.

Greater uncertainty exists on Wednesday, with differences in the strength and timing of a trough approaching from the Upper Midwest. Stayed close to the ensemble blend, resulting in shower and possible thunderstorm chances returning through the day.

Temperatures mainly in the 80-85 degree range (outside of the higher terrain) are expected Sunday and Monday with a 1000-500 mb height of 582 dm, and 850 mb temperatures ranging from 12-14 deg C. Cooler, but still above average, temperatures should return Tuesday behind the front.

AVIATION /14Z THURSDAY THROUGH MONDAY/
MVFR stratocumulus is impacting most of the area to start the TAF period, with some light rain/drizzle even being observed around the LBE area. These clouds will be slow to erode this morning, but VFR conditions are generally expected to return by midday as a dry northeast flow sets up and daytime heating allows deeper mixing to occur. Winds will remain light and once VFR conditions return, they should prevail throughout the remainder of the TAF period.

Outlook
VFR conditions are expected Thursday and Friday.

The probability of showers and isolated thunderstorms increases Saturday. This will come with increasing probabilities for restrictions as well.

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

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