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FXUS61 KPBZ 241146 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 746 AM EDT Wed Apr 24 2024

SYNOPSIS
Showers will continue this morning with the passage of a cold front. Dry weather returns tonight through Friday as high pressure builds across the region. Shower chances return Friday night and Saturday with a warm front.

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

- Showers will gradually taper off later today after the passage of a cold front

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Updated the forecast to input the hourly temperatures and dew points and trend them into the mid morning hours. The forecast is on track for the most part.

Previous discussion...The latest surface analysis shows a prefrontal trough crossing central PA, with the main cold front across Lake Erie to NW Ohio. Showers associated with the prefrontal trough and a low level jet will continue to exit from west to east early this morning. Additional showers will soon follow with the crossing cold front and shortwave trough axis.

Dry weather should return by mid to late afternoon as surface high pressure begins to build across the region under a broad mid and upper level trough. Cold advection in NW flow, and moisture below a strengthening subsidence inversion, should keep a persistent stratocu cloud layer across the region through at least this evening. Temperatures will recover some behind the cold front, though will still be around 10 degrees below average.

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

- Freeze watch continues north and west of Pittsburgh - Some frost possible outside of the freeze watch - Dry and warmer Thursday and Friday - Showers return Friday night with a warm front ----------------------------------------------------------------

Clouds are expected to persist into the evening with moisture below a subsidence inversion, and cool NW flow. The highest amount of uncertainty exists in how fast the cloud will clear overnight. Clearing is likely from north to south as high pressure builds further across the Lower Great Lakes and Upper Ohio Valley region, though the speed that this occurs is in question. Model soundings indicate the clouds will hold from near Pittsburgh and points S-SE much of the night. HRRR cloud cover guidance also indicates this potential. Clearing will likely occur in the far north after midnight. With this uncertainty, maintained the Freeze Watch as is in coordination with surrounding NWS offices. Frost is possible outside of this watch, but will be highly dependent on the cloud cover.

Otherwise, dry weather is expected through Friday as the high tracks slowly eastward to the New England region. Southeasterly flow, warm advection, and rising 100-500mb heights with a building ridge should return temperatures back to the 60s and 70s.

The ridge axis will shift east of the area Friday night.
Warm, moist advection ascent will increase Friday night in southwest flow aloft behind the ridge axis, with showers overspreading the region.

LONG TERM /SATURDAY THROUGH TUESDAY/
KEY MESSAGES:

- Much warmer through the weekend - Highest chance for showers on Saturday, and again Monday through Tuesday -------------------------------------------------------------------

Model ensembles indicate the initial shortwave and warm front supported rain will continue to cross the region on Saturday. The front is expected to lift north of the region Saturday night, as a strong ridge builds across the SE CONUS to the Upper Ohio Valley region.

Mainly dry weather is expected Saturday night and Sunday with the ridge axis across the area. There could be enough diurnally driven instability to result in an isolated afternoon thunderstorm Sunday, though most of the day should be dry, with temperatures in the upper 70s to the mid 80s. 1000-500mb height approach 583dm Sunday into Monday, with 850 mb temperatures peaking around 14 deg C.

Model ensembles indicate the ridge should slowly shift eastward to the East Coast late Monday and Monday night, as the next shortwave trough and surface cold front approach from the Midwest. Scattered showers and thunderstorms are possible Monday with building diurnal instability in moist SW flow ahead of the trough. More numerous showers and possible thunderstorms are expected Tuesday as the trough/cold front cross the region.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
Expect a few showers through the morning hours today. These are expected to dissipate and move off to the east by 16Z. The scattered MVFR and IFR conditions this morning should improve slightly by this afternoon with MVFR cigs expected. Winds will begin to shift to the northwest today with the cold frontal passage. Expect some daytime wind gusts up to 20knots at times.

MVFR cigs looks to remain through the evening and overnight hours with improvement possible toward 12Z tomorrow morning.
Its not out of the question to still get some breaks at times in the cloud cover through the TAF period as well.

Outlook
VFR conditions are expected Thursday and Friday.

The probability of showers and isolated thunderstorms increases Saturday. This will come with additional restrictions likely.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...Freeze Watch from this evening through Thursday morning for PAZ007>009-013>016-020-022-077.
OH...Freeze Watch from this evening through Thursday morning for OHZ039>041-048-057.
WV...None.

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