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FXUS61 KPBZ 040503 AAC AFDPBZ

Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 103 AM EDT Sat May 4 2024

SYNOPSIS
Intermittent rain and a few storms are possible through the weekend. With clouds and rain, temperatures will be cooler today, but will rebound Sunday as a southerly flow returns. A brief break in the rain is possible Monday.

NEAR TERM /THROUGH TODAY/
KEY MESSAGES:

- Showers taper off overnight.
- Showers slowly move back over the region later this morning.
- Cooler temperatures today.
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Showers are expected to dissipate overnight as the weak wave riding on the backside of the east coast ridge drifts north of the region. Clouds will blanket the area and keep overnight lows well above normal.

East coast ridge will move very little today and amplify this morning in response to trough digging into the northern Plains.
We will continue to rest on the western side of the ridge where a shortwave will drift northward throughout the day.

Deep moisture will flow northward on the backside of the ridge axis keeping in plenty of clouds and the risk for showers all day. An increasing southeasterly flow at the surface will pump Atlantic moisture into the region aiding in the shower development. For the most part, rainfall should be on the light side. HRRR probs for 24 hour rainfall ending at midnight tonight for >0.25 generally range from 30 to 50% with some pockets of 60 to 70% over portions of northern WV and the higher elevations.

Clouds, showers and a cool easterly flow will keep temperatures slightly below normal today.

SHORT TERM /TONIGHT THROUGH MONDAY/
KEY MESSAGES:

- Unsettled pattern remains with rain chances continuing through Sunday. Thunder possible on Sunday.
- Temperatures push back above normal Sunday and Monday.

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East coast ridge will flatten and drift eastward on Sunday. The shortwaves riding northward on the western flank of the ridge will also shift to the east. Shower coverage looks to dissipate Sunday morning. A weak cold front will slowly cross Ohio Sunday. Models are hinting that scattered storms could develop ahead of the front Sunday afternoon. However, ample cloud cover,limited instability, and lack of upper level support should work to shunt storm development and intensity.

Temperatures will warm on Sunday as the low-level flow veers to the southwest ahead of the front.

Ensembles have been consistent in showing a shortwave trough over the Middle Ohio Valley approaching, but weakening, on Monday as it interacts with a weak ridge over our region. A south-to-north gradient in PoP values still seems appropriate for the Monday/Monday night period.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
KEY MESSAGES:

- Rain chances continue next week but more uncertainty lends to lower confidence.
- Temperatures favored to remain above normal.
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Uncertainty still reigns after Monday. Most guidance depicts a ridge centered over the Great Lakes at 12Z Tuesday, along with a deep closed upper low in or near the Dakotas. The upper low appears likely to fill during the midweek period, and as it does so, shortwaves rotating around it appear to flatten out the ridge as it moves across the Upper Ohio Valley, finally eroding it almost completely in the northeast CONUS. Some strength and timing issues remain with the details of this process, which in turn could impact precipitation amounts and timing.

Nevertheless, a warm front is likely to cross on Tuesday as the ridge progresses eastward. This will lead to the persistence of a warm and moist airmass, with precipitable water values at or above the 90th percentile in the climatology. Along with the previously mentioned shortwave activity, this will keep an active weather pattern in place for our region, with decent daily precipitation chances through Friday. Deep-layer shear will increase as well behind the departing ridge, so severe weather chances will need to be monitored as well. According to CSU machine-learning guidance and NBM CWASP probabilities, Wednesday and Thursday may be the days to watch.

AVIATION /05Z SATURDAY THROUGH WEDNESDAY/
VFR ceilings and scattered light showers are ongoing across the area this evening. Removed the mention of thunder from 00Z TAFs as instability is waning and any lingering occurrences of lightning would be brief and isolated, with little impact to area terminals. Into tonight, convection is expected to subside in coverage, with only some light lingering showers possible primarily southeast of a ZZV-PIT-DUJ line. Meanwhile, saturation from the rain and cooling temperatures may allow an MVFR cloud deck to settle in by daybreak as winds shift to southeasterly.
The highest probabilities for ceiling restrictions, per the latest hi-res ensemble guidance, exist north and west of Pittsburgh, across portions of eastern Ohio and northwestern PA. East of PIT, it appears downsloping southeasterly winds may help keep low-level moisture profiles slightly less saturated and thus, mitigate the formation of widespread MVFR/IFR ceilings.

Widespread rain chances increase again after 18Z Saturday.
Locally lower ceilings and visibilities can be expected in the heavier showers. Continued to leave thunder out of the TAFs during that period given uncertainty surrounding how much instability will develop. If lightning does occur, the best chances according to hi-res ensembles would be southwest of PIT, so a mention of thunder at ZZV and HLG may be needed in future updates.


Outlook
Restriction potential continues through Sunday morning, with additional storm chances Sunday afternoon. Periodic restrictions may continue through early next week as multiple disturbances pass through the region.

CLIMATE
Some record warm minimum temperatures may be approached on Saturday.
Below is a table showing the latest forecasted low temperature for each climate site, their respective record value, and the year it was set.

Forecast Record Year Pittsburgh 60 65 1938 Wheeling 62 63 1931, 1939, 1941 Morgantown 61 63 2021 New Philadelphia 60 60 2012 Zanesville 63 65 1902

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

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