Sunrise 5:55 AM   Sunset 8:34 PM Moonrise 4:56 PM   Moonset 3:15 AM

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FXUS61 KPBZ 200511 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 111 AM EDT Mon May 20 2024

SYNOPSIS
Mostly dry weather and a warming trend is expected through Tuesday. Shower and thunderstorm chances return Wednesday and continue through Thursday, with severe weather a possibility.

NEAR TERM /THROUGH TODAY/
KEY MESSAGES:

- Dry and warm day with plenty of sunshine.
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No major changes to the overnight period.

Eastern ridge will amplify today and the area will lie beneath the ridge axis. This will keep the area dry, allow for lots of sun, and support well above normal temperatures.

SHORT TERM /TONIGHT THROUGH WEDNESDAY/
KEY MESSAGES:

- Mostly dry weather is forecast through Tuesday night.
- Temperatures continue to climb to 10-15 degrees above normal, with a few record high values possibly approached on Tuesday.
- Risk for storms increases Wednesday.
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A weak shortwave trough will drift across Ohio on Tuesday. This will flatten the ridge and shove it over the Atlantic coast.
Moisture will be limited with this feature and the stronger lift within the trough will swing south of the area. For now, models are just showing an increase in high clouds on Tuesday.

The bigger story during this period remains the well-above normal temperatures. Plenty of sun, a drying ground, and 850 mb temps climbing into the 14-16C range will contribute to highs reaching well into the 80s Tuesday. Tuesday may be the warmest day on an areawide basis. NBM probabilities of 90 degree or higher temperatures are 50 to 70 percent range in river valleys and metro areas on that day. The May 21st record high at DuBois (86, from 2022) looks to be in greatest jeopardy. However, if the warmer end of guidance proves to be correct, other records at Pitt International (92, from 1911), Morgantown (92, from 1934) and New Philadelphia (91, from 1962) could at least be approached.

Model guidance still favors an upper low/trough in or near the northwestern Great Lakes by Wednesday afternoon. Given the increased shear expected with the system, as well as the potential for decent instability in the warm and humid conditions ahead of the front Wednesday, the afternoon/evening period of that day appears to hold the best potential for severe weather. CIPS/CSU guidance, NBM-based CWASP progs, and SPC all seem to suggest this possibility, with areas west of Pittsburgh showing the best potential. This will of course be given increased scrutiny as we approach the midweek period.
Temperatures will likely be muted a bit by the approaching clouds and rain Wednesday afternoon, especially west of Pittsburgh, but will still remain well above normal.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
KEY MESSAGES:

- Storm threat continue into Thursday, with some potential for strong thunderstorms.
- Near to just above seasonable temperatures and lower rain chances are expected Friday and into the weekend.
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A second shortwave trough, will cross the Michigan area Wednesday night and get absorbed into the larger trough. Minor strength and timing issues remain, but overall, the pattern still favors higher PoPs with the second shortwave, bridging the Wednesday night/Thursday period, which will likely also involve a cold frontal passage at the surface during the day on Thursday.

It appears that the Thursday night/Friday period will be relatively quiet with weak surface ridging indicated, along with temperatures closer to climatology. Model details become more unclear over the weekend, but with the possibility of weak shortwaves crossing the Middle/Upper Ohio Valley in WSW flow aloft, some lower-end PoPs in the 20 to 40 percent range are necessary for both Saturday and Sunday. Temperatures may nudge up to a few degrees above normal.

AVIATION /05Z MONDAY THROUGH FRIDAY/
Overnight conditions are coming in a little bit drier then the prior update. Correspondingly, dense fog probabilities remain low at most ports, save DUJ. Better chances of fog formation will come in valleys, generally east of the Pittsburgh metro.

High clouds will move in ahead of some convection in Ohio, but no restrictions are expected through morning from cigs.

Into the day, any fog will rapidly clear and give way to light south-southeast winds with mostly clear skies with VFR. This will persist through tomorrow night, where even lower fog probabilities are forecast.


Outlook
VFR and dry weather continues Tuesday under high pressure.
Precipitation chances and associated restrictions return Wednesday with the passage of a cold front.

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

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