Sunrise 6:10 AM   Sunset 8:22 PM Moonrise 4:12 AM   Moonset 5:57 PM

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FXUS61 KPBZ 061514 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 1114 AM EDT Mon May 6 2024

SYNOPSIS
Probability of rain showers and isolated thunderstorms increase for areas south of Pittsburgh after 4pm this evening with an approaching disturbance. Fog potential returns early Tuesday morning for portions of the region. Severe weather potential increases Tuesday evening, after 6pm and could last into the overnight hours.

NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:

- Rain and thunderstorm chances increases this evening.
Lightning and areas of heavy rainfall rates will be the main concern.

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A stationary boundary is currently straddling along I-70 early this morning. Clouds will continue to stream through the region as a shortwave trough enters the Appalachians. As the shortwaves tracks through central West Virginia, showers and isolated thunderstorms will likely develop for areas south of Pittsburgh. Storms are not expected to be organized with marginal shear (effective shear less than 30kts) despite MLCAPE ranging between 900J/kg to 1100J/kg on sampled soundings near MGW. There was a noted layer of drier air on the KPIT morning sounding (between 700mb to 500mb) that would have been good for downdraft potential, however that layer of drier will likely dissolve this afternoon with a flux of mid-level moisture.

Like yesterday, with very saturated environment (PWATS values ranging between 1.30 to 1.45) and marginal shear, isolated storms can prompt heavy rainfall rates. Urban areas will likely be the places of interest today for any lingering or back- building storm due.

Probability of fog (less than a half a mile in visibility)
ranges from 45% to 65% for areas south of I-70 during the overnight time period. Weak moisture boundary layer convergence will likely cause probabilities to increase and isolated areas, and could create visibility issues for travelers. A Special Weather Statement or Dense Fog Advisory may need to issued for forecast zones south of Pittsburgh in the next 12 to 18 hours.

SHORT TERM /TUESDAY THROUGH WEDNESDAY/
KEY MESSAGES:

-Warm front will bring the next risk for showers and storms late Tuesday and Tuesday night.
- Ridging over the Great Lakes is expected to reduce precipitation chances briefly Wednesday.

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An ejecting trough out of the Rockies, that will eventually move over the northern Plains, and ridging over Florida, will reinforce a surge of moisture into the Ohio River Valley Tuesday under southwest flow. Severe storms have the potential to develop late Tuesday and Tuesday night under a destabilizing airmass and effective shear rapidly increasing from 20kts to 50kts. The Storm Prediction Center has noted the severe potential with issuing a Slight/Marginal Risk for portions on Day 3. Based on model soundings and hodographs, hail and damaging winds will likely be the biggest threat.

A break in the activity is possible Wednesday with weak ridging aloft.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
KEY MESSAGES:

- A new disturbance is expect to return showers and thunderstorms late Wednesday night into early Thursday morning.
- Ensemble models suggest a very wet pattern into the weekend.
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An active weather pattern will remain in place for our region, with decent daily precipitation chances through the weekend.
Therefore, flooding concerns will need to be monitor in the long term.

The potential of a period of severe weather Wednesday night into early Thursday with a passing disturbance will need to be monitored closely. Organized convection could be initiated if sufficient moisture advances north into the Ohio River Valley. Confidence is high that the wind shear will be available, it is a matter of destabilization that could pose a problem for severe convection development.

AVIATION /14Z MONDAY THROUGH FRIDAY/
Any lingering fog should improve by mid-morning with cigs lifting through the morning amid dry advection, with return to VFR anticipated by 18z. A crossing shortwave will trigger additional showers and possibly a thunderstorm mainly south of I-70 later this afternoon and evening.

Winds remain light through the period.

Outlook
An active pattern will keep periods of precipitation and related restrictions through much of the week.

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

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