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FXUS61 KPBZ 141353 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 953 AM EDT Tue May 14 2024

SYNOPSIS
Showers and a few thunderstorms will be possible today and Wednesday and again Friday through the weekend as multiple disturbances cross the region. Temperatures will remain slightly above normal.

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

- Shower/thunderstorm chances return today.
- No severe threat.
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Made some adjustments to PoPs and wind in the near-term grids, but the thinking for today overall has not changed. Weak vorticity advection, mainly through the midday hours, will continue to support scattered light rain showers. Coverage may drop off a bit during the afternoon hours in weakening lift and even some weak subsidence between waves. Instability/shear parameters are still unimpressive with regards to severe potential, but a thunderstorm or two remains possible.

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

- Shower/thunderstorm chances continue through Wednesday.
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As the mentioned upper trough over the Midwest tracks eastward across the Ohio Valley into Wednesday and eventually sliding east of the area by Wednesday night, increasing moisture and ascent will result in a greater coverage of showers and thunderstorms across the entire area through that time, with activity tapering off Wednesday night as an upper ridge begins to build in from the west in the wake of the trough. Rainfall amounts are expected to remain generally light through this system, with widespread amounts forecast to remain in the 0.25-0.75 inch range. Ensemble probabilities of storm total QPF greater than 0.5" is roughly 60-70% south of I-70 and 40-50% farther north. In fact, probabilities for an inch of rain in this 48 hour window are near or less than 30% everywhere. That said, while widespread rainfall amounts will be generally light, locally higher amounts will remain possible if any locations see multiple rounds of thunderstorms during this period, since the heaviest rates can be expected in any storms. The severe weather threat remains low as both instability and bulk shear will be marginal at best during this period.

LONG TERM /THURSDAY THROUGH MONDAY/
KEY MESSAGES:

- Dry conditions briefly return Thursday.
- Ensemble spread is still relatively high, but another trough appears to bring showers and thunderstorms back to the forecast late Thursday through the end of the week.
- Above normal temperatures continue.
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A weak upper ridge quickly builds into the area in the wake of the departing trough, bringing a brief period of dry weather early on Thursday. However, another upstream trough will be hot on its heels, digging into the Great Lakes region and quickly ushering the upper ridge off to the east. This will bring increasing chances for showers and storms back to the area Thursday afternoon through the end of the week.

AVIATION /14Z TUESDAY THROUGH SATURDAY/
Cigs will lower to low VFR/isolated MVFR this morning as a shortwave trough, embedded in SW flow ahead of a parent trough across the Midwest, approaches and crosses the region producing scattered showers. The showers should become more isolated this afternoon as the initial wave exits to the northeast.

Removed the prob30 for thunderstorms for most airports this afternoon. The latest CAMs show very little instability and forcing available this afternoon. This is supported by the latest upstream mesoanalysis.

Low VFR cigs and scattered showers are expected tonight as the next wave rotates around the main trough. DUJ should see cigs drop to IFR this evening, in a moist easterly flow.

Outlook
Restrictions are likely, along with showers and possible thunderstorms, Wednesday as slow moving low pressure crosses the region. A brief return to VFR is possible Thursday as ridging briefly builds in. Restrictions and showers return Friday and Saturday with another slow moving low pressure system.

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

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