Plaincast

What has changed

The highest potential for severe weather has shifted slightly westward today into tonight, with a Slight Risk across NW PA through E OH. A Marginal Risk remains across western PA and northern WV.

Messages

Showers and thunderstorms at times through tonight, with some severe and locally heavy rain potential

Showers and thunderstorms continue into Tuesday, with decreasing severe weather potential

Showers decreasing W-E Wednesday and Thursday, then mainly dry and seasonable through Saturday

Discussion

KEY MESSAGE 1. Convection was developing across the Great Lakes region early this afternoon, and will continue to track southeastward. The latest mesoanalysis shows increasing daily instability across the region, with ML storm energy ranging from 1000-2000 j/kg. Capping was observed on the 12Z PIT sounding just under 700mb, which will likely initially limit convective potential across the area early this afternoon. Some erosion of the cap is expected through the day, though a warm layer remains around 700mb through early this evening.

Expect scattered convection to develop across areas north of I-70 this afternoon as convective temperatures are reached, and as the cap slowly erodes. Additional showers and thunderstorms could become focused along a lake breeze, and with outflow from convection upstream. Some storms could contain damaging wind gusts, with increasing shear and dry mid level air. The latest day one outlook from the Storm Prediction Center maintained a Slight Risk for severe storms across NW PA into ern OH, with a Marginal Risk elsewhere.

Additional showers and thunderstorms are expected to cross the Upper Ohio Valley region tonight ahead of an approaching shortwave trough and surface cold front. A potential MCS could clip some of the Ohio counties later this evening as well. The most favorable instability (1500-2500 j/kg ML storm energy), and shear (30-40kt) is expected to be across Ohio, with lesser values to the east. This lines up well with the latest day one outlook from SPC. The severe potential should wane somewhat overnight, through there should be enough instability to maintain thunderstorms. Locally heavy rainfall will be possible if any training occurs, though the limited potential and uncertainty precludes a flood watch at this time.

KEY MESSAGE 2. Expect some ongoing convection and cloud cover Tuesday morning as the cold front/shortwave continue to approach. Increasing instability near and SE of the cold front should result in a Marginal Risk of severe storms, mainly south of a DUJ-BTP-ZZV line. The extent of any morning convection and cloud cover will have an impact on the amount of instability, and resulting severe weather potential through the day.

Showers and thunderstorms should begin to diminish by evening as the front crosses and begins to exit the region, and as instability decreases.

KEY MESSAGE 3. The shortwave trough is progged to deepen into an upper low across the NE CONUS by mid week. Wrap around moisture and lift should result in shower chances continuing east of I-77 on Wednesday, decreasing further from W-E on Thursday as the low drifts eastward. Shortwave ridging is then progged to move across the Upper Ohio Valley region later Thursday through Saturday, with dry and seasonable weather expected. The next chance for showers and thunderstorms is expected Saturday night and Sunday with the next approaching shortwave trough.