Area Forecast Discussion

WHAT HAS CHANGED

Updated aviation discussion.

KEY MESSAGES

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

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

3) 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 diurnal instability across the region, with ML CAPE 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 CAPE), 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.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

Line of convection approaching the OH/PA border will move east through 03Z, likely weakening as it does so. Have handled this line with brief TEMPO IFR/MVFR visibility in heavier rain, but do not foresee significant wind gusts at this time.

After a lull during the late evening/early overnight, additional convection is likely overnight until around sunrise as a shortwave trough crosses. Exact evolution of this convection remains a bit questionable, but we have good confidence that the main mesoscale convective system will track to our west, across western Ohio. Nevertheless, one or more lines of showers and thunderstorms are expected during the period, with likely MVFR/IFR restrictions. Have used TEMPO groups at most terminals for this activity. The main impacts are likely to be the downpours and some non-severe wind gusts, perhaps in the 25 to 35 MPH range.

Past this convection, MVFR/IFR ceilings and mist are possible for a few hours during the morning. Diurnal destabilization ahead of an approaching cold front is likely to produce at least scattered convection during the afternoon. Again, coverage and timing remain low confidence, and have used PROB30 groups to illustrate this.

Outlook...Showers may linger in the post-frontal environment Tuesday night due to cold NW flow aloft maintaining some buoyancy.

High pressure builds through the mid-week period to increase the duration of VFR periods with dry weather, with any restrictions mainly occurring during the morning hours due to low clouds and/or fog.

PBZ WATCHES / WARNINGS / ADVISORIES

PA...None. OH...None. WV...None.