textproduct: Wilmington

WHAT HAS CHANGED

Added key message for Friday system.

KEY MESSAGES

1) A strong storm system will move through the region Tuesday night into Wednesday bringing the potential for severe weather, flooding, and gusty winds.

2) Low pressure will move through the Great Lakes during end of the week bringing the next chance of precipitation to the area, along with a period of gusty winds.

DISCUSSION

KEY MESSAGE 1) A strong storm system will move through the region during the middle of the week bringing the potential for severe weather, flooding, and gusty winds.

Confidence remains high that an active weather pattern will impact the Ohio Valley Tuesday into Wednesday as a strong low pressure and cold front move through the region. SPC severe weather outlooks do highlight potential for severe weather both on Tuesday and Wednesday with the expectation that Tuesday's threat is during the overnight hours.

Severe threat-Tuesday night: For the local area, thunderstorm chances are likely limited to the late evening and overnight hours on Tuesday with the warm front too far northwest. Convective initiation during the evening is expected across Illinois, northern Indiana and southern Michigan. If convective modes can upscale in these areas, a line of thunderstorms could eventually move into far northwest Ohio. Otherwise, warm- air advection ascent Tuesday night with the strong LLJ will result in the best thunderstorm coverage over the local area. Forecast soundings show that a strong cap will develop as the LLJ brings in warmer air between 700-800 mb. This would favor elevated thunderstorms throughout the overnight hours, with hail the primary threat.

Severe threat-Wednesday: Zooming out, the secondary trough over the southern Plains fails to phase with the northern trough, reducing the potential for jet amplification over the Ohio Valley Wednesday. This favors a faster progression with the cold front through the local area on Wednesday afternoon and evening. Moving through the morning hours on Wednesday, ongoing showers and thunderstorms complicate the evolution of the severe threat into the afternoon. Over time, heating will support more surface- based thunderstorms, but the area of concern is expected to be limited to areas along and south of I-71. This is supported by the updated joint probability of CAPE and shear of 30 to 40 percent highlighted in this same area. All severe modes are possible as the cold front moves through the area, with the best chances for these threats during the afternoon and early evening hours. The front moves through quickly, brining temperatures down into the 30s and 40s, ending the severe threat.

Heavy rain/flooding threat-Tuesday night into Wednesday: Precipitable water values are well above climatology throughout the period with strongest jet stream flow advecting deep moisture into the Ohio Valley. This threat will exist over much of the area, but the best chance of flooding will occur in locations where thunderstorms occur multiple times. Confidence is low on any particular location with overnight convection on Tuesday night likely scattered over the area. Some organization may develop on the front Wednesday, but the movement of the front southeastward may limit the ability for repetitive thunderstorms in one location.

Wind gusts: Ahead of the passage of the cold front, strong southerly winds are forecast Wednesday afternoon. Probability for wind gusts over 35 mph are highest north of the Ohio River, generally in the 30 to 50 percent range. Wind gusts remain elevated into the overnight as strong northwest winds bring much cooler air into the area.

2) Low pressure moving through the Great Lakes during end of the week brings the next chance of precipitation to the area, along with a period of gusty winds.

The next low pressure is quite deep over the Great Lakes Friday, even though the deep moisture remains trapped to the southern United States. While some mixed precipitation is possible, the greatest concern is for a period of gusty winds. Probability of advisory level winds across eastern Indiana and Ohio are already in the 30 to 40 percent range Friday afternoon. 90th percentile winds within the NBM ensemble are typically favored in these scenarios, and these values are around 50 mph for peak wind gusts.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Southwest winds gusting to around 20 knots can be expected during the day on Monday with prevailing VFR conditions.

Toward the late afternoon and evening, chances will increase for lower level clouds to begin making their way northeast into the Ohio Valley. Confidence in IFR CIGs is highest during the overnight hours as low level moisture continues to move in from the southwest. LIFR CIGs are possible along with MVFR VIS. Toward the late morning hours on Tuesday, these CIGs likely climb back to low- end MVFR.

OUTLOOK...MVFR to IFR ceilings possible Tuesday through Thursday morning. Wind gusts above 30 kt possible Wednesday. Thunderstorms possible Tuesday night into Wednesday evening. Wind gusts above 40 kt possible Friday.

ILN WATCHES/WARNINGS/ADVISORIES

OH...None. KY...None. IN...None.