Area Forecast Discussion

WHAT HAS CHANGED

A Severe Thunderstorm Watch has been issued for most of the area east of Interstate 77. Damaging winds are the main threat, but hail and an isolated tornado or two cannot be ruled out.

A Flood Watch is also in effect through tomorrow for the entire area.

KEY MESSAGES

1) A Severe Thunderstorm Watch is in effect through 10 PM tonight, and a Flood Watch in effect for the entire area through tomorrow for strong to severe showers and thunderstorms.

DISCUSSION

KEY MESSAGE 1...A Severe Thunderstorm Watch is in effect through 10 PM tonight, and a Flood Watch in effect for the entire area through tomorrow for strong to severe showers and thunderstorms.

The latest surface analysis shows a warm front well northeast of the area, with a cold front stretching from the eastern Great Lakes to IL and westward. This will be the main driving force for severe weather later this evening. Aloft, troughing encompasses much of the eastern states along and north of the Mid Atlantic region.

The first wave of positive vorticity advection was shifting into the area and had sparked a line of storms moving through SE WV and into northern VA. These storms are mainly a flood threat if they continue to train. As they shift south and interact with addition instability this afternoon and evening, expect a few strong to severe storms. Along the cold front, more widespread clusters of multicells push south after 4 to 5 pm and tonight. Wet microbursts will be the main concern today and tonight, although all convection may have torrential rainfall. Shear between 0-6 km increases to 35 to 45 kts by later this afternoon and evening as the nose of the 300mb upper level jet reaches the area, along and north of the front. Also concerning will be the increasing 0-1 km shear that may reach 25 kts, in the vicinity of the front where surface winds may back. This points towards increasing low level rotation resulting in a few supercells and a small tornado risk.

The cold front looks to slow down as it crosses the forecast area from north to south, stalling somewhere in VA or northern NC overnight. Thus the high threat for urban, small stream, and flash flooding will continue overnight into tomorrow with training cells along the boundary. CAMs are also hinting at an MCV or two in the area tomorrow morning, which would support stronger and heavier storms. Additional development is expected tomorrow, with additional short wave energy and favorable kinematics moving into the Mid Atlantic region. Along the front, the flooding threat will continue through into tomorrow night. As drier air begins to work in from the north by Thursday, chances for rain sink south. After a brief break, more chances for showers and storms return Friday into the weekend, as additional mid level short waves move through. With the numerous chances for rain and cloud cover in the forecast, temperatures will be in the 70s for the entire area Thursday through Saturday.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Mostly VFR conditions observed across the area, with a few pockets of MVFR at this time, though ceilings are less than 2kft in some places. Another round of rain with some embedded thunderstorms is moving into the mountains, though the strongest storms are still over central and northern WV currently. Some uncertainty in how far east the thunderstorms make it, but higher confidence in rain continuing through the overnight. Expect periods of MVFR to IFR within some of the heavier rain showers, with quick reductions in visibility. Storms will wane by 06Z or so, with showers lingering for a few more hours. Wind gusts between 15 and 20 knots will also continue into the overnight hours, and could gust higher near thunderstorms. These showers and thunderstorms will have the potential for producing strong and erratic winds, as well as some hail and an isolated tornado can't be ruled out.

More scattered showers and storms are likely Wednesday afternoon, but most model guidance has it staying south of Interstate 64, so have not included any mention of thunder for KLWB for tomorrow at this time. However, there is higher probability of fog developing at KLWB tonight through Wednesday morning.

Winds will turn more westerly in the mountains for tomorrow, after the frontal passage, but mostly southwesterly in the Piedmont. Wind speeds should stay between 5 to 10 knots until after the current TAF period ends, at 00Z Thursday.

Forecast confidence is moderate.

EXTENDED AVIATION OUTLOOK...

Drier conditions move in for Thursday and Friday, with no rain chances outside of DAN, though only isolated in coverage. Better rain chances return for Saturday, and Sunday looks to dry out. Overnight fog will remain possible each night, particularly at LWB.

RNK WATCHES / WARNINGS / ADVISORIES

VA...Flood Watch through Wednesday morning for VAZ007-009>020- 022>024. Flood Watch through Wednesday evening for VAZ032>035-043>047- 058-059. NC...Flood Watch through Wednesday morning for NCZ001-002-018. Flood Watch through Wednesday evening for NCZ003>006-019-020. WV...Flood Watch through Wednesday morning for WVZ042>044-507-508.