textproduct: Baltimore/Washington

WHAT HAS CHANGED

No major changes were made to the forecast overnight as we continue to monitor the strong to severe thunderstorm risk for this afternoon.

KEY MESSAGES

- 1) A passing cold front brings beneficial rainfall this morning, followed by shower and thunderstorm chances this afternoon.

- 2) Daily chances of showers & thunderstorms this weekend.

DISCUSSION

KEY MESSAGE 1...A passing cold front brings beneficial rainfall this morning, followed by shower and thunderstorm chances this afternoon.

A cold front is expected to slowly track from northwest to southeast across the forecast area throughout today. Light stratiform rain overspreads the area this morning before exiting to the southeast early this afternoon. Later this afternoon and into the evening, thunderstorms are expected to develop along the frontal boundary as it tracks across the area. SPC has the entire area, with the exception of Garrett county, in a general thunderstorm outlook with any chances of severe weather remaining uncertain. The biggest hindrance in severe development will be CAPE and how much destabilization occurs in the wake of morning stratiform rainfall. However, there will be plenty of shear as an upper level jet pivots overhead. The best conditions for thunderstorm development are east of the Blue Ridge as the front tracks across the metros.

KEY MESSAGE 2...Daily chances of showers & thunderstorms this weekend.

An upper level atmospheric perturbation results in a shortwave trough moving through the area on Saturday, where a few showers and thunderstorms are possible in the afternoon & evening. Temperatures start to creep back up into the 70s and low 80s this weekend, before another cold front moves in from the Great Lakes, bringing additional rain and thunderstorms starting Sunday afternoon and into Monday. NCAR's AI Medium-Range convective hazards forecast currently has the region included in its 5%-15% probability for severe weather during this event, but will have to see how far north or south the low is tracking by then.

High pressure moves into the region on Tuesday, bringing drier air and clearing skies early next week.

AVIATION /07Z WEDNESDAY THROUGH SUNDAY/

Stratiform rain moves into the area from northwest to southeast this morning with reduced ceilings and visiblities expected. MVFR to possibly IFR conditions are expected beginning around 15Z and persisting through the early afternoon. Stratiform rain showers move out early in the afternoon with additional showers and thunderstorms possible later in the afternoon. Thunderstorms and lingering light rain showers are represented in PROB30 groups across all terminals. Precipitation moves out Thursday afternoon with dry conditions expected through Friday.

Winds shift to north/northwest behind the front and are expected to remain light, blowing 5 to 10 knots with gusts near 15 knots in the afternoon. Winds shift to southerly on Friday.

Southerly winds temporarily shift west as a shortwave trough meanders through Saturday night, before shifting south again Sunday morning. Expect periods of sub-VFR conditions across terminals on both Saturday & Sunday as showers and thunderstorms move through the region during the afternoon/evening hours.

MARINE

A Small Craft Advisory remains in effect 6PM this evening as south winds gust up to 25 knots. A cold front moves across the waters late this afternoon and into the evening. Thunderstorms are possible as the front passes through which may lead to SMWs needing to be issued. In the wake of the front, winds shift to north/northwesterly and are expected to remain below SCA criteria through Friday.

Southerly winds gust near SCA criteria on Saturday before diminishing in the evening. Winds stay below SCA criteria for most of the day Sunday, but increase to potential SCA thresholds later that evening.

LWX WATCHES/WARNINGS/ADVISORIES

DC...None. MD...Small Craft Advisory until 6 PM EDT this evening for MDZ008. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ530>543.