textproduct: Baltimore/Washington

WHAT HAS CHANGED

No major changes were made to the forecast.

KEY MESSAGES

- 1) Strong to severe thunderstorms along with locally heavy rainfall possible on Monday.

- 2) After a mid week dry spell, daily thunderstorm chances will return for the end of the week.

DISCUSSION

KEY MESSAGE 1...Strong to severe thunderstorms along with locally heavy rainfall possible on Monday.

After a seasonable and less humid weekend, a low pressure system is forecast to track from the Ohio River Valley northeast on Monday. The associated warm front will lift north across the region Monday afternoon and into the evening, bringing the next chance at severe weather. There still remains a good bit of uncertainty regarding timing and severity of storms, given the model guidance discrepancy in the track of the low pressure system and associated fronts. With southerly flow, a warm and moist airmass is expected leading to adequate instability. Additionally, steep low-level lapse rates will lead to possible damaging wind gusts as the primary hazard type. SPC has the entire forecast area in a Marginal Risk for severe weather.

In addition to the severe threat, PWATs nearing 2 inches will lead to locally heavy rainfall within the strongest storms. The Weather Prediction Center as most of the area in a Slight Risk for excessive rainfall with scattered instances of flooding possible.

KEY MESSAGE 2...After a mid week dry spell, daily thunderstorm chances will return for the end of the week.

It's now looking like the cold front may not make it entirely through the area by Tuesday. Therefore, there may be some renewal of showers and thunderstorms as a shortwave trough serves to kick the front eastward. The greatest chances will be along and east of I-95. Temperatures will be cooler than Monday, however.

High pressure will move across the area Wednesday, resulting in the most pleasant day of the week. Temperatures will be near normal in the mid 80s with relatively low dew points in the 50s and mostly sunny skies.

A slow moving upper level trough/closed low and broad surface low pressure will slow lift through the Great Lakes Thursday and Friday. While temperatures may not rise appreciably, there will be a return to muggier dew points. Specific forcing may be nebulous, but there is a decent model signal of at least scattered showers and thunderstorms each day. Some shear will be present, but instability may be limited, so the severe weather threat appears to be low (supported by various ML guidance probs).

Rain chances on Saturday may be lower as the upper level pattern flattens and weak high pressure likely builds somewhere near the east coast. However, model spread increases as an upper low moves into the Pacific northwest and downstream jet stream ripples could still result in some showers or thunderstorms in the warm and humid airmass.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

VFR conditions continue today and tomorrow as surface pressure remains overhead. Winds gust 15 to 25 knots out of the west/Northwest today before diminishing overnight. Winds gust 15 to 20 knots tomorrow, remaining out of the west/northwest. Showers and thunderstorms are possible on Monday with flight restrictions likely. Outside of storms, southerly winds could gust to 25 kt assuming a warm front clears the area to the north.

With a slower moving cold front, thunderstorms could develop again on Tuesday afternoon, especially for the metro terminals. Wednesday will likely be dry. Thunderstorms are possible again on Thursday.

MARINE

A Small Craft Advisory remains in effect until 8PM this evening for all waters with west/northwest winds expected to gust up to 25 knots. Winds diminish overnight, although additional SCAs are possible across the northern portions of the waters as winds near criteria. Winds shift to southerly on Monday with Small Craft Advisory likely needed. Additionally, showers and thunderstorms are expected across the waters Monday afternoon and evening with SMWs possibly needed.

Northwest winds behind a cold front may present marginal advisory conditions on Tuesday. Another round of thunderstorms could develop Tuesday afternoon as the front is now expected to be slower. Light winds are expected Wednesday under high pressure. The next upper level disturbance could bring more thunderstorms Thursday afternoon. Southerly channeling on the bay may also require SCAs by late in the day.

LWX WATCHES/WARNINGS/ADVISORIES

DC...None. MD...Small Craft Advisory until 8 PM EDT this evening for MDZ008. VA...None. WV...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ530>543.