Marine Weather and Tide Forecast for Ashton-Sandy Spring, MD

KEY MESSAGES
- 1) Daily shower and thunderstorm chances are expected through early next week.

DISCUSSION

KEY MESSAGE...Daily shower and thunderstorm chances are expected through early next week.

A deep southerly flow will continue around high pressure over the Atlantic, ushering plenty of moisture. PWATS will be near or greater than 2" in the valleys with 1-2" in the mountains, which is about 1- 2 SD above climo. A surface trough and shortwave energy will trigger scattered showers/thunderstorms, but it should not be a washout this afternoon/evening. The main threat will be brief heavy downpours and gusty winds. However, shear is on the lower side, so the probability of severe storms is lower. If some storms train over the same area, localized flash flooding can occur. The pattern does favor the possibility for training convection (cloud layer winds nearly parallel to low-level wind), but the coverage should be isolated.

A similar pattern will hold on for Thursday and Friday while the subtropical jet strengthens to the north and west. Therefore, more showers and thunderstorms are likely along with the threat for isolated instances of flash flooding and locally damaging wind gusts. Hotter conditions may cause relatively steeper low-level lapse rates and the wind field strengthens a bit (especially Friday).

A quasi-zonal flow aloft will develop for the weekend into next week, bringing more seasonably hot and humid conditions along with daily chances for showers and thunderstorms.

AVIATION /19Z WEDNESDAY THROUGH MONDAY/
VFR conditions are expected most of the time through tonight. A thunderstorm cannot be ruled out this afternoon/evening with the best chance around KMRB.

Winds shift to mainly south to southwesterly for the foreseeable future as a Bermuda high pressure system persists across the western Atlantic. Daily convective chances each afternoon and evening will support convective-driven restrictions. With little change in the upcoming pattern, this sort of forecast will likely hold for the next several days.



MARINE
Small Craft Advisories could be needed for parts of the waters at times this week, mainly in the late afternoon to evening.
Otherwise, winds remain around 10 knots. Daily showers and thunderstorms expected each afternoon this week. Special Marine Warnings would accompany any of the stronger thunderstorms capable of producing frequent lightning and wind gusts over 35 knots.



TIDES/COASTAL FLOODING
Anomalies climb late this week in response to return southerly flow. Periods of coastal flooding are possible at times of high tide at sensitive locations.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ533- 534-543.