Marine Weather and Tide Forecast for Bel Air South, MD

KEY MESSAGES
- 1) Severe Thunderstorms are possible this evening as a strong cold front moves through.

- 2) Frost and/or freezing temperatures are possible this weekend.

- 3) Nor'easter to develop off the Carolina coast late in the weekend lingers much of next week.

DISCUSSION
KEY MESSAGE 1...Severe Thunderstorms are possible this evening as a strong cold front moves through.

Skies remain mostly sunny across the majority of the forecast area, which has allowed temperatures to climb into the lower to mid 80s. Dewpoints have also risen into the 60s to near 70 within southerly flow. This unseasonably warm and humid airmass coupled with cooling temperatures aloft are allowing instability to build over the area. Thunderstorms are in the process of forming along a strong cold front which is just starting to move into western MD and the WV Panhandle. The coverage of storms is expected to gradually increase as the front moves into an environment further east characterized by slightly higher instability, with the greatest coverage of storms expected to the east of the Blue Ridge this evening where the highest dewpoints (upper 60s to near 70) are located.

Confidence in the timing of the storms is very high since they're forming directly along the front. The storms are located over Western MD and the WV Panhandle currently, should reach the Blue Ridge by around 5-6 PM, impact the I-95 corridor between 6 and 8 PM, and then Southern MD shortly thereafter.

In terms of hazards, damaging winds appears to be the primary threat, with ample flow in place just off the surface. With around 40-50 knots of effective bulk shear, some supercellular or bowing structures could be possible, which could locally enhance the threat for damaging winds. However, relatively weak low-level lapse rates could be a limiting factor for damaging winds. As thunderstorm coverage increases to the east of the Blue Ridge, we'll also be losing daytime heating, which will only make the low-level lapse rates even poorer. While the environment doesn't appear to be the most favorable for tornadoes, a brief tornado or two can't be completely ruled out. The threat for severe thunderstorms will immediately come to an end once the front moves through, with winds picking up out of the northwest behind the front. A Severe Thunderstorm Watch remains in effect for the majority of the forecast are through 8 PM.

KEY MESSAGE 2...Frost and/or freezing temperatures are possible this weekend.

Strong cold advection will ensue within northwesterly flow behind the cold front tonight through the day tomorrow. Upslope showers in the Alleghenies may even end as a few flakes of snow late tonight, but no accumulation is expected. Temperatures are forecast to drop into the 40s by daybreak tomorrow (mid- upper 30s mountains). A few showers could linger from Central Virginia to Southern Maryland tomorrow morning, but gradual clearing is expected tomorrow afternoon as the upper trough axis progresses to our east and large scale subsidence starts to increase.
Temperatures will be much cooler tomorrow, with highs in the 50s (40s mountains).

High pressure will gradually build in from the west tomorrow night as a nor'easter simultaneously starts to develop off the Carolina coastline. The main question tomorrow night is which locations will decouple. The setup for radiational cooling will be nearly ideal in locations that go calm, with clear skies expected and dewpoints in the 20s. Temperatures will likely plummet into the 20s and lower 30s where winds go calm.
Confidence is currently the highest for winds going calm to the west of the Blue Ridge, with greater uncertainty with respect to the winds further east as the nor'easter develops offshore. A Freeze Watch has been issued to the west of the Blue Ridge, where confidence is highest for sub-freezing temperatures. Some frost or sub-freezing temperatures can't be ruled out further east, either. Forecast confidence decreases further moving into Sunday. Forecast models show considerable spread with respect to the location of the aforementioned nor'easter during that time period. Some solutions keep the system offshore, while others have it retrograding further westward, which could lead to impacts locally.

KEY MESSAGE 3...Nor'easter to develop off the Carolina coast late in the weekend lingers much of next week.

Part of the upper trough that swings through tonight into Saturday will cutoff along the front stalling to the south later this weekend. This result in the development of a nor'easter off the Carolina coast. This system then meanders offshore/near the coast, but guidance varies widely on its placement and strength. Since it will be cut off from the main steering flow, it could persist much of next week. Northeast breezes and occasional rain chances are possible, with the highest chances further east.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
Conditions have improved back to VFR. Winds will gust to around 15-25 knots out of the south to southwest this afternoon. A cold front will approach from the northwest later this afternoon into this evening. A line of thunderstorms is expected to form along the front, and will move through the terminals from west to east over the next several hours, potentially leading to a brief period of restrictions. Winds shift to out of the northwest and pick up behind the front this evening. North to northwesterly winds will then gust to around 20 to 30 knots through the day tomorrow. Other then a potential brief period of MVFR ceilings at CHO late tonight, VFR conditions are expected tonight through this weekend. Winds this weekend will be out of the north to northeast as a coastal low develops offshore.

Some rain or sub-VFR could develop Mon-Tue with a nor'easter lurking offshore, especially for areas further east. NE winds could become breezy at times depending on how close the system gets.

MARINE
Small Craft Advisory conditions will continue through the afternoon in southerly flow. A line of thunderstorms is expected to form along an approaching cold front this afternoon and then move over the waters this evening. SMWs may be needed as thunderstorms move over the waters this evening. Winds then shift to out of the northwest behind the front tonight, with SCA gusts continuing. Gale Warnings go into effect to the south of the Bay Bridge tomorrow and continue tomorrow night. SCAs remain in effect elsewhere through tomorrow night. After that, attention turns to a nor'easter that is forecast to develop offshore. SCA conditions likely continue through the day Sunday in northeasterly flow, but forecast uncertainty during that time period remains high.

NE winds around a nor'easter to the south may remain gusty much of next week. In fact, gales are possible at times over the wider/southern waters.

TIDES/COASTAL FLOODING
Anomalies will remain elevated within southerly flow this afternoon into this evening. Annapolis remain under a Coastal Flood Advisory through the tide cycle this evening.

Water levels are forecast to rapidly decrease within northwesterly flow behind a strong cold front tonight into Saturday. Water levels may rapidly rise again on Sunday as a coastal low develops offshore and winds turn to more out of the northeast.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Small Craft Advisory until 6 AM EDT Sunday for MDZ008.
Freeze Watch from late Saturday night through Sunday morning for MDZ003-501-502-509-510.
Coastal Flood Advisory until 11 PM EDT this evening for MDZ014.
VA...Freeze Watch from late Saturday night through Sunday morning for VAZ025>031-503-504-507-508.
WV...Freeze Watch from late Saturday night through Sunday morning for WVZ050>053-055-501>506.
MARINE...Small Craft Advisory until 6 AM EDT Sunday for ANZ530-531- 538>542.
Small Craft Advisory until 6 AM EDT Saturday for ANZ532>534- 537-543.
Gale Warning from 6 AM Saturday to 6 AM EDT Sunday for ANZ532>534-537-543.
Small Craft Advisory until 11 PM EDT Saturday for ANZ535-536.