Marine Weather and Tide Forecast for North Chevy Chase, MD

KEY MESSAGES
- 1) A few showers and thunderstorms remain possible until a cold front crosses later today.

- 2) Thunderstorm chances return Wednesday night into Thursday, and continue into next weekend.

DISCUSSION
KEY MESSAGE 1...A few showers and thunderstorms remain possible until a cold front crosses later today.

Radar as of 1015Z/615AM EDT shows scattered shower activity near and west of the Allegheny Front.

A couple of convectively-augmented shortwaves remain across the southern Ohio Valley and Coalfields. These waves would cross the region this afternoon, along with some right- entrance ascent from a 70-knot upper jet streak roughly near the PA/NY border. A lack of low-level convergence due to mostly unidirectional light northwest flow should keep convective coverage low, despite the mid/upper waves at a favorable time.
Steepened low-level lapse rates with lingering low-level moisture could result in a few gusty thunderstorms (35-50 mph perhaps), along with some downpours and lightning. Heating and instability will be a bit more pronounced across central VA, so areas generally along the I-64 corridor would probably stand the highest chance at seeing anything at or near severe thresholds (which is 58 mph). DCAPE will be very marginal (400-600 J/kg)
due to lingering mid- level moisture and meager lapse rates aloft. Typically, values of at least 600-800 J/kg are needed to accelerate downdraft winds to severe levels.

The low-level synoptic cold front, currently from near Detroit to Indianapolis, will cross the region tonight. A bit of an increase in low-level convergence on the tail of the mid/upper waves, as well as a theta-e ridge could cause a bit of an uptick in activity a little later than usual (6-10pm). Overall modest thermodynamics and increasing nocturnal stability coupled with disjointed forcing should keep any strong to severe threat low, though some lightning strikes and downpours are still possible.

If any of the upstream waves trend a bit stronger, and/or CAPE verifies a bit higher than currently progged, then perhaps a couple more stronger storms would be possible through this evening. Otherwise, activity should dwindle overnight as the front swings through.

KEY MESSAGE 2...Thunderstorm chances return Wednesday night into Thursday, and continue into next weekend.

With a cold front drifting south of our region on Thursday, shower and thunderstorm chances return through next weekend. The best chance for activity occurring is on Thursday. At this time, it's not certain if there will be enough instability, or enough overlap with higher shear values, to present a severe weather threat. It's possible the front will stall or only move just south of the area, which will play a role in precipitation chances Friday. After the frontal passage and heading into the weekend, we could see a slight cool down Friday though Sunday with highs in the 70s and 80s.

On Saturday, a shortwave trough may cause low pressure to develop along the front, which could bring more rain, even if we are north of its track. The next cold front could approach from the Great Lakes next Sunday. Temperatures may fluctuate a little depending on what side of the front we're on, but likely fall some by next weekend, assuming the front pushes to the southeast.

AVIATION /15Z MONDAY THROUGH FRIDAY/
Mainly VFR with lowering precip chances through tonight. Widely scattered TS possible this afternoon/evening. Incoming 12Z computer models are a bit more consistent on timing and coverage, so added PROB30 groups with 15Z amendments. NW flow 7-12 kts is expected, perhaps becoming briefly a bit more W this evening before shifting to N by daybreak Tue. IFR CIGs /fog possible especially near MRB/CHO after 06Z tonight.

VFR with return to S flow Wednesday, then potential showers and thunderstorms re-enter the forecast through Friday.

MARINE
Generally light winds are expected through the upcoming week. A brief period of marginal SCA southerly channeling is possible Wednesday evening. Otherwise, NW winds today briefly shift to W this evening, then N Tuesday before returning to S Wednesday. A few thunderstorms are possible and may prompt a couple Special Marine Warnings this afternoon and evening. A cold front may bring additional thunderstorms Thursday into Friday.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.