Tidal Potomac from Cobb Island MD to Smith Point VA Marine Forecast
|Overnight...N Winds 5 Kt. Waves Less Than 1 Ft.|
|Sat...Nw Winds 5 To 10 Kt. Waves 1 To 2 Ft.|
|Sat Night...N Winds 5 To 10 Kt. Waves 1 Ft.|
|Sun...E Winds 5 Kt. Waves Less Than 1 Ft.|
|Sun Night...Se Winds 10 To 15 Kt With Gusts To 20 Kt. Waves 1 To 2 Ft. Rain.|
|Mon...Se Winds 10 To 15 Kt...Becoming S In The Afternoon. Gusts Up To 25 Kt. Waves 3 Ft. Rain.|
|Mon Night...W Winds 10 Kt With Gusts To 20 Kt. Waves 1 To 2 Ft.|
|Tue...W Winds 10 To 15 Kt. Waves 2 Ft.|
|Wed...W Winds 5 To 10 Kt. Waves 1 Ft.|
| Area Forecast Discussion|
National Weather Service Baltimore MD/Washington DC
915pm EST Fri Nov 27 2020
Weak high pressure remains situated over our region this afternoon. A weak cold front will pass through our region on Saturday with high pressure returning for the second half of the weekend. A strong system will impact our region late Sunday through early Tuesday. High pressure builds into our region from the south Tuesday through the middle parts of next week.
Near Term - Through Saturday
A weak cold front has crossed southeast of the region, with another upstream over the lower Great Lakes as of mid evening. The trailing front has the aid of an upper-level shortwave trough/vorticity ribbon. Given the upstream satellite/observations and trough, I'm hesitant to think clouds will clear much prior to daybreak. Additional mid-level clouds are expanding toward the region from convection over the Gulf Coast, as well.
There are a few breaks in the clouds, and for that reason temperatures will likely fall a few degrees given the light wind in place, but probably won't fall much lower than the upper 30s to lower 40s. A sprinkle can't be ruled out, but chances are low given meager forcing east of the Allegheny Front. Along and west of the Allegheny Front, upslope flow may result in patchy light rain or drizzle, some of which may freeze at elevations above 3,000 to 3,500 feet.
Clouds should break by around midday Saturday as a northwesterly breeze kicks up behind the front. Wind gusts up to 25 mph are possible, and the downsloping component coupled with clearing should result in high temperatures in the 50s to near 60.
Short Term - Saturday Night Through Sunday Night
Weak upper level ridging will be in place over our region on Sunday with high pressure slowly shifting eastward out of our region later in the day. Clear skies along with light winds will continue through Sunday afternoon. The main change in the winds will be a slight shift out of the south but moisture transport should be minimal. Daytime temperatures will be similar to Saturday if not slightly cooler due to a lower morning start than the previous two days.
The weather pattern starts to change late Saturday afternoon and into Saturday evening. High pressure shifts off the coast and winds become more southeasterly. A strong frontal system will approach our region from the southwest Saturday evening. An upper level trough will move through parts of the southern US while a surface low slowly moves northeastward along the western side of the Appalachians. A secondary low is forecast to form off the east coast and move eastward early on Monday. The low moving along the Appalachians is forecast to occlude toward the upper level low and a triple point low will form as the system approaches our region. Precipitation associated with this system will start to impact our region after 00z Monday and widespread precipitation is forecast by 12Z. There remains some uncertainty on the timing and position of the multiple lows but a threat for strong gusty and thunderstorms will continue to be possible on Monday.
Long Term - Monday Through Friday
More agreement beginning to churn on the location of the cutoff low that will be impacting the area by late Sunday night into early Monday morning. Most models are agreeing on the center of the low to be over the WV/OH border by 12z Monday. Any variations in the dynamics of this system could cause a major shift in the forecast. For now, expect the likelihood for heavy rain and isolated instances of damaging winds possible Monday during the afternoon and early evening. Surface convective instability remains questionable at this point for the potential for thunderstorms. Given the chance for strengthening low and mid-level wind fields during the time period, expect gusty winds to be our main concern for Monday into early Tuesday. Flooding concerns remain low at this time given the speed of this system with Quantitative Precipitation Forecast values only reaching around 1.25" for a 36 hour timeframe.
Upslope snow threat for along and west of the Allegheny Front will be the main concern after the low moves off and backside cold air moves in. This will continue from around Monday night until possibly Wednesday morning, confidence in duration and intensity is low at this time with respect to wintry impacts for those particular areas. On Monday, temperatures will be the warmest for the extended period at around 60F with this surge of moisture from the SSW keeping us in a warm, unstable pattern. Conditions should dry out for most of the area (aside from wintry precipitation for the western zones) Tuesday into Thursday with high pressure building in from the deep south. After the low passes on Monday night/Tuesday morning, we will see temperatures drop into the low to mid 40s for most of the workweek with overnight lows possibly getting to at or below freezing. Our western zones will be a few degrees colder for the duration, allowing for the chance for the wintry precipitation to occur at higher elevations.
A light wind is forecast over the marine district overnight behind a weak cold front. A second weak cold front will cross Saturday by about midday, with a period of 15-20 kt gusts forecast Saturday afternoon. A Small Craft Advisory has been issued for the upper tidal Potomac River and the Chesapeake Bay and adjoining estuaries north of Drum Point MD. Further south, confidence in SCA (Small Craft Advisory) level gusts is lower, but if it happens it could persist into the evening.
Light wind is forecast Saturday night through Sunday evening as high pressure passes overhead. SE flow likely increases markedly by daybreak Monday.
Gales likely Monday with low pressure passing through our waters. Winds will shift from the southeast to westerly by late Monday night. SCAs (Small Craft Advisories) likely to remain through Tuesday behind the passing low.
Tides / Coastal Flooding
Onshore flow will increase Monday. Most guidance that goes out that far shows at least minor flooding, with SFAS showing moderate at Annapolis. The S/SE trajectory combined with strong low pressure passing just west of the waters supports widespread tidal flooding, but confidence in moderate flooding is low at this juncture given the quick-moving nature of the system.
NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...None. MD...None. VA...None. WV...None.
Small Craft Advisory from noon to 6pm EST Saturday for ANZ530>533-535-538>541.