Marine Weather Net

Tidal Potomac from Indian Head to Cobb Island MD Marine Forecast


REST OF THIS AFTERNOON

W
WINDS
5 KNOTS

TONIGHT

W
WINDS
5 - 10
KNOTS

WED

NW
WINDS
10 - 15
KNOTS

WED NIGHT

NW
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ536 Forecast Issued: 343 PM EST Tue Jan 19 2021

SMALL CRAFT ADVISORY IN EFFECT UNTIL 6 PM EST THIS EVENING ...SMALL CRAFT ADVISORY IN EFFECT FROM WEDNESDAY MORNING THROUGH WEDNESDAY AFTERNOON...
Rest Of This Afternoon...W Winds 5 Kt. Waves Less Than 1 Ft.
Tonight...W Winds 5 To 10 Kt. Waves 1 Ft.
Wed...Nw Winds 10 To 15 Kt With Gusts To 30 Kt. Waves 2 To 3 Ft. Scattered Flurries.
Wed Night...Nw Winds 5 To 10 Kt...Becoming S After Midnight. Waves 1 Ft.
Thu...Sw Winds 5 To 10 Kt With Gusts To 20 Kt. Waves 1 Ft.
Thu Night...W Winds 5 To 10 Kt With Gusts To 20 Kt. Waves 1 Ft.
Fri...Nw Winds 5 To 10 Kt. Waves 1 Ft.
Sat...Nw Winds 5 To 10 Kt. Waves 1 Ft.
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
259pm EST Tuesday Jan 19 2021

Synopsis
A low pressure system sliding through the Great Lakes region into the northeast will bring a cold front through the region late tonight into Wednesday morning. An upper level disturbance will swing through on Wednesday. A cold front will cross the area Thursday night, before high pressure builds back in from the northwest through the weekend.

Near Term - Through Tonight
A stratocumulus deck lingers across the southern one- third of our CWA. Mainly sunny skies in the northern two- thirds of our zones the remainder of this afternoon. We have bumped up our high temperatures in the north and central zones due to plenty of sunshine and a downslope flow from the west. High temperatures will be above average, reaching into the upper 40s to lower 50s. The highest ridges out west will have below freezing temperatures as upslope snow tapers and then ends by late this afternoon.

A vigorous shortwave will dive across our region overnight into Wednesday morning. This will allow for upslope snow showers along/west of the Allegheny Front. Most of this activity falls in the morning hours on Wednesday, but snow showers will continue into the afternoon, as well. Accumulations of 2 to 4 inches are expected. A Winter Weather Advisory for Garrett County in western MD, and western Grant and Pendleton counties in eastern WV remain in effect from 1am tonight through 1pm Wednesday.

Elsewhere, a couple of snow showers could venture across northern Virginia and northcentral Maryland along the Mason- Dixon line. Perhaps we could even get a few flurries or a snow shower as far south as DC. Best timing for this would be the middle of the night through mid-morning Wednesday. We still don't think much will stick given the surface temperatures will be in the middle 30s. Primarily the grassy surfaces could see a coating to nearly an inch.

Short Term - Wednesday Through Thursday Night
Along with some early and mid-morning snow showers or flurries, gusty northwest winds will become a factor Wednesday. Wind gusts will increase shortly after sunrise, with wind gusts up to 40 mph possible through sunset Wednesday. High temperatures only in the mid 30s to low 40s, this will keep wind chills into the mid 20s to low 30s for the non- mountainous regions. For the mountains, wind chills will reach the single digits, and may even drop below 0.

Winds should diminish by later Wednesday evening as the pressure gradient weakens and the main mid-level support pivots to our east. By the overnight hours, lows will dip into the low to mid 20s in most areas, with low to mid teens expected across the mountains.

Quiet weather returns for Thursday. High pressure to the south will be slowly trying to push offshore, bringing temperatures back up into the mid 40s. A front will approach from the northwest. This boundary has very little in the way of an air mass change to come along with it, and will have no moisture either. So other than a push of gusty winds during the afternoon, not much to speak of with this system. Low temperatures Thursday night dip into the 20s and low 30s.

Long Term - Friday Through Tuesday
Zonal flow aloft on Friday will yield quiet weather conditions across the area. Winds at low levels will also be westerly, so downslope flow will allow temps to climb to near or slightly above normal Friday afternoon. A shortwave embedded within the zonal flow aloft will pass through the area Friday evening, ultimately driving a cold front through at the surface Friday Night. A little upslope snow may be possible along the Allegheny Front in the wake of the front Friday Night, but this activity should quickly wind down on Saturday as subsidence builds in behind the departing shortwave. Saturday will be windy and noticeably cooler, with highs in the 30s for most. High pressure will build overhead Saturday Night into Sunday, causing winds to weaken. Temperatures will remain cool on Sunday, with high again only in the 30s to near 40.

The pattern turns more active heading into early next week. A cutoff upper low over the Desert Southwest/Northern Mexico will be whisked eastward and reabsorbed into the westerlies later Sunday into Monday. As it tracks rapidly east, it will tap into deep moisture in the Gulf and start to draw that north toward our area. This moisture should eventually overrun cold air in place at the surface, with a high initially situated off to our north and east. A lot can change over the next several days, but wintry precipitation at least appears possible, especially over far northern portions of the forecast area. We'll continue to monitor this system over the upcoming week.

Marine
A Small Craft Advisory remains in effect through 6pm this evening. Winds will diminish rather quickly into the evening hours.

As for Wednesday, gusty northwest winds are expected and a Small Craft Advisory is in effect for the waters. A Gale Warning may be needed for portions of the waters during this time. However, confidence for Gale Force winds were not high enough at this time for a warning, since there is some uncertainty as to exactly how high the mixing layer will be, and consequently whether there will be 35 kt at the top of the mixing layer vs winds around 30 kt. Winds will diminish Wednesday night as high pressure builds overhead, but an SCA (Small Craft Advisory) will likely be needed for portions of the waters, especially Wednesday evening.

For Thursday, Small Craft Advisories again possible, especially over the lower Bay and lower tidal Potomac. This in response to an approaching frontal boundary.

Small Craft Advisories will likely be needed on both Friday and Saturday as a result of strong northwesterly flow.

NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...None. MD...Winter Weather Advisory from 1am to 1pm EST Wednesday for MDZ001. VA...None. WV...Winter Weather Advisory from 1am to 1pm EST Wednesday for WVZ501-505.
MARINE...
Small Craft Advisory until 6pm EST this evening for ANZ530>543. Small Craft Advisory from 5am to 6pm EST Wednesday for ANZ531>534-537-539>541-543. Small Craft Advisory from 8am to 6pm EST Wednesday for ANZ530-535-536-538-542.