Marine Weather Net

Tidal Potomac from Indian Head to Cobb Island MD Marine Forecast


TONIGHT

S
WINDS
10 - 15
KNOTS

THU

S
WINDS
20 - 25
KNOTS

THU NIGHT

W
WINDS
5 - 10
KNOTS

FRI

W
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ536 Forecast Issued: 641 PM EST Wed Jan 23 2019

GALE WARNING IN EFFECT THROUGH THURSDAY AFTERNOON
Tonight...S Winds 10 To 15 Kt With Gusts To 20 Kt... Increasing To 20 Kt With Gusts To 30 Kt Late. Waves 1 To 2 Ft. Rain. Vsby 1 Nm Or Less After Midnight.
Thu...S Winds 20 To 25 Kt With Gusts To 35 Kt... Becoming W 10 To 15 Kt With Gusts To 30 Kt Late In The Morning, Then Becoming Nw With Gusts To 25 Kt In The Afternoon. Waves 2 To 3 Ft. Rain. Vsby 1 Nm Or Less.
Thu Night...W Winds 5 To 10 Kt. Waves 1 Ft.
Fri...W Winds 5 To 10 Kt. Waves 1 Ft.
Fri Night...N Winds 5 To 10 Kt. Waves 1 Ft.
Sat...S Winds Around 5 Kt. Waves 1 Ft.
Sat Night...S Winds 5 Kt. Waves Less Than 1 Ft.
Sun...W Winds 5 To 10 Kt. Waves 1 Ft.
Mon...S Winds 5 Kt. Waves Less Than 1 Ft.
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
250pm EST Wednesday Jan 23 2019

Synopsis: A cold front approaching from the Ohio Valley will cross the Mid-Atlantic by Thursday afternoon. A disturbance will cross the region Friday. High pressure will follow for this weekend. Low pressure may affect the region early next week.

Near Term - Through Thursday
A cold front is moving east into the Ohio Valley as high pressure sits east of us. A southerly flow has settled over us allowing for warm and moist air advection. Temperatures are currently in the 40s for most areas, including a few 50s, and they are expected to increase overnight. Locations near or east of I-95 could get into the upper 50s, maybe some 60s tonight into Thursday morning.

Wind gusts today are in the upper teens and into the 20s as gradient increases (a few near 30 mph in the lowlands), also with a strong low level jet. At the ridges, wind gusts have been observed at 50+ mph, and with forecast soundings suggesting strong winds continuing overnight, we have issued a Wind Advisory through tonight for these locations. Elsewhere, breezy (sub advisory) conditions expected. A High Wind Warning is in effect for the central Virginia Blue Ridge where peaks are above the inversion and poking into a 65 kt LLJ.

As the cold front approaches our area this evening and into tonight, chances of rain and drizzle increases. The front is expected to move across our CWA on Thursday morning. Shortwave energy along with the strong low level jet will allow for more widespread rain, which could be heavy at times, with total Quantitative Precipitation Forecast values between 0.80 and 1.5 inches across our CWA, with isolated higher amounts up to 2 inches. Some of this may fall in a period of about 3 hours late tonight into early Thursday morning. A Flood Watch is in effect from late tonight into Thursday afternoon over areas where we expect the deepest moisture (central VA and east of Blue Ridge). Isolated flooding over other locations may be possible. See Hydro Section below for more details.

A period of damaging wind gusts is possible ahead of the cold front Thursday morning as hi-res guidance unanimously shows a strong narrow cold frontal rain band coincident with LLJ of 65+ kts at 2-3kft. Wind Advisory in effect to account for hybrid synoptic/convective winds tomorrow morning (right around rush hour) in the Baltimore/DC metros and S MD.

Temperatures will fall behind the front late Thursday morning and into the afternoon with northwesterly flow settling in. Rain will also be moving away, and a possible period of snow is possible west of the Allegheny Front into Thursday afternoon

Short Term - Thursday Night Through Friday Night
Cold front/low pressure and initial upper trough will push east Thursday night. A stout trailing upper level trough will pivot across the region Friday. Snow Squall Parameters light up across the northern half of the CWA around midday Friday (factors in instability, moisture and wind; values over 1 indicate snow squall potential and values up to 5 are forecast over N MD). For this reason, even though models aren't printing out much Quantitative Precipitation Forecast explicitly, have a chance of snow showers near and north of US-50 focused around midday.

Gusty NW winds will usher in a reinforcing shot of Arctic air Friday night.

Long Term - Saturday Through Wednesday
For the weekend, the region remains entrenched underneath the base of an upper-level trough. At the surface, high pressure will be stretched along the eastern US. This will result in a dry pattern overall for much of the CWA. However, a few impulses of shortwave energy will swing through the area around the base of the primary upper trough, which could bring a few chances for some precipitation. The first of those swings through Saturday, with the only precipitation threat being some upslope snow showers along the Allegheny Front. Otherwise, the rest of the region remains dry, with temperatures in the low to mid 30s. On Sunday, a weak area of low pressure will track across southern Canada, swinging a cold front through the area by Sunday evening. This front has a chance to bring some rain or snow showers to the region Sunday night, with areas west of the Blue Ridge having the greatest chance. High temperatures will be a bit milder Sunday when compared to Saturday.

Monday and Tuesday, things start to get a little more active. A short wave will slide down into the central CONUS out of southwest Canada, bringing a potent surface low pressure system along with it. Ahead of this area of low pressure, will get a period of warm advection on Monday. Keeping slight chance POPs in the forecast for Monday in association with the warm front, but not looking very likely at this point. The best chance of precipitation comes on Tuesday, as the cold front approaches, while the surface low tracks to our northwest at this time, though it should be noted the upper pattern is highly volatile. Some guidance has been hinting at two pieces of energy phasing, bringing a low pressure system up the eastern seaboard during this time

Marine Discussion
Southerly flow over the waters will continue into tonight ahead of a cold front as a high pressure sits offshore. This cold front is expected to move across the waters on Thursday morning, with winds shifting to the northwest behind it. A Small Craft Advisory in effect through tonight as gradient increases ahead of the front. A Gale Warning is in effect over the waters from Thursday morning and into the afternoon as winds likely gust 35-40 knots along and ahead a convective line/strong front that will move across the waters Thursday morning. Gusty winds behind the front could also reach Gale Warning criteria briefly. A few gusts around 50 kts can't be ruled out right ahead of the front late Thursday morning.

Small Craft Advisory gusts possible behind reinforcing cold front Friday afternoon and night.

High pressure will reside over the waters on Saturday with light winds and sub Small Craft Advisory conditions expected. Winds will increase Saturday night through Sunday night as the high shifts offshore and return flow increases ahead of another cold front, bringing the potential for Small Craft Advisory conditions over portions of the waters.

Hydrology
Overall, not much has changed in the water-related setup for the overnight/Thursday event. Rain of generally around an inch (with isolated higher amounts, especially in a potential developing line east of the Blue Ridge) plus some snowmelt, will promote significant within-bank rises on most rivers, and some out-of-bank rises on more susceptible rivers. A Flood Warning is now in effect for Opequon Creek near Martinsburg (again). Flood Watches are out for the South Branch Potomac at Franklin WV, and the Cacapon River in Morgan County WV. Other small streams have flood potential as well, and the overall Flood Watch remains in place for counties/cities where the heaviest rain is currently expected, mostly east of the Blue Ridge.

Looking further ahead, mainstem river flooding on the Potomac is possible Friday through Saturday, but uncertainty in rain amounts and snowmelt precludes issuance of watches for these areas at this time. This will be assessed again on Thursday

Tides / Coastal Flooding
Tidal anomalies will continue to increase into Thursday as southerly flow persists over the waters. The potential for minor flooding will exist as a result, however, given a large spread in guidance and uncertainty in the strength of surface winds, confidence is low at this time

NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...Flood Watch from late tonight through Thursday afternoon for DCZ001.
Wind Advisory from 6am to noon EST Thursday for DCZ001. MD...Flood Watch from late tonight through Thursday afternoon for MDZ004>006-011-013-014-016-503>508.
Wind Advisory from 6am to noon EST Thursday for MDZ011-013- 014-016>018-503>506. VA...Flood Watch from 10pm EST this evening through Thursday morning for VAZ025-036-503-504-508.
Wind Advisory until 6am EST Thursday for VAZ503-507. High Wind Warning until 6am EST Thursday for VAZ508.
Flood Watch from midnight EST tonight through Thursday afternoon for VAZ037>040-050-051-507.
Flood Watch from late tonight through Thursday afternoon for VAZ052>056-501-502-505-506.
Wind Advisory from 6am to noon EST Thursday for VAZ052>057- 502-506. WV...Wind Advisory until 6am EST Thursday for WVZ505.
MARINE...
Small Craft Advisory until 6am EST Thursday for ANZ530>543.
Gale Warning from 6am to 6pm EST Thursday for ANZ530>543

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