Marine Weather Net

Tidal Potomac from Indian Head to Cobb Island MD Marine Forecast


THIS AFTERNOON

S
WINDS
5 KNOTS

TONIGHT

SW
WINDS
5 - 10
KNOTS

SUN

SW
WINDS
5 - 10
KNOTS

SUN NIGHT

NW
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ536 Forecast Issued: 138 PM EDT Sat May 21 2022

This Afternoon...S Winds 5 Kt. Waves Less Than 1 Ft.
Tonight...Sw Winds 5 To 10 Kt. Waves 1 Ft.
Sun...Sw Winds 5 To 10 Kt. Waves 1 Ft. Showers And Tstms Likely.
Sun Night...Nw Winds 5 To 10 Kt. Waves 1 Ft. Showers And Tstms Likely.
Mon...N Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers.
Mon Night...N Winds 5 Kt. Waves Less Than 1 Ft. A Chance Of Showers.
Tue...E Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers Through The Day. A Chance Of Showers After Midnight.
Wed...Se Winds 5 Kt. Waves Less Than 1 Ft. A Chance Of Showers. Winds And Waves Higher And Visibilities Lower In And Near Tstms.
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
304pm EDT Sat May 21 2022

Synopsis
High pressure will remain off the southeast coast through Sunday. A strong cold front will cross the region late Sunday into Sunday night before stalling over the Carolinas early next week. The boundary will likely return north as a warm front Wednesday through Thursday as low pressure passes by to the west. The cold front associated with that low may impact the area late next week.

Near Term - Through Tonight
Upper-level ridging combined with a southerly flow around high pressure over the Atlantic is causing unseasonably hot conditions this afternoon. Highs will be in the lower to middle 90s for many locations with heat indices in the mid to upper 90s. The mountains will be cooler as well as locations along the shore of the Chesapeake Bay (highs in the 80s).

A capping inversion persists this afternoon, but it may be eroded some as shortwave energy approaches from the south. A weak surface trough and terrain circulation will act as lifting mechanisms late this afternoon and evening. This may trigger a few showers and t-storms near and west of the Blue Ridge and Catoctin Mountains. Still feel that coverage will be isolated given the capping inversion, weak shear, and weakening mid-level lapse rates. However, with the intense heat in place there is enough instability for any storm to produce gusty winds/hail.

The shortwave will pass through late this evening and overnight. This may trigger a couple showers, but again coverage will be isolated since instability will be limited given the loss of daytime heating. Will also have to watch a convective system from the west that will approach during this same time. Most guidance shows that weakening as it gets into our area, and this makes sense given the unfavorable timing when this will be moving through. Warm and humid conditions are expected tonight with lows in the 60s and 70s (warmest near and east of Interstate 95).

Short Term - Sunday Through Monday Night
High pressure will remain over the western Atlantic Sunday, and a southwest flow will cause more hot and humid conditions. A cold front will approach from the northwest through midday before passing through Sunday afternoon into Sunday evening. The upper-level disturbance associated with this system will pass by well to the north and west, but it will increase the deep layer shear a bit (20-30 knots most likely). Moderate CAPE is expected ahead of the cold front due to the high heat and humidity, and this will combine with forcing from the cold front and a surface trough, significantly increasing the chances for showers and thunderstorms.

Steep low-level lapse rates, mid-level dry air, stronger forcing, and moderate CAPE suggests that storms may be strong to severe, with damaging wind gusts and large hail being the primary threats. The most likely time period for strong to severe storms will be between 1pm and 9pm (earlier to the north and west, and later to the south and east).

The cold front will move off to the south Sunday night before stalling over the Carolinas for Monday through Monday night. Much cooler air is expected to move in behind the boundary beginning Sunday night. Drier conditions will move in for most areas Sunday night behind the cold front. However, a longwave upper-level trough will build over the central CONUS and lower pressures will cause the low-level flow will turn to the south, allowing for warm and moist air to overrun the cooler air in place. This will result in plenty of clouds along with a chance for rain.

Long Term - Tuesday Through Saturday
A front will remain to the south of the region on Tuesday. The positioning of the front to the south will result in onshore flow through the day on Tuesday with forecast soundings showing saturated low to mid levels resulting in the potential for showers and drizzle throughout the day. This will result in continued cloudcover with highs only in the 70s. Undercut NBM guidance on Tuesday due to continued issues with NBM resulting in positive high temperature biases in CAD/onshore flow set-ups.

This front will move northward Wednesday as a warm front. This will result in a return flow developing out of the south resulting in a moisture and temperature return. Thursday the region likely remains in the warm sector with the associated cold front to the west of the region across the Ohio valley. Guidance continues to remain in decent agreement with the cold front moving through the region Friday. Subtle differences exist with the timing of the front, which in turn will play a role in how much instability develops ahead of the frontal passage. The forcing is better to the north, but nonetheless the potential for showers and thunderstorms are possible along the frontal passage.

Marine
A south to southwest flow will channel up the middle portion of the Bay and lower Tidal Potomac River tonight into Sunday morning. An SCA (Small Craft Advisory) is in effect. A cold front will pass through the waters late Sunday into Sunday evening. An SCA (Small Craft Advisory) may be needed for portions of the waters later Sunday night into Monday behind the cold front. An onshore flow will develop early next week.

Thunderstorms are likely over the waters Sunday afternoon and evening. Strong winds are possible and Special Marine Warnings will likely be warranted.

Winds begin easterly on Tuesday before veering to southerly by Wednesday. Winds likely remain below SCA (Small Craft Advisory) levels, however marine fog is possible during this time.

Tides / Coastal Flooding
A persistent southerly flow will lead to elevated tide levels with a few tidal sites reaching action stage over the next 48 hours.

Climate
Hot weather is forecast today through Sunday with temperatures likely 10 to 20 degrees above normal. Below is a list of temperature records today and Sunday (May 21st-22nd).

Winds begin easterly on Tuesday before veering to southerly by Wednesday. Winds likely remain below SCA (Small Craft Advisory) levels, however marine fog is possible during this time. -------------------------------------------------------------- Record Daily Warm Low Temperatures for May 21st -------------------------------------------------------------- Washington DC area........71 F (set in 1996).................. Baltimore MD area.........71 F (set in 1934).................. Sterling/Dulles VA area...67 F (set in 2013 and 1996)......... Martinsburg WV area.......65 F (set in 1996 and 1911)......... --------------------------------------------------------------

-------------------------------------------------------------- Record Daily High Temperatures for May 21st -------------------------------------------------------------- Washington DC area........95 F (set in 1934).................. Baltimore MD area.........96 F (set in 1934).................. Sterling/Dulles VA area...92 F (set in 1996).................. Martinsburg WV area......100 F (set in 1934).................. --------------------------------------------------------------

-------------------------------------------------------------- Record Daily Warm Low Temperatures for May 22nd -------------------------------------------------------------- Washington DC area........71 F (set in 1959).................. Baltimore MD area.........71 F (set in 1903).................. Sterling/Dulles VA area...67 F (set in 1975).................. Martinsburg WV area.......68 F (set in 1959).................. --------------------------------------------------------------

-------------------------------------------------------------- Record Daily High Temperatures for May 22nd -------------------------------------------------------------- Washington DC area........96 F (set in 1941).................. Baltimore MD area.........98 F (set in 1941).................. Sterling/Dulles VA area...89 F (set in 2021).................. Martinsburg WV area.......98 F (set in 1934).................. --------------------------------------------------------------

Temperature records for the Washington DC area have been recorded at what is now Ronald Reagan Washington National Airport (KDCA) since 1941. The official weather record consists of that data back to 1945, and observations taken in downtown Washington from 1872 through 1944.

Temperature records for the Baltimore MD area have been recorded at what is now Baltimore-Washington International Thurgood Marshall Airport (KBWI) since 1950. The official weather record consists of that data, and observations taken in downtown Baltimore from 1872 through 1949.

Temperature records for the Sterling/Dulles VA area have been recorded at what is now Washington Dulles International Airport (KIAD) since 1960. The official weather record consists solely of that data.

Temperature records for the Martinsburg WV area have been recorded at what is now Eastern West Virginia Regional Airport (KMRB) since 1938. The official weather record consists of that data back to 1944, and observations taken in downtown Martinsburg from 1891 through 1943.

All climate data is considered preliminary until reviewed and certified by the National Centers for Environmental Information (NCEI).

NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...None. MD...None. VA...None. WV...None.

Marine
Small Craft Advisory from 6pm this evening to 10am EDT Sunday for ANZ533-534-537-543.