Tidal Potomac from Cobb Island MD to Smith Point VA Marine Forecast
|This Afternoon...E Winds 10 To 15 Kt With Gusts To 20 Kt. Waves 2 Ft. Scattered Showers With Isolated Tstms.|
|Tonight...Ne Winds 10 To 15 Kt. Gusts Up To 25 Kt. Waves 2 To 3 Ft. A Chance Of Showers. Vsby 1 Nm Or Less.|
|Fri...N Winds 10 To 15 Kt With Gusts To 25 Kt. Waves 2 To 3 Ft. Showers Likely. Vsby 1 Nm Or Less.|
|Fri Night...W Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers.|
|Sat...Sw Winds 5 To 10 Kt. Waves 1 Ft. Showers Likely With A Chance Of Tstms.|
|Sat Night...Sw Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers And Tstms.|
|Sun...Sw Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers And Tstms.|
|Mon...Sw Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Tstms. A Chance Of Showers. Winds And Waves Higher And Visibilities Lower In And Near Tstms.|
Area Forecast Discussion|
National Weather Service Baltimore MD/Washington DC
303pm EDT Thu July 9 2020
Low pressure to the south of the Outer Banks will slowly move northward along the mid-Atlantic Coast through Friday before moving off to the northeast Friday night. The low may develop tropical characteristics during this time. This possibility will have to be monitored. An upper level trough of low pressure will build overhead Saturday while a cold front passes through the area. The upper level trough will hang around for early next week.
Near Term - Until 6am Friday Morning
The outer periphery of cirrus bands of the low pressure to the south of the Outer Banks are spiraling over lower southern Maryland at this time. Very little shower activity, if any, crossing over southern Maryland on radar. There could be a couple of sprinkles or a brief shower over southern Maryland during the next couple of hours. Rain amounts will be light.
The low pressure will move northward along the mid-Atlantic Coast this afternoon and tonight. Additional rain showers will develop and move across southern Maryland and far eastern Virginia into tonight. There is still some uncertainty to whether the low pressure develops tropically and how close it is or moves over the mid-Atlantic Coast.
While the 12z GFS hasn't changed its path of the low moving over the Delmarva Peninsula and New Jersey, the 12z NAM and the EUROPEAN model have switched places in the track of the low. The NAM now keeps it and takes it farther offshore, while the EUROPEAN model moves it over the Delmarva Peninsula. Consensus of the convective models and the 12z NAM has the western edge or gradient of the heavier rainfall to be over the western Chesapeake Bay and along the western shore. The GFS and EUROPEAN have a consensus of dropping 1 to 2 inches of rain from St. Mary's County to Harford County. Nonetheless, whichever solution or combination of solutions, there appears to be a tight gradient of rainfall, from zero to a couple of inches. We are just not sure where that gradient sets up...west of the Chesapeake Bay or east of the Chesapeake Bay.
Short Term - 6am Friday Morning Through Saturday Night
The low will continue to move up the Mid-Atlantic Coast Friday before moving away from the area Friday night. While the gradient of the heaviest rainfall is yet to be determined, a more potent upper- level trough axis will approach from the west Friday afternoon and this may trigger a few showers and thunderstorms around the Potomac Highlands and Shenandoah Valley.
Drier conditions will likely return Friday night as the low moves away from the area. Still could see a few showers and perhaps a thunderstorm over the Potomac Highlands in response to the upper-level trough moving in from the west.
The upper-level trough will build overhead Saturday while a cold front slowly passes through the area later Saturday into Saturday night. This will bring the likelihood for showers and scattered thunderstorms. Some storms may be strong due to higher amounts of instability and increasing shear profiles. Convection should diminish later Saturday night with the loss of daytime heating.
Long Term - Sunday Through Wednesday
A cold front will pass through our region early Sunday morning and stall to the southeast of our region. Behind the frontal passage, winds will become light and mainly out of the west. An upper level trough will remain situated over our region through the day Sunday leading to lingering showers throughout the day Sunday. Temperatures will still be warm in the upper 80s to lower 90s during the day with overnight lows in the upper 60s to mid 70s.
Weak high pressure tries to build over our region through the early and middle parts of next week. Showers will be possible as the front to the southeast will be slow to shift out of our area and a weak upper level trough moves through Monday through Wednesday. The GFS does try to drop another low through our area Monday but this remains uncertain would bring a more widespread chance for showers and thunderstorms. 90 degree weather looks to continue through next week with the coolest day being Tuesday. Showers and even an isolated thunderstorm will continue to be possible through Wednesday due to the continued warm and humid conditions along with the weak trough a loft.
Low pressure will slowly move up the Mid-Atlantic Coast through Friday before moving off to the northeast Friday night. An increasing gradient will gradually cause northeast winds to increase tonight into Friday before turning toward the north and eventually northwest Friday night. A SCA (Small Craft Advisory) is in effect for the bay and lower Tidal Potomac during this time. The strongest winds are most likely late tonight through midday Friday with gusts around 30 knots possible south of Drum Point. The SCA (Small Craft Advisory) may need to be extended in area to include the upper Tidal Potomac River, but confidence is too low at this time due to uncertainties with the track and strength of the low.
Will have to continue to monitor the low, because it may develop tropical characteristics and there is still some uncertainty in regards to its exact track.
A cold front will pass through the waters later Saturday into Saturday night. A few stronger storms are possible Saturday afternoon and evening.
No Small Craft Advisories expected at this time but periods of stronger gusts will be possible within convective showers and thunderstorms.
Tides / Coastal Flooding
Anomalies near the DC waterfront could come close to reaching criteria as the low pressure moves to the north later this afternoon through Friday evening.
Easterly winds are expected to persist tonight into early Friday morning as low pressure tracks up the Mid- Atlantic coast. This will bring a continued threat for minor tidal flooding through the high tide cycle Friday morning, with the threat subsiding thereafter as northerly flow emerges.
NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...None. MD...None. VA...None. WV...None.
Small Craft Advisory from 6am to 6pm EDT Friday for ANZ530- 531-538-539. Small Craft Advisory from 6pm this evening to 6pm EDT Friday for ANZ532-533-540>542. Small Craft Advisory until 6pm EDT Friday for ANZ534-537-543.