Tidal Potomac from Indian Head to Cobb Island MD Marine Forecast
| Rest Of This Afternoon...Se Winds 10 Kt With Gusts To 20 Kt. Waves 1 Ft. A Chance Of Showers And Tstms. |
| Tonight...Se Winds 10 To 15 Kt With Gusts To 20 Kt... Becoming E 5 Kt Late. Waves 1 Ft. |
| Mon...E Winds 5 To 10 Kt. Waves 1 Ft. |
| Mon Night...Se Winds 5 To 10 Kt. Waves 1 Ft Or Less. |
| Tue...E Winds Around 5 Kt. Waves 1 Ft Or Less. |
| Tue Night...Sw Winds Around 5 Kt. Waves 1 Ft. |
| Wed...Sw Winds 5 To 10 Kt. Waves 1 Ft. |
| Thu...Nw Winds Around 5 Kt. Waves 1 Ft. Winds And Waves Higher And Visibilities Lower In And Near Tstms. |
| Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 312pm EDT Sunday July 12 2026 .WHAT HAS CHANGED... No major changes have been made to the forecast this afternoon. We continue to monitor showers and thunderstorms currently developing across the area. .KEY MESSAGES... - 1) Showers and a few thunderstorms are expected this afternoon into this evening. - 2) Heat and humidity return for the middle and second half of the week. - 3) Scattered thunderstorm development is anticipated during the the second half of the week in a moderately unstable and sheared environment. KEY MESSAGE 1...Showers and a few thunderstorms are expected this afternoon into this evening. The front that moved through overnight has now stalled out across northern NC and southwestern VA. Winds have turned out of the east to northeast to the north of the front. A warm, humid airmass remains in place at low-levels, with surface dewpoints still in the upper 60s and lower 70s. Showers and thunderstorms have started to Probability of Precipitation up across the area, with the greatest coverage currently from DC southward along the I-95 corridor, and then westward into Central Virginia and the Central Shenandoah Valley. The most well developed area of showers and storms is located over the Potomac at the moment, and will continue to drift westward over time, primarily impacting Central Virginia, and then eventually the Central Shenandoah Valley. The 12z IAD sounding shows near saturation up to about 650 hPa, with drier air in the mid to upper levels of the atmosphere. In contrast, the 12z RNK sounding shows near saturation all the way through the depth of the troposphere (highlighting the more favorable environment for showers and storms to the south). Model guidance also shows this gradient in mid- upper level moisture from north to south across the forecast area. Thus far, showers have progressed from east to west within the low- level easterly flow. There is a bit of west to northwesterly flow at higher levels of the atmosphere, so if storms were to deepen, they may actually slow down, with most model soundings and the 12z IAD sounding showing LCL-EL mean winds of less than 5 kt. Deeper convection, and by proxy slower storm motions, may become more favored to the south (across Central Virginia and the Central Shenandoah Valley), where the deeper moisture may promote storms growing taller and tapping into the west to northwesterly flow aloft, which would counter low-level easterlies and create slower storm motions. The deeper moisture would also limit cold pool(a region of relatively cold air) development and associated propagation compared to storms further to the north. With the around 1000 J/kg of MLCAPE, slow storm motions, and deep warm cloud layers (around 14k ft) heavy rainfall should be the primary threat with storms today. There could potentially be an isolated instance or two of flash flooding from the Central Shenandoah Valley to Central Virginia today, especially if any storms are able to anchor to higher terrain in the light easterly upslope flow. However, background drought conditions and resultant high flash flood guidance values could potentially be limiting factors. WPC currently has far southwestern portions of the forecast area (Charlottesville, Staunton area) outlooked in a Slight Risk (level 2 of 4) for excessive rainfall, with a Marginal Risk (level 1 of 4) extending northeastward to a line roughly from Fredericksburg to Culpeper to Petersburg. Chances for showers and thunderstorms should wind down later this evening with loss of daytime heating. Primarily dry conditions are expected overnight. KEY MESSAGE 2...Heat and humidity return for the middle and second half of the week. Upper high centered over the Dakotas early in the week is expected to expand eastward cresting over the area Tuesday evening. This will support high temperatures in the upper 90s, but dewpoints will not be terribly too high in the 60s. By Thu and Fri, low level moisture returns into the area with dewpoints in the upper 60s to near 70 resulting in heat indices near 100 degs which is still below heat advisory criteria. While it will be hot, it won't be as hot as it was during the first weekend of July. KEY MESSAGE 3...Scattered thunderstorm development is anticipated during the the second half of the week in a moderately unstable and sheared environment. During the second half of the week, the upper ridge centered over the Dakotas early in the week will build westward with time while the eastern Canada trough digs southward. This results in moderately strong flow aloft across the area with the synoptic pattern becoming favorable for thunderstorm clusters or MCSs to form over the upper Great Lakes and upper Midwest to track southeastward into the OH Valley and Mid-Atlantic states. The earliest we could see thunderstorms it seems to be Thu, but with higher probs of thunderstorms Fri into Sat and likely extending it beyond that. Marine Winds will remain out of the east this afternoon. SCAs (Small Craft Advisories) are in effect later this afternoon through tonight for the Lower Tidal Potomac and our southernmost Bay zones. Elsewhere, MWSs or SMWs may be needed at times as showers and thunderstorms move over the waters. Any showers or thunderstorms should come to an end this evening shortly after sunset. Thereafter, great boating weather is expected Monday through mid week with no thunderstorm potential. Winds will generally be out of the southeast tomorrow, south on Tuesday, southwest on Wednesday, and northwest on Thursday. Tides / Coastal Flooding Elevated water levels will persist for the next couple of days with minor coastal flooding becoming increasingly likely Monday into Tuesday as southerly flow strengthens. NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories DC...None. MD...None. VA...None. WV...None. Marine Small Craft Advisory until 4am EDT Monday for ANZ534-537-543. |
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