Tidal Potomac from Cobb Island MD to Smith Point VA Marine Forecast
| Rest Of Tonight...Se Winds 10 To 15 Kt With Gusts To 20 Kt. Waves 2 Ft. Scattered Showers With A Slight Chance Of Tstms Late This Evening, Then Showers Likely With Vsby 1 To 3 Nm. |
| Tue...Se Winds 15 To 20 Kt With Gusts To 25 Kt. Waves 2 To 3 Ft. Showers. Vsby 1 Nm Or Less. |
| Tue Night...Se Winds 15 To 20 Kt. Gusts Up To 25 Kt Until Early Morning. Waves 3 Ft. Showers With A Chance Of Tstms. Vsby 1 Nm Or Less. |
| Wed...Se Winds 5 To 10 Kt. Waves 1 To 2 Ft. Showers Likely With A Chance Of Tstms. |
| Wed Night...S Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers And Tstms. |
| Thu...S Winds Around 5 Kt. Waves 1 Ft Or Less. A Chance Of Showers. |
| Thu Night...S Winds 5 Kt. Waves Less Than 1 Ft. |
| Fri...Sw Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers And Tstms Through The Night. A Chance Of Showers After Midnight. |
| Sat...Sw Winds 5 To 10 Kt. Waves 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 927pm EDT Monday May 12 2025 Synopsis An upper low will slowly drift northeastward toward the area through Wednesday, before shearing out and lifting to our northeast on Thursday. An area of low pressure will track into the Northern Plains/Western Great Lakes by Friday, before tracking eastward across Ontario, Quebec, and the Northeast this weekend. Near Term - Through Tuesday As of 9pm, water vapor imagery shows a well defined upper low centered over northern Alabama, with its attendant circulation encompassing much of the eastern US. At the surface, an accompanying surface low is located over east-central Alabama as well, with high pressure in place offshore. The latest upper air sounding shows some dry air in the lower 2000 feet of the atmosphere, then in portions of the mid-levels. Above the mid- levels, saturation is much more defined. It is a matter of time late this evening until more light intermittent or steady rain reaches the ground. For now, much of any rainfall of this magnitude or persistent will hit the ground mainly along and west of the Blue Ridge Mountains. To the east, sprinkles to perhaps an occasional shower will be felt. These could be some exception in Northeast Maryland as it is much drier in many levels so it may take an additional few hours into the past midnight timeframe until the rain reaches the ground. Most of the rain overnight should stay light, but a few embedded thunderstorms can't be ruled out. Any of these thunderstorms could be capable of producing a quick half inch to an inch of rain in an hour, but coverage of storms is expected to be low. A Flood Watch goes into effect for locations in the vicinity of the Blue Ridge at 2 AM, but most flooding impacts are expected to hold off until Tuesday into Tuesday night. Temperatures will remain mild overnight, with lows generally in the 60s (upper 50s mountains). Short Term - Tuesday Night Through Wednesday Night Previous discussion... The aforementioned upper low will continue to drift northeastward toward the area tomorrow, and will eventually become centered overhead during the day on Wednesday. A steady rain will continue through much of the morning tomorrow within the zone of large scale ascent downstream of the approaching upper low. As we work into the afternoon hours, a mid-level dry slot may start to work in from the southwest, which may allow for a few breaks of sun and some limited surface heating/development of surface based instability. If this occurs, thunderstorms may start to develop within the dry slot and lift northward into the area during the late afternoon/evening hours. These thunderstorms may be capable of producing heavier rainfall rates, and may potentially lead to some instances of flooding. The earlier issued Flood Watch was expanded to include all of the WV Panhandle, most of Northern Virginia, and Allegany County in Maryland. A general 2-4 inches of rain is expected by late Tuesday night across the watch area, with localized higher totals along the eastern facing slopes of the Blue Ridge and Alleghenies, where upslope southeasterly flow should enhance totals. Further north and east, rainfall totals are expected to be slightly lower, but an instance or two of flooding can't be completely ruled out. The steadier rain should come to an end from southwest to northeast during the second half of the night, with the Flood Watch ending as well late Tuesday night. The upper low will drift overhead on Wednesday. Some more breaks in the cloud cover are expected to form compared to Tuesday, which should lead to a bit stronger surface heating and a bit more instability. Showers and thunderstorms will form in response to that surface heating, and most locations will experience on and off showers and storms through the afternoon and evening hours. Although there doesn't appear to be a boundary to focus any thunderstorm activity, storm motions will be relatively slow beneath the upper low, and storms will be capable of producing heavy rainfall. Following heavy rains on Monday and Tuesday, some more localized instances of flooding may be possible. High temperatures on Wednesday should generally be in the 70s. Long Term - Thursday Through Monday A continued high amplitude pattern remains in place across the nation. The early week trough is likely to be exiting off the Atlantic coast on Thursday morning. As this occurs, a strong subtropical ridge over the Gulf of America will begin to nudge northward. The period of height rises should be rather short lived as the upstream upper low crosses the Upper Midwest late Thursday into Friday morning. Although the core of lower heigheights with this system remain confined to latitudes north of the Mason-Dixon Line, a grazing blow from this trough is expected. The potent nature of this trough is reflected in the 40 to 50 knot westerly winds streaming overhead at 500-mb. By Friday, continued warm/moist advection ushers temperatures well into the 80s, accompanied by dew points reaching the upper 60s to low 70s. This will contribute to decent instability profiles with surface-based CAPEs (Convective Available Potential Energy - high values indicate potential for severe weather) around 1,500 to 2,000 J/kg. However, some guidance indicate some inhibition the atmosphere may be contending with. The combination of deep-layer shear and ample instability will support a severe thunderstorm risk over the area on Friday into Friday night. If capping inversions and earlier anvil cirrus do not get in the way, a decent severe episode may unfold. The broad upper low to the north is forecast to track across the lower Great Lakes by Saturday. This is accompanied by a series of additional shortwaves which race across the Ohio Valley into the Mid- Atlantic region. Thermodynamically speaking, temperatures and dew points drop off by around 3 to 5 degrees on Saturday. Overall instability profiles may not be quite as potent as the previous day. However, forcing from the trough amidst strong atmospheric flow may afford an additional threat for strong to severe thunderstorms. Winds begin to turn westerly behind a cold front by Saturday evening. A post-frontal air mass fills out the region into the second half of the weekend. This favors a drier finish on Sunday with highs in the upper 70s to low 80s. The westerly downslope flow also begins to decrease humidity levels heading into the new work week. By Monday, high pressure builds to the north of the region before another frontal system approaches from the middle of the country. Based on the global ensembles, the local area will be in between systems as a trough sits offshore of the Eastern Seaboard and another amplifies across the Rockies. Some shower chances should eventually emerge toward the middle of next week. Marine Sub- SCA (Small Craft Advisory) level southeasterly winds are expected. The southeasterly winds will start to pick up late tonight into tomorrow, when SCAs (Small Craft Advisories) are in effect for all waters. A few models indicate that winds may even near low-end Gale levels tomorrow evening. Sub- SCA (Small Craft Advisory) level easterly winds are expected on Wednesday. A stray thunderstorm can't be ruled out over the waters this evening through tomorrow evening. Expect sub-advisory caliber winds on Thursday and Friday with winds shifting from southerly to southwesterly during this period. There will be a risk of thunderstorms each day, particularly on Friday as stronger storms may impact the waters. Special Marine Warnings may be necessary for the more robust convection. Tides / Coastal Flooding As a low pressure system slowly approaches through mid week, continued onshore flow will gradually build anomalies. Sensitive shoreline could approach minor tidal flood levels between Tuesday and early Thursday. NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories DC...None. MD...Small Craft Advisory from 10am to 6pm EDT Tuesday for MDZ008. Flood Watch from 6am EDT Tuesday through late Tuesday night for MDZ501-502-510. VA...Flood Watch from 6am EDT Tuesday through late Tuesday night for VAZ028-031-050-051-053>056-501-502-505-506-526-527. Flood Watch through late Tuesday night for VAZ025>027-029-030- 036>040-503-504-507-508. WV...Flood Watch from 6am EDT Tuesday through late Tuesday night for WVZ050>053-503-504. Flood Watch through late Tuesday night for WVZ055-501-502-505- 506. Marine Small Craft Advisory from 10am to 6pm EDT Tuesday for ANZ530>532-535-536-538>542. Small Craft Advisory from 6am to 6pm EDT Tuesday for ANZ533- 534-537-543. |
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