Tidal Potomac from Cobb Island MD to Smith Point VA Marine Forecast
|Rest Of The Overnight...Ne Winds 5 Kt. Waves Flat. A Chance Of Rain.|
|Today...Se Winds 5 To 10 Kt. Waves 1 Ft. Rain Likely. Vsby 1 To 3 Nm.|
|Tonight...Sw Winds 5 To 10 Kt. Waves 1 Ft. Rain Likely.|
|Mon...Nw Winds 5 To 10 Kt. Waves 1 Ft. Showers.|
|Mon Night...Nw Winds 15 To 20 Kt. Gusts Up To 20 Kt...Increasing To 30 Kt After Midnight. Waves 2 Ft... Building To 4 Ft After Midnight.|
|Tue...Nw Winds 10 To 15 Kt. Gusts Up To 30 Kt... Diminishing To 20 Kt In The Afternoon. Waves 2 To 3 Ft.|
|Tue Night...S Winds 5 To 10 Kt. Waves 1 Ft.|
|Wed...W Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Rain Through The Day.|
|Thu...Nw Winds 5 To 10 Kt. Waves 1 Ft.|
| Area Forecast Discussion|
National Weather Service Baltimore MD/Washington DC
401am EST Sunday Feb 28 2021
Two waves of low pressure will cross the region through Monday. High pressure will build from the Great Lakes toward the Middle Atlantic by Tuesday. Low pressure will likely pass to the south Wednesday, then another area of low pressure may pass to the south at the end of the week as high pressure builds in from the north and west.
Near Term - Through Monday
The GOES-16 mid-level water vapor channel depicts a well established moisture plume emanating from the subtropical Pacific. This atmospheric river of sorts is transporting anomalous moisture northeastward across the Southern Plains, through the Tennessee Valley and into the Mid-Atlantic. 00Z upper air profiles from upstream locations show precipitable values averaging around 1.25 inches. This air mass continues to be transported by a quasi-unidirectional west-southwesterly steering profile. Regional radar imagery shows a brunt of this activity tracking through sections of Kentucky and Ohio. 3-hour amounts have generally maximized in the quarter to half inch range. Ultimately, the expectation is for this to be the norm along the Allegheny Front, locally augmented by upslope component to the flow. High-resolution models keep a fairly steady axis of precipitation affecting the area throughout much of Sunday and into early Monday. The current forecast paints anywhere from 1.75 to 2.25 inches along the Allegheny Front with 1.00 to 1.25 inches being commonplace north of I-66 and Highway 50.
With the inherent snowpack containing quite a bit of snow- liquid equivalent (generally up to 2 to 3 inches), an areal flood risk exists as rain assists in the melting process. Typically a 50 degree dew point is optimal for rapid melting which is currently about 5 to 10 degrees short at this point. However, ample rainfall in conjunction with the melting snow may lead to instances of flooding, particularly west of I-81. A Flood Watch is currently in effect until 4am Monday across far western Maryland, east-central West Virginia, and Highland County in Virginia. Farther east, cannot rule out nuisance flooding in the typical more vulnerable locations. While yesterday only brought a tenth to quarter of an inch of rainfall, the remnant saturated soils could support any such instance of flooding. Overall, the chances for rainfall across the region will wind down by early Monday afternoon as the last bit of precipitation moves toward the Eastern Shore.
Looking at the temperatures and wind forecast ahead, the guidance has finally caught on by favoring a more southward displaced warm front. Continued rain-cooled air coupled by general easterly flow off the cool marine waters will keep temperatures in the 40s across much of the region. Some 50s are possible south of I-66 and perhaps into the Potomac Highlands given enough breaks in the clouds. Mild conditions continue overnight and into the first half of Monday. Thereafter, in response to height falls attached to a sub-504 dm upper low crossing New England will drive a powerful cold front through on Monday. The true cold advection and blustery nature of the wind fields do not come in until the second half of the day. A deep, well-mixed boundary layer could drive some of the 35 to 45 mph winds down to the surface at times. This should especially be the case at higher elevations being located at the level of these winds. While the air mass is quite dry, some snow shower streamers coming off the Great Lakes could reach Garrett County late Monday.
Short Term - Monday Night Through Tuesday Night
Temperatures will plummet overnight with lows at, or below freezing in all locations. The Allegheny Highlands could see lows well into the teens with ample wind gusts still blowing at night. The current wind chill forecast suggests near 0 readings overnight with teens to low/mid 20s elsewhere. While Meteorological Spring commences on Monday, it will hardly feel that way that night and into Tuesday. Northwesterly flow persists into Tuesday, albeit in a more weakened state as the barreling upper low exits New England. Residual cyclonic flow on the back side will make for a chilly Tuesday but with continued sunshine. Highs should top out in the low to mid 40s with 30s in the mountains. A transient surface ridge tracks through Tuesday night which should further decrease the winds with lows coming up by around 5 degrees.
Long Term - Wednesday Through Saturday
Model guidance appears to be reaching a broad consensus for a wave of low pressure forecast to pass to the south Wednesday, with a track west to east across the Deep South then offshore of the Carolinas/Georgia. Although most 00z deterministic guidance is dry across much of the area Wednesday, any slight deviation northward would bring some precipitation to the region due to the closer proximity of the upper wave. There are also still several ensemble members with measurable precipitation as far north as Pennsylvania, so we have maintained low Probability of Precipitation for this forecast cycle. The timing of precipitation (if it occurs) looks several hours slower than it did 24 hours ago, minimizing any wintry precipitation risk.
Guidance has also come into somewhat better agreement with the evolution of broad troughing over the eastern CONUS late in the week. Though differences remain, it appears a northern stream trough/upper low will retrograde out of eastern Newfoundland toward northern New England. The orientation of the trough in most guidance keeps a southern stream wave suppressed to our south with subsequent phasing occurring well offshore. A much farther westward retrograde of the upper low over northern New England (or no retrograde at all/an eastward drift instead) would be required to draw the southern stream wave/associated precipitation northward. In other words, the current projected position of the northern stream upper low appears to be in just the right spot to suppress the incoming southern stream wave to the south. This pattern would, however, result in lowering heigheights and persistent troughing (and the potential for below normal temperatures) through much of the upcoming weekend. Spokes of energy spiraling around the low may offer periods of clouds or even a few rain or snow showers from time to time, but pinning down exact timing is exceedingly difficult this far in advance.
While the lower Chesapeake Bay and tidal Potomac may get close to small craft criteria levels, it should ultimately fall short. Southerly winds pick up across similar locations late tonight and into early Monday which could support a brief period of SCA (Small Craft Advisory) conditions. A sharp wind shift to west-northwesterly is likely on Monday morning with 18 knot plus winds emerging in the marine waters by just after noon. Further increases in wind will come as a strong upper trough passes through. Gale force winds are expected by late Monday evening, continuing into the overnight hours. This may continue into Tuesday morning with residual gusts over 30 knots possible. Winds should weaken to below 20 knots for the second half of Tuesday.
A few gusts to around 20 kt are possible out of the SW Wednesday as low pressure passes well to the south. Similar gusts are possible Thu, though confidence is low given model spread.
NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...None. MD...Flood Watch through late tonight for MDZ001-501-502. VA...Flood Watch through late tonight for VAZ503-504. WV...Flood Watch through late tonight for WVZ050-055-501>506. MARINE...None.