Marine Weather and Tide Forecast for Calvert Beach, MD

KEY MESSAGES
- 1) Multiple disturbances will bring snow to parts of the area through Sunday.

- 2) An Arctic outbreak is likely early next week, with near to below normal temperatures continuing through the remainder of the week.

DISCUSSION
KEY MESSAGE 1...Multiple disturbances will bring snow to parts of the area through Sunday.

Update:

Bands of moderate to heavier snow started a little earlier than models had projected. Beneath these bands, wet bulb cooling allowed temperatures to drop to or below freezing. Combined with residual cold surfaces, roadway accumulations have been resulting in hazardous travel and accidents from portions of northern Virginia across north central and northeast Maryland.
Particularly across north central Maryland, there has been enough residence time of the bands to start bumping totals over an inch. Given at least and hour or two of additional snowfall, issued a Winter Weather Advisory to cover the associated impacts in this area. Closer to Interstate 95, the combination of warmer temperatures and a shorter duration of precipitation should reduce impacts. However, some locations could still pick up a coating of snow, especially from the Baltimore area to the northeast.

Previous discussion:

System number 1 will push across the area today. WAA ahead of this wave (anchored by low pressure over the Great Lakes)
resulted in a coating to a couple inches of snow overnight over far western MD down along and west of the Allegheny Front into eastern WV (highest in NW Garrett Co. MD). Another round of snow is expected through mid to late morning, before becoming more showery and intermittent in nature this afternoon and possibly into this evening. Will need to continue to closely monitor extent of snow showers later today (possible advisory extension)
and southward extent (possible advisory expansion). Although the steadiest snow is expected this morning, some shower/squall potential exists tonight in more favorable upslope low-level flow with modest CAPE into the DGZ.

System number two - a shortwave diving into the Deep South (rounding the base of a trough to the west a bit quicker this morning) - will begin to take aim at the Mid-Atlantic late tonight. Model guidance overnight has come into much better agreement with the amplitude of the upper wave, and the track and strength of surface low pressure moving up off the coast, tucking it a bit closer thanks to a linger low-level frontal zone. This increases confidence in some light snow or a rain/snow mix (depending on boundary layer temps) on Sunday, mainly east of the Blue Ridge. The most likely scenario is for a light coating of snow mainly on grassy and elevated/untreated surfaces. The hourly temp forecast indicates mostly above freezing (mid 30s), but 30-32 F is more likely in areas/brief periods of any steadier precip. A reasonable high-end snowfall forecast would paint a few inches near/east of US-15, but the ceiling doesn't appear much higher than that given the quick- moving nature of the system and marginal surface temps.

KEY MESSAGE 2...An Arctic outbreak is likely early next week, with near to below normal temperatures continuing through the remainder of the week.

A reinforcing Arctic front will cross the Mid-Atlantic Monday.
This may bring a few snow showers to the Alleghenies, but the bigger story will be the very cold weather in its wake.

Temperatures will crash into the single digits along and west of the Blue Ridge/Catoctin Mountains by daybreak Tuesday, with low to mid teens to the east. Combined with 10-20 mph blustery northwest winds (20-30 mph at higher elevations), this will send wind chills into the single digits for most south of I-70 and east of the Blue Ridge Mountains, with single digits below zero likely over northern MD and along/west of the Blue Ridge Mountains.
Wind chills of 15 to 30 below zero are anticipated over the Appalachians by early Tuesday morning.

Not much of a "warm-up" is expected during the day Tuesday.
Temperatures in the lower to middle 20s Tuesday afternoon are about 15 degrees below average for this time in January. Dry conditions are anticipated throughout the day Tuesday through Wednesday night. The transition to milder temperatures will be from Tuesday into Wednesday as high pressure moves to the east and a southerly flow develops helping to modify the air. Highs Wednesday may still be a few degrees below average but only by about 3 to 5 degrees.

With the high pressure shifting farther to the east Wednesday into Thursday, this makes way for an approaching cold front from the northwest Thursday into Friday. Models tend to show this front aligned more east-northeast to west-southwest versus north-northeast to south-southwest. This indicates that the front may not have much of a fast push through our region, but rather slide or sink across our area as reinforcing Arctic air tries to move in from the northwest. The timing and temperatures may mean everything Thursday into Friday with regards to wintry precipitation or liquid precipitation and whether the front pushes through Thursday, Thursday night, or Friday. Moisture is obviously needed to get precipitation, which shouldn't be an issue given the return of southerly winds into the front. Model consensus reveals the front does move through the area toward the southeast, but there is uncertainty as to when. Either way, we need to anticipate the possibility of wintry precipitation at some point with this front later in the upcoming week or next weekend. Temperatures should modify even more into the upper 30s to lower 40s on Thursday ahead of the frontal passage.
Friday's temperatures appear to be colder and becoming below average once again with the possibility of light wintry precipitation.

AVIATION /14Z SATURDAY THROUGH WEDNESDAY/
A brief period of MVFR or even IFR conditions is possible across the metro areas until roughly 18Z from west to east as a band of precip (snow, sleet, and perhaps eventually rain) moves across the area. This precipitation could be briefly moderate in intensity. VFR conditions will return this afternoon. S/SW winds today becoming W/NW tonight mainly AOB 10 kts (though some 15-20 kt gusts are likely 15Z-22Z or so).

Low pressure passing up along the coast will likely bring a little snow or a rain/snow mix mainly to the I-95 terminals Sunday, though there has been a westward shift. Some light accums and at least brief reductions are becoming increasingly likely, though temps will be marginal and the system will be fast-moving so it may still be a stretch to get anything widespread "plowable". N/NW winds may briefly gust to around 15 kts Sun PM as the low pulls away.

Blustery and cold conditions are expected early next week as a reinforcing Arctic front pushes across. Winds may gust 20-25 kts Monday shifting from S/SW to W/NW.

VFR conditions are expected Tuesday through Wednesday night.
Winds Tuesday will be NW 5 to 10 knots, becoming SW 5 to 10 knots Wednesday.

MARINE
South to southwest winds are still fairly light this morning, but should increase a bit late this morning into this afternoon with gusts of 20 knots. By late afternoon, winds are expected to diminish as a cold front moves through. A period of light snow or a rain/snow mix is possible especially near the upper tidal Potomac River and the upper Chesapeake Bay this morning into early afternoon.

Lighter northwest winds are anticipated in the wake of the front tonight, with a slight uptick possible for a time Sunday afternoon and evening as low pressure passes offshore. This low is expected to bring light snow or a rain/snow mix, which will reduce visibility over the waters on Sunday.

Blustery and very cold conditions are expected early next week.
SCAs are likely Monday into Tuesday as SW winds turn NW. SCAs are possible again Wednesday in southerly flow.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Small Craft Advisory until 4 PM EST this afternoon for MDZ008.
Winter Weather Advisory until noon EST today for MDZ005-006- 503-505-507.
Winter Weather Advisory until 4 PM EST this afternoon for MDZ509.
VA...None.
WV...Winter Weather Advisory until 4 PM EST this afternoon for WVZ501.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ530>543.