Marine Weather and Tide Forecast for Frederick, MD

NEAR TERM /THROUGH TONIGHT/
Skies have largely cleared out early this morning to the east of the mountains as last evening's system departs off toward the east. High pressure will gradually build toward the area from the Ohio Valley today into tonight, leading to dry conditions outside of some flurries or light snow showers in the Alleghenies within upslope flow. Mostly sunny skies are expected for most, but it will remain cold. High temperatures will be in the 20s and lower 30s for most, with teens in the mountains.
Winds will remain gusty out of the northwest, which will keep wind chills in the single digits and teens for much of the day.
Cold Weather Advisories remain in effect in the Alleghenies through midday.

Winds will finally begin to decrease this evening as high pressure continues to build eastward and the pressure gradient starts to relax. It will be another cold night, but the winds will be much lighter, and may even go calm in many places, making it feel comparatively warmer than preceding nights.
Overnight lows will be in the low-mid teens for most, with single digits in the mountains and upper teens to near 20 in downtown DC and Baltimore.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
High pressure will retreat offshore as a clipper system dives southeastward from the Great Lakes toward the area on Thursday.
This system will bring a prolonged period of snow to the Alleghenies Thursday into Thursday night as synoptic scale ascent overlaps with upslope flow. A Winter Storm Watch has been issued for Garrett, western Grant, and western Pendleton Counties from 7 AM Thursday morning until 7 AM Friday morning.
Around 6 to 8 inches of snow is expected in those locations during that time period, with localized higher totals possible.

Snow showers will start to spill east of the mountains Thursday afternoon. Coverage of these snow showers is expected to be greatest to the west of the Blue Ridge, and then closer to the MD/PA border further east, but any location could see a brief snow shower. Temperatures are forecast to climb into the lower to middle 30s to the east of the mountains, but wet bulb temperatures will be well below freezing, so the precipitation type should be snow for all. Accumulations will be less than an inch to the east of the mountains, and mostly confined to grassy/elevated surfaces. However, light accumulations on roads can't be ruled out in any locally heavier bursts of snow. Snow showers to the east of the mountains will come to an end Thursday evening as synoptic scale ascent moves off to our east.
However, snow showers will continue in the Alleghenies Thursday night within upslope flow.

High pressure will build back in for Friday, leading to mostly sunny skies and milder temperatures. High temperatures on Friday are forecast to reach into the upper 30s and lower 40s at lower elevations, with 20s in the mountains.

LONG TERM /SATURDAY THROUGH TUESDAY/
Broad troughing is expected over the CONUS with ridging in place off the West Coast. Guidance is in agreement on the broad upper trough generally digging southward in the west/central CONUS, and recent runs have formed a much better consensus regarding the progression of smaller features within the broad trough. At this time, the features of most concern appear to be a shortwave over the southwest US moving into the Southeast/Mid-Atlantic on Saturday, and the strength and position of the upper low over east/central Canada and any embedded shortwaves Sunday. These two time periods appear to be the most likely shots for precip in the extended (east of the mountains).

As the upper trough digs south, our area will be squarely in W/SW flow aloft as Arctic area descends into the Plains. As a result, increasingly colder temperatures are expected through the extended.
Saturday is expected to be a bit milder in the mid-upper 40s with southerly flow ahead of an approaching cold front. Confidence is increasing for the area seeing at precip Saturday, mostly in the form of rain given the temperatures. Wintry precip is likely in the mountains, and could mix in along the PA/MD border early Saturday before we warm up in the afternoon.

Guidance has come into agreement on the potential Sunday/Monday system, with the vast majority of ensembles and deterministic models limiting the precip to Sunday as an upper shortwave rounds the trough. A wintry solution of some kind is likely as a strong burst of cold air accompanies the front. Temperatures drop about 20 degrees between Sunday and Monday, to highs in the teens and 20s.
Precip type and amounts will be determined by where precip falls in relation to how quickly cold air advances. Northwest winds gusting to around 20 mph brings wind chills in the single digits (negative teens for the mountains) by late Sunday night into Monday morning.

Cold air continues to envelope the region Tuesday, with high temperatures topping out in the low 20s outside of the mountains, and single digits to near zero in the mountains. Low temperatures will range from positive to negative single digits. While winds are expected to lighten as high pressure builds in, it won't take much to bring apparent temperatures to near or just below zero.

AVIATION /09Z WEDNESDAY THROUGH SUNDAY/
VFR conditions are expected today at all terminals, with just a few fair weather clouds possible around FL040. Winds will remain out of the northwest through the day, with gusts to around 25-30 knots this morning, and closer to 20 knots this afternoon. Winds will continue to decrease through the overnight hours as high pressure builds toward the area. Winds will turn out of the south during the day tomorrow. Prevailing VFR conditions are expected for much of the day, but ceilings should gradually lower toward MVFR, and intermittent drops to IFR ceilings/visibilities may be possible in snow showers during the afternoon hours. Improvement to VFR conditions is expected Thursday night, along with a wind shift to westerly. VFR conditions are expected on Friday, with westerly winds during the morning shifting to southerly Friday night.

Sub-VFR conditions are expected both Saturday and Sunday as a series of disturbances move through. Rain will be the most likely precip type for most of the terminals Saturday, but a burst of cold air Sunday could bring wintry precip. Winds could gust 15-20 kts out of the south on Saturday and again out of the NW Sunday behind the front.

MARINE
Gale conditions continue in northwesterly flow early this morning over the waters. A Gale Warning remains in effect for all waters through 6 AM. The Gale will likely need to be replaced with a Small Craft Advisory for the daylight hours today through tonight. Sub-SCA level south to southwesterly winds are expected during the day tomorrow. Winds will turn westerly Thursday night, then southerly again on Friday. Winds may near low-end SCA levels both Thursday night and Friday night over the widest waters.

Southerly winds likely remain near SCA criteria into Saturday afternoon. Winds turn NW and diminish Saturday night. Gusty NW winds arrive Sunday and could necessitate SCAs by the afternoon.

TIDES/COASTAL FLOODING
Offshore flow behind a series of fronts is resulting in declining water levels. The strongest negative surge is ongoing through this morning, and blowout conditions are possible. Water levels will return closer to normal by Thursday as winds take a more southwesterly direction.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Gale Warning until 6 AM EST early this morning for MDZ008.
Cold Weather Advisory until noon EST today for MDZ001.
Winter Storm Watch from Thursday morning through Friday morning for MDZ001.
Cold Weather Advisory until 10 AM EST this morning for MDZ501.
VA...Cold Weather Advisory until noon EST today for VAZ503.
Cold Weather Advisory until 10 AM EST this morning for VAZ504- 507-508.
WV...Cold Weather Advisory until noon EST today for WVZ501-505.
Winter Storm Watch from Thursday morning through Friday morning for WVZ501-505.
Cold Weather Advisory until 10 AM EST this morning for WVZ503- 506.
MARINE...Gale Warning until 6 AM EST early this morning for ANZ530>543.