Marine Weather and Tide Forecast for Naval Academy, MD

KEY MESSAGES
- 1) Low pressure passing offshore will result in a second round of rain and snow, mostly along and east of Interstate 95 through early evening.

- 2) Very cold conditions are expected over the region Monday night through Tuesday night.

- 3) Seasonal conditions Thursday turn cold into next weekend with the possibility of wintry precipitation.

DISCUSSION
KEY MESSAGE 1...Low pressure passing offshore will result in a second round of rain and snow, mostly along and east of Interstate 95 through early evening.

Low pressure is located east of the Outer Banks this afternoon, moving northeastward. A mid/upper level trough and associated jet streak are interacting with the trailing baroclinic zone to spread precipitation well west of the low track. Light precipitation is entering central Virginia and southern Maryland areas, with the edge of the precipitation shield trailing into the central Carolinas. Temperatures east of the Blue Ridge are largely in the mid to upper 30s. Across southern Maryland, even the dew points are still above freezing, although dry low level air continues to advect on northwest winds. Thus some areas may initially see rain, although snow will become increasingly common as the precipitation advects northward into and is undercut by the colder/drier air. Given the marginal thermal environment and relatively short duration of potential snow (perhaps 3-4 hours at most), forecasts for additional accumulations have trended downward. Most locations will see an inch or less. If a changeover occurs quickly enough, southern Maryland could end up with the highest amounts. Secondarily, Cecil County will also be near the western edge of the steadier precipitation, and with colder air in place there (especially the northern part of the county), have left the existing Winter Weather Advisory in place until 6 PM. While there is still a bit of uncertainty, the back edge of steadiest precipitation is still expected to closely align with Interstate 95, although a westward bulge has resulted in brief snow around the Charlottesville area which will lift northeastward through the piedmont.

The low will pull away and precipitation will end early this evening. Given cold temperatures and not a lot of wind, any residual moisture will likely refreeze on untreated surfaces overnight given low temperatures from the mid teens to mid 20s.

Secondarily, some light snow showers or flurries are affecting the Allegheny Mountains this afternoon due to shallow moisture and lift in the DGZ. However, minimal accumulations are expected.

KEY MESSAGE 2...Very cold conditions are expected over the region Monday night through Tuesday night.

An Arctic front will sweep through the area Monday, ushering in gusty winds and a very cold airmass. Westerly winds will gust 20 to 35 mph during the day, with locally to around 45 mph in the higher elevations. It will be close to Wind Advisory criteria there, but think areas with higher gusts will be isolated. While highs will reach the 30s and lower 40s in the lower elevations during the day, temperatures will rapidly fall after sunset.
Winds will decrease somewhat overnight, but air temperatures will drop to the teens, with single digits in the higher elevations. Monday night will have the lowest wind chill values, generally 0 to 10 in the lower elevations and below 0 in the higher elevations. A Cold Weather Advisory has been issued along and west of the Allegheny Front where there will be widespread wind chills between -10 and -20. This advisory will continue through 1 PM Tuesday, as temperatures will be slow to climb and winds will remain gusty. Temperatures have trended upward slightly for Tuesday, with locations across central Virginia and southern Maryland potentially rising above freezing briefly.
Most other locations will stay in the mid to upper 20s. Winds will also be slightly less than Monday but still keep wind chills from getting any higher than the teens and lower 20s.

A shortwave trough will also cross the northwestern part of the CWA as the Arctic front passes. Some scattered upslope snow showers will be possible Monday along the Allegheny Mountains.
Very little moisture is expected, but high snow ratios in the cold airmass could result in a fluffy inch of snow in spots.

The center of the strong high will build over Tuesday night with mostly clear skies in place. Due to the radiational cooling component with lighter winds in place, some of the outlying valleys could have colder air temperatures compared to Monday night (single digits). Otherwise lows in the teens are expected across the lower elevations. Some residual wind in the higher elevations could result in wind chills below 0.

As the high slides east Wednesday, gusty south winds will push most of the area into the mid 30s to lower 40s. During the afternoon and overnight, some snow showers may enter the Alleghenies as the next low pressure system moves into the Great Lakes.

KEY MESSAGE 3...Seasonal conditions Thursday turn cold into next weekend with the possibility of wintry precipitation.

Surface high pressure slides offshore Thursday as an area of low pressure passes by to our north. The return of southerly flow brings highs up to their seasonal values in the low to mid 40s east of the mountains. An approaching upper trough and an associated surface cold front bring a period of upslope mountain snow showers, with several inches of accumulating snow possible. The cold front crosses the area Thursday evening/night.

An Arctic airmass settles in over the region Friday into next weekend, with well below normal temperatures possible. We could be looking at highs in the 20s and 30s for next weekend, and overnight lows in the teens to low 20s. Truly frigid air could arrive next Sunday night into the start of the following week.

Models continue to indicate the interaction of the northern and southern jet streams over the central U.S. producing a potent area of low pressure. There is a lot of uncertainty regarding the timing, location, and track of this system. Depending on what occurs, there could be wintry precipitation of varying types across our area sometime next weekend. To add some probabilistic perspective, the 13Z NBM has around a 30pct chance for 1-2 inches of snow, and around a 20pct chance for a glaze of ice. Continue to monitor the forecast during the upcoming week.

AVIATION /19Z SUNDAY THROUGH FRIDAY/
As a wave of low pressure moves off the coast, the secondary area of precipitation is spreading northward from the Carolinas, although it is battling dry air on the northwest side. With that said, precipitation is reaching the ground on the western side of the model guidance envelope, even if it won't accumulate much (should be less than 1 inch). Snow has reached CHO, and will likely graze IAD for an hour or so as well. At this rate, snow is more certain for DCA/BWI/MTN, with the longer duration at the latter two. However, it should only be a 3-4 hour duration at most, and could start as rain for a time. While IFR conditions are possible, the snow will most likely remain light in intensity. Snow should end by 23Z with VFR conditions returning, but temperatures will quickly fall and winds will remain rather light out of the northwest, so any residual moisture could refreeze on untreated surfaces.

Winds will become south or southwest by Monday morning, then an Arctic front will sweep through during the midday hours, shifting winds to the west. No precipitation is expected, but these winds will gust 20-30 kt during the afternoon and early evening before subsiding somewhat overnight. Wind gusts of 20-25 kt will return Tuesday, becoming light Tuesday night as high pressure builds overhead. In its wake, southerly winds may gust to 20 kt on Wednesday.

VFR conditions likely continue into Thursday when a cold front moves through the area. Winds veering from southwest to northwest from morning to evening, and could see gusts to around 20 knots.

MARINE
North to northwest winds will remain elevated into the night as low pressure passes offshore. A Small Craft Advisory is in effect for most of the waters until 4 AM. A period of rain/snow is also expected this afternoon into early evening. Winds shift briefly to southerly Monday morning ahead of a reinforcing Arctic front which will turn winds west to northwest Monday afternoon through Tuesday. Gusts of 20 to 30 knots are most likely from roughly midday Monday through Monday evening, gradually decreasing late Monday night. A Small Craft Advisory has been issued for this period as well, and a few gusts could approach gale force Monday evening. Advisories will likely be needed for most if not all waters Tuesday as westerly winds remain gusty, but not as strong as Monday. Light winds are expected Tuesday night as high pressure builds overhead.
Southerly winds will quickly increase in its wake Wednesday, with SCAs likely needed into Wednesday night.

SCA conditions are possible Thursday as a cold front moves across the local waters.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Small Craft Advisory until 4 AM EST Monday for MDZ008.
Small Craft Advisory from 9 AM Monday to 6 AM EST Tuesday for MDZ008.
Winter Weather Advisory until 6 PM EST this evening for MDZ008.
Cold Weather Advisory from 8 PM Monday to 1 PM EST Tuesday for MDZ501-509-510.
VA...Cold Weather Advisory from 8 PM Monday to 1 PM EST Tuesday for VAZ503.
WV...Cold Weather Advisory from 8 PM Monday to 1 PM EST Tuesday for WVZ501-503-505.
MARINE...Small Craft Advisory until 4 AM EST Monday for ANZ530>534-537- 539>541-543.
Small Craft Advisory from 9 AM Monday to 6 AM EST Tuesday for ANZ530>534-537>543.
Winter Weather Advisory until 6 PM EST this evening for ANZ530.
Small Craft Advisory from 9 AM Monday to 1 AM EST Tuesday for ANZ535-536.