Marine Weather and Tide Forecast for Potomac Heights, MD

NEAR TERM /THROUGH TONIGHT/
The current temperatures continue to rise ahead of a lot of the statistical model guidance, generally 3 to 5 degrees to be exact. The 12Z IAD sounding as well as recent aircraft soundings show a well established subsidence inversion around 875-750 mb.
Below this stable layer is a well mixed boundary layer amidst unidirectional westerlies. However, gusts are pretty much non- existent given only 5 to 10 knots just below the inversion top.
The net effect of this set up has been to bump temperatures into the upper 30s to low 40s. Interestingly, the snowpack on the ground has seemed to offer only minimal resistance to these gains in temperatures. Skies remain mostly sunny aside from some thin mid/high level clouds streaking in from West Virginia.
Eventual high temperatures may be a degree or two higher than what current observations (2 PM) show.

Surface high pressure will further retreat to the south tonight as a potent frontal system tracks across the Great Lakes region.
A dry air mass coupled with relatively light winds should afford a decent radiational cooling night ahead. Forecast low temperatures fall into the teens to low 20s. These milder spots will largely be confined to D.C., Baltimore, and along the shorelines of the Chesapeake Bay.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
Monday will provide one more day of increased warmth. While milder in nature, this still only carries forecast high temperatures to around climatology for mid-January. The current forecast package calls for low to mid 40s over a bulk of the area, with the mildest spots being south of I-66 in Virginia and over portions of the Shenandoah Valley.

Mid/upper ridging across the area eventually buckles as an expansive closed low drops down from the Upper Midwest. A period of light warm advection will overrun the frigid boundary layer.
This will aid in some light snow shower activity along the Alleghenies. Given the shallow nature of the moisture in place, it remains to be seen if the cloud depth grows large enough to produce ice crystals, and thus snowflake development. Hence, some patchy freezing drizzle cannot be ruled out for the highest elevations of the Alleghenies on Monday morning.
Moisture should gradually increase ahead of the upstream frontal system. This is likely to support a shift to isolated to scattered snow showers along the Alleghenies through Monday into the night. Perhaps up to an inch of snow is possible during this timeframe.

The parent cold front clears the region Monday evening which ushers in the next round of modified Arctic air to the local area. While a bulk of the area sits in the teens to low 20s on Monday night, single digits are looking likely along the Allegheny Front. Wind fields will be quite blustery in nature which helps really drop the wind chill temperatures. Overnight wind chills are forecast to be around 0 to -10 degrees over the Alleghenies, locally approaching -15 degrees in spots.

Tuesday certainly reveals the shift in weather patterns as high temperatures struggle to escape the mid 20s to mid 30s (mainly teens to mid 20s in the mountains). The robust upper low initially across the Upper Midwest will work its way into the northeastern U.S. on Tuesday. The passage of this trough aloft results in a further enhancement of synoptic wind fields. Most can expect blustery winds gusting to around 25 to 35 mph, but up to 40 to 50 mph in the mountains. Wind chills drop considerably in the process. Additionally, an enhanced upslope flow carries with it another round of upslope snow showers. Around 1 to 3 inches are possible, locally approaching 4 inches in the high spots along the Alleghenies. This may even include a threat for some snow squalls. Given high Froude numbers, some snow showers could spill over toward the Shenandoah Valley, perhaps further.

Tuesday night sees widespread low temperatures fall into the upper single digits to teens (lower single digits for the Allegheny Front). Wind chills turn very cold overnight which may warrant Cold Weather Advisories for a large chunk of the area.
While the mountains could see winds chills into the -10 to -20 degree range, area-wide readings are forecast to drop to near 0 degrees or slightly lower.

LONG TERM /WEDNESDAY THROUGH SUNDAY/
Wednesday will likely be the coldest day of this forecast period as arctic high pressure approaches from the northwest and troughing remains locked in over the northeast CONUS. High temperatures look to stay in the 20s for most, with single digits to low teens in the higher elevations. Winds gusting in the 20 to 25 mph range during the day will make it feel even colder, with wind chills into the teens for most, and below zero to single digits in the mountains.

While winds will be tapering off Wednesday night, still expect around 8 to 12 mph, which paired with very cold lows in the teens (near 0 in the mountains) will lead to dangerously cold wind chills yet again overnight. Cold Weather headlines may once again be needed over the mountains. While we may not hit criteria elsewhere, it will still be very cold during this timeframe, with wind chills in the single digits to low teens.

High pressure pushes offshore Thursday into Friday as upper-level ridging moves overhead. This will lead to an overall warming trend with dry conditions expected for most. However, as that ridge builds in, there will be one more piece of shortwave energy that traverses across central PA/northern MD. This will likely set off another period of upslope snow showers along the Allegheny Front. There is even some indication that they could spill east of the mountains, but very low certainty at this time. If that were to occur, it would likely be in the form of flurries or a light snow shower. Highs on Thursday rise to the low to mid 30s and then into the upper 30s to low 40s by Friday.

Looking towards next weekend, the weather pattern becomes much more unsettled. An area of low pressure over the Great Lakes will push a cold front through the region Saturday into Saturday night.
Meanwhile, a piece of upper-level energy embedded within the subtropical jet across the southeast CONUS will spawn another area of low pressure along this front down near the Gulf Coast. This system quickly gets yanked northeastward by the aforementioned Great Lakes system. This will result in rain on Saturday for much of the region. Timing and low track with this system are still somewhat uncertain, though guidance is coming into slightly better agreement on a late Saturday arrival time and a track near or northwest of our area. This should keep the event mostly rain outside of perhaps the higher elevations. Some cold air may linger around long enough if the system were to move in a bit quicker. If this were to occur, there may be just enough cold air around for some wintry precip at the onset. This seems unlikely at this point, but the best chance for that cold air to hold on would be in our northern and western areas as well as on the ridges.

AVIATION /19Z SUNDAY THROUGH FRIDAY/
VFR conditions are expected through the middle of the week across the area terminals. The forecast is dry although a few snow showers could move off the terrain toward KMRB on Tuesday afternoon. Light and variable winds continue today with high pressure off to the south. A strong cold front pushes across the area Monday afternoon into the evening with a more potent wind field overspreading the region. By Tuesday, west to northwesterly gusts push into the 25 to 30 knot range, perhaps even slightly higher.

Gusty WNW winds on Wednesday afternoon will be the primary aviation concern in the long-term period. Winds will gust around 15 to 20 kts during this timeframe while VFR conditions persist.

By Thursday, winds will taper off as high pressure moves overhead briefly. This will also turn winds out of the SSW during the afternoon. Could see a few flurries, mainly at MRB, as snow showers potentially spill east of the mountains, but low confidence in that at this time.

MARINE
Sub-advisory caliber winds persist through the rest of the day and into a good portion of Monday. A formidable cold front does push across the waterways Monday evening which will eventually yield a marked uptick in winds. Small Craft Advisories will be needed by late Monday into Tuesday. A secondary surge of cold air arrives with a strong upper trough passage by Tuesday evening. This results in gale-force winds over much of the Chesapeake Bay as well as lower portions of the tidal Potomac. A Gale Watch is now in effect for these areas from 6 PM Tuesday until 6 AM Wednesday.

Gale conditions may persist into Wednesday morning. Otherwise, Small Craft Advisories will likely be needed the rest of Wednesday due to gusty WNW winds in the wake of the earlier cold front.

Winds will taper off Wednesday night into Thursday, with SCAs seeming less likely at this time.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Gale Watch from Tuesday evening through late Tuesday night for ANZ531>534-537-539>541-543.