Marine Weather and Tide Forecast for Woodstock, VA

KEY MESSAGES
- 1) A meandering front will bring highly variable temperatures, occasional rain/storm chances, and nighttime fog through Saturday.

- 2) Sunny and calm conditions will start to take over next week, before another potential cold front pushes through the region midweek.

DISCUSSION
KEY MESSAGE 1..A meandering front will bring highly variable temperatures, occasional rain/storm chances, and nighttime fog through Saturday.

High pressure is centered well off to our northeast this afternoon across Northern New England and the Canadian Maritimes. However, a wedge of cold air damming induced high pressure extends southwestward into the Mid-Atlantic. This CAD wedge is in place to the east of the Blue Ridge/Catoctins north of Charlottesville, and also just to west of the Catoctins in the vicinity of Martinsburg and Hagerstown. While earlier fog has largely dissipated, low clouds have held strong within the CAD wedge, helping to keep temperatures down. Temperatures are only in the 40s to lower 50s within the CAD wedge (including the DC/Baltimore metro areas), while further to the south and west, temperatures have climbed well into the 60s and 70s beneath a mix of sun and clouds. Showers have also started to form this afternoon to the west of the Blue Ridge as ascent associated with a weak disturbance aloft moves through. These showers (and potentially a few thunderstorms) will remain possible to the west of the Blue Ridge this afternoon. This activity will slowly progress eastward this evening, with a stray shower possible anywhere later this evening into the first half of the overnight.

Low clouds will expand in coverage once again tonight, with fog also possible in many locations late tonight into tomorrow morning. Temperatures will remain mild overnight with lows in the 40s and 50s.

High pressure will shift further east tomorrow, while a potent shortwave and associated area of low pressure rapidly track northeastward from the Upper Midwest/Great Lakes toward Quebec.
As this occurs, winds at the surface will turn southerly and winds aloft will increase out of the southwest. While the day will once again start out with low clouds and fog across much of the forecast area, southerly winds will likely allow the cold air damming wedge to finally break to the east of the Blue Ridge by the afternoon and evening hours. As a result, temperatures are forecast to be warmer than today, with most of the forecast area (with the exception being Northeast Maryland) climbing into the 60s and 70s by mid-late afternoon. The combination of deeper moisture advecting into the area in southerly flow (dewpoints reaching into the upper 50s to lower 60s), daytime heating, and glancing ascent as the shortwave passes to our north and west will enable showers and thunderstorms to develop by later tomorrow afternoon into tomorrow evening.

We're expecting two rounds of storms tomorrow. The first round is expected to form within a surface trough just to the east of the Alleghenies during the mid-late afternoon hours. Model soundings show a fair amount of dry air in place aloft, and large scale forcing for ascent won't be overly strong, so areal coverage with this first round of storms is only expected to be isolated to scattered in nature. If storms do become well established, the background environment will have enough instability (around 1000 J/kg of MLCAPE) and shear (around 40 knots in the 0-6 km layer) to promote updraft rotation.
Isolated instances of damaging winds or hail may be possible with these storms as they move eastward from the Potomac Highlands toward the I-81 corridor and then the Blue Ridge/Catoctins during the mid-late afternoon hours. Conditions will likely remain dry to the east of US-15 during the daylight hours.

A second round of pre-existing storms will approach from the Ohio Valley, reaching the Allegheny Front around sunset. This round of storms could be well organized into a squall line, and may potentially be quite intense. With the loss of daytime heating, the trend will likely be downward with the strength of this activity as it moves into our area, but damaging winds may still be possible, especially along and west of the Allegheny Front. Large scale forcing for ascent may enable these storms to hold together in a weakened form as they move eastward across the forecast area during the first half of the night.

As of now, SPC has Garrett County in Slight Risk for severe thunderstorms, with locations further east to about US-15 in a Marginal Risk.

The actual surface cold front will move through the area late Saturday night into Sunday morning. There is still some disagreement amongst guidance regarding the timing of the frontal passage, and how much daytime heating will occur ahead of the front during the day on Sunday. We'll likely have some lingering cloud cover and showers during the morning ahead of the front. Depending on how fast the front progresses, some daytime heating could occur ahead of the front across southern Maryland, potentially leading to the development of a few thunderstorms. Clearing is expected from northwest to southeast during the afternoon and evening hours as drier air starts to work in behind the front. High temperatures on Sunday will be in the 60s and 70s for most, with 50s in the mountains.

KEY MESSAGE 2...Sunny and calm conditions will start to take over next week, before another potential cold front pushes through the region midweek.

Sunshine and warm temperatures to start the week before showers and a few thunderstorms move into the region middle to late week. A cold front will cool conditions off and bring drier air into the region late week. Temperatures mainly in the 70s and 80s Monday through Wednesday with highs in the 50s to follow on Thursday into Friday with a cold frontal passage.



AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
Ceilings have improved to MVFR at DCA and IAD, with IFR conditions holding strong further north and east at BWI, MTN, and MRB. CHO has broken out into clear skies. Showers and a few thunderstorms have formed along the I-81 corridor this afternoon, and are in the process of slowly spreading east.
PROB30 groups have been added at many of the TAF sites to account for the potential of these showers reaching the terminals. With stable air in place further east, no thunder is expected at any of the terminals.

Conditions are expected to deteriorate back to IFR/LIFR again tonight as low clouds and fog move back in. Gradual improvement is expected through the day tomorrow, with conditions clearing out first at CHO, and last at MTN. Ceilings will likely climb a few hours quicker than today during the day tomorrow as winds turn out of the south. Showers and thunderstorms will approach from the west tomorrow evening, but will likely be weakening as they do so. An afternoon storm could also be possible at MRB.
A cold front will move through on Sunday, leading to a return to VFR conditions and a shift to westerly winds.

VFR conditions on Monday and Tuesday. A shower or thunderstorm late Tuesday could reduce conditions to MVFR. Winds south to southwest 5 to 10 knots through the period.

MARINE
Sub-SCA level easterly winds are expected over the waters today.
Winds will turn out of the south tomorrow, and remain sub-SCA in nature through much of the day. Winds could near low-end SCA levels tomorrow evening, but warm air moving over cooler waters will likely be a limiting factor. Winds will shift out of the west by Sunday afternoon as a cold front moves over the waters.

No marine hazards Monday through Tuesday night. Winds generally south to southwest 5 to 10 knots.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.