Marine Weather and Tide Forecast for Forest Heights, MD

KEY MESSAGES
1) Gusty thunderstorms are possible this afternoon and evening.

2) Above average temperatures are likely for the weekend into early next week.

DISCUSSION
KEY MESSAGE 1...Gusty thunderstorms are possible this afternoon and evening.

Low pressure is located over Lake Huron this morning, with high pressure situated off the Mid Atlantic coast. Due to the gradient between these features, steady SE or S winds are already in place for many areas, and will only increase with mixing after sunrise. Some gusts up to 30 mph are possible today. Currently showers are located across the Apps well ahead of the surface cold front. This lead disturbance will cross the area later this morning through the afternoon, quickly increasing cloud cover. While an embedded rumble of thunder is possible, instability will largely be lacking with this first round. Combined with residual dry air in place and showers outrunning the forcing, it's possible they greatly diminish by the time they reach the I-95 corridor in the afternoon. The current high temperature forecast is well into the 70s for most locations, but it could turn out cooler depending on the coverage of rain and clouds with this first round.

A second round of showers and thunderstorms is then forecast to form in the upper Ohio Valley ahead of the cold front in the afternoon. There will be only a few hours for the atmosphere to recover from the previous showers, so instability will likely be limited. However, forcing, moisture, and shear will be present, so some stronger storms could still develop as the axis moves eastward across the Appalachians during the late afternoon or early evening. Strong outflow winds will be the main threat with any stronger storms/linear segments. With sunset and weaker antecedent instability east of the Blue Ridge Mountains, it appears thunderstorms will weaken, with mostly showers reaching the I-95 corridor mid to late evening. Most locations are expected to receive less than a half inch of rain, and it's possible some could miss out altogether. Some residual showers could linger until the cold front passes late, and upslope rain showers will start in the Allegheny Mountains. If any clearing can occur between the main rain and the wind shift to northwest, some fog may develop.

Upper level low pressure will pivot over the northern Mid Atlantic on Thursday while surface low pressure redevelops over New England. This will result in gusty northwest winds and plentiful stratocumulus. Rain showers appear mostly limited to upslope areas in the Alleghenies, but can't totally rule out an isolated shower or sprinkle elsewhere. Temperatures will be cooler beneath the trough as well, with most lower elevations in the 60s. There could even be a few wet snowflakes mixed in on the high peaks above 4000 feet Thursday morning.

KEY MESSAGE 2...Above average temperatures are likely for the weekend into early next week.

Surface high pressure moves into the region on Friday as the upper low pulls away, resulting in temperatures returning closer to normal despite continued gusty northwest winds. Further height rises on Saturday will mark a significant warm- up with highs in the upper 80s likely across a majority of the area. A few afternoon & evening rain showers/thunderstorms are possible through the weekend as a shortwave trough briefly passes through, but this will likely be focused to the mountains and areas west of the I- 81 corridor. Drier air moves into the region on Monday, minimizing rain chances. However, some isolated diurnal terrain convection is possible both Monday and Tuesday. As upper level ridging continues to build overhead, early temperature outlooks continue to show highs in the low- to- mid 90s by next Monday and Tuesday.

Looking ahead, an upper level trough developing over the northern Plains begins to move through the region late Tuesday, potentially bringing additional showers and a cold front at some point in the middle of the week.

AVIATION /14Z WEDNESDAY THROUGH SUNDAY/
Southerly gusts to 25 kts continue. There may be multiple rounds of showers and embedded tstorms, one during the afternoon to early evening, and the second following a few hours later during the evening. Instability is fairly weak with the first round, so have left out thunder mentions, but did try to show the break with the second round. The second round will likely be weakening with eastward extent, so only have PROB30 TSRA at MRB, CHO, and IAD. Any stronger storms could contain gusty outflow, especially at MRB. Winds will likely shift to the west after the second round of showers but be light or even calm in spots, which could lead to fog development should any clearing take place. However, some guidance suggest MVFR to IFR ceilings will develop, especially over the metro terminals near and just after showers end. A wind shift to northwest late at night should assist in improving conditions.

An upper level low will be nearby Thursday before moving east Friday. This will likely result in stratocumulus ceilings, with a worst case being MVFR. Northwesterly winds will also gust 20 to 25 kt both days.

A shortwave trough coming in from the southwest could bring scattered showers & thunderstorms during the Saturday and Sunday afternoon/evening timeframe at KCHO and KMRB, but VFR conditions are otherwise expected. Light winds shift southwest Saturday afternoon, then flow south by Sunday evening.

MARINE
Southerly flow has increased this morning between low pressure in the Great Lakes and high pressure off the coast. Small Craft Advisories are in effect for all waters through the day. Some gusts up to 30 kt are possible. A few thunderstorms could reach the waters this evening, but at this time the threat for Special Marine Warnings appears low as activity should be weakening. The SCA was extended through the evening along the bay. Winds will be lighter for a time before the cold front brings a shift to the northwest early Thursday morning. The length of this gap is a bit uncertain, but advisories will definitely be needed after sunrise Thursday with gusts to 25 kt. Gusty NW winds and advisories will continue into Friday for some if not all waters.
Winds fall below SCA criteria by Friday evening.

Winds shift southerly on Saturday. Besides a brief period Saturday afternoon where winds could be borderline, winds stay below SCA criteria through the weekend.

TIDES/COASTAL FLOODING
Water levels are gradually increasing in gusty southerly flow ahead of a low pressure system. For the most part, peaks in action stage are expected, with the highest tide occurring tonight.
The Stevens ensemble shows the potential for Minor tidal flooding at Annapolis, but other guidance is just below. Expect anomalies to fall thereafter as winds shift to northwesterly.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Small Craft Advisory until 1 AM EDT Thursday for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 1 AM EDT Thursday for ANZ530>534- 537>543.
Small Craft Advisory until 8 PM EDT this evening for ANZ535- 536.