Marine Weather and Tide Forecast for Aquia Harbour, VA

NEAR TERM /THROUGH TONIGHT/
Dry today with a gusty breeze as high pressure builds into the region. Temperatures will be colder than yesterday with highs more seasonable in the upper 50s to lower 60s (colder in the mountains). There is a mention of fire weather today in the fire weather discussion below as well, but in short, much less concerned than yesterday given the lack of overlap between stronger winds and lower RHs.

Cooler temperatures tonight and light winds have prompted the issuance of a Frost Advisory for the remaining areas where the growing season hasn't ended, generally along and east of I-95.
Lows in the low to mid 30s are expected for most tonight.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
An upper trough of low pressure begins to dig in the Ohio Valley on Friday as high pressure overhead moves to the east. A strong cold front is expected to approach late Friday into Saturday.
This system will lack a substantial moisture connection to the Gulf of America, thus making any significant rainfall hard to achieve.

Also of note, fire weather could be an issued on Friday for the Shenandoah Valley. For more details, see the Fire Weather discussion below.

Dry conditions on Saturday, especially around midday into Saturday afternoon behind frontal passage and a building high pressure center. High temperatures will jump back well into the 60s and even low 70s.

LONG TERM /SUNDAY THROUGH THURSDAY/
A weak wave of low pressure passes to our north early on Sunday, then a second area of low pressure develops over our area and jets off toward the northeast Sunday afternoon/evening. This is in response to a powerful upper trough that swings from the Great Lakes to the Mid-Atlantic. The low level cyclone will bring a period of showers to the area Sunday morning to afternoon, then we should clear out by late afternoon to evening. The high temp on Sunday is going to occur early in the day as most areas get to the mid to upper 60s, then cooler air drops temps back down by the evening.

For the Alleghenies, these rain showers will transition to snow showers Sunday night as very cold air surges in. Accumulating snow appears likely, but how much snow falls is still uncertain. The ensemble consensus is around an inch or two of snow is possible, though the spread is still from a few tenths to several inches.
Upslope snow showers in the Alleghenies continue into Monday as the mid/upper trough goes overhead, then departs to the east on Tuesday.

Also, some of these snow showers could produce brief, intense bursts of snow. The GFS snow squall parameter is showing this is most possible Monday morning to afternoon when (and if) there is enough moisture being fed from the Great Lakes. Any heavier bursts of snow could add on to the snow totals. Still a lot of uncertainty, so continue to monitor as this could result in travel disruptions for some areas in the Alleghenies on Monday.

Cold and blustery conditions likely on Monday as highs struggle to reach the mid to upper 40s. Northwest winds gusting around 15-20 mph will keep wind chills in the 30s even during the middle of the day.
A widespread freeze is expected Monday night, which should effectively end the growing season across the area. Lows are forecast to drop to the 20s to around 30F, with upper teens in the Alleghenies. Winds remain elevated, so wind chills will be in the teens to low 20s, with single digits in the mountains.

The airmass moving into the region Monday night is going to be extremely cold, possibly approaching some of the coldest temps ever sampled for the Tuesday 12Z IAD sounding. The GFS and ECMWF both show the potential for 500mb temps to be at or colder than -35C.
Looking at the NAEFS ensemble tables, the 500mb and 700mb temps are around -4 standard deviations, and the 850mb temps are around -3 standard deviations (the 850mb temps are forecast to be around -10C to -13C). As a result, cannot rule out flurries or light snow showers east of the Alleghenies Monday night if moisture can linger before very dry air moves in.

Cold conditions remain Tuesday with temperatures similar to Monday, though temps do start to moderate Tuesday night. Upper 50s to low 60s return Wednesday as gusty southwest winds return. Conditions remain dry through mid-week though additional mountain snow showers will be possible during this time.

AVIATION /19Z THURSDAY THROUGH TUESDAY/
VFR conditions through today as high pressure builds nearby. WNW winds will continue to gust 20-25 kt through today. Then winds should rapidly decrease toward sunset later today.

An area of low pressure and potent cold front will begin to approach the region Friday, so winds will increase substantially out of the south, with gusts up to 25-30 knots possible. As the first in a series of cold fronts pushes through Friday, rain is expected overnight Friday, which will likely briefly yield sub- VFR conditions.

VFR conditions return Saturday once frontal passage occurs.

An area of low pressure and cold front are forecast to move across the area Sunday. This will bring periods of sub-VFR conditions Sunday morning to afternoon, then conditions clear out by Sunday evening. Becoming much colder on Monday as northwest winds gust around 20-25 knots.

MARINE
Winds will gradually diminish below SCA levels through the afternoon into tonight. SCAs will be allowed to drop at 4 PM as scheduled.

Ahead of the next frontal passage, strong southerly winds will bring SCA conditions to all waters Friday. An SCA was issued as a result, and goes through Friday night.

Winds quickly taper off Saturday morning, turning out of the west. SCAs should not be necessary until Sunday.

South to southwest winds ahead of a strong cold front on Sunday will be gusting around 15-20 knots most of the day. SCA conditions fully take hold Sunday night into Monday as northwest winds behind the cold front gust between 20-30 knots. Gale conditions are possible in the middle Chesapeake Bay Monday night.

FIRE WEATHER
Afternoon RH values have gone even lower than forecast today, dropping into the teens and low 20s yet again, especially South of I-66 and up the Shenandoah Valley into eastern WV.
Thankfully, winds have dropped significantly compared to yesterday, though am still seeing some 15-20 mph gusts.

A cold front will approach the region Friday before moving through Friday night into Saturday. Latest model guidance does show an uptick in the RH values for the most part, but still dropping into the upper 30s to low 40s during the afternoon for most.
Locally, the Shenadoah Valley may see much lower RH values, particularly in the northern portions and up into eastern WV/west-cetnral MD. The strong southerly winds will create a downsloping effect on the northwest side of the Blue Ridge mountains, and some guidance has RHs dropping back down into the 20s. Additionally, winds tomorrow will be around 15-20 mph, with gusts up to 35 mph out of the south. The combination of these two elements, paired with very dry fuels from recent days, could lead to an elevated risk for wildfire spread Friday afternoon. New starts may be more difficult, owing to cloudcover and temps in the low 60s, but any ongoing fires could face some challenges.

The aforementioned cold front pushes through Friday night, but it likely to only yield a few hundredths of an inch of precipitation in any one given location.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Frost Advisory from 1 AM to 8 AM EST Friday for DCZ001.
MD...Small Craft Advisory until 4 PM EST this afternoon for MDZ008.
Small Craft Advisory from 9 AM Friday to 5 AM EST Saturday for MDZ008.
Frost Advisory from 1 AM to 8 AM EST Friday for MDZ008-011-013- 014-016>018-504-506-508.
VA...Frost Advisory from 1 AM to 8 AM EST Friday for VAZ053>055-057- 527.
WV...None.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ530>543.
Small Craft Advisory from 9 AM Friday to 5 AM EST Saturday for ANZ530>534-537-539>543.
Frost Advisory from 1 AM to 8 AM EST Friday for ANZ530.
Small Craft Advisory from 9 AM Friday to 1 AM EST Saturday for ANZ535-536-538.