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ANZ536 Tidal Potomac From Indian Head To Cobb Island- 1233 Am Est Fri Dec 8 2023
Overnight..SW winds 5 kt. Waves less than 1 ft.
Fri..S winds around 5 kt. Waves 1 ft.
Fri night..S winds 5 kt. Waves less than 1 ft.
Sat..S winds 5 kt. Waves less than 1 ft.
Sat night..S winds 5 to 10 kt. Waves 1 ft. A chance of showers.
Sun..S winds 15 to 20 kt with gusts to 30 kt. Waves 2 ft. Showers.
Sun night..SW winds 15 to 20 kt...becoming nw after midnight. Gusts up to 30 kt. Waves 2 ft. Showers.
Mon..NW winds 15 to 20 kt...diminishing to 5 to 10 kt after midnight. Waves 2 to 3 ft...subsiding to 1 ft.
Tue..SW winds 5 to 10 kt. Waves 1 ft.

ANZ500 1233 Am Est Fri Dec 8 2023
Synopsis for the tidal potomac and md portion of the chesapeake bay..
high pressure will build across the southeast states through Saturday. A strong frontal system will impact the region on Sunday. High pressure will return Monday. Small craft advisories may be needed starting Saturday night, and are likely Sunday into Monday. Gales are possible Sunday into Monday, as well.

FXUS61 KLWX 080207 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 907 PM EST Thu Dec 7 2023

SYNOPSIS
High pressure will build across the Southeast states through Saturday. A strong frontal system will impact the region on Sunday.
High pressure will return Monday.

NEAR TERM /THROUGH FRIDAY/
Clouds have been slow to clear northern parts of the area, with one streak of mid level clouds extending southeast from the Great Lakes, while lower stratocumulus persist across north central/northeast Maryland. In theory these clouds should erode after midnight as 850-700 mb ridging builds eastward. However, cirrus will likely overspread the area by sunrise, although upstream satellite shows they are thin in nature.

Otherwise, high pressure will remain south of the area. Tonight won't be quite as cold with most of the area dropping into the low 30s (into the upper 20s at locations where winds go calm).

SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/
High pressure will move offshore Friday into Saturday. This will allow for light southerly return flow and moderating temperatures.

Friday should be mainly sunny with ridging overhead, but high clouds likely start to increase as early as midday Saturday as a large and powerful trough/frontal system takes shape over the Midwest. This trough will be the next impactful weather maker for our area heading into the second half of the weekend (see more in the Long Term section below).

LONG TERM /SUNDAY THROUGH THURSDAY/
A potent weather system will track toward the area on Sunday. A highly amplified and positively-tilted upper trough will reside over the center of the country to start the day Sunday, with southwesterly flow downstream across the eastern US. This trough will take on more of a neutral tilt as it progresses eastward through the day, and then eventually a negative tilt as it passes overhead Sunday evening.

Rain will break out from west to east Sunday morning as large scale ascent ahead of the approaching upper trough gradually overspreads the area. A soaking rainfall is expected through much of the day Sunday as strong warm/moist advection ensues at low levels within an environment characterized by highly anomalous precipitable water values (around 1.5 inches, which is near 3-4 sigma for this time of year). Nearly all model solutions show a widespread 1-3 inch rainfall across the forecast area, with the highest totals to the east of the Blue Ridge. Normally this would raise flooding concerns, but with ongoing drought across the area, flooding concerns are expected to be rather isolated and confined to more sensitive urban locations.

Many model solutions also show limited surface-based instability developing Sunday afternoon into Sunday evening. As a result, thunderstorms will be possible. With a very strong wind field in place aloft (60+ kt low-level jet) providing ample shear, and the approaching trough and strong cold front providing focused forcing for ascent, some strong to severe thunderstorms may also be possible late Sunday afternoon into Sunday evening.

A strong cold front will move through the area Sunday evening into Sunday night, leading to an abrupt drop in temperatures from the 50s/60s to the 30s. With strong differential cyclonic vorticity advection driven ascent lagging a bit behind the surface cold front, some anafrontal precipitation may be possible. As a result, the precipitation may change over to snow for a brief time Sunday night before ending. The greatest chance for this to occur will be to the west of the Blue Ridge, but a fair amount of ensemble members even show it occurring further east. As with many other aspects of the forecast, the finer scale details of the snow forecast remain highly uncertain four days out.

Upslope snow showers will continue through the night and into Monday morning to the west of the Allegheny Front, where several inches of snow accumulation appears possible. Further east, precipitation should wind down late Sunday night, leading to drier conditions on Monday. Winds will remain gusty out of the west to northwest, and temperatures will be much cooler on Monday, with highs ranging from the upper 20s in the mountains, to the mid 40s to the south and east of I-95. High pressure will move overhead on Tuesday, leading to continued dry conditions and seasonable temperatures.

AVIATION /02Z FRIDAY THROUGH TUESDAY/
VFR conditions are expected through Saturday as high pressure dominates. Mid level ceilings should depart the area by midnight or shortly thereafter, although high level cirrus will arrive toward sunrise.

Otherwise, southerly flow and dry conditions are expected through Saturday. Winds out of the S/SE increase late Saturday night ahead of an approaching system, with gusts 20-25 kts possible east of the Blue Ridge.

Sub-VFR conditions appear likely Sunday into Sunday night. Rain is expected through much of the day Sunday, and some thunderstorms could be possible late Sunday afternoon into Sunday evening. Winds will be gusty out of the south through Sunday. A strong cold front will move through Sunday evening, with winds turning out of the northwest thereafter. The precipitation could potentially end as a brief period of snow, especially at MRB. Gusty west to northwesterly winds and VFR conditions are expected on Monday.

MARINE
Marginal Small Craft Advisory conditions may be occurring on the wide waters of the mid bay based on obs near Tangier. However, other obs have considerably diminished and will likely be canceling some zones of the advisory shortly. Winds diminish over the waters tonight through most of Saturday with high pressure overhead and southerly flow continuing, though brief/marginal channeling is possible Friday evening/night. SCAs may be necessary starting Saturday night as winds increase ahead of an approaching frontal system.

At least SCA conditions appear likely Sunday through Monday evening, with gale conditions also possible at times. Winds will be out of the south through much of Sunday, before turning out of the west Sunday evening behind a strong cold front. Gusty west to northwesterly winds will continue on Monday.

TIDES/COASTAL FLOODING
A snapback of tidal anomalies is occurring tonight as water that piled up near the mouth of the Chesapeake Bay returns north due to the easing offshore flow. Water levels will be near action stage later tonight and Friday.

A southerly flow is expected Saturday, but it should be light.
Therefore, the most likely scenario is for action stages. However, the southerly flow will strengthen Sunday, increasing the chances for minor tidal flooding heading into Sunday night.

A strong offshore flow will return Sunday night into Monday.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 1 AM EST Friday for ANZ533-534-537- 541-543.

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Dahlgren
Click for Map
Thu -- 01:38 AM EST     Moonrise
Thu -- 04:23 AM EST     0.00 feet Low Tide
Thu -- 07:11 AM EST     Sunrise
Thu -- 10:29 AM EST     1.36 feet High Tide
Thu -- 01:38 PM EST     Moonset
Thu -- 04:47 PM EST     Sunset
Thu -- 04:56 PM EST     0.04 feet Low Tide
Thu -- 10:47 PM EST     1.27 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Dahlgren, Upper Machodoc Creek, Virginia, Tide feet

Colonial Beach
Click for Map
Thu -- 01:37 AM EST     Moonrise
Thu -- 03:56 AM EST     0.02 feet Low Tide
Thu -- 07:10 AM EST     Sunrise
Thu -- 10:02 AM EST     1.36 feet High Tide
Thu -- 01:38 PM EST     Moonset
Thu -- 04:29 PM EST     0.06 feet Low Tide
Thu -- 04:47 PM EST     Sunset
Thu -- 10:20 PM EST     1.27 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Colonial Beach, Potomac River, Virginia, Tide feet

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