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ANZ538 Patapsco River Including Baltimore Harbor- 1233 Am Est Sat Dec 9 2023
.gale watch in effect from Sunday evening through Monday afternoon...
Overnight..S winds around 5 kt. Waves flat.
Sat..S winds around 5 kt. Waves flat. Patchy fog. Vsby 1 to 3 nm.
Sat night..S winds 5 to 10 kt. Waves 1 ft or less. A chance of showers.
Sun..S winds 10 to 15 kt. Gusts up to 20 kt... Increasing to 30 kt in the afternoon. Waves 1 to 2 ft. Rain.
Sun night..SW winds 15 to 20 kt...becoming nw after midnight. Gusts up to 35 kt. Waves 2 ft. Rain.
Mon..NW winds 15 to 20 kt with gusts to 35 kt. Waves 2 ft.
Mon night..NW winds 10 to 15 kt with gusts to 25 kt. Waves 1 to 2 ft.
Tue..SW winds 5 to 10 kt. Waves 1 ft.
Wed..NW winds 10 kt. Waves 1 ft.

ANZ500 1233 Am Est Sat Dec 9 2023
Synopsis for the tidal potomac and md portion of the chesapeake bay..
broad high pressure will move offshore to our south through Saturday night. A strong frontal system will impact the region Sunday into Sunday night. High pressure will return early next week. Small craft advisories may be needed starting Saturday night into Sunday afternoon, and again Monday night. Gale conditions are likely across all waters Sunday evening into Monday afternoon.

FXUS61 KLWX 090131 AAA AFDLWX

Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 831 PM EST Fri Dec 8 2023

SYNOPSIS
High pressure will progress offshore to our south and east through Saturday. A potent weather system will impact the area on Sunday, with a strong cold front moving through Sunday night. Low pressure will track off to our north and east on Monday, with high pressure building back in for the middle of next week.

NEAR TERM /THROUGH SATURDAY/

Nothing to add for the overnight hours. Mostly clear skies tonight with passing high level clouds. Still chilly with lows in the mid 30s. Flood Watch has been issued for the I-95 urban corridor for Sunday afternoon through late Sunday night. High confidence on 2 to 3 inches of rain storm total with the heaviest rains falling Sunday afternoon through midnight Sunday night. 3-hr and 6-hr FFG is exactly that for that area.
Confidence has reached 50% that flooding will occur.

Previous afd...

The pressure gradient should remain weak enough for many locations to decouple tonight. When combined with clear skies to start the night, conditions will be ideal for radiational cooling. Temperatures will drop back into the upper 20s and 30s tonight. Some high clouds may move in during the second half of the night, but no precipitation is expected. Some patchy fog may try to form in response to the radiational cooling late tonight, especially across northeastern Maryland.

SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/
High pressure will shift further offshore on Saturday, as troughing digs across the center of the CONUS, and an area of low pressure tracks into the western Great Lakes. A trailing cold front will extend southward from this area of low pressure across the Ohio and Mississippi Valleys. Locally, we'll have another mild December day within southerly flow. Temperatures will climb into the 50s and 60s beneath a mix of sun and clouds.

A potent weather system will track toward the area Saturday night into Sunday. The trough over the center of the country will continue to amplify as it progresses further east Saturday night into Sunday. This initially positively tilted trough will take on more of a neutral tilt as it progresses eastward through the day Sunday, and then eventually a negative tilt as it passes overhead Sunday evening.

Rain will break out from west to east late Saturday night into Sunday morning as large scale ascent ahead of the approaching upper trough gradually overspreads the area. The rain will initially be showery in nature through Sunday morning, but more of a steady and soaking rainfall is expected Sunday afternoon into Sunday evening 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. The rainfall may be largely beneficial, given ongoing drought conditions. However, some isolated instances of flooding may be possible in 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 the primary upper trough, and associated differential cyclonic vorticity advection driven ascent lagging a bit behind the surface cold front, some anafrontal precipitation is expected. As a result, the precipitation may change over to snow for a brief time Sunday night before ending. This will almost certainly occur along and west of the Allegheny Front, as well as along the Blue Ridge.
Further east, and at lower elevations, there's a bit more uncertainty, but many model solutions do show a changeover to snow for a few hours. However, surface temperatures are at 35 or 36 degrees in valley locations while this occurs. So as of right now, the expected scenario is for snow accumulations to remain primarily confined to the west of the Blue Ridge, and at elevations of 1500 feet or greater. In these locations, a couple of inches may accumulate by daybreak Monday. At lower elevations, there may be a changeover to all snow, but it likely won't accumulate with surface temperatures expected to stay well above freezing.

LONG TERM /MONDAY THROUGH FRIDAY/
A few lingering rain or snow showers in parts of central/northeast Maryland, and some upslope accumulating snow showers along the mountain ridges of the Alleghenies early Monday. Otherwise, Monday is expected to be a chilly, gusty and dry day with high pressure building into the region. Winds could gust 30 to 35 mph much of the day, before gradually decreasing Monday night with gusts of 20 to 25 mph. Wind chills will be in the teens to lower 20s in the west and predominantly in the 30s elsewhere. Temperatures will only top out in the 40s east of the Blue Ridge and the middle 20s to the 30s west of the Blue Ridge.

High pressure is expected to build into the region and keep the region dry Tuesday through Thursday. A dry cold front could move across the region on Wednesday, but isn't really expected to produce precipitation due to lack of moisture and fast passage. Temperatures will remain chilly on Tuesday, but are expected to modify Wednesday and Thursday to more seasonable values each afternoon. Seasonable temperatures in the metros for this time in December is upper 40s to near 50 degrees.

AVIATION /01Z SATURDAY THROUGH WEDNESDAY/
It's possible that some low clouds and/or fog may form across northeastern MD late tonight. Have hinted at that potential in the TAFs for BWI and MTN, but they could potentially go IFR for a brief time if fog does form.

Any fog or low clouds would dissipate shortly after sunrise tomorrow. VFR conditions and light southerly winds are expected tomorrow. Sub-VFR ceilings and rain are expected for much of Sunday into Sunday night. Winds will be gusty out of the south during the day Sunday. A strong cold front will cross the area Sunday evening into Sunday night, leading to an abrupt wind shift to out of the west, and very gusty winds behind the front.
Some thunderstorms may form immediately along, or just ahead of the front. As temperatures rapidly drop behind the front, the precipitation may briefly change over to snow before ending. The greatest chance for this to occur would be at MRB.

VFR conditions Monday through Tuesday night. Gusty northwest winds 15 to 25 knots gusts 30 knots Monday, diminishing 10 to 15 knots gusts up to 20 knots Monday night. Winds becoming southwest 10 knots gusts 15 knots Tuesday and Tuesday night

MARINE
Sub-SCA southerly winds are expected through Saturday. Winds will start to pick up out of the south Saturday night, and increase further on Sunday. SCAs may potentially be needed Saturday night, and will likely be needed on Sunday. A strong cold front will move across the waters Sunday night. A brief line of thunderstorms may accompany the frontal passage. Winds will abruptly shift to out of the west behind the front. Gale conditions appear possible Sunday night into Monday. A Gale Watch is in effect for all waters during that time period.

Gale conditions possible Monday morning into Monday afternoon. Small craft advisories likely Monday evening into Monday night. Winds diminishing below SCA criteria Tuesday and Tuesday night. Winds northwest 20 to 25 knots gusts 30 to 35 knots Monday morning. Winds 15 to 25 gusts 25 to 30 knots Monday afternoon into early evening, then diminishing Monday night. Winds becoming southwest 10 to 15 knots Tuesday and Tuesday night.

TIDES/COASTAL FLOODING
Water levels will hover around action stage today and Saturday with light southerly flow over the waters. Southerly winds increase Sunday ahead of an approaching system and increase tidal anomalies, increasing the chances for minor tidal flooding.

A strong offshore flow will return Sunday night into Monday.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Flood Watch from Sunday afternoon through late Sunday night for DCZ001.
MD...Flood Watch from Sunday afternoon through late Sunday night for MDZ006-008-011-013-014-016-504-506>508.
VA...Flood Watch from Sunday afternoon through late Sunday night for VAZ053>055-502-527.
WV...None.
MARINE...Gale Watch from Sunday evening through Monday afternoon for ANZ530>543.

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Brewer Point
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Fri -- 01:14 AM EST     0.66 feet High Tide
Fri -- 02:36 AM EST     Moonrise
Fri -- 07:12 AM EST     Sunrise
Fri -- 07:50 AM EST     -0.05 feet Low Tide
Fri -- 01:57 PM EST     Moonset
Fri -- 02:26 PM EST     0.79 feet High Tide
Fri -- 04:43 PM EST     Sunset
Fri -- 09:03 PM EST     0.22 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Brewer Point, Maryland, Tide feet

Baltimore Harbor Approach
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Fri -- 01:28 AM EST     0.39 knots Max Flood
Fri -- 02:35 AM EST     Moonrise
Fri -- 03:56 AM EST     -0.00 knots Slack
Fri -- 07:11 AM EST     Sunrise
Fri -- 07:15 AM EST     -0.65 knots Max Ebb
Fri -- 10:11 AM EST     0.00 knots Slack
Fri -- 01:50 PM EST     0.96 knots Max Flood
Fri -- 01:57 PM EST     Moonset
Fri -- 04:42 PM EST     Sunset
Fri -- 05:24 PM EST     -0.00 knots Slack
Fri -- 08:32 PM EST     -0.76 knots Max Ebb
Tide / Current data from XTide NOT FOR NAVIGATION

Baltimore Harbor Approach, Maryland Current, knots

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