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ANZ538 Patapsco River Including Baltimore Harbor- 953 Pm Est Tue Dec 5 2023
.small craft advisory in effect from 9 am est Wednesday through Wednesday evening...
Rest of tonight..N winds 5 kt. Waves flat. Scattered showers.
Wed..NW winds 10 to 15 kt with gusts to 20 kt. Waves 1 ft. Scattered showers. Vsby 1 to 3 nm.
Wed night..NW winds 10 to 15 kt. Gusts up to 20 kt until early morning. Waves 1 ft.
Thu..W winds 5 to 10 kt. Waves 1 ft.
Thu night..SW winds around 5 kt. Waves 1 ft or less.
Fri..S winds 5 kt. Waves less than 1 ft.
Fri night..SW winds 5 kt. Waves less than 1 ft.
Sat..S winds 5 to 10 kt. Waves 1 ft or less.
Sun..S winds 10 to 15 kt...increasing to 20 kt in the afternoon, then becoming w. Waves 2 ft. Rain through the day. Showers likely in the evening, then a chance of showers after midnight.

ANZ500 953 Pm Est Tue Dec 5 2023
Synopsis for the tidal potomac and md portion of the chesapeake bay..
a quick moving low pressure system will cross the area through early Wednesday. High pressure will build over the region Thursday through Friday night. Small craft advisories may be needed Saturday night.

FXUS61 KCTP 060058 AFDCTP

Area Forecast Discussion National Weather Service State College PA 758 PM EST Tue Dec 5 2023

SYNOPSIS
A weak clipper system will spread light snow, mixed with rain in the valleys, across the area this evening through Wednesday morning. Another period of light rain and snow is possible across the northern tier of PA on Thursday ahead of a noticeable warmup into the weekend. The mild spell Friday into Saturday will precede a late weekend storm with the potential to bring heavy rainfall and strong wind gusts on Sunday.

NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
Upper level trough with 2-3 embedded Meso-B shortwaves and an associated weak sfc low(s) will move ESE across the Ohio Valley and Central Appalachians late this afternoon and tonight.

The upper level trough is slightly positive the tilt of its axis with a few spokes of enhanced small scale DPVA and FGEN forcing generating enough UVVEL to create brief periods of moderate snowfall rates (with ~1/2SM vsby). This supports our forecast 1-2 inches of snow across the Laurels (with perhaps around 3 inches on the ridges above 2500 msl) by late Wed morning.

That being said, the larger-scale jet structure (with the unfavorable, thermally direct/descending branch of the jet brushing the region and its primary axis well south of the CWA)
will act to limit snowfall amounts from exceeding values noted above. The broader lift generating the enhanced higher/layer and textured clouds as seen on regional vis and IR satellite imagery was essentially wasted on deep dry air, producing mainly virga and perhaps some intermittent very light rain/snow.

A look at the regional radar mosaic loop across the Ohio Valley supports this analysis and short range forecast of periods of light to briefly moderate snow associated with small scale jet maxes and bands of enhanced FGEN forcing. This is also supported by the spattering of several small areas of slightly anomalous LLVL -U component to the LLVL flow via the latest GEFS.

18Z temps are just a deg or two shy of their forecast maxes, which range from the mid 30s across the Northern and Western Mtns to the mid 40s throughout the Mid and Lower Susq Valley.

As the clipper weakens late tonight into Wednesday morning with jet energy jumping over the Appalachians to the main baroclinic zone along the Carolina Coast, a secondary low will develop offshore the OBX of NC.

The impact for our area will be that increasingly colder NNW flow could generate up to an inch of additional/lake enhanced snow over the NW mtns.

Elsewhere, any light snow/flurries should produce nothing more than a dusting to 0.5" of snow over most of Central PA. Across parts of the Lower Susq Valley, model soundings indicate any very light precip could fall as either snow or rain, but surface temps should remain too warm for even a coating.

SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/
The main, large scale mid/upper level trough axis reaches the East Coast by 15Z Wed with some lingering light snow ending by noon over and to the east of the Susq Valley, while areas of primarily snow showers falls over the Alleghenies of Wrn PA through Wednesday afternoon as cold air deepens/lapse rates steepen following passage of the upper trough.

Wednesday will turn out to be the coldest day the week with highs averaging 5 to 10F below normal for early December or in the 30-40F range.

A narrow sfc ridge axis should spell a brief break in the snow showers (decreasing POPs) by Wednesday evening. However, surge of warm advection preceding a warm front lifting through the Grt Lks could potentially produce a brief period of light snow and rain across mainly northeast and eastern PA late Wednesday night into AM Thursday. A coating to an inch of accumulation is possible.

Despite warming aloft, a good deal of cloudiness should hold max temps to near or a bit below seasonal normals Thursday, with highs ranging from the mid 30s to low 40s. Lows Thursday night will vary from west (warmer) to east (cooler) thanks to elevation/gradient WSW flow and boundary layer decoupling. Some sites in the western part of the CWA may even see a non- diurnal temp trend develop late Thu night into early Friday morning.

LONG TERM /FRIDAY THROUGH TUESDAY/
Medium range guidance supports fair and increasingly mild conditions late this week, as upper level ridging builds along the east coast. The bulk of guidance tracks a deepening surface low west of PA late next weekend. Without a blocking high to the northeast of PA, expect well above normal temps to continue until the arrival of a trailing cold front Sunday PM or Monday AM. High temperatures on Saturday and Sunday are progged to be +10 to +15F above normal corresponding to highs in the 50s across the region. A slower arrival of the cold front on Sunday afternoon could allow temperatures to crest the 60 degree mark.

A deep plume of GOMEX moisture and strong upper level divergence ahead of an upstream trough should produce a period of moderate to heavy rain ahead of the front Sunday afternoon and evening.
Latest guidance has trended a bit slower on the arrival of precipitation, but some uncertainty remains. Ensemble plumes indicate most likely rainfall will fall between 0.75 and 1.50 inches. Strong/gusty southerly winds are possible if the region can break into the warm sector Sunday PM. However, climatology suggests the strongest winds will come in the cold advection regime behind the cold front Sunday night into Monday. Latest ECENS plumes indicate a possibility of wind gusts in excess of 40kts during this time frame. A return to cooler weather appears likely Monday, as upper level trough shifts into the region, accompanied by lingering orographic rain/snow showers over the W Mtns. Wind gusts will be on the decrease by Tuesday as the deep cyclone pulls away.

AVIATION /01Z WEDNESDAY THROUGH SUNDAY/
Clipper system has pushed light snow and rain across the airspace though coverage is spotty as precip is encountering dry air. Associated sfc low should track south of the state tonight. Periods of enhanced lift will produce light to briefly moderate snowfall rates will lead to widespread IFR to LIFR CIGS and MVFR to IFR vsbys across the western mtn airfields (KJST and KBFD) with mainly MVFR cigs and vsbys through 12Z at the the central PA airfields. VFR cigs in the Susq Valley may dip to the mid and upper MVFR range at times in occasional very light snow overnight.

The constant light snow could get moderate (1/2SM) at JST but lighten up in the wee hours of the morning. A thin coating to an inch of snow accum is poss at valley locations by the time precip ends early Wed, with more on the ridge tops of the Laurels (JST), where locally 2+ inches can't be ruled out.

De-icing is going to be necessary at JST and BFD, and probable at UNV/AOO/IPT before ops shut down overnight tonight.

Improvements on Wed as a high pressure ridge moves in from the west. The high will be centered to our south, but have a narrow neck stick northward over us and into Canada. The subsidence should help break up the clouds downwind of the mountains. But, the low clouds will hang tough for much of the rest of the area. Warm air starts to flow in aloft from the west on Thursday, and some snow will likely fall along and east of the warm front which will cross the area.

Outlook...

Thu...Light snow, mainly N. Restrictions likely.

Fri...Mainly VFR.

Sat...VFR early. Showers late.

Sun...Widespread reductions in rain/snow.

CTP WATCHES/WARNINGS/ADVISORIES
None.

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Middle Branch
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Tue -- 12:31 AM EST     1.03 feet High Tide
Tue -- 12:51 AM EST     Last Quarter
Tue -- 07:10 AM EST     Sunrise
Tue -- 07:35 AM EST     0.17 feet Low Tide
Tue -- 12:55 PM EST     Moonset
Tue -- 01:00 PM EST     0.76 feet High Tide
Tue -- 04:43 PM EST     Sunset
Tue -- 07:01 PM EST     0.21 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Middle Branch, Baltimore Harbor, Maryland, Tide feet

Baltimore (Fort McHenry)
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Tue -- 12:05 AM EST     1.14 feet High Tide
Tue -- 12:51 AM EST     Last Quarter
Tue -- 07:07 AM EST     0.19 feet Low Tide
Tue -- 07:10 AM EST     Sunrise
Tue -- 12:34 PM EST     0.84 feet High Tide
Tue -- 12:55 PM EST     Moonset
Tue -- 04:43 PM EST     Sunset
Tue -- 06:33 PM EST     0.23 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Baltimore (Fort McHenry), Maryland, Tide feet

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