Williamsport, MD Marine Weather and Tide Forecast
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Marine Weather and Tide Forecast for Williamsport, MD

April 17, 2024 5:21 AM EDT (09:21 UTC) Change Location
Sunrise 6:27 AM   Sunset 7:52 PM
Moonrise 12:56 PM   Moonset 2:55 AM 
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NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION.

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Marine Forecasts
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ANZ535 Tidal Potomac From Key Bridge To Indian Head- 435 Am Edt Wed Apr 17 2024

Rest of the overnight - S winds 5 kt. Waves less than 1 ft.

Today - S winds 5 kt. Waves less than 1 ft. Scattered showers.

Tonight - S winds 5 to 10 kt - .becoming W late. Waves 1 ft. Scattered showers.

Thu - NW winds 5 to 10 kt. Waves 1 ft.

Thu night - NE winds 5 to 10 kt. Waves 1 ft.

Fri - SE winds 5 to 10 kt. Waves 1 ft. A chance of showers.

Fri night - S winds 5 to 10 kt - .becoming nw after midnight. Waves 1 ft. A chance of showers.

Sat - NW winds 10 to 15 kt. Waves 1 ft.

Sun - N winds 5 to 10 kt. Waves 1 ft.

ANZ500 435 Am Edt Wed Apr 17 2024

Synopsis for the tidal potomac and md portion of the chesapeake bay -
a stationary front will gradually return northward as a warm front today. This system is expected to stall nearby through late tonight before a cold front tracks through on Thursday morning. A stronger cold front approaches the region on Friday into Saturday morning. High pressure gradually pushes in from the west by late in the weekend. Small craft advisories may be needed at times from Thursday into the weekend.


7 Day Forecast for Marine Location Near Williamsport, MD
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Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 170759 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 359 AM EDT Wed Apr 17 2024

SYNOPSIS
A stationary front will slowly lift northward as a warm front today, eventually pulling north of the region by early Thursday.
A weak cold front will track through on Thursday before a stronger cold front arrives on Saturday. High pressure returns on Sunday and into early next week.

NEAR TERM /THROUGH TONIGHT/
A stationary front remains draped across central Virginia extending back into far western Maryland. Based on the latest observations, moisture content appears to be the biggest difference as temperatures and wind direction are fairly similar. The prevailing southerly flow has maintained a very mild air mass early this morning. Most spots remain in the mid 50s to low 60s, accompanied by some mid to high clouds tracking overhead.

Expect clouds to continue to increase through the morning and afternoon as an upstream moisture plume migrates toward the Eastern Seaboard. Despite the uptick in cloud cover, it should prove to be another warm mid-April day owing to persistent southerly winds. There will likely be a north/south disparity in today's temperatures which is dependent on the position of the wavy warm front. Most solutions stall this boundary somewhere between U.S. 50 and I-70. Thus, the cool spots today may be over northeastern Maryland and mountain tops with highs confined to the mid/upper 60s. Elsewhere, low to mid 70s are more likely.

Recent guidance has continued the downward trend in forecast rainfall amounts. Although an upstream shortwave pushes toward the area, the main forcing/lift likely moves up into the Lower Great Lakes. Weak height falls coupled with several subtle perturbations in the flow aloft will bring a few rounds of rain shower chances to the area. Instability levels are not terribly impressive, generally averaging around 250 to 500 J/kg, accompanied by some areas of non-zero inhibition (CIN). Thus, have capped the convective threat at isolated given the above unknowns. The best chance for any severe thunderstorms would be over far western Maryland where the Storm Prediction Center paints a Marginal risk. The primary severe threats would be damaging wind gusts and a spotty larger hailstone.

Overall, the threat for showers should diminish overnight with low clouds beginning to take over. A thickening stratus deck will favor another mild night with lows in the 50s to low 60s.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
As the mentioned warm front slowly pulls north toward the Mason-Dixon Line, an upstream cold front begins to push across the Allegheny Front. Although somewhat diffuse in nature, it will carry a wind shift as west-northwesterlies ensue on Thursday. A few showers may fall over the Alleghenies on Thursday morning, but the rest of the area likely stays dry thanks to a downsloping component to the flow. The latter artifact of the wind fields should help raise temperatures given well-mixed boundary layers. The latest model soundings indicate dry adiabatic profiles up to around 825-mb. With forecast 850-mb temperatures around 12C in central Virginia, dry adiabatic mixing to the surface would yield highs in the low 80s. Area wide high temperatures should stay in that mid 70s to low 80s range, with mid/upper 60s in the mountains and across northeastern Maryland. The latter area may be stuck in thick cloud cover which keeps temperatures down relative to other locations. Overall cloud cover increases across the entire area on Thursday night. Any nocturnal shower chances should be relegated to western Maryland. The post-frontal air mass will be cooler as most areas north of I-66/U.S. 50 are forecast to be in the mid/upper 40s.

Shower chances increase across the area on Friday. A broad longwave trough extending across the northern tier of the country into the Great Lakes will lead to an expanding precipitation shield. All of this activity moves eastward ahead of a stronger cold front set to arrive late Friday into the early weekend. Temperatures come down given the mostly cloudy skies and showers. The forecast keeps most in the 60s although low/mid 70s can still be found south of I-66, over portions of the Shenandoah Valley, and Allegheny mountain valleys. The influence of the cold front becomes noticed at night as lows fall into the 40s across a bulk of the area. Any shower chances ends from west to east overnight.

LONG TERM /SATURDAY THROUGH TUESDAY/
The cold front will likely be south of the area by Saturday morning.
However, with gusty downsloping winds and gradual cold advection aloft, temperatures will likely still be above normal for much of the area (mid 60s-mid 70s). The front will be stalling out over the southeastern states. Sunday should largely be dry, but cooler than preceding days with high temperatures slightly below normal (upper 50s-mid 60s). An area of low pressure will ride along the front late Sunday into early Monday as a trough approaches from the west.
Although most of the rain will remain south of the area, there remains some potential of light rain reaching the forecast area during this time.

High pressure will likely build in from the west Monday, although model spread begins to increase in the height pattern aloft.
Temperatures will likely remain near to below normal. The next shortwave may approach from the Great Lakes on Tuesday, resulting in a chance of showers. 00Z guidance has trended toward a slower solution however. With southerly flow developing, a warming trend will commence.

AVIATION /07Z WEDNESDAY THROUGH SUNDAY/
A warm front sprawled across the area will gradually lift north toward the Mason-Dixon Line. Expect light southerly winds, accompanied by a few rounds of shower opportunities. Although isolated thunderstorms are in the forecast, confidence is fairly low in where/when these will occur given questionable instability. Heading into the late evening to overnight, a thickening stratus deck will likely carry all TAF sites to MVFR, locally IFR around the Baltimore terminals. These low ceilings may linger into early Thursday morning before a weak cold front tracks through.

This boundary should make for a mostly dry Thursday, accompanied by VFR conditions after any lingering low clouds erode.
Prevailing west-northwesterly winds are expected before shifting to east-northeasterly on Thursday night. A better chance for showers looms on Friday which will support MVFR to IFR ceilings at times. The best thunder chances appear to be confined to areas west of I-81. A more defined cold front tracks through late Friday which yields a shift from southerlies back to northwesterlies.

Gusty WNW winds are likely on Saturday. A low pressure system will pass south of the area Sunday, but minimal impacts are expected at this time.

MARINE
After a couple hour uptick in southerly winds, nearly all locations have seen gusts drop to 15 knots or less. Some showers may impact the area today, with an isolated threat for thunderstorms. Uncertainty in the instability of the atmosphere casts some doubts on these thunder chances. Some southerly channeling effects may warrant Small Craft Advisories over the lower waters late this evening into portions of the night. A weak cold front pushes across the waters Thursday morning which results in a shift to northwesterly flow. Very warm air temperatures on top of the cooler waters will likely limit vertical mixing. Any higher gusts would be restricted near the land/bay interface.

Winds on Friday largely stay below advisory levels, but there will be an uptick with a more formidable cold front. As this system pushes across the waters late Friday night, 20 knot gusts become possible. Small Craft Advisories will likely be needed by then.

SCA conditions are likely on Saturday and Saturday night in gusty WNW postfrontal flow. Winds will lessen Sunday, but still might be near the advisory threshold.

TIDES/COASTAL FLOODING
While some action stages may be reached through Thursday night (anomalies 1-1.5 feet above normal), the greater water level rises and potential for minor flooding will be toward Friday and Friday night as onshore or southerly flow develops ahead of a low pressure system.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.




Weather Reporting Stations
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Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisSkyWeatherTempDewPtRHinHg
KHGR HAGERSTOWN RGNLRICHARD A HENSON FLD,MD 10 sm28 minESE 0510 smClear59°F46°F63%30.06
KMRB EASTERN WV RGNL/SHEPHERD FLD,WV 15 sm28 mincalm10 smClear52°F46°F82%30.05
Link to 5 minute data for KHGR


Wind History from HGR
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Tide / Current for Chain Bridge, D.C.
   
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Chain Bridge
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Wed -- 03:50 AM EDT     Moonset
Wed -- 04:37 AM EDT     2.85 feet High Tide
Wed -- 06:28 AM EDT     Sunrise
Wed -- 10:56 AM EDT     0.62 feet Low Tide
Wed -- 01:54 PM EDT     Moonrise
Wed -- 04:58 PM EDT     2.90 feet High Tide
Wed -- 07:48 PM EDT     Sunset
Wed -- 11:41 PM EDT     0.61 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

Chain Bridge, D.C., Tide feet
12
am
0.9
1
am
1.4
2
am
2
3
am
2.5
4
am
2.8
5
am
2.8
6
am
2.5
7
am
2
8
am
1.5
9
am
1
10
am
0.7
11
am
0.6
12
pm
0.8
1
pm
1.3
2
pm
1.9
3
pm
2.4
4
pm
2.8
5
pm
2.9
6
pm
2.7
7
pm
2.3
8
pm
1.8
9
pm
1.4
10
pm
1
11
pm
0.7



Tide / Current for Chain Bridge, one mile below, D.C.
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Chain Bridge
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Wed -- 03:50 AM EDT     Moonset
Wed -- 04:32 AM EDT     2.85 feet High Tide
Wed -- 06:28 AM EDT     Sunrise
Wed -- 10:51 AM EDT     0.62 feet Low Tide
Wed -- 01:54 PM EDT     Moonrise
Wed -- 04:53 PM EDT     2.90 feet High Tide
Wed -- 07:48 PM EDT     Sunset
Wed -- 11:36 PM EDT     0.61 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

Chain Bridge, one mile below, D.C., Tide feet
12
am
0.9
1
am
1.5
2
am
2.1
3
am
2.5
4
am
2.8
5
am
2.8
6
am
2.5
7
am
2
8
am
1.4
9
am
1
10
am
0.7
11
am
0.6
12
pm
0.8
1
pm
1.4
2
pm
2
3
pm
2.5
4
pm
2.8
5
pm
2.9
6
pm
2.7
7
pm
2.3
8
pm
1.8
9
pm
1.3
10
pm
1
11
pm
0.7




Weather Map
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GEOS Local Image of east us   
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Sterling, VA,



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