Saturday, January16, 2021
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Marine Weather and Tides
Halfway, MD

Version 3.4
NOTICE
8/26/2020 The 7 day forecast is taking about 5 seconds to load but it will eventually load. NOAA is still working on it.
8/18/2020 NOAA continues to have trouble. Wind guest will occasionally be left off graphs. I am working with NOAA to resolve the issue.
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.

Sunrise 7:27AMSunset 5:13PM Saturday January 16, 2021 2:58 AM EST (07:58 UTC) Moonrise 10:01AMMoonset 9:00PM Illumination 9% Phase: Waxing Crescent; Moon at 3 days in cycle
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.
Marine Forecasts
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ANZ535 Tidal Potomac From Key Bridge To Indian Head- 1241 Am Est Sat Jan 16 2021
.small craft advisory in effect from this evening through late tonight...
Overnight..W winds 5 kt. Waves less than 1 ft. A chance of showers. Patchy fog. Vsby 1 to 3 nm.
Sat..W winds 5 kt. Waves less than 1 ft. A chance of showers. Vsby 1 to 3 nm.
Sat night..SW winds 5 to 10 kt. Waves 1 ft.
Sun..W winds 5 to 10 kt. Waves 1 ft.
Sun night..SW winds 5 kt. Waves less than 1 ft.
Mon..W winds 5 to 10 kt with gusts to 20 kt. Waves 1 ft.
Mon night..W winds 5 to 10 kt. Waves 1 ft.
Tue..W winds 5 to 10 kt. Waves 1 ft.
Wed..W winds 5 to 10 kt. Waves 1 ft.
ANZ500 1241 Am Est Sat Jan 16 2021
Synopsis for the tidal potomac and md portion of the chesapeake bay.. An upper level will low passes through the waters today with high pressure building across the southern united states through early next week as several disturbances cross the region in northwesterly flow. Small craft advisories may be needed for portions of the waters Sunday and Monday.


7 Day Forecast for Marine Location Near Halfway, MD
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location: 39.62, -77.79     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 160234 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 934 PM EST Fri Jan 15 2021

SYNOPSIS. A strong cold front approaching from the Ohio Valley will sweep across the area through tonight. Low pressure will develop along the front, strengthening as it tracks up the coast and into New England on Saturday. High pressure will then build south of the region once again through the first half of next week before another potential storm system approaches the latter half of next week.

NEAR TERM /THROUGH SATURDAY/.

The cold front is slowly moving through our region this evening. Behind the frontal passage, dry air is slowly filtering into parts of central Virginia which has lead to areas of scattering cloud cover. The clearing skies along with moist ground has led to areas of fog forming in central Virginia. Areas west of the Blue Ridge Mountains are hovering near freezing which has led to the concern for freezing fog. We will need to monitor over the next few hours to see if more dry air is able to move into central Virginia before making the call on a Dense Fog advisory.

.Previous Discussion.

Satellite imagery and surface analysis depicts low pressure at the surface and aloft churning over the upper Mississippi River Valley this afternoon, with an associated cold front stretching north to south from the Ohio Valley into the Panhandle of Florida. Clouds are lowering and thickening across the CWA as the front pushes eastward toward the Alleghenies, and the region resides on the eastern flank of the large upper trough/low and the upper jet pushes northward into the Mid Atlantic.

Temperatures this afternoon are in the 30s across the Alleghenies, with middle 40s to lower 50s being observed elsewhere. Showers associated with the front are encroaching on the Allegheny Front as we speak. These showers will make eastward progress into the I-81 corridor over the next couple of hours, and reaching the I-95 corridor during the late afternoon and early evening hours.

The colder air across the Alleghenies will support any rain/snow mix initially to transition to all snow with the help of wet bulbing. Sub advisory level snow is expected across the higher elevations of the Potomac and Allegheny Highlands as the front crosses, primarily above 2000 feet. Minor accumulations will also be possible along the Blue Ridge Mountains in central Virginia, with ridges above 2000 feet the most favorable to see minor snow accumulations.

The front and associated showers will press eastward this evening and the first half of the overnight period, with the front moving east of the Bay a couple hours after midnight. Drier conditions are expected as the front pulls through the area and temperatures fall into the 20s to middle 30s. With the gradient wind expected to remain on the lighter side behind the front, could be some patchy fog with the elevated low level saturation, as well as some icy spots on those surfaces that are unable to dry out before temperatures drop. Best chance for icy spots will reside along and west of the Blue Ridge Mountains, where those sub freezing temperatures will be most prevalent. With middle 30s holding on in the metro areas, thinking the threat for icy conditions would be limited.

SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/. The primary upper level low will shift overhead Saturday, resulting in an increase in westerly winds as it shifts across the region. Moisture wrapping around on the backside of the upper low with temperatures aloft crashing will deliver a resurgence of snow showers across the Alleghenies Saturday afternoon and night, with accumulating snow expected. The potential for a Winter Weather Advisory will exist for portions of the Allegheny Front, and will allow the evening/overnight shifts to better assess this potential.

Further east, given the lift associated with the aforementioned upper low, scattered rain/snow showers are expected to extend across the Blue Ridge Mountains and perhaps into the metro areas. With temperatures well above freezing, accumulating snow is not expected east of the I-81 corridor. Along and west of I-81 and into the Shenandoah Valley, the ingredients appear to be there for the potential for snow squalls Saturday afternoon and evening with steepening low level lapse rates, crashing temperatures aloft, and the lift from the upper low crossing the region. Could see some minor snow accumulations in any heavier squalls as they track east of the Alleghenies, despite temperatures projected to be in the mid to upper 30s. Those heavier snowfall rates within any squalls would be able to overcome those warmer temperatures, potentially leading to some isolated slick spots as they pass. Skies will be on the cloudy side Saturday and Saturday night as the upper low shifts through the region and drier air begins to filter in on the heels of increasing westerly breezes.

Weak ridging will crest of the Mid Atlantic during the day on Sunday before another upper disturbance moves into the region, resulting in additional snow showers across the Allegheny Front Sunday night. Temperatures Sunday and Sunday night will hover slightly above climatological normals for this time of year.

LONG TERM /MONDAY THROUGH FRIDAY/. Another trough will swing through during the day on Monday. With westerly flow at low-levels, and limited moisture available to the system, most locations to the east of the Alleghenies should stay precipitation free. However, a stray instability driven rain or snow shower can't be ruled out as the core of the mid-level cold air associated with the trough swings through (1000-500 hPa thicknesses drop into the low 520s). Upslope snow showers are expected along and west of the Allegheny Front. These snow showers along the Allegheny Front may continue into Monday Night and Tuesday in westerly low- level flow, even as the upper trough progresses off to the east. Quiet weather conditions are expected elsewhere on Tuesday as zonal flow becomes established aloft and a weak area of high pressure builds to our south at the surface.

A fast moving shortwave with pass to our north Tuesday Night, driving a reinforcing cold front through the area. An uptick in upslope snow shower activity is expected along the Allegheny Front once again, but little in the way of precipitation is expected to the east of the mountains Tuesday Night. The aforementioned trough will progress off to the east on Wednesday. Subsidence in the wake of the departing trough should bring any snow showers along the Allegheny Front to an end, and maintain dry conditions further to the east. Wind gusts of up to 30 mph will be possible Wednesday afternoon in the wake of the departing cold front. Forecast confidence decreases moving into Thursday, with considerable spread amongst the various sources of model guidance. High temperatures in the long term period will run near normal (low-mid 40s for most), and low temperatures will run slightly above normal (mid 20s to around 30).

AVIATION /03Z SATURDAY THROUGH WEDNESDAY/.

Dry air is moving into parts of central Virginia behind a frontal passage which has allowed for some clearing of sky cover. Fog has formed which is impacting the CHO terminal with LIFR ceilings. It looks like dry air should continue to build into the CHO terminal but we will need to monitor to see how long it will take to overcome the fog.

.Previous Discussion.

VFR conditions early this afternoon will over the next few hours and persist into the overnight hours as a cold front sweeps across the terminals with increasing shower chances. MVFR/IFR VIS/CIGS will overspread the terminals during this time, with some improvement after 06z in the wake of the front. Light southeasterly winds will turn southwest through this evening, then eventually westward as the front crosses, all the while remain at 10 knots or less.

An upper level low will cross the terminals Saturday and Saturday evening, helping spawn scattered rain/snow showers. Could be some brief reductions to VIS in any heavier showers, with the most probable terminal to see any restrictions being MRB. Otherwise, VFR conditions and increasing westerly winds can be expected through Saturday night. VFR conditions are expected to continue Sunday and Sunday night as westerly winds relax.

VFR conditions are expected at the terminals on both Monday and Tuesday. Winds will be primarily out of the west, and could gust to around 20 knots on Monday.

MARINE. Light southeasterly flow prevailing over the waters this afternoon, out ahead of an approaching cold front. The front will cross the waters around midnight, with showers coming to an end and winds remaining light and westerly. The gradient is expected to tighten late Saturday and Saturday night as an upper low crosses the region and a surface low strengthens over New England. As a result, gusty westerly winds are expected to develop over the waters Saturday evening and persist into Sunday morning. A Small Craft Advisory has been issued for all waters Saturday night, and will likely need extended through at least the first portion of the day Sunday before the gradient relaxes. Lighter westerly breezes and sub SCA conditions will prevail late Sunday afternoon through Sunday night.

Gusts may reach Small Craft Advisory criteria on Monday and Tuesday in westerly flow.

TIDES/COASTAL FLOODING. Water levels will remain elevated this afternoon and this evening under southeasterly winds ahead of an approaching cold front. While not explicitly forecast, minor flooding will be possible at Annapolis and Southwest Waterfront during this evenings high tide cycle. Water levels will remain slightly elevated during the high tide cycles through the day on Saturday before westerly winds increase Saturday night and anomalies decrease.

LWX WATCHES/WARNINGS/ADVISORIES. DC . Coastal Flood Advisory until midnight EST tonight for DCZ001. MD . None. VA . None. WV . None. MARINE . Small Craft Advisory from 6 PM Saturday to 6 AM EST Sunday for ANZ530>543.

SYNOPSIS . BKF NEAR TERM . BKF/JMG SHORT TERM . BKF LONG TERM . KJP AVIATION . BKF/KJP/JMG MARINE . BKF/KJP TIDES/COASTAL FLOODING .


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 66 mi59 min NW 6 G 12 44°F 40°F1003 hPa (-1.2)
BLTM2 - 8574680 - Baltimore, MD 69 mi59 min Calm G 0 44°F 40°F1002 hPa (-2.2)
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 72 mi59 min Calm G 1.9 44°F 1002.3 hPa (-2.7)

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Hagerstown, Washington County Regional Airport, MD7 mi66 minWNW 310.00 miOvercast38°F35°F89%1004.4 hPa
Eastern WV Regional Airport/Shepherd Field, WV18 mi66 minN 010.00 miFair31°F30°F96%1003.3 hPa

Link to 5 minute data for KHGR

Wind History from HGR (wind in knots)
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Last 24hrCalmCalmNW3E4E6SE4E4SE5SE9
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1 day agoCalmS3S4CalmSW4S43CalmCalmCalm433S4E4E5E6NE5E5NE3E4E3NW3Calm
2 days agoSW3SW4SW5S5SW3S3Calm3SW8SW8SW55S7S11S5S5S5S5S5CalmCalmCalmCalmCalm

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Sat -- 05:24 AM EST     -0.33 feet Low Tide
Sat -- 07:25 AM EST     Sunrise
Sat -- 09:56 AM EST     Moonrise
Sat -- 10:56 AM EST     2.63 feet High Tide
Sat -- 05:11 PM EST     Sunset
Sat -- 05:32 PM EST     -0.29 feet Low Tide
Sat -- 08:58 PM EST     Moonset
Sat -- 11:17 PM EST     2.78 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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2.41.81.20.60.1-0.3-0.20.41.222.52.62.41.81.20.60.1-0.2-0.20.21.11.92.52.8

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Sat -- 05:19 AM EST     -0.33 feet Low Tide
Sat -- 07:25 AM EST     Sunrise
Sat -- 09:56 AM EST     Moonrise
Sat -- 10:51 AM EST     2.63 feet High Tide
Sat -- 05:11 PM EST     Sunset
Sat -- 05:27 PM EST     -0.29 feet Low Tide
Sat -- 08:58 PM EST     Moonset
Sat -- 11:12 PM EST     2.78 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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2.41.81.20.60.1-0.3-0.20.41.322.52.62.31.81.10.60.1-0.2-0.20.31.122.52.8

Weather Map
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GEOS Local Image of    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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