Thursday, September24, 2020
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Marine Weather and Tides
Poolesville, 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 6:59AMSunset 7:04PM Thursday September 24, 2020 7:42 PM EDT (23:42 UTC) Moonrise 2:10PMMoonset 11:36PM Illumination 52% Phase: First Quarter Moon; Moon at 8 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- 736 Pm Edt Thu Sep 24 2020
Tonight..SW winds 5 kt. Waves less than 1 ft.
Fri..S winds 5 kt. Waves less than 1 ft. A chance of showers.
Fri night..SE winds around 5 kt. Waves 1 ft. A chance of showers. Patchy fog. Vsby 1 to 3 nm.
Sat..SE winds around 5 kt. Waves 1 ft. A chance of showers. Patchy fog.
Sat night..S winds around 5 kt. Waves 1 ft.
Sun..S winds around 5 kt. Waves 1 ft.
Sun night..S winds around 5 kt. Waves 1 ft.
Mon..SW winds 5 to 10 kt. Waves 1 ft. A chance of showers.
Tue..S winds 5 kt. Waves less than 1 ft. A chance of showers.
ANZ500 736 Pm Edt Thu Sep 24 2020
Synopsis for the tidal potomac and md portion of the chesapeake bay.. High pressure will continue to move away tonight into the overnight hours. The remnants of beta will likely pass to the south while weakening Friday into Saturday. A pair of cold fronts are expected to approach from the great lakes and ohio river valley late in the weekend into early next week. Small craft advisories may be needed for portions of the waters Sunday through Tuesday.


7 Day Forecast for Marine Location Near Poolesville, MD
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location: 39.18, -77.48     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 241918 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 318 PM EDT Thu Sep 24 2020

SYNOPSIS. High pressure centered over the western Atlantic will promote a return flow over the region as the remnants of Beta cross into the Carolinas while weakening Friday into Saturday. High pressure will remain in control for the latter half of the weekend before a cold front drops southeastward from the Great Lakes early next week.

NEAR TERM /THROUGH TONIGHT/. High pressure shifting off the Mid-Atlantic coast will allow for a light southerly wind to develop across the region through tonight as the remnants of Beta track east northeastward into the Southeast U.S. Locally, mostly cloudy skies will prevail the remainder of the afternoon and tonight with the upper jet and a disturbance aloft moves overhead. Have had light echos on regional radars today, but little if any precip has been observed down at the surface across central Virginia. With ample cloud cover, temperatures have been held in check so far, topping out in the low to middle 70s by days end.

Plentiful clouds tonight under a weak WAA regime will result in slightly above normal temps, with 50s to near 60 degrees expected. Much of the area will remain dry through daybreak Friday, with our extreme southern zones across central Virginia having a chance of seeing light rain late in the night.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/. Latest guidance favors keeping the heaviest precip associated with the remnants of Beta to our south, mainly across extreme southern Virginia and the Carolinas Friday into Friday night. That being said, am carrying middle of the road chance POPs south of the District Friday afternoon and evening, with central Virginia carrying the highest chances and QPF potential once again. Ample cloud cover will keep temperatures in the upper 60s to near 70 degrees over our southern zones, with low to middle 70s further north where slight rain chances exist.

The primary upper trough axis crosses the area Friday night, so will maintain chance POPs into Saturday morning for areas east of the Blue Ridge and over the Chesapeake Bay. Slightly above normal temperatures will persist through Friday night.

Lingering showers will be possible Saturday morning over the eastern half of the CWA as the upper trough exits to our east, however a light onshore flow may aid in keeping clouds around through a good portion of the day before some clearing commences. High pressure will nudge back overhead Saturday night as an upper ridge builds overhead. Near to slightly above normal temperatures expected Saturday and Saturday night as dewpoints elevate into the 60s. With increasing low level moisture, patchy fog will be possible Saturday night as well.

LONG TERM /SUNDAY THROUGH THURSDAY/. Global models show a split jet configuration with a residual southern stream impulse ejecting out of the Ozarks early Sunday. This will likely shear on its northeastward progress into the Mid- Atlantic during the overnight hours. Within the northern branch of the jet, synoptic flow is forecast to be amplified and progressive. A fairly potent jet streak will likely accompany these height falls with an array of solutions noted in the guidance. While the core of lower heights remain along the Ontario/Great Lakes border, some of the global models show an embedded impulse which may attain a negative tilt on its pursuit toward the Eastern Seaboard. Forecast solutions are quite variable in terms of placement, magnitude, and timing. Thus, confidence is low at this juncture, but showers and thunderstorms are likely early next week. Eventually a cold frontal passage will ensue ushering in cooler, drier air as cyclonic flow sets up across the northeastern quadrant of the U.S. by mid-week.

To conclude the weekend, warm and humid conditions will prevail as southwesterly flow steers Gulf moisture up the East Coast. Sunday's dew point temperatures are forecast to reach the upper 60s accompanied by highs in the low 80s. While pre-frontal, Monday could cool down a bit given the increase in cloud cover from warm advection processes. Even upon cold frontal passage, initial cooling will be stunted given well-mixed downsloping flow. Eventually highs around 70 degrees are possible by mid-week although quite a bit of spread is noted in the ensemble spread plots.

AVIATION /19Z THURSDAY THROUGH TUESDAY/. Predominate VFR conditions expected through tonight as high pressure off the coast promotes a light southerly flow. Patchy fog will be possible near CHO tonight as low level moisture increases, as well as increasing rain chances.

Better chance of showers exists Friday at CHO as the remnants of Beta cross into the Carolinas. Light rain will attempt to creep northward toward IAD/DCA during the afternoon and evening hours, however precip will be of the light variety, with brief if any restrictions to VIS/CIGs north of CHO.

Low level moisture will remain a plenty on Saturday as winds remain light and onshore, but shower chances will wane the first half of the day, with drier conditions expected Saturday night. With dewpoints in the 60s Saturday night, patchy fog may deliver restrictions to the terminals.

VFR conditions are likely for Sunday but increasing shower and thunderstorm chances on Monday could bring reduced visual flight rules given periodic lower ceilings and visibilities.

MARINE. High pressure off the coast will promote a light southerly flow over the waters through Saturday as the remnants of Beta track to our south and weaken in the process. Given a weak gradient over the area during this time, sub SCA conditions are expected through Saturday night.

Breezy southerly winds on Sunday and Monday could lead to Small Craft Advisory issuances. Additionally, there will be the chance for locally gusty winds from any developing showers and thunderstorms on Monday. Small Craft Advisories are possible into the middle of next week.

TIDES/COASTAL FLOODING. Minor tidal flooding will remain possible with the high tide cycle this afternoon and overnight, as a light southerly flow develops. Currently, only Annapolis is explicitly forecast to cross the minor flood threshold late this evening, however SW D.C. and Straits Point will flirt with it as well.

EQUIPMENT. The KLWX (Sterling, VA) WSR-88D remains out of service until further notice. The outage is due to a failure within the Radar Data Acquisition Functional Area that occurred early in the morning on September 20, 2020.

Technicians from the National Weather Service Radar Operations Center will arrive in Sterling on Saturday, September 26, to diagnose the failure. At that time, they will determine the full scope of the failure, and work with WFO Sterling electronics program staff in taking subsequent maintenance actions. Action and diagnosis includes repairing the gear box and assessing the health of the bull- gear.

Users of KLWX can utilize adjacent weather radars located in Dover DE (KDOX), Mt. Holly NJ (KDIX), Pittsburgh PA (KPBZ), Charleston WV (KRLX), Blacksburg VA (KFCX), and Wakefield VA (KAKQ).

LWX WATCHES/WARNINGS/ADVISORIES. DC . Coastal Flood Advisory until 4 PM EDT this afternoon for DCZ001. MD . None. VA . None. WV . None. MARINE . None.

SYNOPSIS . BKF NEAR TERM . BKF SHORT TERM . BKF LONG TERM . BRO AVIATION . BKF/BRO MARINE . BKF/BRO TIDES/COASTAL FLOODING . BKF EQUIPMENT . LWX


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 32 mi55 min S 2.9 G 4.1 70°F 69°F1016.6 hPa
BLTM2 - 8574680 - Baltimore, MD 48 mi55 min SW 1.9 G 5.1 70°F 75°F1015.8 hPa
BSLM2 - Chesapeake Bay, MD 49 mi133 min S 2.9 1016 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Leesburg / Godfrey, VA8 mi48 minS 410.00 miFair68°F62°F83%1017.3 hPa
Washington/Dulles International Airport, DC, VA15 mi51 minN 010.00 miMostly Cloudy68°F60°F76%1016.5 hPa
Gaithersburg - Montgomery County Airport, MD17 mi47 minS 310.00 miFair68°F60°F76%1018.3 hPa
Frederick Municipal Airport, MD17 mi56 minN 010.00 miClear70°F62°F78%1016.6 hPa

Link to 5 minute data for KJYO

Wind History from JYO (wind in knots)
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Last 24hrW5W6W3W5NW5NW6NW4NW5CalmCalmCalmCalmCalmCalmCalmCalmN3NW3CalmCalmCalmCalmS3SW3
1 day agoCalmW3W4NW4CalmNW7NW4NW4NW6CalmCalmCalmW4NW4NW8
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2 days agoCalmCalmCalmCalmCalmCalmCalmW3CalmCalmCalmCalmCalmN5N4NW6N4N5N7NW8NW7W7W3Calm

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Thu -- 02:32 AM EDT     3.45 feet High Tide
Thu -- 06:58 AM EDT     Sunrise
Thu -- 09:49 AM EDT     0.37 feet Low Tide
Thu -- 03:07 PM EDT     Moonrise
Thu -- 03:18 PM EDT     2.90 feet High Tide
Thu -- 07:01 PM EDT     Sunset
Thu -- 09:44 PM EDT     0.43 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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2.43.13.43.43.12.51.91.40.90.50.40.71.42.12.62.92.82.41.81.30.80.50.40.7

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Thu -- 02:27 AM EDT     3.45 feet High Tide
Thu -- 06:58 AM EDT     Sunrise
Thu -- 09:44 AM EDT     0.37 feet Low Tide
Thu -- 03:07 PM EDT     Moonrise
Thu -- 03:13 PM EDT     2.90 feet High Tide
Thu -- 07:01 PM EDT     Sunset
Thu -- 09:39 PM EDT     0.43 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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2.43.13.43.432.51.91.30.90.50.40.81.52.22.72.92.82.31.81.20.80.50.50.8

Weather Map
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wmap_A
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.
Link to Loop

Other links: Northern Pacific     Contential US     Full GOES-East
Ground Weather Radar Station Sterling, VA
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