Sunday, August9, 2020
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Marine Weather and Tides
Ashburn, VA

Version 3.4
NOTICE
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 6:17AMSunset 8:13PM Sunday August 9, 2020 4:03 PM EDT (20:03 UTC) Moonrise 10:30PMMoonset 10:53AM Illumination 67% Phase: Waning Gibbous; Moon at 21 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- 137 Pm Edt Sun Aug 9 2020
This afternoon..S winds 5 kt. Waves less than 1 ft. Scattered showers with isolated tstms.
Tonight..S winds 5 kt. Waves less than 1 ft.
Mon..S winds around 5 kt. Waves 1 ft.
Mon night..S winds 5 kt. Waves less than 1 ft.
Tue..S winds around 5 kt. Waves 1 ft. A chance of showers and tstms.
Tue night..S winds 5 kt. Waves less than 1 ft.
Wed..S winds around 5 kt. Waves 1 ft. A chance of tstms. A chance of showers.
Thu..S winds around 5 kt. Waves 1 ft. Showers and tstms likely, then a chance of showers after midnight. Winds and waves higher and visibilities lower in and near tstms.
ANZ500 137 Pm Edt Sun Aug 9 2020
Synopsis for the tidal potomac and md portion of the chesapeake bay.. High pressure will build across the waters over the next few days. A cold front will approach from the northwest next week, stalling in the area as the week progresses.


7 Day Forecast for Marine Location Near Ashburn, VA
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location: 39.03, -77.47     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 091847 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 247 PM EDT Sun Aug 9 2020

SYNOPSIS. High pressure will be settled overhead this afternoon into Monday. A cold front will approach late Tuesday into Tuesday night and remain stalled near our area through the end of the week.

NEAR TERM /THROUGH TONIGHT/. A couple of slow moving showers are over Nelson County, Culpeper County and Fairfax County in Virginia, as well as over the District of Columbia area. The main concern will be downpours over a matter of minutes and occasional lightning. Additional isolated showers and a thunderstorm or two could develop along and east of the Blue Ridge Mountains into early this evening as weak mid-level energy interacts with some daytime heating. Isolated gusty winds can't be ruled out. High temperatures will reach the upper 80s to near 90. After showers and thunderstorms dissipate, some low clouds and patchy fog could develop overnight. Lows tonight will be in the 60s and 70s.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/. Weak high pressure will be in control Monday as southerly flow settles over our region. This will be advecting moisture into our area, which could allow for the development of a few isolated showers and thunderstorms in the afternoon and evening. Development is expected to be mainly over higher elevations due to terrain circulation, with lack of a strong forcing aloft. Heat index values could reach the upper 90s over most areas across our CWA. Dry conditions are expected Monday night.

Southerly flow will continue on Tuesday ahead of an approaching front and high pressure centered over the western Atlantic. Warm and moist air advection will again allow for heat index values to reach the upper 90s, maybe a few areas in the tipple digits. Shortwave energy aloft associated with the front and diurnal heat will allow for another day of afternoon, evening and even nighttime showers and thunderstorms as the front continues to approach our area.

LONG TERM /WEDNESDAY THROUGH SUNDAY/. High pressure will remain over the Atlantic Ocean for Wednesday, and a light southerly flow will allow for more hot and humid conditions. The heat and humidity will likely lead to isolated/scattered showers and thunderstorms, especially during the afternoon and evening hours.

An upper-level trough (and perhaps even a closed upper-level low) will develop over the Ohio Valley into the Tennessee Valley Thursday through Sunday while high pressure builds over New England. A backdoor boundary will move into the region from the north and east during this time. The exact details are uncertain this far out, but the combination of the boundary, and easterly component from the Atlantic, and lower heights from the upper-level trough nearby will enhance the chances for showers and thunderstorms. Some may produce heavy rainfall during this time.

AVIATION /19Z SUNDAY THROUGH FRIDAY/. VFR conditions expected, except brief MVFR or IFR cigs in heavy showers or thunderstorms, mainly near CHO, DCA and BWI. A drier pattern will remain into Monday night with less chance of any thunderstorm developing over our region. Tuesday chance of afternoon convection increases ahead of an approaching front.

Patchy low clouds and fog are possible during Wednesday morning due to plenty of moisture in place, and the possibility of it getting trapped underneath the nocturnal inversion. A few afternoon and evening showers and thunderstorms are possible as well, but coverage should be isolated to scattered.

Shower and thunderstorm coverage may become more widespread for Thursday and Friday as a backdoor cool front moves into the area. An easterly component to the low-level flow may also increase the coverage of low clouds and subVFR conditions.

MARINE. Winds are expected to remain below Small Craft Advisory criteria into Monday night. Some convection could bring gusty winds this afternoon and evening. There will be less chance for any convection Monday into Monday night, with an increase on Tuesday afternoon and evening ahead of a front.

High pressure will remain over the Atlantic Wednesday, and a southerly flow will remain in place. Winds may approach SCA criteria over portions of the waters during this time. Isolated to scattered showers and thunderstorms are possible during this time.

A backdoor boundary will move into the area for Thursday and Friday, perhaps causing shower and thunderstorm coverage to be more widespread.

TIDES/COASTAL FLOODING. Elevated water levels will persist over the next couple days. The flow will be relatively light, so the most likely scenario is that sensitive areas will be around action stage.

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

SYNOPSIS . KLW NEAR TERM . KLW SHORT TERM . KLW LONG TERM . BJL AVIATION . BJL/KLW MARINE . BJL/KLW


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 26 mi46 min 84°F 83°F1018.7 hPa
BSLM2 - Chesapeake Bay, MD 44 mi94 min SSE 5.1 1018 hPa
BLTM2 - 8574680 - Baltimore, MD 50 mi46 min 86°F 83°F1017.8 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Washington/Dulles International Airport, DC, VA5 mi72 minS 310.00 miPartly Cloudy89°F70°F53%1018.6 hPa
Leesburg / Godfrey, VA6 mi69 minWNW 410.00 miFair86°F68°F55%1019.6 hPa
Gaithersburg - Montgomery County Airport, MD19 mi68 minVar 510.00 miPartly Cloudy88°F70°F55%1020.6 hPa
Manassas, Manassas Regional Airport/Harry P. Davis Field, VA22 mi68 minSSW 710.00 miMostly Cloudy91°F73°F57%1019.3 hPa

Link to 5 minute data for KIAD

Wind History from IAD (wind in knots)
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Last 24hr3E4CalmSE4CalmSE3CalmCalmCalmS3S3CalmCalmSE4CalmCalmCalmCalmNW5SW3SW4S3S35
1 day agoSW6W7SW3W4NW4NE8NE8E5CalmNW6N5NW6N5NE5NE6NE6NE4NE4NE4NE4CalmNW5NW3NW4
2 days agoE8SE7SE7SE8SE10
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CalmS4SW4S3CalmE3S4CalmCalmCalmSE5SW4S5S6S6SW6W5S4

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Sun -- 01:07 AM EDT     3.12 feet High Tide
Sun -- 06:17 AM EDT     Sunrise
Sun -- 07:44 AM EDT     0.62 feet Low Tide
Sun -- 11:51 AM EDT     Moonset
Sun -- 01:25 PM EDT     2.94 feet High Tide
Sun -- 07:41 PM EDT     0.43 feet Low Tide
Sun -- 08:10 PM EDT     Sunset
Sun -- 11:28 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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2.93.132.51.91.40.90.70.60.91.52.22.72.92.92.51.91.30.80.50.40.71.22

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Sun -- 01:02 AM EDT     3.12 feet High Tide
Sun -- 06:16 AM EDT     Sunrise
Sun -- 07:39 AM EDT     0.62 feet Low Tide
Sun -- 11:51 AM EDT     Moonset
Sun -- 01:20 PM EDT     2.94 feet High Tide
Sun -- 07:36 PM EDT     0.43 feet Low Tide
Sun -- 08:10 PM EDT     Sunset
Sun -- 11:28 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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33.132.51.91.30.90.70.60.91.52.22.72.92.92.51.91.30.70.50.40.71.32.1

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
Wind Forecast for Baltimore, MD/Washington (16,3,4,5)
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Ground Weather Radar Station Sterling, VA
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Disclaimer:
The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerous of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.