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Marine Weather and Tides
Version 3.4 |
10/6/2018 Colors of tide XTide graphs changed to emphasize that they were upgraded. See next note. Comments welcome. 10/4/2018 I have fixed XTide and updated the harmonic files. There were some name changes so you might have to click EDIT to find the new station name. |
Sunrise 6:55AM | Sunset 5:57PM | Thursday February 21, 2019 4:44 PM EST (21:44 UTC) | Moonrise 8:34PM | Moonset 8:26AM | Illumination 94% | ![]() |
ANZ535 Tidal Potomac From Key Bridge To Indian Head- 336 Pm Est Thu Feb 21 2019
Rest of this afternoon..NW winds 10 kt. Waves 1 ft.
Tonight..NW winds 5 to 10 kt. Waves 1 ft. Rain likely.
Fri..N winds 5 kt. Waves less than 1 ft.
Fri night..E winds around 5 kt. Waves 1 ft.
Sat..SE winds around 5 kt. Waves 1 ft. Rain.
Sat night..S winds around 5 kt. Waves 1 ft. Rain.
Sun..SW winds 10 to 15 kt...becoming w. Waves 1 ft.
Mon..NW winds 10 to 15 kt...diminishing to 5 kt after midnight. Waves 1 ft.
Rest of this afternoon..NW winds 10 kt. Waves 1 ft.
Tonight..NW winds 5 to 10 kt. Waves 1 ft. Rain likely.
Fri..N winds 5 kt. Waves less than 1 ft.
Fri night..E winds around 5 kt. Waves 1 ft.
Sat..SE winds around 5 kt. Waves 1 ft. Rain.
Sat night..S winds around 5 kt. Waves 1 ft. Rain.
Sun..SW winds 10 to 15 kt...becoming w. Waves 1 ft.
Mon..NW winds 10 to 15 kt...diminishing to 5 kt after midnight. Waves 1 ft.
ANZ500 336 Pm Est Thu Feb 21 2019
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A cold front will stall out well to our south through Friday night while high pressure builds to the north. The boundary will return north as a warm front Saturday through Sunday while stronger low pressure passes through the great lakes. A cold front will pass through the waters late Sunday and high pressure will return for early next week. A small craft advisory will likely be needed for the waters Sunday and Monday, and a gale warning may be needed for portions of the waters late Sunday through Monday.
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A cold front will stall out well to our south through Friday night while high pressure builds to the north. The boundary will return north as a warm front Saturday through Sunday while stronger low pressure passes through the great lakes. A cold front will pass through the waters late Sunday and high pressure will return for early next week. A small craft advisory will likely be needed for the waters Sunday and Monday, and a gale warning may be needed for portions of the waters late Sunday through Monday.
7 Day Forecast for Marine Location Near Shenandoah Farms, VA
Hourly EDIT Helplocation: 39.01, -78.02 debug
Area Discussion for - Baltimore, MD/Washington
  (on/off)  Help NOTE: mouseover dotted underlined text for definitionFxus61 klwx 212031 afdlwx area forecast discussion national weather service baltimore md washington dc 331 pm est Thu feb 21 2019 Synopsis Surface high pressure will continue to build toward the region tonight, but an upper-level disturbance will also pass through. High pressure will continue to build toward the region Friday through Friday night from the north. Low pressure will track through the midwest Saturday and the great lakes Sunday. The warm front associated with the low will approach Saturday into Sunday before the cold front associated with the low passes through late Sunday. High pressure will return for early next week and low pressure may impact the area during the middle portion of next week. Near term through tonight A weak cold front will continue to push to our south and east through late this afternoon while high pressure approaches from the north. Low clouds and fog have mixed out across most areas, so some sunshine will allow for the strong inversion to mix out... Leading to a mild afternoon. High pressure will continue to build toward the area from the north tonight, but an upper-level disturbance is expected to pass through in the west to southwest flow aloft. Our area will be in the right entrance region of a large upper-level jet that separates an upper-level trough over the rockies and the subtropical ridge over the southeastern conus. The large scale lift associated with the upper-level jet should combine with the upper-level disturbance to provide enough lift for a period of rain tonight, especially late tonight across central and southern areas (including the washington metropolitan area). Rainfall amounts should be light given the fact that little moisture will be associated with this system. For the potomac highlands of virginia and pendleton county in west virginia, there should be enough of a cold layer from evaporative cooling, causing the likelihood for a period of freezing rain. Elsewhere, temperatures should remain above freezing or precipitation is not expected when temperatures are below freezing. Short term Friday through Saturday night High pressure will continue to build in from the north Friday through Saturday while a cold front stalls well to our south over the southeastern conus. A couple upper-level disturbances will pas through in the westerly flow aloft Friday through Friday night. For most of the area, dry conditions will persist with just some high and mid-level clouds and it will be seasonably chilly. However, across central virginia into southern maryland there may be some light rain with these systems. Confidence is low at this time since the stronger lift and overrunning will be to our south, closer to the boundary. Low pressure will track through the midwest Saturday and into the great lakes Saturday night. The cold front well to our south will begin to retreat north as a warm front late Saturday and Saturday night, but it will remain well to our south. However, the low and mid-level flow will turn southerly and this will allow for warm and moist air from the gulf of mexico to overrun the low-level colder air in place. This will increase the chances for rain during this time, and with copious amounts of moisture in place some rain may be locally heavy, especially later Saturday and Saturday night. Will have to watch for the possibility of a period of freezing rain across northern maryland into the allegheny and potomac highlands blue ridge mountains. Temperatures will be near freezing when precipitation is arriving and light ice accumulations are possible. Long term Sunday through Thursday A cold front will move through our region during the day on Sunday. Winds will continue out of the south leading to continued advection of warm and moist air into our region. Models are showing pwats reaching above a inch and close to a inch and a half in some areas. This is pretty high for february. This suggest a lot of moisture to fuel rain as the front passes through. There is pretty good agreement that the cold front should be through our area by Sunday evening with winds becoming westerly. As temperatures rise and rain will be likely along with snow melt, there will be a concern for flooding on Sunday and continuing into early Monday. High pressure is expected to build into our region Monday through |
early Wednesday. Upslope induced showers will be possible over the higher elevations early on Monday. An upper level trough over canada is forecast to dip southward into the central united states and the great lakes region. A shortwave associated with this trough will move to our north kicking off a surface low that moves through pa. Another low will move through the southeast us and then shift of the eastern sea board. Showers will be possible on Wednesday as the low moves to our north. Aviation 17z Thursday through Monday High pressure will continue to build from the north through late this afternoon, andVFR conditions are expected. Northwest winds may gust around 15 to 20 knots across the northern terminals before sunset. A period of rain is expected for kcho and likely for kiad and kdca later tonight, and MVFR conditions are possible. Drier air should hang around for kmrb. High pressure will bringVFR conditions for Friday and Friday night, but lower clouds and increasing chances for rain are expected Saturday and Saturday night. Rain will be likely on Sunday as a cold front moves through our region. Strong winds will be possible out of the south and will become westerly by the evening periods. Subvfr conditions are likely. On Monday, skies will clear with winds continuing out of the west. Vfr conditions expected at this time. Marine A brief pressure surge behind a cold front an increased mixing will cause northwest winds to gust around 20 knots this afternoon over the northern portions of the chesapeake bay. A small craft advisory is in effect for these areas. The SCA may need to be extended into the upper tidal potomac river, but confidence is too low at this time. Winds should remain below sca criteria tonight through Saturday, and probably Saturday night as high pressure builds in from the north. On Sunday, rain will move through the waters with winds out of the south. Winds will likely reach above small craft advisory levels with the potential for a gale warning. Monday, winds will remain elevated out of the west. Small craft advisories will likely be needed again with gale warnings possible. Hydrology Some melting and sublimation of the snowpack is ongoing today, and will continue (but to a much lesser extent) tomorrow, with temperatures above freezing. Streams are already above their normal levels for february, but the snowmelt will elevate them even further. The next system affects us over the weekend, basically all in the form of rain. Rainfall totals of 1 to 2 inches are expected, with the range of possibilities being from a half inch to perhaps over 2 inches. If there's still snow on the ground, and especially if the higher rainfall amounts are realized, this combination would produce flooding both on small and larger streams starting Saturday through possibly early next week. The tipping point all winter for experiencing flooding has been about 1.25-1.5 inches of rain, and we are right around that range for the forecast. Our official forecast already takes opequon creek in west virginia above flood stage on Sunday morning, but it is too early for issuance of a flood watch at this time, particularly given the snowpack uncertainty. Lwx watches warnings advisories Dc... None. Md... None. Va... None. Wv... None. Marine... Small craft advisory until 5 pm est this afternoon for anz530>532-538>540. Synopsis... Bjl near term... Bjl short term... Bjl long term... Jmg aviation... Bjl jmg marine... Bjl jmg hydrology... Je |
Weather Reporting Stations
EDIT (on/off)  Help NOTE: Click on distance to see the station location on a mapStations | Dist | Age | Wind | Air Temp | Water Temp | Waves | Pressure | DewPt |
WASD2 - 8594900 - Washington, DC | 54 mi | 68 min | WNW 6 G 9.9 | 57°F | 41°F | 1017.7 hPa | ||
BSLM2 - Chesapeake Bay, MD | 71 mi | 134 min | NNW 4.1 | 56°F | 1017 hPa | 41°F | ||
BLTM2 - 8574680 - Baltimore, MD | 78 mi | 68 min | N 5.1 G 9.9 | 57°F | 38°F | 1016.8 hPa |
Wind History for Washington, DC
(wind in knots) EDIT (on/off)  Help4 PM | 5 PM | 6 PM | 7 PM | 8 PM | 9 PM | 10 PM | 11 PM | 12 AM | 1 AM | 2 AM | 3 AM | -12 PM | 5 AM | 6 AM | 7 AM | 8 AM | 9 AM | 10 AM | -12 PM | 12 PM | 1 PM | 2 PM | 3 PM | |
Last 24hr | NE | E | NE G5 | N | NE | NE | N | W | NW | W | W | W | SW | W | SW | W | SW | SW | SW | S | W G8 | NW | ||
1 day ago | NW | NW G9 | NW | NE | NE | E | SE | E | SE | E | SE | SE G7 | SE G8 | E | E | E | E G7 | E G7 | E | SE G7 | -- | E | ||
2 days ago | NW G28 | NW G19 | NW G18 | NW | N G14 | NW G19 | NW G18 | NW G16 | NW G13 | NW G14 | N G13 | N G11 | NW G11 | NW G16 | N G13 | NW G10 | NW G12 | N G10 | NW | NW | NW G9 | W G11 | NW G11 | NW G8 |
Airport Reports
EDIT (on/off)  Help Click EDIT to display multiple airportsAirport | Dist | Age | Wind kt | Visibility | Sky/Weather | Temp | DewPt | Humidity | Pressure |
Winchester Regional, VA | 12 mi | 69 min | NW 10 | 10.00 mi | Fair | 50°F | 26°F | 40% | 1017.9 hPa |
Leesburg / Godfrey, VA | 24 mi | 69 min | NW 10 | 10.00 mi | Fair | 54°F | 30°F | 41% | 1017.6 hPa |
Wind History from OKV (wind in knots)
5 PM | 6 PM | 7 PM | 8 PM | 9 PM | 10 PM | 11 PM | -12 PM | 1 AM | 2 AM | 3 AM | 4 AM | 5 AM | 6 AM | 7 AM | 8 AM | 9 AM | 10 AM | 11 AM | 12 PM | 1 PM | 2 PM | 3 PM | 4 PM | |
Last 24hr | SE | SE | SE | SE | E | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | Calm | NW | NW | NW | NW |
1 day ago | Calm | E | Calm | Calm | Calm | Calm | Calm | E | E | E | Calm | SE | SE | E | Calm | SE | E | E | SE | SE G17 | SE | SE | SE | SE |
2 days ago | NW G24 | NW G19 | NW | NW G15 | NW | NW G16 | NW G21 | NW G16 | NW | NW | NW | NW | Calm | NW | NW | NW | NW | NW | N G14 | NW | NW | N | Calm | NE |
Tide / Current Tables for Chain Bridge, D.C.
EDIT RT Ports Option Weekend mode (on/off) (on/off)  Help One Week of DataChain Bridge
Click for Map
Thu -- 04:16 AM EST -0.46 feet Low Tide
Thu -- 06:52 AM EST Sunrise
Thu -- 08:22 AM EST Moonset
Thu -- 09:47 AM EST 3.23 feet High Tide
Thu -- 04:38 PM EST -0.50 feet Low Tide
Thu -- 05:52 PM EST Sunset
Thu -- 08:30 PM EST Moonrise
Thu -- 10:13 PM EST 3.26 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Click for Map
Thu -- 04:16 AM EST -0.46 feet Low Tide
Thu -- 06:52 AM EST Sunrise
Thu -- 08:22 AM EST Moonset
Thu -- 09:47 AM EST 3.23 feet High Tide
Thu -- 04:38 PM EST -0.50 feet Low Tide
Thu -- 05:52 PM EST Sunset
Thu -- 08:30 PM EST Moonrise
Thu -- 10:13 PM EST 3.26 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
12 am | 1 am | 2 am | 3 am | 4 am | 5 am | 6 am | 7 am | 8 am | 9 am | 10 am | 11 am | 12 pm | 1 pm | 2 pm | 3 pm | 4 pm | 5 pm | 6 pm | 7 pm | 8 pm | 9 pm | 10 pm | 11 pm |
1.9 | 1.2 | 0.5 | -0.1 | -0.4 | -0.3 | 0.5 | 1.6 | 2.5 | 3.1 | 3.2 | 2.9 | 2.2 | 1.4 | 0.7 | 0.1 | -0.4 | -0.5 | 0.1 | 1.1 | 2.2 | 2.9 | 3.3 | 3.1 |
Tide / Current Tables for Chain Bridge, one mile below, D.C.
EDIT (on/off)  Help One Week of DataChain Bridge
Click for Map
Thu -- 04:11 AM EST -0.46 feet Low Tide
Thu -- 06:52 AM EST Sunrise
Thu -- 08:22 AM EST Moonset
Thu -- 09:42 AM EST 3.23 feet High Tide
Thu -- 04:33 PM EST -0.50 feet Low Tide
Thu -- 05:52 PM EST Sunset
Thu -- 08:30 PM EST Moonrise
Thu -- 10:08 PM EST 3.26 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Click for Map
Thu -- 04:11 AM EST -0.46 feet Low Tide
Thu -- 06:52 AM EST Sunrise
Thu -- 08:22 AM EST Moonset
Thu -- 09:42 AM EST 3.23 feet High Tide
Thu -- 04:33 PM EST -0.50 feet Low Tide
Thu -- 05:52 PM EST Sunset
Thu -- 08:30 PM EST Moonrise
Thu -- 10:08 PM EST 3.26 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
12 am | 1 am | 2 am | 3 am | 4 am | 5 am | 6 am | 7 am | 8 am | 9 am | 10 am | 11 am | 12 pm | 1 pm | 2 pm | 3 pm | 4 pm | 5 pm | 6 pm | 7 pm | 8 pm | 9 pm | 10 pm | 11 pm |
1.9 | 1.1 | 0.5 | -0.1 | -0.4 | -0.3 | 0.5 | 1.7 | 2.6 | 3.1 | 3.2 | 2.8 | 2.1 | 1.3 | 0.6 | 0 | -0.4 | -0.4 | 0.1 | 1.2 | 2.3 | 3 | 3.3 | 3.1 |
Weather Map and Satellite Images
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GOES 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 numerious 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. |