Tuesday, July14, 2020
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Marine Weather and Tides
Washington, DC

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 5:53AMSunset 8:34PM Tuesday July 14, 2020 7:09 PM EDT (23:09 UTC) Moonrise 12:27AMMoonset 2:00PM Illumination 29% Phase: Waning Crescent; Moon at 24 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- 436 Pm Edt Tue Jul 14 2020
Rest of this afternoon..NW winds 5 kt. Waves less than 1 ft.
Tonight..NW winds around 5 kt. Waves 1 ft or less.
Wed..SE winds around 5 kt. Waves 1 ft or less.
Wed night..SE winds 5 kt. Waves less than 1 ft.
Thu..SE winds 5 to 10 kt. Waves 1 ft.
Thu night..S winds 5 to 10 kt. Waves 1 ft.
Fri..SW winds around 5 kt. Waves 1 ft. A chance of showers.
Sat..SW winds around 5 kt. Waves 1 ft. A chance of showers. A chance of tstms. Winds and waves higher and visibilities lower in and near tstms.
ANZ500 436 Pm Edt Tue Jul 14 2020
Synopsis for the tidal potomac and md portion of the chesapeake bay.. High pressure will then build across the area through Wednesday before moving offshore. A front may approach from the north late in the week. A small craft advisory may be needed for portions of the waters late Thursday.


7 Day Forecast for Marine Location Near Washington, DC
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location: 38.89, -77.03     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 141858 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 258 PM EDT Tue Jul 14 2020

SYNOPSIS. High pressure will build across the area through Wednesday before moving offshore. A front may approach from the north late in the week, before returning back north over the weekend.

NEAR TERM /THROUGH TONIGHT/. High pressure will expand eastward today from the Great Lakes/Ohio Valley in the wake of a departing upper low over New England. 12z IAD sounding shows a subsidence inversion around 600 hPa, with ample mid-level dry air in place. Some CAMs try to produce a few showers over the central Shenandoah Valley this afternoon, where minimal instability exists, but think that the combination of the subsidence inversion, mid-level dry air, and limited instability/low-level moisture will inhibit the formation of showers. Elsewhere, expect mostly sunny skies, with just a few fair weather cumulus around. Temperatures should top out in the upper 80s for most, and humidity levels will be noticeably lower compared to previous days, with dewpoints in the upper 50s to near 60.

Quiet conditions will continue overnight, as high pressure becomes centered over Pennsylvania. With clear skies and very light or calm winds in place, patchy areas of fog may form later tonight, especially in sheltered valleys to the west of the Blue Ridge. Lows tonight will range from the upper 50s in the Potomac Highlands to the lower 70s in downtown DC and Baltimore.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/. High pressure will continue to press eastward across New England on Wednesday, as the upper level ridge progresses east from the Ohio Valley toward the spine of the Appalachians. Low level winds will become easterly on Wednesday, which will start to transport moisture back into the forecast area. There may be just enough low-level moisture return to trigger a few popup showers or a brief thunderstorm over southwestern portions of the forecast area, but the vast majority of the area will remain dry, with a mix of sun and clouds in place. Highs on Wednesday will be a few degrees warmer than today, with highs predominantly in the upper 80s to lower 90s. Dewpoints will also uptick slightly, rising back into the mid 60s.

High pressure will stall just off the New England coastline Wednesday Night. Continued east to southeasterly flow will bring a bit of a marine influence into the area at low levels. Guidance hints that low clouds may form to the east of the Blue Ridge Wednesday Night.

On Thursday, a shortwave disturbance will track out of Ohio Valley/Great Lakes and progress to our north. This lead shortwave may spark the development of showers, or even a few storms Thursday morning to the west of the Blue Ridge. There's a wide amount of spread with respect to the handling of this morning activity, and as a result, there's also a large amount of spread with respect to how much heating will occur to the west of the Blue Ridge. If strong heating occurs in advance of peak heating, a few strong storms may be possible across western portions of the forecast area during the afternoon hours given decent flow in place for mid-July (20-30 knots 0-6 km shear) ahead of an upstream shortwave over the Great Lakes. However, if we don't destabilize, there may not be much of a threat. Coverage of showers and storms is expected to be lesser to the east of the Blue Ridge. Uncertainty in the high temperature forecast exists there as well, with questions about how long low clouds from Wednesday Night will remain in place to the east of the Blue Ridge. If those clouds remain in place through much of the morning, we may not make it out of the 80s, but if we mix fully, temperatures should rise into the lower 90s.

LONG TERM /FRIDAY THROUGH MONDAY/. Overall good agreement in the guidance concerning the long term. A weak cold front will approach the region by late Friday. With temperatures ranging from the upper 80s to low-mid 90s, and dew points in the mid 70s, chances for afternoon showers and thunderstorms will remain elevated. The boundary will linger over the region on Saturday, which will keep the threat for convection high, especially during the afternoon/early evening as the extra instability, along with daytime convecting heating will likely be enough of a trigger to spark convection.

Another uptick in the heat/humidity begins on Sunday as a Bermuda high offshore redirects the flow to the south. There is some question as to an approaching shortwave tracking along the Mason Dixon Line Sunday which will further act as a lifting mechanism to trigger convection. Regardless, hot and humid conditions are likely to continue into the middle of next week as the Bermuda high persists offshore. While the jet stream remains well displaced to the north, there doesn't appear to be any big shortwaves or upper level lows at this time. With the amount of heat/humidity in place, there will be plenty of energy to spark, possibly severe, convection. However, given the placement of the jet, shear is rather weak. So while the long term remains somewhat uncertain, the overall pattern supports the potential for strong convection, especially during the first half of next week.

AVIATION /18Z TUESDAY THROUGH SUNDAY/. High pressure will be in control through Wednesday, allowing for VFR conditions across the terminals. Winds today will be light out of the northwest, before going light tonight and then switching around to easterly tomorrow into tomorrow night. With clear skies and light or calm winds in place overnight, some patchy fog can't be ruled out at MRB later tonight, but didn't have the confidence to put it in the TAF yet. Low clouds may be possible tomorrow night in easterly low-level flow. Most likely location for sub-VFR ceilings will be BWI/MTN, but can't rule out sub-VFR ceilings anywhere to the east of the Blue Ridge.

Prevailing VFR conditions are expected on Thursday, but temporary drops to sub-VFR may be possible in association with any showers or storms that form. MRB would stand the highest of seeing a shower or storm.

Overall VFR conditions are expected across the terminals Friday and Saturday. Potential for afternoon showers/thunderstorms remain elevated which could result in periods of CIG/VSBY restrictions and gusty winds through the early evening hours.

MARINE. Light NW winds/sub-SCA conditions will continue today. High pressure will be in control through Wednesday allowing for sub- SCA conditions with flow becoming more E/SE by Wednesday into Wednesday Night. Stronger S/SE flow will develop by Thursday, with potential SCA conditions by late in the day/Thursday night. Most storms should stay west of the waters on Thursday.

No marine hazards expected Friday through Saturday night except for a chance of thunderstorms each day. Winds south 10 knots Friday and Friday night. Winds shifting northwest 10 knots Saturday, then veering around to the southeast 5 to 10 knots Saturday night.

TIDES/COASTAL FLOODING. No coastal flooding issues are expected through Wednesday. Stronger south/southeast flow will return by late Thursday and could push some locations to near minor flooding thresholds by the evening high tide.

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

SYNOPSIS . ADS/KJP NEAR TERM . KJP SHORT TERM . KJP LONG TERM . MSS AVIATION . MSS/KJP MARINE . MSS/KJP/ADS TIDES/COASTAL FLOODING . ADS


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 1 mi70 min 85°F
BSLM2 - Chesapeake Bay, MD 19 mi160 min N 1 1015 hPa
APAM2 - 8575512 - Annapolis, MD 30 mi70 min 85°F
TPLM2 - Thomas Point, MD 31 mi70 min ESE 1.9 G 2.9 83°F 82°F1016.9 hPa (-0.0)61°F
BLTM2 - 8574680 - Baltimore, MD 35 mi70 min 79°F
NCDV2 39 mi70 min 89°F
44062 - Gooses Reef, MD 40 mi34 min Calm G 0 85°F 87°F
TCBM2 - 8573364 - Tolchester Beach, MD 47 mi70 min 84°F

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Washington/Reagan National Airport, DC, VA2 mi78 minVar 510.00 miPartly Cloudy89°F54°F30%1016 hPa
Camp Springs / Andrews Air Force Base, MD9 mi74 minN 010.00 miFair85°F56°F37%1016.4 hPa
College Park Airport, MD9 mi75 minNNW 410.00 miFair85°F52°F32%1015.9 hPa
Fort Belvoir, VA14 mi74 minNW 510.00 miFair90°F53°F29%1016.1 hPa
Fort Meade / Tipton, MD20 mi75 minSW 410.00 miMostly Cloudy82°F62°F51%1016.6 hPa
Gaithersburg - Montgomery County Airport, MD21 mi74 minWNW 510.00 miFair85°F60°F43%1018.1 hPa
Washington/Dulles International Airport, DC, VA23 mi78 minVar 410.00 miA Few Clouds88°F54°F31%1016.1 hPa

Link to 5 minute data for KDCA

Wind History from DCA (wind in knots)
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Last 24hrNE9E6E3E3S4S4S4SW3CalmN4N7N8N7N7N5N7N11
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6N6NW8N55NW10
1 day agoW11W4SW9SW7NW5NW5NW6NW8NW8NW5NW3NW5N6N7N5N8N8NE5343NW6N8N6
2 days agoNW11NW8N5W4W6W7W7W5SW5CalmS4S5S3S6SE4S8S10S10S9S9SE8SE7S9S8

Tide / Current Tables for Washington, Potomac River, D.C.
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Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.


Tide / Current Tables for Bladensburg, Anacostia River, Maryland
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Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.


Weather Map
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wmap_A
GEOS Local Image of Mid-Atlantic    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 (19,4,5,8)
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Ground Weather Radar Station Sterling, VA
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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.