Thursday, December12, 2019
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Marine Weather and Tides
Olney, MD

Version 3.4
NOTICE
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.
6/2/2019. Many thanks to a user for reporting an error on one of the Edit pages. The switch to PHP 7.2 caused many pages that previously worked to quit working. I fixed many but I still depend on users to report ones I missed. Please report errors HERE or send an email to me at L-36.com. Allen

Sunrise 7:16AMSunset 4:47PM Thursday December 12, 2019 11:49 PM EST (04:49 UTC) Moonrise 5:22PMMoonset 7:35AM Illumination 98% Phase: Waning Gibbous; Moon at 16 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- 937 Pm Est Thu Dec 12 2019
Rest of tonight..NE winds 5 kt. Waves less than 1 ft. A slight chance of freezing rain.
Fri..NE winds around 5 kt. Waves 1 ft. Rain likely or a chance of freezing rain.
Fri night..NW winds around 5 kt. Waves 1 ft. Rain. Vsby 1 to 3 nm.
Sat..W winds 5 to 10 kt. Waves 1 ft. Rain likely.
Sat night..W winds 5 to 10 kt. Waves 1 ft. A chance of showers.
Sun..W winds 5 to 10 kt with gusts to 20 kt. Waves 1 ft.
Sun night..NW winds 5 to 10 kt. Waves 1 ft.
Mon..SE winds around 5 kt. Waves 1 ft. Rain or snow likely in the morning, then rain.
Tue..NW winds 5 to 10 kt. Waves 1 ft. Showers likely, mainly in the morning.
ANZ500 937 Pm Est Thu Dec 12 2019
Synopsis for the tidal potomac and md portion of the chesapeake bay.. High pressure over the region will shift offshore through this tonight. A low pressure system developing over the northern gulf of mexico will move northeastward toward the region Friday into Saturday. Small craft advisories may be needed Saturday through Sunday morning.


7 Day Forecast for Marine Location Near Olney, MD
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location: 39.15, -77.07     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 130235 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 935 PM EST Thu Dec 12 2019

SYNOPSIS. High pressure will slide offshore tonight. Low pressure will start developing along the Gulf Coast tonight and then head northward up the East Coast Friday and Saturday. High pressure will return briefly on Sunday before another system potentially affects the region Monday and Monday night. Cold high pressure will then follow for the middle of next week.

NEAR TERM /THROUGH FRIDAY NIGHT/.

Skies were briefly mostly clear this evening, which when coupled with light or calm winds has allowed temperatures to drop back to near or below freezing across most of the area. High clouds are now streaming in aloft well ahead of the main disturbance at mid-upper levels, and will continue to thicken through the night. With these high cloud moving in, the drop in temperatures should slow, but expect that temps will still drop a degree or two further through the remainder of the night. This sub- freezing air at the surface will set the stage for light freezing rain or freezing drizzle early tomorrow morning across portions of the forecast area.

The current water vapor imagery shows a shortwave disturbance located over Arkansas embedded within a much larger longwave trough. This shortwave will move rapidly northeastward toward our area tonight into early tomorrow. A broad zone of warm advection will ensue just above the surface in advance of this feature. Isentropic lift associated with the warm advection will lead to the development of light precipitation around daybreak tomorrow across southwestern portions of the forecast area. This should spread north and east through the morning. Although all of the precip looks to be light, the highest amounts of precipitation should be across western portions of the forecast area, where they'll be located closer to the shortwave disturbance. As the shortwave departs off to our northeast, we may experience a brief lull in the precip associated with subsidence in its wake from early afternoon until around dark. As other shortwave disturbances descend down the back side of the longwave trough, the longwave trough will dig into the lower Mississippi Valley tomorrow evening, inducing the formation of surface low pressure downstream in TN/KY. As this low tracks northeastward into WV and ascent in advance of the main trough overspreads our area tomorrow evening, precipitation is expected to blossom across the area once again. This time around, the precipitation is expected to be steadier, with moderate rain possible through much of the night.

In terms of precipitation type, freezing rain will be possible early tomorrow morning, primarily to the west of the Blue Ridge, where a Winter Weather Advisory is in effect. Temperatures should gradually warm through the day, with most locations to the west of the Blue Ridge transitioning to plain rain before noon. In the most sheltered mountain valleys, freezing rain may hang on through the afternoon and possibly into the early evening hours. However, precipitation is expected to be plain rain for all by the time the second round of precipitation works in late tomorrow evening. To the east of the Blue Ridge, the expectation is that precipitation should fall in the form of plain rain throughout the entire event. However, there is a non- zero (but very low chance) that a brief period of freezing drizzle or light freezing rain could occur on the front edge of the precip very late tonight or early tomorrow morning. But currently, that isn't expected. We will continue to monitor the situation and make adjustments to the Winter Weather Advisory if needed.

SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/.

Low pressure will slide to the northeast on Saturday, leaving showers behind. Cold advection behind the system will begin to bring upslope showers to the Allegheny Front. These will changeover to snow quickly into the late afternoon/early evening as colder air pushes in. Only light accumulations are expected, with no winter weather advisories for snow currently anticipated. Further east, Saturday afternoon and evening will be slowly drying out, with relatively mild temps near 50 in the afternoon dropping into the 30s at night.

LONG TERM /SUNDAY THROUGH THURSDAY/. High pressure will briefly build over our region on Sunday behind a exiting coastal low system to the northeast. A westerly flow will form that may lead to some upslope snow showers Sunday morning along the western slopes of the Allegheny Mountain range. Temperatures will be near average during the day in the low to mid 40w with overnight lows in the 30s Sunday night.

A warm front is forecast to lift up through our area early on Monday. A weak high pressure looks to create a cold air damming situation on the eastern side of the Appalachians. Models starting to agree that a near surface layer of near to below freezing temperatures will be in place for a period Sunday overnight through Monday afternoon. As the precipitation shield associated with the warm front moves through our region, wintry precipitation will be possible on Monday. Models have consistent shown a above freezing layer at the mid-levels which would be an ideal setup for freezing rain but it remains uncertain at this time on how widespread wintry precipitation will become. Monday continues to be a concerning setup especially with decent agreement on some sort of cold damming situation. As the surface cold front lifts through our area, winds will become more southerly leading to a warm up late Monday and into early Tuesday. This suggest a changeover to all rain. The timing of this warm air moving into our region will need to continue to monitor to determine how much wintry precipitation will be possible.

Showers could linger into early Tuesday as the frontal system lifts out of our region. Most precipitation is forecast to be fully out of our area by Tuesday afternoon. High pressure will then build back into our region Tuesday afternoon through Thursday next week.

AVIATION /01Z FRIDAY THROUGH TUESDAY/. VFR conditions are expected through this evening and the early part of the overnight hours, with light winds generally out of the northeast. Lowering CIGs and RA/FZRA will become a concern early Friday morning. FZRA is likely at CHO by 11z or so and at MRB by around 14z. Much less (but still some) risk IAD. Not particularly concerned at DCA/BWI/MTN for FZRA given later arrival of precip and warming easterly flow. Low CIGs and VSBY likely Friday night with rain. Improving to MVFR/VFR on Saturday as low lifts north and rain ends, though scattered showers may linger.

Weak high pressure over our region will lead to mainly VFR conditions but with a westerly flow some midlevel cloud decks will be possible on Sunday.

A warm front will lift up through all terminals. Precipitation will be likely with some of it potentially falling as wintry precip likely in the form of freezing rain. SubVFR conditions will be possible.

MARINE. High pressure will slide east as low pressure moves up from the south tonight through Friday night, but not yet particularly concerned about SCA issues given stable air mass in place. SCA could become an issue as low pressure pulls away Saturday into Sunday.

A coastal low will exit our region on Sunday but some lingering strong winds could lead to the need for Small Craft Advisories on Sunday. Another system will move through our region on Monday which could lead to the need for further Small Craft Advisories.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . Winter Weather Advisory from 9 AM to 3 PM EST Friday for MDZ003-004. Winter Weather Advisory from 9 AM to 6 PM EST Friday for MDZ501-502. VA . Winter Weather Advisory from 4 AM to 3 PM EST Friday for VAZ025-026-036>038-503-504-508. Winter Weather Advisory from 9 AM to 3 PM EST Friday for VAZ505. Winter Weather Advisory from 7 AM to 3 PM EST Friday for VAZ027>031-039-040-501-507. WV . Winter Weather Advisory from 4 AM to 3 PM EST Friday for WVZ505-506. Winter Weather Advisory from 9 AM to 3 PM EST Friday for WVZ051>053. Winter Weather Advisory from 7 AM to 3 PM EST Friday for WVZ050-055-501-502. Winter Weather Advisory from 7 AM to 6 PM EST Friday for WVZ503-504. MARINE . None.

SYNOPSIS . RCM NEAR TERM . KJP SHORT TERM . RCM/CJL LONG TERM . JMG AVIATION . CJL/JMG MARINE . CJL/JMG


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 19 mi50 min ESE 1.9 G 2.9 35°F 44°F1035.8 hPa (-1.6)
BLTM2 - 8574680 - Baltimore, MD 27 mi56 min ESE 4.1 G 6 34°F 45°F1035.4 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 29 mi50 min E 6 G 7 35°F 1035.6 hPa (-2.0)
FSNM2 29 mi62 min E 7 G 8.9 35°F 1034.8 hPa
BSLM2 - Chesapeake Bay, MD 32 mi140 min NNW 1 28°F 1036 hPa24°F
APAM2 - 8575512 - Annapolis, MD 33 mi50 min 36°F 1035.1 hPa (-2.0)
44063 - Annapolis 35 mi26 min ESE 7.8 G 9.7 36°F 44°F1035.5 hPa
CPVM2 38 mi56 min 36°F
TPLM2 - Thomas Point, MD 38 mi50 min ENE 8 G 9.9 36°F 44°F1036.3 hPa (-2.2)29°F
TCBM2 - 8573364 - Tolchester Beach, MD 44 mi56 min E 4.1 G 6 32°F 43°F1035.9 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Gaithersburg - Montgomery County Airport, MD5 mi54 minSE 510.00 miOvercast29°F19°F66%1036.9 hPa
College Park Airport, MD14 mi74 minN 010.00 miOvercast30°F17°F59%1035.9 hPa
Fort Meade / Tipton, MD16 mi56 minN 010.00 miOvercast28°F23°F80%1036.2 hPa
Washington/Reagan National Airport, DC, VA20 mi58 minENE 310.00 miOvercast35°F23°F61%1035.9 hPa
Baltimore, Baltimore-Washington International Airport, MD21 mi56 minE 510.00 miOvercast33°F25°F72%1035.4 hPa
Washington/Dulles International Airport, DC, VA24 mi58 minSE 610.00 miOvercast31°F19°F61%1035.1 hPa

Link to 5 minute data for KGAI

Wind History from GAI (wind in knots)
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Last 24hrNW5NW4CalmNE3CalmN3NE4Calm4NE5E53S43SE7SE7S8SE4SE5E3SE4E4CalmSE5
1 day agoNW8
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Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Thu -- 12:14 AM EST     Full Moon
Thu -- 03:00 AM EST     -0.10 feet Low Tide
Thu -- 07:17 AM EST     Sunrise
Thu -- 07:34 AM EST     Moonset
Thu -- 08:26 AM EST     2.53 feet High Tide
Thu -- 02:44 PM EST     -0.09 feet Low Tide
Thu -- 04:46 PM EST     Sunset
Thu -- 05:22 PM EST     Moonrise
Thu -- 08:28 PM EST     3.04 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.90.40.1-0.10.10.81.62.22.52.52.11.40.80.3-0-0.10.20.91.82.6332.62

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Thu -- 12:14 AM EST     Full Moon
Thu -- 02:55 AM EST     -0.10 feet Low Tide
Thu -- 07:17 AM EST     Sunrise
Thu -- 07:33 AM EST     Moonset
Thu -- 08:21 AM EST     2.53 feet High Tide
Thu -- 02:39 PM EST     -0.09 feet Low Tide
Thu -- 04:46 PM EST     Sunset
Thu -- 05:22 PM EST     Moonrise
Thu -- 08:23 PM EST     3.04 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.90.40-0.10.10.81.72.22.52.421.40.80.3-0-0.10.211.92.7332.61.9

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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Wind Forecast for Baltimore, MD/Washington (23,6,7,8)
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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 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.