Tuesday, December1, 2020
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Marine Weather and Tides
Olney, 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 7:07AMSunset 4:47PM Tuesday December 1, 2020 3:15 AM EST (08:15 UTC) Moonrise 5:48PMMoonset 8:15AM Illumination 99% 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- 1242 Am Est Tue Dec 1 2020
.small craft advisory in effect from 9 am est this morning through this afternoon...
Overnight..SW winds 5 to 10 kt. Waves 1 ft.
Tue..W winds 10 to 15 kt. Gusts up to 20 kt. Waves 1 ft.
Tue night..SW winds 5 to 10 kt. Waves 1 ft.
Wed..W winds 5 to 10 kt. Waves 1 ft.
Wed night..W winds around 5 kt. Waves 1 ft.
Thu..SW winds around 5 kt. Waves 1 ft.
Thu night..SW winds around 5 kt. Waves 1 ft.
Fri..NW winds around 5 kt. Waves 1 ft. A chance of showers.
Sat..W winds 5 to 10 kt. Waves 1 ft.
ANZ500 1242 Am Est Tue Dec 1 2020
Synopsis for the tidal potomac and md portion of the chesapeake bay.. Strong low pressure will depart to the north into new york and quebec through Tuesday. High pressure will build from the midwest to off the southern middle atlantic coast Wednesday into Thursday, then another low pressure system will likely approach from the tennessee river valley Friday. Small craft advisories may be needed Wednesday.


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 010252 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 952 PM EST Mon Nov 30 2020

SYNOPSIS. An upper-level trough will remain overhead through Tuesday night. High pressure will gradually build over the area by Thursday morning. Another storm system may impact the area at the end of the week or early next week.

NEAR TERM /UNTIL 6 AM TUESDAY MORNING/. A closed upper low along with its associated surface low will remain over upstate New York tonight while the cold front associated with this system moves off to our east. A west to southwest flow will usher in colder air that has wrapped around the low. Min temps will range from the 20s in the mountains, to the 30s for most other locations, to the lower 40s in downtown Washington and Baltimore.

Dry conditions are expected for most areas. However, an upslope flow along with moisture wrapping around the low will cause snow to continue developing along locations near/west of the Allegheny Front. Winter Storm Warnings are in effect for Garrett, western Grant, and western Pendleton Counties. Snow should become steadier between 06z and 10z as the upper- level trough axis swings through, and winds behind this become more orthogonal to the terrain while lift deepens through the lower levels and into the mid-levels of the atmosphere.

The morning commute for Tuesday will be impacted by snow along/west of the Allegheny Front.

SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/. The closed upper-level low will slowly lift into southeastern Canada Tuesday through Tuesday night, while the upper-level trough associated with this system remains overhead. Vorticity advection along with cold advection should result in mostly cloudy/cloudy skies and nearly steady temperatures in the 30s and 40s (20s in the mountains). Winds will remain brisk out of the west to southwest with gusts to nearly 30 mph creating wind chills in the 30s for most areas, but much colder in the mountains (teens and even single digits along the Allegheny Front).

An upslope flow along with moisture wrapping around the closed upper-level low will continue to bring snow showers to locations along and west of the Allegheny Front. A couple light showers or snow showers may spill east of the mountains Tuesday morning as the upper-level trough axis passes through the area. For Tuesday afternoon, a few snow showers may make it into eastern WV, northern VA, and central MD due to limited instability underneath the subsidence inversion. However, it appears that the accumulating snow should be confined to locations near/west of the Allegheny Front.

Despite weak instability and much of the moisture not lining up in the dendritic snow growth zone, there should be plenty of moisture and lift from the trough axis to cause a prolonged period of upslope snow. Therefore, Winter Storm Warnings continue for Garrett, western Grant, and western Pendleton for 5 to 10 inches of snow (the highest snow amounts around and above 3kft). A Winter Weather Advisory is in effect for western Allegany, western Mineral, and western Highland Counties for 2 to 5 inches of snow mainly above 2500 feet.

Fair weather expected on Wed, but on the brisk side as upper low moves east and subsidence inversion strengthens. Winds could gust up to 30 mph with wind chills remaining in the 30s.

LONG TERM /THURSDAY THROUGH MONDAY/. Quite the interesting and active pattern continues for the latter portion of this week into the weekend. Overall, guidance is in fairly good agreement in regards to the long term forecast. A retrograding low over northern Quebec persists while a double barrel upper level low induces a quasi-Fujiwhara effect over the Southern Plains. Slight ridging over the southeastern CONUS will keep surface high pressure just offshore Thursday; keeping the region dry. However, the upper level trough over Quebec will dive southward over the Ohio Valley just enough where it will pick up one of the upper level lows over the Southern Plains. As a result, a surface cold front will push through the region Friday into Saturday; reviving the risk for showers.

A Rex Block will then develop over the western CONUS, which will amplify the upper level trough over the Eastern US. While the placement of the trough will keep our region dry under a strong NW flow, brisk conditions will likely return to the area for the weekend before another storm system possibly approaches early next week.

AVIATION /03Z TUESDAY THROUGH SATURDAY/. A brief surge behind a cold front may cause westerly winds to gust around 15 to 20 knots. Winds may diminish for a period overnight, but gusty west to southwest winds are expected by mid morning Tuesday continuing into Tuesday evening. Gusts around 25 knots are possible. High pressure will build toward the area later Tuesday night through Wednesday.

VFR conditions are likely Thursday with high pressure offshore inducing a southerly flow. Sub-VFR possible by late Fri PM due to increasing chance for showers as the wind turns SE.

MARINE. A brief surge in winds is expected late this evening over the upper Tidal Potomac River and northern Chesapeake Bay. Winds may diminish for a period late tonight before increasing Tuesday morning. A Small Craft Advisory is in effect late this evening, then again Tuesday for these areas. Across the rest of the waters, and SCA is in effect through Tuesday for west to southwest winds. The SCA may need to be extended Tuesday night and Wednesday for portions of the waters.

A light southwesterly wind is forecast Thursday as high pressure passes to the south, becoming southerly Thursday night into Friday as the high moves offshore. The wind may begin to increase as it turns southeasterly ahead of a low pressure system approaching from the Tennessee River Valley by late Friday.

TIDES/COASTAL FLOODING. Tidal anomalies will gradually fall overnight due to an offshore flow. A Coastal Flood Advisory remains in effect for southeastern Harford County for the high tide cycle late this evening.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . Winter Weather Advisory from 6 AM to 9 PM EST Tuesday for MDZ501. Winter Storm Warning from 1 AM Tuesday to 7 AM EST Wednesday for MDZ001. Coastal Flood Advisory until midnight EST tonight for MDZ508. VA . Winter Weather Advisory from 6 AM to 9 PM EST Tuesday for VAZ503. WV . Winter Weather Advisory from 6 AM to 9 PM EST Tuesday for WVZ503. Winter Storm Warning from 1 AM Tuesday to 7 AM EST Wednesday for WVZ501-505. MARINE . Small Craft Advisory until 6 PM EST Tuesday for ANZ531>534-537- 539>541-543. Small Craft Advisory until 1 AM EST Tuesday for ANZ530-535-536- 538-542. Small Craft Advisory from 9 AM to 6 PM EST Tuesday for ANZ530- 535-536-538-542.

SYNOPSIS . LFR NEAR TERM . BJL/LFR SHORT TERM . LFR LONG TERM . MSS AVIATION . BJL/MSS/LFR MARINE . BJL/MSS/LFR TIDES/COASTAL FLOODING . BJL


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 19 mi45 min NW 1.9 G 6 48°F 51°F1000.5 hPa
BLTM2 - 8574680 - Baltimore, MD 27 mi45 min NW 4.1 G 8.9 47°F 54°F999.3 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 29 mi45 min W 11 G 13 47°F 999.7 hPa
FSNM2 29 mi45 min W 11 G 14 47°F 999.3 hPa
BSLM2 - Chesapeake Bay, MD 32 mi45 min Calm 1000 hPa
APAM2 - 8575512 - Annapolis, MD 33 mi45 min WSW 2.9 G 7 48°F 54°F999.6 hPa
44063 - Annapolis 35 mi15 min 7.8 G 9.7 48°F 53°F1003.3 hPa (+0.8)
CPVM2 38 mi45 min 49°F 37°F
TPLM2 - Thomas Point, MD 38 mi15 min W 11 G 12 48°F 53°F1001.2 hPa (+0.9)35°F
TCBM2 - 8573364 - Tolchester Beach, MD 44 mi45 min W 8.9 G 11 49°F 53°F1000 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Gaithersburg - Montgomery County Airport, MD5 mi19 minWNW 410.00 miOvercast43°F30°F63%1001.6 hPa
College Park Airport, MD14 mi20 minN 010.00 miOvercast46°F30°F55%1000.3 hPa
Fort Meade / Tipton, MD16 mi20 minW 410.00 miOvercast43°F35°F76%1001 hPa
Washington/Reagan National Airport, DC, VA20 mi23 minN 410.00 miMostly Cloudy47°F35°F63%1000.6 hPa
Baltimore, Baltimore-Washington International Airport, MD21 mi21 minWSW 810.00 miMostly Cloudy46°F34°F63%999.8 hPa
Washington/Dulles International Airport, DC, VA24 mi23 minN 010.00 miOvercast46°F33°F61%1000.1 hPa

Link to 5 minute data for KGAI

Wind History from GAI (wind in knots)
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Last 24hr5E6E5E8E9SE5SE9SE4S7S4S5S4W6NW9W10
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1 day agoCalmCalmCalmCalmCalmCalmSW5SW5S83S7S4S7SE6SE5E5E5E5E6E4SE6E5SE54
2 days agoCalmCalmCalmCalmNW3W4NW10W15
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Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Tue -- 03:39 AM EST     0.06 feet Low Tide
Tue -- 07:08 AM EST     Sunrise
Tue -- 08:14 AM EST     Moonset
Tue -- 09:09 AM EST     2.49 feet High Tide
Tue -- 03:16 PM EST     0.08 feet Low Tide
Tue -- 04:46 PM EST     Sunset
Tue -- 05:48 PM EST     Moonrise
Tue -- 09:05 PM EST     2.94 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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1.40.90.40.10.10.41.11.92.32.52.41.91.30.70.30.10.20.61.42.22.82.92.82.3

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Tue -- 03:34 AM EST     0.06 feet Low Tide
Tue -- 07:08 AM EST     Sunrise
Tue -- 08:14 AM EST     Moonset
Tue -- 09:04 AM EST     2.49 feet High Tide
Tue -- 03:11 PM EST     0.08 feet Low Tide
Tue -- 04:46 PM EST     Sunset
Tue -- 05:48 PM EST     Moonrise
Tue -- 09:00 PM EST     2.94 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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1.40.80.40.10.10.51.21.92.32.52.31.81.20.70.30.10.20.61.42.32.82.92.82.3

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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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.