Saturday, August15, 2020
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Marine Weather and Tides
Frederick, MD

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 6:21AMSunset 8:06PM Saturday August 15, 2020 1:23 PM EDT (17:23 UTC) Moonrise 1:25AMMoonset 4:49PM Illumination 11% Phase: Waning Crescent; Moon at 26 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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ANZ538 Patapsco River Including Baltimore Harbor- 1038 Am Edt Sat Aug 15 2020
.small craft advisory in effect from 8 pm edt this evening through Sunday afternoon...
Rest of today..E winds 5 to 10 kt. Waves 1 ft. A slight chance of showers.
Tonight..E winds 5 to 10 kt. Waves 1 ft. Showers likely.
Sun..NE winds 10 kt with gusts to 20 kt. Waves 1 ft. Showers likely.
Sun night..N winds 5 to 10 kt. Waves 1 ft. A chance of showers.
Mon..NW winds 5 kt. Waves flat.
Mon night..SW winds 5 kt. Waves flat.
Tue..W winds around 5 kt. Waves flat.
Wed..S winds around 5 kt. Waves 1 ft or less. A chance of showers.
ANZ500 1038 Am Edt Sat Aug 15 2020
Synopsis for the tidal potomac and md portion of the chesapeake bay.. Low pressure will move along a stationary front to our south today through Sunday. Onshore flow ahead of this system will increase tonight and continue into Sunday, with a small craft advisory in effect for that period. A cold front will approach early next week.


7 Day Forecast for Marine Location Near Frederick, MD
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location: 39.43, -77.41     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 151432 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1032 AM EDT Sat Aug 15 2020

SYNOPSIS. Low pressure over the Ohio River Valley will track eastward along a stalled front over Virginia this weekend. A second cold front will follow Monday. High pressure then returns through the middle of next week. Unsettled weather may return during the second half of next week.

NEAR TERM /THROUGH TONIGHT/. An upper-level trough will approach from the west through this afternoon while a boundary remains over northern North Carolina and southern Virginia, and another boundary remains west of the Appalachians. An east to northeast flow on the cool side of the boundary along with plenty of cloud cover will cause noticeably cooler conditions today compared to recent days. Max temps will range from the 60s in the mountains, to the 70s for most other areas, with perhaps lower 80s in the metro areas where the cloud deck will be thinner.

Plenty of warm and moist air will overrun the surface cooler air in place, and when combined with mid-level convergence ahead of the approaching trough, this will continue to cause showers across portions of the CWA. The best chance for showers will be across the Allegheny and Potomac Highlands as well as central Virginia and southern Maryland, closer to the boundaries. Farther north and east across the metro areas, much of the time may turn out dry and any shower coverage will be isolated to scattered since there is noticeably drier air at the low-levels (this can be seen on the SPC mesoanalysis). Will continue with the Flash Flood Watch across our southwestern Zones into early this afternoon, mainly for the antecedent conditions.

The upper-level trough will move overhead tonight, and this will cause the low-level boundary (925-850 boundary), to approach our area as a warm front. Showers will become more widespread through tonight as the trough builds over the area, but the best chance for heavier rainfall will be closer to the low-level boundary and that is most likely to set up near central Virginia and southern Maryland. Elevated CAPE will also advect into these areas along with anomalously high PWATS. This increases the flood/flash flood threat, especially overnight across these areas. However, confidence is still low since the boundary may set up just to our south, keeping the best chance for heaviest rainfall rates just to our south and east. Will continue to monitor throughout this afternoon to see if a headline is needed for these areas. Elsewhere, rainfall should be lighter farther away from the boundary and with less atmospheric moisture to work with.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/. Guidance has continued to speed up the departure of the heaviest rainfall from our region, with some taking it out of the area by mid- morning. With the trough still passing overhead, still could see some lingering showers throughout the day though. Temperatures will be significantly below average, only reaching the mid 70s (low to mid 60s in the higher elevations).

A weak cold front will swing through on Monday, which should bring very little in terms of precipitation to the region. Can't rule out an isolated shower or thunderstorm however. Will see a significant rebound in temps, with highs back into the mid 80s again.

LONG TERM /TUESDAY THROUGH FRIDAY/. Troughiness will dominate the East Coast states the first half of next week keeping temps aob normal. It will be relatively quiet or uneventful Tue with moisture increasing Wed as a stationary front to the south tries to retreat north. There should be adequate moisture and instability to support sct afternoon t-storms Wed given forcing with approach of mid-upper level trough axis.

Ridging starts building along the East Coast during the second half of next week downstream from a developing cutoff mid-upper level trough along the MS River. As heights rise, anticipating a decrease of the areal coverage of afternoon convection. Not looking bad at all next week with very low risk of seeing excessive rainfall.

AVIATION /14Z SATURDAY THROUGH WEDNESDAY/. Low CIGs will gradually work their way north late this afternoon through tonight. IFR conditions are likely to develop by late tonight, or perhaps lower (especially towards CHO). This is all in response to onshore flow ahead of an approaching low pressure system from the west. Rain chances increase during this time as well, peaking tonight near KCHO/KMRB and overnight into Sunday morning in the metros. Some rain may be moderate at times, especially near KCHO.

Rain should be moving out of the area by early to mid afternoon on Sunday, with VFR conditions returning through Tuesday.

Sct afternoon t-storms expected Wed afternoon.

MARINE. An onshore flow will gradually increase through this evening. A Small Craft Advisory is in effect for portions of the middle Chesapeake Bay and the lower Tidal Potomac River through this afternoon, and for the entire Bay and lower Tidal Potomac River tonight through Sunday afternoon.

Moderate rain expected tonight into early Sunday, with low pressure passing by to the south.

SCA conditions are possible early next week especially Monday morning. Winds should diminish by Tuesday.

Winds are expected to remain below 10 kt through the end of next week except in the vicinity of t-storms.

TIDES/COASTAL FLOODING. Minor coastal flooding is still possible late tonight into Sun morning as onshore flow strengthens as low pressure passes to the south. The most favored location is Annapolis. However, surge models have trended lower with the peak surge since yesterday and only borderline minor flooding is now fcst at Annapolis.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . None. VA . Flash Flood Watch until 2 PM EDT this afternoon for VAZ025-026- 036-037-503-504-508. WV . Flash Flood Watch until 2 PM EDT this afternoon for WVZ505-506. MARINE . Small Craft Advisory from 8 PM this evening to 6 PM EDT Sunday for ANZ530>532-538>540-542. Small Craft Advisory until 6 PM EDT Sunday for ANZ533-534-537- 541-543.

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


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 44 mi53 min ESE 1.9 G 6 78°F 84°F1015.3 hPa
BLTM2 - 8574680 - Baltimore, MD 45 mi53 min ESE 8 G 12 79°F 83°F1014.9 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 49 mi53 min ENE 9.9 G 12 78°F 1015.3 hPa
FSNM2 49 mi53 min ENE 13 G 17 77°F 1015.3 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Frederick Municipal Airport, MD2 mi2.6 hrsN 09.00 miPartly Cloudy75°F69°F83%1016.3 hPa
Gaithersburg - Montgomery County Airport, MD22 mi27 minVar 310.00 miMostly Cloudy76°F66°F74%1017.3 hPa

Link to 5 minute data for KFDK

Wind History from FDK (wind in knots)
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Last 24hrNE5NE5E8E5E5NE5NE5SE9
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SE8CalmCalmCalmCalmCalmCalmCalmCalmCalmCalmNE4CalmCalm--NE4
1 day agoCalmE8SE3E6E6SE8E3CalmCalmCalmCalmCalmCalmCalmN4NE3NE4N5NE6NE6----N7E6
2 days agoCalmS3CalmCalmE9
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SE4E3CalmCalmCalmCalmCalmCalmCalmCalmCalmCalmCalmCalmCalmCalm33

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Sat -- 02:24 AM EDT     Moonrise
Sat -- 06:00 AM EDT     3.22 feet High Tide
Sat -- 06:22 AM EDT     Sunrise
Sat -- 01:08 PM EDT     0.54 feet Low Tide
Sat -- 05:46 PM EDT     Moonset
Sat -- 06:47 PM EDT     2.78 feet High Tide
Sat -- 08:02 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.60.71.222.73.13.23.12.62.11.510.70.50.71.21.92.42.72.82.521.40.9

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Sat -- 02:24 AM EDT     Moonrise
Sat -- 05:55 AM EDT     3.22 feet High Tide
Sat -- 06:22 AM EDT     Sunrise
Sat -- 01:03 PM EDT     0.54 feet Low Tide
Sat -- 05:46 PM EDT     Moonset
Sat -- 06:42 PM EDT     2.78 feet High Tide
Sat -- 08:02 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.60.81.32.12.83.13.232.621.510.70.50.71.21.92.42.72.82.51.91.40.9

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 (13,3,4,5)
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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.