Wednesday, April1, 2020
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Marine Weather and Tides
Poolesville, 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 6:52AMSunset 7:35PM Wednesday April 1, 2020 3:33 AM EDT (07:33 UTC) Moonrise 11:12AMMoonset 1:37AM Illumination 58% Phase: First Quarter Moon; Moon at 8 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- 142 Am Edt Wed Apr 1 2020
Overnight..NE winds 5 kt. Waves less than 1 ft. Rain. Vsby 1 to 3 nm.
Wed..N winds 5 kt. Waves less than 1 ft.
Wed night..NW winds 5 kt. Waves less than 1 ft.
Thu..NW winds 10 to 15 kt with gusts to 20 kt. Waves 1 ft.
Thu night..NW winds 5 to 10 kt. Waves 1 ft.
Fri..NW winds 5 to 10 kt. Waves 1 ft.
Fri night..N winds 5 to 10 kt. Waves 1 ft.
Sat..S winds around 5 kt. Waves 1 ft.
Sun..W winds around 5 kt. Waves 1 ft.
ANZ500 142 Am Edt Wed Apr 1 2020
Synopsis for the tidal potomac and md portion of the chesapeake bay.. Low pressure will exit the carolina coastline tonight and move out to sea Wednesday while strengthening. High pressure will slowly build in from the midwest through the end of the week. Small craft advisories may be needed late Wednesday night through Friday.


7 Day Forecast for Marine Location Near Poolesville, MD
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location: 39.18, -77.48     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 010119 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 919 PM EDT Tue Mar 31 2020

SYNOPSIS. Low pressure will move offshore of South Carolina this evening, then head out to sea Wednesday as it strengthens. High pressure will slowly build in from the Midwest through the end of the week. The high will gradually move offshore over the weekend. A cold front may approach from the Ohio Valley by early next week.

NEAR TERM /THROUGH WEDNESDAY/. Coastal low pressure along the North Carolina coast this evening will intensify as it moves east offshore late tonight. The upper-level low associated with this system will move through our area this evening and then offshore overnight.

The upper-level low has bought rain to the area this evening. However, as the upper-level low slides offshore overnight, this will allow for some drier air to work its way into the area from the northeast. Therefore, rain will gradually taper off overnight. However, some showers will linger near/west of the Blue Ridge Mountains where any dry air advection will be weak and there will still be a little lift from a weak surface and upper-level trough. Temperatures along the highest ridges will be marginally supportive of snow this evening before tapering off to snow showers overnight, although amounts are expected to be below advisory levels. Low temperatures will settle into the mid 30s to lower 40s for most.

Upper level troughing will remain overhead on Wednesday, which will likely promote cloud cover to persist much of the day. A few showers are possible in the afternoon as a vort max crosses, mainly near and west of the Blue Ridge and Catoctin Mountains. With continued cold advection and cloud cover, temperatures will be held in the 50s.

SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/. A secondary boundary will slip southward Wednesday night. It should be dry, but winds may pick up a bit. So even though low temperatures will be in the mid 30s to around 40, the probability of any frost is low.

Gusty winds will continue into Thursday between the deep low pressure off the coast and high pressure extending across the Great Lakes. Skies should be clearer overall though, with high temperatures in the mid 50s to the lower 60s. Lows will again be in the mid 30s to lower 40s as winds being to diminish.

LONG TERM /FRIDAY THROUGH TUESDAY/. Split zonal flow will be the story for Friday and Saturday, with little to no chance of precipitation either day. Meanwhile, surface ridge axis will be settled over the Ohio Valley, slowly moving east over the region later Saturday. Temperatures on both days will be seasonable, with highs in the upper 50s to low 60s.

A very weak cold front may push through the region on Sunday, but precipitation chances with this seem rather low at this point. If anything, just some light showers. Temperatures will be warmer though, as winds turn more southerly ahead of the approaching front, and behind the departing surface ridge. Highs expected to be closer to the mid 60s.

Not much of a temperature drop at all behind the aforementioned front, as highs on Monday expected to be in the upper 60s to near 70. This is a result of surface high pressure moving offshore of the northeastern U.S. and turning winds back out of the southeast once again. Showers will again be possible Monday.

AVIATION /01Z WEDNESDAY THROUGH SUNDAY/. Rain this evening will gradually taper off overnight as low pressure moves offshore. MVFR conditions are expected for most of the time tonight, but a period of IFR conditions are possible to the south and west (KMRB, KIAD, and KCHO). The drier air will bring rising ceilings Wednesday morning.

Upper level energy will keep VFR stratocumulus across the area Wednesday and perhaps a brief shower in the afternoon. Ceilings will clear out Wednesday night. Northwest winds will be gusty (up to 25 kt) on Thursday.

VFR conditions expected Friday and Saturday, as high pressure builds in from the west.

MARINE. Low pressure will move off the North Carolina Coast tonight, causing east to northeast winds this evening to gradually turn to the north overnight. The gradient will be strong enough for gusts around 20 to 30 knots, with the highest gusts closer to Smith Point. An SCA is in effect for the Bay and lower/middle Potomac River through midday Wednesday. After a lull late Wednesday, another front combined with high pressure building in likely leads to another period of SCA conditions late Wednesday night and Thursday. SCA conditions may linger into Friday on portions of the water as the strong offshore low only slowly moves away.

No marine hazards expected on Saturday into Sunday, as high pressure will be building in from the west.

TIDES/COASTAL FLOODING. Tidal anomalies have increased to around 1 to 2 feet above normal due to an easterly flow this evening. The flow will gradually turn to the north late tonight into Wednesday, so that does add some uncertainty as to how the trend in anomalies.

However, it appears minor inundation is most likely for the more sensitive sites during the Wednesday morning/midday high tide cycle. A Coastal Flood Advisory is in effect for St Marys County for Wednesday morning and additional advisories may be needed farther north up the Bay and Potomac River. Will re- assess the anomaly trend overnight.

For Washington DC, the tide cycle overnight will be close to minor flooding. Anomalies have sharply increased upstream over the lower Tidal Potomac River, but not sure how much will make it up the Potomac River with the wind turning more toward the north.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . Coastal Flood Advisory from 4 AM to 11 AM EDT Wednesday for MDZ017. VA . None. WV . None. MARINE . Small Craft Advisory until 3 PM EDT Wednesday for ANZ530>533- 536-538>542. Small Craft Advisory until 6 PM EDT Wednesday for ANZ534-537- 543.

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


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 32 mi45 min NE 4.1 G 8.9 43°F 56°F1009 hPa
BLTM2 - 8574680 - Baltimore, MD 48 mi45 min ENE 11 G 14 43°F 52°F1008.8 hPa
BSLM2 - Chesapeake Bay, MD 49 mi123 min NE 5.1 1009 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Leesburg / Godfrey, VA8 mi38 minNE 510.00 miOvercast37°F35°F93%1009.8 hPa
Washington/Dulles International Airport, DC, VA15 mi41 minNNE 810.00 miOvercast41°F36°F82%1009 hPa
Gaithersburg - Montgomery County Airport, MD17 mi37 minNE 610.00 miOvercast38°F35°F89%1010.7 hPa
Frederick Municipal Airport, MD17 mi43 minNNE 67.00 miOvercast41°F37°F87%1010.2 hPa

Link to 5 minute data for KJYO

Wind History from JYO (wind in knots)
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Last 24hrCalmN3NE3N4N5CalmNE5NE4E3SE4E4NE5E5E6E7
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1 day agoE3CalmCalmE4S4S6S11S7S11
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2 days agoE4CalmCalmCalmE3CalmS4SE5SE6
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S9S5S4S9S10S4NE4NE5N5NE5CalmN4CalmCalmCalm

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Wed -- 02:34 AM EDT     Moonset
Wed -- 02:51 AM EDT     2.73 feet High Tide
Wed -- 06:21 AM EDT     First Quarter
Wed -- 06:52 AM EDT     Sunrise
Wed -- 09:02 AM EDT     0.51 feet Low Tide
Wed -- 12:11 PM EDT     Moonrise
Wed -- 02:56 PM EDT     3.12 feet High Tide
Wed -- 07:32 PM EDT     Sunset
Wed -- 10:13 PM EDT     0.51 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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1.52.22.62.72.62.11.61.10.70.50.60.91.62.433.12.92.521.410.60.50.6

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Wed -- 02:34 AM EDT     Moonset
Wed -- 02:47 AM EDT     2.73 feet High Tide
Wed -- 06:21 AM EDT     First Quarter
Wed -- 06:52 AM EDT     Sunrise
Wed -- 08:57 AM EDT     0.51 feet Low Tide
Wed -- 12:11 PM EDT     Moonrise
Wed -- 02:51 PM EDT     3.12 feet High Tide
Wed -- 07:32 PM EDT     Sunset
Wed -- 10:08 PM EDT     0.51 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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1.62.32.72.72.52.11.510.60.50.611.72.533.12.92.51.91.40.90.60.50.6

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.
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Other links: Northern Pacific     Contential US     Full GOES-East
Wind Forecast for Baltimore, MD/Washington (3,6,7,8)
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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 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.