Monday, June21, 2021
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Marine Weather and Tides
Ashton-Sandy Spring, MD

Version 3.4
NOTICE
3/30/2021 -- ANZ330 has been split into ANZ331 and ANZ332. Click EDIT in Marine Forecast and select your new zone.
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.

Sunrise 5:40AMSunset 8:39PM Monday June 21, 2021 4:07 AM EDT (08:07 UTC) Moonrise 4:15PMMoonset 2:05AM Illumination 86% Phase: Waxing Gibbous; Moon at 11 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- 136 Am Edt Mon Jun 21 2021
Overnight..S winds 10 kt. Waves 1 ft.
Mon..S winds 10 to 15 kt. Gusts up to 20 kt. Waves 1 ft.
Mon night..S winds 5 to 10 kt...becoming W after midnight. Gusts up to 20 kt. Waves 1 ft. A chance of showers and tstms.
Tue..NW winds 5 to 10 kt. Waves 1 ft. Showers with a chance of tstms.
Tue night..NW winds 5 to 10 kt. Waves 1 ft.
Wed..N winds 5 to 10 kt. Waves 1 ft.
Wed night..E winds around 5 kt. Waves flat.
Thu..E winds around 5 kt. Waves 1 ft.
Fri..SE winds around 5 kt. Waves 1 ft. Winds and waves higher and visibilities lower in and near tstms.
ANZ500 136 Am Edt Mon Jun 21 2021
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A strong cold front will approach from the ohio river valley late today, then cross the region Tuesday. High pressure will build over the waters for the middle portion of the week. May be needed for portions of the waters Monday evening and Tuesday.


7 Day Forecast for Marine Location Near Ashton-Sandy Spring, MD
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location: 39.15, -77     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 210750 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 350 AM EDT Mon Jun 21 2021

SYNOPSIS. Claudette will pass southeast of the area today and a strong cold front will pass through the area late tonight into Tuesday. High pressure will build overhead for Wednesday and Thursday before moving offshore late in the week.

NEAR TERM /THROUGH TONIGHT/. High pressure will remain over the Atlantic while a strong cold front moves southeast through the Ohio Valley today. Claudette will pass by to our southeast during this time as well.

A south to southwest flow along with subsidence to the north of Claudette will allow for sunshine along with hot and humid conditions. Heat indices will range from the mid to upper 90s for most valleys west of the Blue Ridge to the lower 100s east of the Blue Ridge. It is not out of the question that a Heat Advisory could be needed, but confidence is too low at this time since dewpoints may mix down just a bit. Either way, it will be hot and humid.

Chances for showers and thunderstorms will increase, especially later this afternoon into this evening ahead of the cold front that will be approaching from the Ohio Valley and also along a surface trough that is expected to develop over northern VA/northern MD into the metro areas. Falling heights, strengthening shear profiles, and moderate to perhaps even high CAPE suggests that some storms may become severe. Locally damaging wind gusts will be the primary threat, but large hail cannot be ruled out due to the high amounts of instability progged to be in the -10-20C range.

Convection should wane late this evening and overnight for most areas, but showers are still likely overnight near the Allegheny Highlands as an upper-level trough approaches from the west.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/. The cold front will slowly build to our south Tuesday while the upper-level trough swings through the area. There will be a period of showers associated with the upper-level trough, especially Tuesday morning through mid-afternoon. Drier air associated with subsidence behind the trough axis will cause precipitation to end from west to east during the afternoon hours. An isolated t-storm cannot be ruled out, but instability will be limited for most areas due to cooler temperatures and plenty of clouds. The best chance for a stronger storm will be across extreme southern MD.

High pressure will build overhead for Tuesday night, bringing dry and noticeably cooler and less humid conditions. High pressure will bring plenty of sunshine and low humidity for Wednesday, and Wednesday night will turn out dry and cool.

LONG TERM /THURSDAY THROUGH SUNDAY/. Some models are hinting at the possibility of a coastal low forming off of Cape Hatteras late Wednesday and into early Thursday before shifting northward. Depending on the track and intensity, expect increased cloud coverage and precipitation chances the further south and east in our CWA you go. Impacts look to be minimal in nature for this event with high pressure exiting off the eastern seaboard. For now, will keep low end PoPs for the period.

For Friday, southerly winds will bring a warming trend into the weekend with only the usual summertime diurnal heating induced thunderstorm chances. Otherwise, remaining mostly dry with some scattered cloud coverage. Saturday, shortwave energy tied to an upper level disturbance near the Great Lakes will pose the threat for some showers and potential thunderstorms across the area. GEFS showing the potential for around 1000 j/kg MUCAPE with fairly weak bulk shear so for now severe potential looks to be fairly low but non zero at this time. Timing with these disturbances have been in disagreement with the ensembles so will have to wait to see a more confident solution in timing and potential intensity for these systems. For Sunday and the start of the workweek, expect a slight cool down with increased shower potential throughout the day with thunderstorms possible in the afternoon.

AVIATION /07Z MONDAY THROUGH FRIDAY/. A period of low clouds are possible (and patchy fog around KMRB) early this morning, especially between 09-14z. MVFR conditions are forecast, but IFR conditions cannot be ruled out during this time. Low clouds should burn off by mid-morning.

Scattered thunderstorms are expected this afternoon and evening. Some storms may produce damaging wind gusts and perhaps even large hail. The best chance for a stronger storm will be late this afternoon and evening (around 20z-02z).

Convection should wane overnight, but showers are expected Tuesday. An isolated t-storm cannot be ruled out, but the stronger storms should remain to the south. High pressure will bring VFR conditions Tuesday night through Wednesday night.

VFR conditions expected most of the day on Thursday with isolated instances of sub-VFR, mainly for the SE terminals with any passing shower or storm that crosses the terminals. Friday, expect VFR conditions with isolated sub-VFR with any afternoon showers/thunderstorms.

MARINE. A southerly flow is expected today and winds will increase some as the gradient increases this afternoon. An SCA is in effect for our extreme southern waters this morning, and for most of the Bay and lower Tidal Potomac River this afternoon and evening.

Scattered storms are expected late this afternoon and evening. Some storms may produce gusty winds and hail.

A cold front will pass through late tonight into Tuesday. Northwest winds behind the cold front may gust around SCA criteria Tuesday into Tuesday night. High pressure will build over the waters Wednesday and Wednesday night.

An isolated SMW possible for the water Thursday as a coastal low pressure tracks further north near the bay. Otherwise, sub-SCA winds expected outside of these isolated cells Thursday and Friday.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . None. VA . None. WV . None. MARINE . Small Craft Advisory from noon today to 10 PM EDT this evening for ANZ530>533-539>541. Small Craft Advisory until midnight EDT tonight for ANZ534-537- 543.

SYNOPSIS . BJL NEAR TERM . BJL SHORT TERM . BJL LONG TERM . ADM AVIATION . BJL/ADM MARINE . BJL/ADM


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 19 mi50 min SSW 4.1 G 8 76°F 79°F1007.5 hPa
BLTM2 - 8574680 - Baltimore, MD 24 mi50 min SSW 1 G 2.9 75°F 76°F1006.8 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 25 mi50 min SSW 8 G 8.9 75°F 1007.1 hPa
FSNM2 26 mi50 min SSW 7 G 8.9 75°F 1007.2 hPa
APAM2 - 8575512 - Annapolis, MD 30 mi50 min SE 2.9 G 5.1 76°F 78°F1007.1 hPa
BSLM2 - Chesapeake Bay, MD 30 mi98 min WSW 2.9 70°F 1007 hPa69°F
44063 - Annapolis 32 mi44 min SSW 5.8 G 7.8 73°F 75°F1 ft1008.2 hPa
CPVM2 34 mi50 min 75°F 74°F
TPLM2 - Thomas Point, MD 35 mi68 min SSE 13 G 14 75°F 74°F1008.3 hPa (-1.3)75°F
TCBM2 - 8573364 - Tolchester Beach, MD 40 mi50 min S 6 G 8.9 75°F 77°F1007.4 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Gaithersburg - Montgomery County Airport, MD9 mi72 minSW 310.00 miFair74°F70°F88%1009 hPa
College Park Airport, MD12 mi2.2 hrsS 310.00 miFair75°F69°F82%1007.4 hPa
Fort Meade / Tipton, MD13 mi2.2 hrsN 07.00 miFair0°F0°F%1008.5 hPa
Baltimore, Baltimore-Washington International Airport, MD18 mi74 minS 310.00 miMostly Cloudy75°F70°F84%1007 hPa
Washington/Reagan National Airport, DC, VA20 mi76 minS 910.00 miMostly Cloudy75°F71°F88%1007.5 hPa
Camp Springs / Andrews Air Force Base, MD23 mi72 minS 810.00 miFair73°F72°F97%1007.5 hPa

Link to 5 minute data for KGAI

Wind History from GAI (wind in knots)
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Last 24hrCalmSE4CalmCalmS4SW3W54Calm55SE8SE8S11S9S10S65S4S4S63SW3S3
1 day agoS3CalmCalmCalmCalmSW33NW94W5W9W12
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2 days agoCalmCalmCalmSW3SW5SW8SW76SW6W7W8SW8W8S7SW6S5S5S5S66343SW3

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Mon -- 03:06 AM EDT     Moonset
Mon -- 05:43 AM EDT     Sunrise
Mon -- 05:53 AM EDT     3.59 feet High Tide
Mon -- 01:04 PM EDT     0.30 feet Low Tide
Mon -- 05:15 PM EDT     Moonrise
Mon -- 06:30 PM EDT     2.98 feet High Tide
Mon -- 08:37 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.30.51.122.93.43.63.32.721.40.90.50.30.51.11.92.62.92.92.51.81.20.6

Tide / Current Tables for Benning Bridge, D.C.
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Benning Bridge
Click for Map
Mon -- 03:05 AM EDT     Moonset
Mon -- 05:42 AM EDT     Sunrise
Mon -- 05:49 AM EDT     3.73 feet High Tide
Mon -- 12:58 PM EDT     0.32 feet Low Tide
Mon -- 05:14 PM EDT     Moonrise
Mon -- 06:26 PM EDT     3.09 feet High Tide
Mon -- 08:36 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.30.51.22.23.13.63.73.42.82.11.40.90.50.30.61.22.12.73.132.51.91.20.6

Weather Map
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NOTE: This section has been updated as of 1/26/2021. If the image you are expecting is not showing, please let me know. You may use the EDIT function to update your location.
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