Saturday, September25, 2021
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Marine Weather and Tides
Round Hill, VA

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 6:59AMSunset 7:03PM Saturday September 25, 2021 5:39 PM EDT (21:39 UTC) Moonrise 8:36PMMoonset 10:28AM Illumination 80% Phase: Waning Gibbous; Moon at 19 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- 436 Pm Edt Sat Sep 25 2021
.small craft advisory in effect from Sunday morning through Sunday afternoon...
Rest of this afternoon..W winds 5 kt. Waves less than 1 ft.
Tonight..W winds 5 to 10 kt. Waves 1 ft.
Sun..NW winds 5 to 10 kt with gusts to 20 kt. Waves 1 ft.
Sun night..SW winds 5 to 10 kt. Waves 1 ft.
Mon..SW winds 5 kt. Waves less than 1 ft.
Mon night..SW winds 5 to 10 kt. Waves 1 ft.
Tue..W winds around 5 kt. Waves 1 ft. A chance of showers and tstms through the night. A chance of showers after midnight.
Wed..N winds 5 to 10 kt. Waves 1 ft. Winds and waves higher and visibilities lower in and near tstms.
ANZ500 436 Pm Edt Sat Sep 25 2021
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A weak cold front will cross the area tonight into Sunday, with high pressure returning into early next week. Another cold front is poised to cross the waters late Tuesday. Small craft advisories may be needed for portions of the waters late Monday through Tuesday.


7 Day Forecast for Marine Location Near Round Hill, VA
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location: 39.12, -77.77     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 251835 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 235 PM EDT Sat Sep 25 2021

SYNOPSIS. Weak cold front passage will briefly alleviate high pressure overhead. High pressure returns Sunday and Monday from the southeast ahead of the next cold front passage Tuesday.

NEAR TERM /THROUGH TONIGHT/. High pressure nearby today will be slowly overtaken by a weak moisture starved cold front moving down from the Great Lakes. High cirrus clouds will continue over the next few hours before denser clouds move in along the front. A few showers are possible along the Allegheny Front for a few hours this afternoon into the early evening. Areas further east should remain fairly dry with westerly downsloping in place and an already low moisture content front in place.

Behind the front tonight, skies should continue to clear out with only a few lingering high thin clouds proceeding. Some light drizzle could continue into the morning for the Allegheny Front (this would be a typical light upslope snow setup if low temperatures were a bit colder). Lows tonight should be in the upper 40s and 50s for most areas, trending a bit warmer than the last few nights. This trend will continue over the next couple of nights.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/. A broad area of high pressure will be situated across the southeast for the end of the weekend into Monday. Main story behind the cold front passage will be an uptick in winds with a northwesterly flow in place. Gusts 15-20 knots will be common across much of the area during the middle portion of the day on Sunday, eventually calming by the late afternoon/early evening hours.

Continued light amount of clouds on Monday during the day as high pressure begins to exit with a progressive cold front approaching from the NW. Clouds will begin to increase by the evening/overnight hours with the chance for a few showers across the northwest zones as a westerly low level jet forms ahead of the cold front passage expected to cross the area on Tuesday. Highs for the period will climb into the 60s and 70s across most areas aside from the Allegheny Front with lows briefly dropping on Sunday night into the upper 40s to low 50s before increasing Monday night into the 50s to near 60 ahead of the cold front.

LONG TERM /TUESDAY THROUGH SATURDAY/. An upper-level trough will build into New England Tuesday and the cold front associated with the trough will approach from the north Tuesday before passing through Tuesday night. High pressure will remain over the southeastern CONUS during this time. A return flow around that high and ahead of the cold front will allow for warmer and more humid conditions with dewpoints creeping back into the 60s.

The increased moisture will cause marginal to moderate instability ahead of the cold front, so scattered showers and thunderstorms are possible ahead of the boundary Tuesday into Tuesday evening. Increased shear associated with the trough along with the instability does suggest that a few storms could produce strong to perhaps even damaging wind gusts, but confidence remains low due to some uncertainty with timing of the frontal passage relative to peak heating.

The cold front will pass through later Tuesday night and Canadian high pressure will build toward the region from the north for Wednesday while the upper-level trough shifts closer toward the New England and Mid-Atlantic coast. This will provide a northerly flow that brings noticeably cooler and less humid conditions. Surface high pressure will remain nearby to the north, likely bringing below climo temperatures through the end of the week. However, there is still uncertainty as to whether or not the pattern will be unsettled. A blocking pattern is likely to develop. In fact, the EPS and GEFS along with the deterministic runs are showing signs of an Omega block (closed upper-level low over northeastern US and closed upper-level low over western US with ridging in between). The position of the upper-level low over the northeastern US will be critical for our weather pattern. If the low is farther west, then more clouds and showers will occur for Thursday and Friday, but it if is farther east, then more sunshine and dry conditions will occur. For now, the forecast continues to lean closer toward the second scenario that keeps the upper-level low to our northeast, allowing for more of drier northwest flow aloft. However, this will have to be monitored closely due to the high uncertainty.

AVIATION /19Z SATURDAY THROUGH THURSDAY/. For the remainder of the afternoon and early evening, some higher thin cirrus clouds will be common across the terminals before a slightly more dense group of clouds track across the area associated with a cold front. VFR conditions expected for the terminals tonight with an outside chance for a stray shower (mainly near MRB) but otherwise remaining dry. Sunday, winds will start out fairly light out of the NW before shifting out of the SW and becoming gusty at times from anywhere between 16z and 23z for most terminals. After that, light southerly winds will prevail with maybe an isolated shower for MRB Monday night, all while remaining VFR.

A cold front will approach the terminals Tuesday before passing through Tuesday night. Scattered showers and thunderstorms are possible Tuesday, and some storms may produce gusty winds, especially Tuesday afternoon/evening. VFR conditions are most likely outside of any thunderstorm.

MARINE. High pressure nearby for today, leading to light winds through the early evening hours. A weak moisture starved cold front will cross the waters late tonight with NW winds proceeding its passage. SCA winds likely during the middle part of Sunday for all the waters most likely. Light winds expected after, with high pressure building for Sunday night into Monday. Return flow on Monday evening may increase the need for SCAs for mainly the open waters.

A cold front will approach the waters Tuesday before passing through Tuesday night. West to southwest winds may gust around SCA criteria ahead of the front Tuesday into Tuesday evening before north to northwest winds increase behind the front late Tuesday night into Wednesday with more SCA conditions possible.

Scattered showers and thunderstorms are possible Tuesday, and some storms may produce gusty winds over the waters, especially Tuesday afternoon/evening.

TIDES/COASTAL FLOODING. Anomalies remain around a half to one foot above normal this afternoon. The flow will be light through this evening, so the elevated water levels will persist. Water levels may come close to minor flood thresholds with the higher of the astronomical high tides this evening into the early overnight hours, particularly around Washington DC and perhaps Annapolis. However, confidence is low due to the light flow.

The offshore flow will strengthen late tonight into Sunday morning, and anomalies will decrease during this time.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . None. VA . None. WV . None. MARINE . Small Craft Advisory from 2 AM to 6 PM EDT Sunday for ANZ530>534-537>543. Small Craft Advisory from 7 AM to 6 PM EDT Sunday for ANZ535- 536.

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


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 43 mi69 min SW 5.1 G 8 75°F 71°F1013.9 hPa
BSLM2 - Chesapeake Bay, MD 61 mi69 min W 2.9 75°F 1014 hPa52°F
BLTM2 - 8574680 - Baltimore, MD 64 mi69 min WSW 1.9 G 6 76°F 77°F1013.4 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Leesburg / Godfrey, VA11 mi44 minN 010.00 miFair73°F55°F53%1014.6 hPa
Winchester Regional, VA20 mi44 minNNW 710.00 miPartly Cloudy70°F52°F53%1014.2 hPa
Washington/Dulles International Airport, DC, VA20 mi47 minSSW 510.00 miMostly Cloudy73°F52°F48%1014.2 hPa
Eastern WV Regional Airport/Shepherd Field, WV23 mi46 minWNW 710.00 miA Few Clouds72°F50°F46%1013.9 hPa

Link to 5 minute data for KJYO

Wind History from JYO (wind in knots)
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Last 24hrSW3SW3CalmCalmCalmCalmCalmCalmCalmCalmNW3NW3CalmCalmCalmCalmCalmCalmSW4W6CalmS4CalmCalm
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Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
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Sat -- 06:51 AM EDT     0.49 feet Low Tide
Sat -- 06:59 AM EDT     Sunrise
Sat -- 11:25 AM EDT     Moonset
Sat -- 12:24 PM EDT     2.96 feet High Tide
Sat -- 06:31 PM EDT     0.44 feet Low Tide
Sat -- 07:00 PM EDT     Sunset
Sat -- 09:33 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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3.43.12.621.40.90.60.50.81.42.12.72.92.92.51.81.20.70.50.50.81.42.32.9

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Sat -- 06:46 AM EDT     0.49 feet Low Tide
Sat -- 06:59 AM EDT     Sunrise
Sat -- 11:25 AM EDT     Moonset
Sat -- 12:19 PM EDT     2.96 feet High Tide
Sat -- 06:26 PM EDT     0.44 feet Low Tide
Sat -- 07:00 PM EDT     Sunset
Sat -- 09:33 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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3.43.12.51.91.30.90.60.50.81.52.22.72.92.92.41.81.20.70.50.50.81.52.43

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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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