Monday, December9, 2019
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Marine Weather and Tides
Washington, DC

Version 3.4
NOTICE
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.
6/2/2019. Many thanks to a user for reporting an error on one of the Edit pages. The switch to PHP 7.2 caused many pages that previously worked to quit working. I fixed many but I still depend on users to report ones I missed. Please report errors HERE or send an email to me at L-36.com. Allen

Sunrise 7:13AMSunset 4:47PM Monday December 9, 2019 7:44 PM EST (00:44 UTC) Moonrise 3:22PMMoonset 4:23AM Illumination 96% Phase: Waxing Gibbous; Moon at 13 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- 639 Pm Est Mon Dec 9 2019
.small craft advisory in effect until 6 am est Tuesday...
Tonight..SW winds 15 kt with gusts to 20 kt. Waves 1 ft. Scattered showers, mainly this evening.
Tue..W winds 5 to 10 kt. Waves 1 ft. Showers. Patchy fog. Vsby 1 to 3 nm.
Tue night..N winds 5 to 10 kt. Waves 1 ft. Rain and snow. Patchy fog. Vsby 1 to 3 nm.
Wed..NW winds 5 kt. Waves less than 1 ft. Snow likely. Patchy fog.
Wed night..NW winds 5 kt. Waves less than 1 ft.
Thu..NE winds around 5 kt. Waves 1 ft.
Thu night..NE winds around 5 kt. Waves 1 ft.
Fri..E winds around 5 kt. Waves 1 ft. A chance of rain through the day, then showers likely through the night.
Sat..W winds around 5 kt. Waves 1 ft. Showers likely through the day, then a chance of showers through the night.
ANZ500 639 Pm Est Mon Dec 9 2019
Synopsis for the tidal potomac and md portion of the chesapeake bay.. Low pressure will move from the great lakes into southeastern canada tonight, dragging its trailing cold front through the region Tuesday into Wednesday. High pressure will follow Wednesday night through Thursday. Small craft advisories will likely be needed Tuesday night and Wednesday.


7 Day Forecast for Marine Location Near Washington, DC
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location: 38.89, -77.03     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 091956 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 256 PM EST Mon Dec 9 2019

SYNOPSIS. Low pressure will move from the Great Lakes into southeastern Canada tonight, dragging its trailing cold front through the region Tuesday into Wednesday. High pressure will follow Wednesday night through Thursday, then shift offshore of New England as low pressure develops over and approaches from the southeastern United States.

NEAR TERM /THROUGH TONIGHT/. The steadiest rain was located over the I-95 corridor as of 2:30PM Monday afternoon, as a lead shortwave impulse in the 700-500 hPa layer overrides a surface warm front lifting north across the area. In the wake of this trough, the warm front should lift north, and forcing will weaken. There's abundant moisture in the column, and this couple with height falls ahead of the approaching upper trough is expected to result in isolated to widely scattered showers overnight. There are much higher probabilities over the Allegheny Highlands where orographic enhancement results in more widespread shower activity re-developing after midnight, but warm temperatures will keep precipitation all rain even at the highest elevations.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/. The latest model guidance has honed in on the 10:00AM to 4:00PM window for greatest coverage of shower activity Tuesday, as low level convergence increases along an eastward advancing cold front and PVA associated with another mid level shortwave pivot across. Showers will probably become a bit less widespread for a time during the late afternoon and evening following the frontal passage, but coverage is expected to increase again by late evening into the overnight in concert with RRQ jet dynamics associated with a very strong upper jet.

Since the low level front will have passed by Tuesday night, temperatures will begin to cool. As such, rain is expected to change to snow. There is still uncertainty in the timing of temperatures becoming cold enough for snow, especially east of the Blue Ridge where downsloping and compressional warming effects tend to be most notable. Even when precipitation changes to snow, surface temperatures will likely be near or above freezing, so snow may have trouble sticking in the lower elevations. Overall, the setup remains largely unchanged, with typical run to run and model to model variability noted. The highest confidence in snowfall accumulations will be over the higher terrain (above about 1000 feet), with the higher elevations of north-central/northwestern Virginia likely to see the highest totals.

Even though boundary layer temperatures are expected to be marginal in the lower elevations and especially in the I-95 corridor, the timing of wintry precipitation lines up with the Wednesday morning commute, and the powerful mid/upper jet dynamics may result in localized heavier bands of precipitation, beneath which snowfall rates could overcome surface temps and result in accumulation even on paved surfaces.

Precipitation should come to an end by midday Wednesday, with gusty northwest winds ushering in an Arctic airmass in its wake.

LONG TERM /THURSDAY THROUGH MONDAY/. Guidance overall is in good agreement with the synoptic pattern concerning the long term. A strong area of high pressure moves eastward out of the Great Lakes region and extends down the majority of the Eastern Seaboard. The resultant is dry yet chilly conditions expected for Thursday. At the same time, low pressure develops over the Gulf of Mexico and will begin to lift northeastward late Thursday night into Friday.

While guidance is in better agreement about the timing of precip, there is still some spread in regards to timing, track and temperatures. The GFS/GEFS bring precipitation into the CWA by Friday morning, while the ECMWF/EPS delay precip onset by about 6 hours. Interesting to note that today's 12Z ECMWF suite advanced the precip by about 6 hours, compared to the 12 hour difference (from the GFS) it showed yesterday. Therefore, there is better confidence that precip onset will occur by Friday afternoon. With the chilly air mass in place, some wintry precipitation (freezing rain), will be possible at the onset, mainly near and west of the Blue Ridge. Elsewhere, mainly plain rain is most likely.

The low will exit the region by early Saturday morning with some partial clearing expected for the afternoon. Dry weather persists through Monday as temperatures remain slightly on the cooler side of normal.

AVIATION /19Z MONDAY THROUGH SATURDAY/. IFR CIGs should begin to lift as a warm front lifts north and low level inversion mixes out between 21-00Z. LLWS will remain prevalent through about 03Z, before better mixing allows surface winds to increase, reducing speed differences between the surface and 2 kft AGL.

Guidance is almost unanimous on VFR returning by or shortly after midnight as low level mixing increases, but sub-VFR could linger a bit given climatological stubbornness of warm fronts overnight in our area (they usually progress a touch slower). Surface gusts out of the SW to around 20 kts are likely overnight at times as mixing increases.

Latest guidance pegs the 15-21Z window Tuesday for most likely showers and sub-VFR CIGs/VSBYs. A brief respite is anticipated Tuesday evening, before precipitation re-develops and changes to snow after midnight. The most likely terminal to see accumulation is MRB, least likely at CHO/DCA, though there could be a quick coating even on paved surfaces at any terminal if a localized heavier band of snow moves overhead, overcoming marginal surface temperatures.

VFR returns by midday Wednesday with gusty NW winds. Another round of rain seems definite Friday afternoon into Saturday as coastal low pressure develops to the southwest and lifts northeast. Expect IFR conditions in moderate rain Fri night and Saturday. Mixed pcpn possible mainly near MRB.

MARINE. Winds have not been mixing down very well this afternoon, but that is expected to change this evening as low level stability decreases, allowing strong winds at a few thousand feet above the surface to mix down. Therefore, left the headlines as is for this afternoon, and expanded to include all waters for a time overnight. There will likely be a lull in the winds Tuesday, so the headline drops to just the lower most Maryland portion of the Chesapeake Bay and lower tidal Potomac. Winds likely increase in NW flow behind a cold front Tuesday night and especially Wednesday.

Winds lighten Wednesday night through Thursday night as high pressure builds overhead.

SCA conditions possible Friday into Saturday as pressure gradient tightens in advance of a coastal low pressure lifting northeast.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . None. VA . None. WV . None. MARINE . Small Craft Advisory from 6 PM this evening to 10 AM EST Tuesday for ANZ531-532-538>540-542. Small Craft Advisory until 6 PM EST Tuesday for ANZ534-537-543. Small Craft Advisory until 10 AM EST Tuesday for ANZ533-541. Small Craft Advisory from 6 PM this evening to 6 AM EST Tuesday for ANZ530. Small Craft Advisory from 9 PM this evening to 6 AM EST Tuesday for ANZ535-536.

SYNOPSIS . DHOF NEAR TERM . DHOF SHORT TERM . DHOF LONG TERM . MSS AVIATION . LFR/DHOF MARINE . LFR/DHOF


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 1 mi146 min 46°F 44°F
BSLM2 - Chesapeake Bay, MD 19 mi134 min SSE 6 46°F 1010 hPa46°F
APAM2 - 8575512 - Annapolis, MD 30 mi176 min 47°F 1010.9 hPa
44063 - Annapolis 31 mi38 min SSW 7.8 G 7.8 47°F 45°F1011 hPa
TPLM2 - Thomas Point, MD 31 mi44 min SSE 13 G 14 48°F 45°F1011.5 hPa (-2.0)48°F
BLTM2 - 8574680 - Baltimore, MD 35 mi152 min 46°F 1010.2 hPa
CPVM2 35 mi152 min 47°F
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 35 mi182 min SSE 6 G 7 47°F 1011.5 hPa
NCDV2 39 mi152 min SW 2.9 G 5.1 49°F1011 hPa
44062 - Gooses Reef, MD 40 mi44 min SW 7.8 G 7.8 49°F 1 ft1012.6 hPa (-0.7)
TCBM2 - 8573364 - Tolchester Beach, MD 47 mi182 min S 5.1 G 8.9 47°F 45°F1011.7 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Washington/Reagan National Airport, DC, VA2 mi53 minSSW 1310.00 miLight Rain48°F46°F93%1010.6 hPa
Camp Springs / Andrews Air Force Base, MD9 mi49 minSSW 1110.00 miLight Drizzle49°F48°F99%1010.9 hPa
College Park Airport, MD9 mi69 minS 410.00 miOvercast47°F45°F93%1010.5 hPa
Fort Belvoir, VA14 mi49 minSSW 510.00 miLight Rain46°F44°F92%1011.1 hPa
Fort Meade / Tipton, MD20 mi51 minSW 8 G 167.00 miOvercast46°F46°F100%1010.8 hPa
Gaithersburg - Montgomery County Airport, MD21 mi49 minSW 11 G 2210.00 miLight Rain48°F46°F93%1011.6 hPa
Washington/Dulles International Airport, DC, VA23 mi53 minSSW 1210.00 miLight Rain47°F44°F90%1009.9 hPa

Link to 5 minute data for KDCA

Wind History from DCA (wind in knots)
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Last 24hrS4SW4SE9S6S5S3CalmSE6SW3W4S4S5S6S6S8S9S7S8S10S9S9S9S12S13
1 day agoN5E4NE4CalmNE3CalmNE3NE4CalmCalmCalmCalmCalmCalmS3S6S6S8S8S10S6S3S4SE5
2 days agoNW6NW10NW7NW19
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N10N7N8N8N7CalmN7N6CalmNW7CalmN56NW6NW6W6NW5

Tide / Current Tables for Washington, D.C.
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Washington
Click for Map
Mon -- 12:21 AM EST     0.09 feet Low Tide
Mon -- 04:23 AM EST     Moonset
Mon -- 05:46 AM EST     2.43 feet High Tide
Mon -- 07:14 AM EST     Sunrise
Mon -- 12:13 PM EST     -0.02 feet Low Tide
Mon -- 03:21 PM EST     Moonrise
Mon -- 04:45 PM EST     Sunset
Mon -- 05:59 PM EST     2.76 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.10.20.71.422.32.42.21.610.50.1-00.10.61.42.22.62.82.62.11.610.5

Tide / Current Tables for Alexandria, Virginia
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Alexandria
Click for Map
Mon -- 12:04 AM EST     0.09 feet Low Tide
Mon -- 04:23 AM EST     Moonset
Mon -- 05:54 AM EST     2.43 feet High Tide
Mon -- 07:14 AM EST     Sunrise
Mon -- 11:56 AM EST     -0.02 feet Low Tide
Mon -- 03:21 PM EST     Moonrise
Mon -- 04:46 PM EST     Sunset
Mon -- 06:07 PM EST     2.76 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.10.20.81.422.32.42.21.610.40.1-00.20.71.52.22.62.82.62.11.50.90.5

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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Wind Forecast for Baltimore, MD/Washington (19,4,5,8)
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Ground Weather Radar Station Sterling, VA
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