Saturday, February24, 2018 L-36.com


Marine Weather and Tides
Ashburn, VA

Version 3.4
What's New / NOTES
6/25/2017 - NOAA is having a major issue that impact the 7 day forecast load times. Many users are reporting problems. The issue has been reported.
5/23/2017 - Worked with NOAA again to speed up the 7 day forecast load times. Thanks to them for being responsive.
5/19/2016 - There were issues with the 3 day airport observation history. I switched to another data source. Let me know if you see any issues with the data feeds.

Sunrise 6:46AMSunset 5:59PM Saturday February 24, 2018 2:56 AM EST (07:56 UTC) Moonrise 12:22PMMoonset 2:05AM Illumination 66% Phase: Waxing Gibbous; Moon at 9 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- 1233 Am Est Sat Feb 24 2018
Overnight..SW winds 5 to 10 kt. Waves 1 ft. Patchy dense fog. Vsby 1 nm or less.
Sat..NE winds 5 kt. Waves less than 1 ft. A chance of showers with patchy heavy drizzle. Patchy fog. Vsby 1 nm or less.
Sat night..E winds 5 kt. Waves less than 1 ft. Showers likely with patchy drizzle. Patchy fog. Vsby 1 to 3 nm.
Sun..SW winds 5 to 10 kt. Waves 1 ft. Showers likely.
Sun night..NW winds 5 to 10 kt. Waves 1 ft. A chance of showers.
Mon..NW winds 5 kt. Waves less than 1 ft.
Mon night..NW winds around 5 kt. Waves 1 ft.
Tue..S winds around 5 kt. Waves 1 ft.
Wed..S winds 5 kt. Waves less than 1 ft. A chance of showers through the night.
ANZ500 1233 Am Est Sat Feb 24 2018
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A boundary will approach the waters as a warm front this morning and it will remain nearby through tonight before eventually moving to the north Sunday. A cold front will pass through from the west late Sunday into Sunday night. Small craft advisories will likely be needed for at least a portion of the waters on Sunday.

7 Day Forecast for Marine Location Near Ashburn, VA
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location: 39.03, -77.47     debug


Area Discussion for - Baltimore, MD/Washington
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Fxus61 klwx 240228 aaa
afdlwx
area forecast discussion... Updated
national weather service baltimore md washington dc
928 pm est Fri feb 23 2018

Synopsis
A warm front will gradually push north across the region
tonight through Sunday morning. A cold front will then cross the
region Sunday night. High pressure will return early next week.

Near term through Saturday
Main changes for the overnight were to issue a dense fog
advisory across the northern half of the fcst area were obs and
live traffic cameras are showing fog developing and where
models unanimously all agree in dense fog developing. It is
possible the dense fog advisory may need to be extended to
include the entire i-95 corridor down to fredericksburg where
rap model shows fog developing and nighttime microphysics rgb
product show more gray (fog) than bright aqua (stratus) colors.

For Saturday, lowered maxt as guidance typically have a warm
bias in cold air damming situations. Used the maxt from today
and applied the 24-hr maxt trend from the latest 24 00z nam12,
so only a 5-7 deg rise across the north and up to 15f degs
warmer in the south. Highs generally in the upper 40s along the
mason dixon line to the mid 60s across the south.

Previous afd...

tonight through Saturday, the low pressure will head eastward to
our north. Southerly flow will encourage the warm front to push
northward as well, but the odds it reaches very far into our cwa
are not high. The more pessimistic but often more realistic (in
these situations, at least) NAM shows the warm front reaching
portions of the west virginia eastern panhandle and the
shenandoah valley, but struggling to reach any portion of the
cwa east of the blue ridge. There may be an attempt at a little
clearing this evening as this all tries to occur, but otherwise,
clouds and drizzle with patchy mist fog will likely continue.

With the main forcing staying to our north, significant rainfall
is not expected across our region, but a few showers could skim
the region, particularly western maryland. Temperatures will be
fairly steady, perhaps even rising a bit, but large changes are
not expected in most of the region.

On Saturday, the front may actually sink back south a bit as the
passage of the low to our north causes the flow to shift a bit
more northerly. Thus, the morning should be more of the
same... Damp and dreary, but not a washout. Later in the morning
and in the afternoon, low pressure developing to the west over
the plains will bring increased warm advection aloft and fgen
across western zones, spreading eastward late in the day. This
will increase the risk of steadier rain. Given ample moisture
available, some locally heavy rain could occur in the western
portions of the forecast area, but confidence is low regarding
any flooding risk, so have not issued any flood watches yet.

Highs on Saturday will be a bit warmer than today as the warm
front once again attempts to lift north, with 50s and 60s
becoming more common. However, if the front ends up further
south than currently expected, it could stay cooler.

Short term Saturday night through Sunday night
Warm front makes more progress northward on Saturday night and
Sunday as low pressure wave pushes northeastward to our
northwest. This should allow temperatures to warm more
significantly after the rain Saturday night, with 70s looking
more likely on Sunday. An interval of relatively pleasant
weather may occur late morning into early afternoon, with more
sunshine, but then the cold front will approach from the
northwest. Still some uncertainty on any severe threat, but
certainly with the available moisture and warmth, some
instability will be present, so allowed slight chance of
thunder into the forecast Sunday afternoon. The front will slide
southeast across the region Sunday night, so a drying, cooling
trend will develop. However, the front will slow down overnight
as yet another wave of low pressure develops to our southwest,
so rain chances will not completely end in southern parts of the
region.

Long term Monday through Friday
With exception to a couple of lingering rain showers near
southern maryland and parts of the central chesapeake bay Monday
morning, conditions will dry out as a ridge of high pressure
builds in from the west. The high will persist through Tuesday
night before moving offshore early Wednesday.

Interaction between the high pressure and a developing low
pressure system over the central great plains will provide a
southerly return flow into our region. Expect milder and more
moist air to return Wednesday and Wednesday night. There could
be a couple of rain showers develop over the appalachians and in
parts of the central shenandoah valley later in the day
Wednesday.

A developing warm front over southwest virginia and western
north carolina will work its way north across our region
Wednesday night. Ahead of and along this warm front, additional
rain showers will develop and spread northeastward across our
region Wednesday night. Even more warmer and moist air is
expected to follow the warm front northward Wednesday night into
Thursday.

Showers, some moderate at times, should persist into Thursday
morning as the warm front moves to the mason-dixon region just
ahead of an approaching cold front that should pass through our
area Thursday night. Some drier and cooler air will work in
behind the passing cold front; however, models are trying to
push a cut-off low pressure system over the great lakes region
eastward. This cut-off low, it's upper level energy support, and
a little daytime heating could spawn additional rain showers
later Thursday night and during the day Friday. Northwesterly
winds could become quite gusty as well in the wake of the
passing surface cold front and ahead of the cut- off low
pressure system.

Overall, temperatures throughout next week will be mild with
highs approaching 60 degrees or higher in any warm sector.

Friday may be the exception and could be cooler, but for now we
will keep temperatures near normal.

Aviation 02z Saturday through Wednesday
Expect fog and low clouds to drop overnight with vlifr
conditions expected except at kcho. The warm front will
probably stay south of all the terminals, save perhaps cho,
during the day Saturday, resulting in more of the same. Steadier
rain may overspread the region, especially the northern
terminals, by Saturday night. Conditions look more likely to
improve from dc on south and west on Sunday as a warm front
lifts northward, but bwi mtn may have trouble breaking out of
the low clouds and fog as the front may struggle to pass that
area. Cold front then finally drops southeast across the region,
bringing showers and perhaps a thunderstorm Sunday afternoon,
but likely resulting conditions finally going back toVFR with
drier air filtering south Sunday night.

Vfr conditions expected Monday through Tuesday night. Winds
northwest 5 knots or less Monday and Monday night. Winds
becoming southwest around 5 knots Tuesday and Tuesday night.

Marine
With weak gradient and a front to the south, expect winds to
stay below small craft advisory strength through Saturday
evening across all waters. Late Saturday night, warm front
approaching from the south may finally lift north of the middle
bay, allowing the strong southerly flow to reach the surface and
bring gusts up to SCA levels, but for now am waiting to issue a
headline. SCA looks likely across at least the southern waters
we cover, perhaps reaching up to the northern bay as well, as
the warm front lifts north and gusty south winds develop in the
warm sector. As with the recent round on Tuesday and Wednesday,
this will be primarily near-shore gusts, with weaker winds over
the open waters due to the chilly water temperatures limiting
mixing. Cold front will push southeast across the waters Sunday
night, but at this time SCA does not appear likely with this
frontal passage.

No marine hazards expected Monday through Tuesday night. Winds
northwest 5 to 10 knots Monday and Monday night. Winds becoming
southwest 5 to 10 knots Tuesday and Tuesday night.

Lwx watches warnings advisories
Dc... Dense fog advisory until 8 am est Saturday for dcz001.

Md... Dense fog advisory until 8 am est Saturday for mdz003>006-011-
013-014-503>508.

Va... Dense fog advisory until 8 am est Saturday for vaz053-054-505-
506.

Wv... Dense fog advisory until 8 am est Saturday for wvz052-053.

Marine... None.

Synopsis... Rcm
near term... Lfr
short term... Rcm
long term... Klw
aviation... Rcm klw
marine... Rcm klw


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 26 mi38 min SSE 1 G 1.9 48°F 48°F1023.4 hPa
BLTM2 - 8574680 - Baltimore, MD 50 mi38 min S 1.9 G 2.9 45°F 44°F1022.6 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Washington/Dulles International Airport, DC, VA5 mi64 minN 00.50 miFog47°F46°F100%1023.3 hPa
Leesburg / Godfrey, VA6 mi61 minN 00.75 miFog/Mist43°F42°F100%1023.4 hPa
Gaithersburg - Montgomery County Airport, MD19 mi60 minSW 30.50 miFog46°F46°F100%1026.4 hPa
Manassas, Manassas Regional Airport/Harry P. Davis Field, VA22 mi60 minNNE 37.00 miOvercast49°F48°F97%1024.6 hPa

Wind History from IAD (wind in knots)
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Last 24hrE4E6E4E3E3E3SE3E4SE6SE5SE6S5S7S6SE4SE3S4CalmS3S4S5CalmS4Calm
1 day agoN9N8N8NE10NE7N9N10N7N9N6E7NE6N12N12N10N9N5NE8E10E9E6E6E8E3
2 days agoS9S10S9S7S9S10S14S12
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S9SW15W4NW5NW5N6N9N10

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Sat -- 02:03 AM EST     Moonset
Sat -- 02:44 AM EST     2.61 feet High Tide
Sat -- 06:48 AM EST     Sunrise
Sat -- 09:06 AM EST     0.10 feet Low Tide
Sat -- 12:21 PM EST     Moonrise
Sat -- 03:00 PM EST     3.03 feet High Tide
Sat -- 05:55 PM EST     Sunset
Sat -- 10:26 PM EST     0.14 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
1.42.12.52.62.31.81.20.60.20.10.20.61.42.32.932.92.41.71.20.70.40.20.2

Tide / Current Tables for Chain Bridge, Washington, D.C.
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Chain Bridge
Click for Map
Sat -- 02:03 AM EST     Moonset
Sat -- 02:44 AM EST     2.64 feet High Tide
Sat -- 06:48 AM EST     Sunrise
Sat -- 09:04 AM EST     0.05 feet Low Tide
Sat -- 12:21 PM EST     Moonrise
Sat -- 03:00 PM EST     3.06 feet High Tide
Sat -- 05:55 PM EST     Sunset
Sat -- 10:23 PM EST     0.10 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
1.42.22.62.62.41.81.10.60.20.10.20.61.42.32.93.12.92.41.71.10.70.30.10.2

Weather Map and Satellite Images
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Weather Map
wmap_A
IR Satellite Image from GEOS
east_satellite

GOES Local Image of Mid-Atlantic    EDIT
Geos

Wind Forecast for Baltimore, MD/Washington (2,6,7,8)
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Ground Weather Radar Station Sterling, VA
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weather_mapweather_map weather_map

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Disclaimer:
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 numerious 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.