Thursday, June22, 2017 L-36.com


Marine Weather and Tides
Ashburn, VA

Version 3.4
What's New / NOTES
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 5:43AMSunset 8:41PM Thursday June 22, 2017 2:35 PM EDT (18:35 UTC) Moonrise 3:34AMMoonset 6:03PM Illumination 2% Phase: Waning Crescent; Moon at 28 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
    EDIT      (on/off)   Help
ANZ535 Tidal Potomac From Key Bridge To Indian Head- 132 Pm Edt Thu Jun 22 2017
.small craft advisory in effect from Friday morning through Friday afternoon...
This afternoon..SW winds 5 kt. Waves less than 1 ft.
Tonight..SW winds 5 kt. Waves less than 1 ft. A chance of showers.
Fri..SW winds 10 to 15 kt. Gusts up to 20 kt in the late morning and afternoon. Waves 1 ft. A chance of showers and tstms.
Fri night..SW winds 10 to 15 kt with gusts to 20 kt. Waves 1 ft. Showers likely.
Sat..W winds 5 to 10 kt. Waves 1 ft. Showers likely with a chance of tstms.
Sat night..NW winds 5 to 10 kt. Waves 1 ft.
Sun..W winds around 5 kt. Waves 1 ft.
Mon..NW winds around 5 kt. Waves 1 ft. Winds and waves higher and visibilities lower in and near tstms.
ANZ500 132 Pm Edt Thu Jun 22 2017
Synopsis for the tidal potomac and md portion of the chesapeake bay.. High pressure will remain offshore today. A slow moving cold front will affect the area from Friday into Saturday. High pressure will return on Sunday. Small craft advisory conditions are possible Friday night through Saturday.

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


Area Discussion for - Baltimore, MD/Washington
      (on/off)   Help   NOTE: mouseover dotted underlined text for definition
Fxus61 klwx 221415 cca
afdlwx
area forecast discussion... Corrected
national weather service baltimore md washington dc
1015 am edt Thu jun 22 2017

Synopsis
High pressure will remain west of the area today. A cold front
will cross the area late Friday night into Saturday, with
tropical moisture streaming into the mid atlantic ahead of the
cold front. High pressure will return Sunday and persist through
early next week.

Near term until 6 pm this evening
Early morning showers have beein dissipating, as rap hrrr output
has been suggesting. Will still have a cluster of low-mid level
clouds crossing the forecast area, in addition to the veil of
cirrus. Have added more clouds to the database today, which should
yield less optimistic skycover forecasts.

A bit of warm advection will result in temperatures rising a
few degrees over yesterday, so expect lower 90s to be more
common. Those aforementioned mid and high clouds could be a
limiting factor though. Theta-e advection will also begin this
afternoon. Assuming warming destabilization does occur, around
1000 j kg of MLCAPE and 1500-2000 j kg of MUCAPE will be
possible, especially over the mountains. Terrain circulations
and a lee trough will help initiate showers and thunderstorms
this afternoon, perhaps assisted by a little increase in upper
level winds.

Hi-res models have various solutions on how far east and south
the thunderstorms will make it. Have slowed development slightly,
but ultimately top out late day pops at the same level as my
predecessor. Deep layer shear is expected to remain less than 30
kt, so storms should be mostly pulse variety unless a cluster
forms along outflow.

Short term 6 pm this evening through Saturday night
Overall setup for the influx of tropical moisture remains
similar from tonight through early Saturday. There will be two
opportunities for a slug of moderate to heavy rainfall (though
likely not long duration), with potential for convection in
between on Friday afternoon.

Lead shortwave LLJ isentropic lift will arrive first tonight.

Have trended pops toward the speedier timing of the NAM wrfs, as
these types of events often arrive and depart faster than
progged. LLJ will be transporting pwats of around 2 inches,
which will then remain in place. However, overall duration of
this rain is on the order of 3-4 hours, so even with efficient
rain rates, am thinking flooding will be a low concern with this
round other than ponding. This round of rain should be departed
by mid morning Friday.

Thermodynamic environment remains uncertain heading into Friday
afternoon as clouds will be abundant and atmosphere will
stabilize some after morning rain. However in the moisture rich
environment, some instability is likely to develop. Deep layer
shear will also be increasing as upper trough digs to our west.

Latest guidance suggests the best chance of storms will be
across northern western portions of the area where convergence
may be a little better along with weak mid level impulses. Will
have to monitor this time period for severe weather as well as
heavy rain rates and flash flooding, though wind fields should
be sufficient to keep storms moving.

Final opportunity for heavy rain will arrive with the remnants
of cindy and a southward moving cold front late Friday night
into Saturday morning. Once again, the forcing will be fast
moving, so prolonged heavy rain is unlikely. However, rates may
be especially intense given the continued high pwat and deep
warm cloud layers. Given ground may be more saturated in some
areas by this point, will have to monitor potential for flash
flooding.

There is some spread on how quickly the cold front sweeps east
on Saturday. There is at least some chance thunderstorms could
redevelop east of i-95 during the afternoon. However, dry
conditions are expected by Saturday night, along with lower
temperatures and humidity.

Long term Sunday through Wednesday
Upper level troughing looks to dominate the region as we head
into next week, centered near the great lakes. This will
position a high pressure in a semi-permanent fashion over the
central us. In turn, this will result in a somewhat unusual
northwesterly flow at low levels through at least the first
half of next week. This will result in slowly cooling
temperatures as weak reinforcing shots of cooler air push
southeastward into the region, likely accompanied by little
precip. Bottom line is that it won't feel very much like late
june. The trough and associated cooler air may move away late in
the week as surface high pressure shifts eastward, eventually
assuming a more bermuda-high like position by next weekend.

Aviation 14z Thursday through Monday
Scattered showers and storms may form near the mountains this
afternoon. Mrb has the highest chance of being affected, though
wouldn't totally rule out something reaching the metros. The
first half of the evening will beVFR.

Main concern the next couple of days will be periods of heavy
rain as tropical moisture flows into the area. One will be late
tonight into Friday morning. The second will be late Friday
night into Saturday morning. MVFR or lower CIGS and vsby will be
possible with each. Thunderstorms may form in between these two
slugs on Friday afternoon, though coverage and intensity are
uncertain. Gradient winds could also gust 20-25 kt Friday
afternoon.

Vfr likely Sunday and Monday.

Marine
There's a very low chance a shower or storm could reach
northern parts of the bay and upper tidal potomac late this
afternoon. Otherwise southwest winds at 10-15 kt will prevail.

Wind fields start increasing late tonight ahead of deepening
storm system and remnants of cindy. SCA conditions will become
likely by Friday, though a period of moderate to heavy rain
could temper winds a bit in the morning. Winds are expected to
remain elevated through Saturday as the remnants and a cold
front cross the area.

High pressure will most likely result in sub-sca winds Sunday. A
weak reinforcing cold front may bring gusts to SCA levels
Monday. If so, they will likely subside again Tuesday.

Hydrology
Given brief nature of the two round of moderate to heavy rain
and scattered showers storms in between, areal average storm
total (tonight through Saturday) rainfall are generally in the
1-2 inch range, possibly less to the southeast. Thus mmefs
indicates little to no potential of mainstem river flooding. The
main concern will be flash flooding in any areas which receive
repeated and or prolonged periods of heavy rain.

Tides coastal flooding
Water levels a few inches above astronomical normals this
morning. These will slowly increase over the next couple of
days. There is the potential for minor flooding by Friday at
sensitive sites, in the gradient flow ahead of a cold front
which would be merged with moisture from the remnants of cindy.

Lwx watches warnings advisories
Dc... None.

Md... None.

Va... None.

Wv... None.

Marine... Small craft advisory from 10 am to 6 pm edt Friday for anz530-
531-535-536-538>540.

Small craft advisory from 2 am to 6 pm edt Friday for
anz532>534-537-541>543.

Synopsis... Rcm
near term... Hts ads
short term... Ads
long term... Rcm
aviation... Ads rcm
marine... Hts ads rcm
hydrology... Ads
tides coastal flooding... Hts rcm


Weather Reporting Stations
   EDIT       (on/off)   Help   NOTE: Click on distance to see the station location on a map
Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 26 mi47 min W 2.9 G 5.1 86°F 82°F1015.1 hPa
44061 - Upper Potomac, MD 28 mi47 min WSW 9.7 G 12 82°F 82°F1016.2 hPa
BSLM2 - Chesapeake Bay, MD 44 mi125 min SW 4.1 84°F 1016 hPa71°F
BLTM2 - 8574680 - Baltimore, MD 50 mi47 min W 7 G 11 85°F 81°F1015.1 hPa

Wind History for Washington, DC
(wind in knots)    EDIT      (on/off)   Help
2
PM
3
PM
4
PM
5
PM
6
PM
7
PM
8
PM
9
PM
10
PM
11
PM
12
AM
1
AM
2
AM
3
AM
4
AM
5
AM
6
AM
7
AM
8
AM
9
AM
10
AM
11
AM
12
PM
1
PM
Last
24hr
W4
G7
NW6
G10
SW7
G10
S10
G14
S9
G12
SW6
G9
SW5
G8
S4
S3
E3
--
S4
SW4
S2
SW2
NW2
E1
SE1
S2
S2
S2
SE3
SW3
NW3
1 day
ago
SW4
G8
W5
SW9
G13
S13
G17
S14
G17
SW11
G15
SW9
G14
S7
G11
S9
G13
S8
SW6
G10
SW3
S6
G9
S4
S4
G7
S5
SW3
G6
SW5
G9
SW7
S6
G9
S8
S9
S5
G8
NW5
G9
2 days
ago
S15
G20
S13
G17
NW8
NW7
G13
SW3
G8
SW4
--
S7
SW6
G10
SW4
G8
SW5
S4
G7
SW3
G8
SW2
SW3
SW2
SW3
S3
SW3
G6
SW3
SW6
G9
W7
G16
W4
G12
SW2

Airport Reports
    EDIT      (on/off)   Help   Click EDIT to display multiple airports
AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Washington/Dulles International Airport, DC, VA5 mi43 minWSW 510.00 miOvercast84°F66°F55%1015.8 hPa
Leesburg / Godfrey, VA6 mi40 minW 710.00 miFair88°F71°F59%1016.6 hPa
Gaithersburg - Montgomery County Airport, MD19 mi2.7 hrsWNW 610.00 miA Few Clouds81°F68°F65%1019.4 hPa
Manassas, Manassas Regional Airport/Harry P. Davis Field, VA22 mi39 minSW 410.00 miMostly Cloudy86°F70°F59%1016.9 hPa

Wind History from IAD (wind in knots)
3
PM
4
PM
5
PM
6
PM
7
PM
8
PM
9
PM
10
PM
11
PM
12
AM
1
AM
2
AM
3
AM
4
AM
5
AM
6
AM
7
AM
8
AM
9
AM
10
AM
11
AM
12
PM
1
PM
2
PM
Last 24hrW5SW5SW10SW11SW6SW4S3CalmSE3CalmCalmS3NW5W4N3CalmCalmCalmCalmW3W4W4W4W5
1 day agoSW8
G16
SW11
G16
S10SW12SW12S12S5S5S5S5S4CalmS7S7S3CalmS3S6S6S7SW85NW9SW7
2 days agoS11
G20
S9SW8S8S6S6SW7S5S6S5S5NW7W6CalmCalmS3S4SW4S6SW7W10W8W9SW7

Tide / Current Tables for Chain Bridge, D.C.
   EDIT   RT Ports Option   Weekend mode (on/off)   (on/off)   Help   One Week of Data
Chain Bridge
Click for Map
Thu -- 01:33 AM EDT     0.18 feet Low Tide
Thu -- 04:32 AM EDT     Moonrise
Thu -- 05:43 AM EDT     Sunrise
Thu -- 07:24 AM EDT     3.77 feet High Tide
Thu -- 02:40 PM EDT     0.05 feet Low Tide
Thu -- 07:01 PM EDT     Moonset
Thu -- 08:03 PM EDT     3.16 feet High Tide
Thu -- 08:37 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
0.50.20.20.61.52.63.43.73.73.22.41.71.10.60.20.10.51.42.32.93.22.92.31.6

Tide / Current Tables for Chain Bridge, Washington, D.C.
   EDIT      (on/off)   Help   One Week of Data
Chain Bridge
Click for Map
Thu -- 01:29 AM EDT     0.19 feet Low Tide
Thu -- 04:32 AM EDT     Moonrise
Thu -- 05:43 AM EDT     Sunrise
Thu -- 07:21 AM EDT     3.75 feet High Tide
Thu -- 02:38 PM EDT     0.07 feet Low Tide
Thu -- 07:01 PM EDT     Moonset
Thu -- 08:01 PM EDT     3.13 feet High Tide
Thu -- 08:37 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
0.50.20.20.61.52.63.43.73.63.12.41.710.50.20.10.61.52.32.93.12.92.31.5

Weather Map and Satellite Images
       (on/off)   Help
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 (14,3,4,5)
      (on/off)   Help

Ground Weather Radar Station Sterling, VA
   (on/off)   Help
weather_mapweather_map weather_map

Ad by Google

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.