Wednesday, January23, 2019 L-36.com


Marine Weather and Tides
Round Hill, VA

Version 3.4
What's New / NOTES
10/6/2018 Colors of tide XTide graphs changed to emphasize that they were upgraded. See next note. Comments welcome.
10/4/2018 I have fixed XTide and updated the harmonic files. There were some name changes so you might have to click EDIT to find the new station name.

Sunrise 7:22AMSunset 5:21PM Wednesday January 23, 2019 5:17 PM EST (22:17 UTC) Moonrise 8:33PMMoonset 9:20AM Illumination 91% Phase: Waning Gibbous; Moon at 18 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- 336 Pm Est Wed Jan 23 2019
.small craft advisory in effect through late tonight...
.gale warning in effect from Thursday morning through Thursday afternoon...
Rest of this afternoon..S winds 10 kt. Waves 1 ft. A chance of rain.
Tonight..S winds 10 to 15 kt. Gusts up to 25 kt late. Waves 1 ft. Rain. Vsby 1 to 3 nm.
Thu..S winds 15 to 20 kt with gusts to 40 kt... Becoming nw 10 to 15 kt with gusts to 35 kt in the late morning and afternoon. Waves 1 ft. Rain. Vsby 1 nm or less.
Thu night..W winds 5 to 10 kt. Waves 1 ft.
Fri..W winds 5 to 10 kt with gusts to 20 kt. Waves 1 ft.
Fri night..NW winds 5 to 10 kt. Waves 1 ft.
Sat..S winds around 5 kt. Waves 1 ft.
Sun..W winds around 5 kt. Waves 1 ft.
ANZ500 336 Pm Est Wed Jan 23 2019
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A cold front approaching from the ohio valley will cross the waters by Thursday afternoon. A reinforcing front will cross Friday, then high pressure will follow for the weekend. Small craft advisories may be needed Friday afternoon and night.


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 231950
afdlwx
area forecast discussion
national weather service baltimore md washington dc
250 pm est Wed jan 23 2019

Synopsis
A cold front approaching from the ohio valley will cross the
mid-atlantic by Thursday afternoon. A disturbance will cross the
region Friday. High pressure will follow for this weekend. Low
pressure may affect the region early next week.

Near term through Thursday
A cold front is moving east into the ohio valley as high pressure
sits east of us. A southerly flow has settled over us allowing
for warm and moist air advection. Temperatures are currently in
the 40s for most areas, including a few 50s, and they are
expected to increase overnight. Locations near or east of i-95
could get into the upper 50s, maybe some 60s tonight into
Thursday morning.

Wind gusts today are in the upper teens and into the 20s as gradient
increases (a few near 30 mph in the lowlands), also with a
strong low level jet. At the ridges, wind gusts have been
observed at 50+ mph, and with forecast soundings suggesting
strong winds continuing overnight, we have issued a wind
advisory through tonight for these locations. Elsewhere, breezy
(sub advisory) conditions expected. A high wind warning is in
effect for the central virginia blue ridge where peaks are above
the inversion and poking into a 65 kt llj.

As the cold front approaches our area this evening and into tonight,
chances of rain and drizzle increases. The front is expected to move
across our CWA on Thursday morning. Shortwave energy along with the
strong low level jet will allow for more widespread rain, which
could be heavy at times, with total QPF values between 0.80 and 1.5
inches across our cwa, with isolated higher amounts up to 2 inches.

Some of this may fall in a period of about 3 hours late tonight
into early Thursday morning. A flood watch is in effect from
late tonight into Thursday afternoon over areas where we expect
the deepest moisture (central va and east of blue ridge).

Isolated flooding over other locations may be possible. See
hydro section below for more details.

A period of damaging wind gusts is possible ahead of the cold
front Thursday morning as hi-res guidance unanimously shows a
strong narrow cold frontal rain band coincident with LLJ of 65+
kts at 2-3kft. Wind advisory in effect to account for hybrid
synoptic convective winds tomorrow morning (right around rush
hour) in the baltimore dc metros and S md.

Temperatures will fall behind the front late Thursday morning and
into the afternoon with northwesterly flow settling in. Rain will
also be moving away, and a possible period of snow is possible west
of the allegheny front into Thursday afternoon.

Short term Thursday night through Friday night
Cold front low pressure and initial upper trough will push east
Thursday night. A stout trailing upper level trough will pivot
across the region Friday. Snow squall parameters light up across
the northern half of the CWA around midday Friday (factors in
instability, moisture and wind; values over 1 indicate snow
squall potential and values up to 5 are forecast over N md). For
this reason, even though models aren't printing out much qpf
explicitly, have a chance of snow showers near and north of
us-50 focused around midday.

Gusty NW winds will usher in a reinforcing shot of arctic air
Friday night.

Long term Saturday through Wednesday
For the weekend, the region remains entrenched underneath the base
of an upper-level trough. At the surface, high pressure will be
stretched along the eastern us. This will result in a dry pattern
overall for much of the cwa. However, a few impulses of shortwave
energy will swing through the area around the base of the primary
upper trough, which could bring a few chances for some precipitation.

The first of those swings through Saturday, with the only
precipitation threat being some upslope snow showers along the
allegheny front. Otherwise, the rest of the region remains dry,
with temperatures in the low to mid 30s. On Sunday, a weak area
of low pressure will track across southern canada, swinging a
cold front through the area by Sunday evening. This front has a
chance to bring some rain or snow showers to the region Sunday
night, with areas west of the blue ridge having the greatest
chance. High temperatures will be a bit milder Sunday when
compared to Saturday.

Monday and Tuesday, things start to get a little more active. A
short wave will slide down into the central CONUS out of southwest
canada, bringing a potent surface low pressure system along with it.

Ahead of this area of low pressure, will get a period of warm
advection on Monday. Keeping slight chance pops in the forecast
for Monday in association with the warm front, but not looking
very likely at this point. The best chance of precipitation
comes on Tuesday, as the cold front approaches, while the
surface low tracks to our northwest at this time, though it
should be noted the upper pattern is highly volatile. Some guidance
has been hinting at two pieces of energy phasing, bringing a
low pressure system up the eastern seaboard during this time.

Aviation 19z Wednesday through Monday
Vfr to MVFR CIGS are observed over the terminals at this time and
expected to continue through the rest of today. Ifr conditions could
develop this evening and into the overnight as a front approaches
and drizzle and or rain increase in coverage over the terminals.

Steady and widespread rain is expected to develop late tonight into
early Thursday morning, with locally heavy rain at times. Strong
wind shear is also expected for the rest of today and into early
Thursday morning. Strong low-level wind shear will persist
through tonight with up to 65 kts at 3kft.

Winds will start from the south early on Thursday and will become
northwesterly behind the cold front. Winds could gust up to 30 knots
at times on Thursday, 40 kts near iad dca bwi especially with
heavier convective elements Thu am. Visibilities and CIGS will
be improving through the day Thursday as the front moves away.

MainlyVFR Thu night-fri night, though brief sub-vfr possible in
-shsn for northern terminals associated with disturbance. Gusty
nw winds behind front possible Fri night.

Vfr conditions are likely on Saturday and Sunday, as high pressure
dominates the region. The best chance for any restrictions will come
on Sunday night, if precip can make it east of the mountains.

Marine
Southerly flow over the waters will continue into tonight ahead of a
cold front as a high pressure sits offshore. This cold front is
expected to move across the waters on Thursday morning, with winds
shifting to the northwest behind it. A small craft advisory in
effect through tonight as gradient increases ahead of the front. A
gale warning is in effect over the waters from Thursday morning and
into the afternoon as winds likely gust 35-40 knots along and
ahead a convective line strong front that will move across the
waters Thursday morning. Gusty winds behind the front could also
reach gale warning criteria briefly. A few gusts around 50 kts
can't be ruled out right ahead of the front late Thursday morning.

Sca gusts possible behind reinforcing cold front Friday
afternoon and night.

High pressure will reside over the waters on Saturday with light
winds and sub SCA conditions expected. Winds will increase Saturday
night through Sunday night as the high shifts offshore and return
flow increases ahead of another cold front, bringing the potential
for SCA conditions over portions of the waters.

Hydrology
Overall, not much has changed in the water-related setup for the
overnight Thursday event. Rain of generally around an inch (with
isolated higher amounts, especially in a potential developing line
east of the blue ridge) plus some snowmelt, will promote significant
within-bank rises on most rivers, and some out-of-bank rises on more
susceptible rivers. A flood warning is now in effect for opequon
creek near martinsburg (again). Flood watches are out for the south
branch potomac at franklin wv, and the cacapon river in morgan
county wv. Other small streams have flood potential as well, and the
overall flood watch remains in place for counties cities where the
heaviest rain is currently expected, mostly east of the blue ridge.

Looking further ahead, mainstem river flooding on the potomac is
possible Friday through Saturday, but uncertainty in rain amounts
and snowmelt precludes issuance of watches for these areas at this
time. This will be assessed again on Thursday.

Tides coastal flooding
Tidal anomalies will continue to increase into Thursday as southerly
flow persists over the waters. The potential for minor flooding will
exist as a result, however, given a large spread in guidance and
uncertainty in the strength of surface winds, confidence is low at
this time.

Lwx watches warnings advisories
Dc... Flood watch from late tonight through Thursday afternoon for
dcz001.

Wind advisory from 6 am to noon est Thursday for dcz001.

Md... Flood watch from late tonight through Thursday afternoon for
mdz004>006-011-013-014-016-503>508.

Wind advisory from 6 am to noon est Thursday for mdz011-013-
014-016>018-503>506.

Va... Flood watch from 10 pm est this evening through Thursday
morning for vaz025-036-503-504-508.

Wind advisory until 6 am est Thursday for vaz503-507.

High wind warning until 6 am est Thursday for vaz508.

Flood watch from midnight est tonight through Thursday
afternoon for vaz037>040-050-051-507.

Flood watch from late tonight through Thursday afternoon for
vaz052>056-501-502-505-506.

Wind advisory from 6 am to noon est Thursday for vaz052>057-
502-506.

Wv... Wind advisory until 6 am est Thursday for wvz505.

Marine... Small craft advisory until 6 am est Thursday for anz530>543.

Gale warning from 6 am to 6 pm est Thursday for anz530>543.

Synopsis... Dhof
near term... Imr
short term... Dhof
long term... Cjl
aviation... Imr cjl
marine... Imr cjl
hydrology... Je
tides coastal flooding... Bkf


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 43 mi47 min S 4.1 G 7 46°F 35°F1017.8 hPa
BSLM2 - Chesapeake Bay, MD 61 mi107 min S 8.9 48°F 1019 hPa37°F
BLTM2 - 8574680 - Baltimore, MD 64 mi47 min S 5.1 G 8 44°F 37°F1017.6 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Leesburg / Godfrey, VA11 mi1.7 hrsSSW 13 G 1910.00 miOvercast46°F37°F71%1017.9 hPa
Winchester Regional, VA20 mi1.7 hrsS 810.00 miOvercast45°F37°F76%1015.9 hPa
Washington/Dulles International Airport, DC, VA20 mi2.4 hrsSSW 12 G 2110.00 miOvercast47°F35°F63%1018.7 hPa
Eastern WV Regional Airport/Shepherd Field, WV23 mi2.4 hrsSSE 410.00 miOvercast46°F37°F73%1016.2 hPa

Wind History from JYO (wind in knots)
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1 day agoNW10
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N7NW10N8NW7NW6N7NW5NW5N5CalmN4N5CalmCalmCalmCalmS7S11S8
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Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Wed -- 04:40 AM EST     -0.55 feet Low Tide
Wed -- 07:21 AM EST     Sunrise
Wed -- 09:16 AM EST     Moonset
Wed -- 10:06 AM EST     2.89 feet High Tide
Wed -- 04:52 PM EST     -0.53 feet Low Tide
Wed -- 05:19 PM EST     Sunset
Wed -- 08:30 PM EST     Moonrise
Wed -- 10:27 PM EST     3.15 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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21.30.60-0.4-0.5-0122.62.92.72.11.40.70.1-0.4-0.5-0.20.71.82.73.13.1

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Wed -- 04:35 AM EST     -0.55 feet Low Tide
Wed -- 07:21 AM EST     Sunrise
Wed -- 09:16 AM EST     Moonset
Wed -- 10:01 AM EST     2.89 feet High Tide
Wed -- 04:47 PM EST     -0.53 feet Low Tide
Wed -- 05:19 PM EST     Sunset
Wed -- 08:30 PM EST     Moonrise
Wed -- 10:22 PM EST     3.15 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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21.20.6-0-0.5-0.50122.72.92.721.30.60-0.4-0.5-0.10.81.92.73.13

Weather Map and Satellite Images
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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 (17,4,5,8)
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Ground Weather Radar Station Sterling, VA
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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.