Saturday, March25, 2017 L-36.com


Marine Weather and Tides
Mercersburg, PA

Version 3.4
What's New / NOTES
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.
3/12/2015 - Added section for Gulf current for users in the GMZ marine zones.
This was requested by a user. If you have requests, please let me know.

Sunrise 7:03AMSunset 7:30PM Saturday March 25, 2017 7:36 AM EDT (11:36 UTC) Moonrise 4:45AMMoonset 3:57PM Illumination 5% Phase: Waning Crescent; Moon at 27 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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ANZ538 Patapsco River Including Baltimore Harbor- 431 Am Edt Sat Mar 25 2017
Rest of the overnight..SW winds 10 kt. Waves 1 ft. Scattered sprinkles.
Today..S winds 5 to 10 kt. Waves 1 ft. Scattered showers.
Tonight..E winds 5 to 10 kt. Waves 1 ft. Patchy drizzle.
Sun..E winds 10 kt. Waves 1 ft. A chance of rain with patchy drizzle.
Sun night..SE winds 10 kt. Waves 1 ft. Rain.
Mon..S winds 5 to 10 kt. Waves 1 ft. A chance of showers.
Mon night..S winds around 5 kt. Waves 1 ft or less. A chance of showers.
Tue..NW winds around 5 kt. Waves 1 ft or less. A chance of showers.
Wed..N winds 5 to 10 kt. Waves 1 ft. A chance of showers in the morning.
ANZ500 431 Am Edt Sat Mar 25 2017
Synopsis for the tidal potomac and md portion of the chesapeake bay.. High pressure will remain over bermuda through today. A backdoor cold front will pass through the area tonight before returning north as a warm front Monday. A cold front is expected to cross the chesapeake bay region Tuesday night. Small craft advisories are possible for portions of the waters late tonight into Sunday and more likely Sunday night through Monday. Another small craft advisory is possible Wednesday behind the cold front.

7 Day Forecast for Marine Location Near Mercersburg , PA
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location: 39.79, -77.93     debug


Area Discussion for - State College, PA
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Fxus61 kctp 251049
afdctp
area forecast discussion
national weather service state college pa
649 am edt Sat mar 25 2017

Synopsis
A cold front will sag southward across pennsylvania today and
tonight, before returning north as a warm front late Sunday and
Sunday night. Very mild conditions are expected early today and
again Sunday night into Monday as we enjoy the warm sector
south of the frontal boundary. However... Thickening clouds and
southeast flow are expected on Sunday as the boundary sags
southward as a backdoor cold front... Bringing cooler conditions
and eventually some patchy drizzle or light rain. Unsettled
conditions will last from late Sunday through Tuesday as a
series of disturbances interact with the front. No heavy rain is
expected during this timeframe however.

Near term /until 6 pm this evening/
Weak surface frontal boundary is along the pennsylvania... New
york border early this morning, and will be drifting slowly to
the south through this afternoon. The cold front should make it
to northern virgina and west virginia before stalling out once
again.

Warm temps will persist this morning. However, the warmup will
be short-lived, as high pressure building into new eng pushes a
backdoor cold front through central pa during the mid
afternoon and evening hours. A good deal of cirrus will hold
temps down a bit, but even just mixing to 925mb supports max
temps in the upper 60s and low 70s south of i-80.

A earlier arrival of the front by just a few hours will result
in a cooler and cloudy day across the northern tier counties,
where southeast flow and nearly saturated soundings in the sfc-
850mb layer suggest patchy drizzle is possible. Further south,
there could be scattered afternoon showers in the increasingly
warm and unstable air over southern pa... But most will stay dry.

Scattered light showers and areas of drizzle will be along and
just to the north of this boundary today into this evening.

The locations most likely to receive some rain today and tonight
will be the northern mountains of the state. Expect less than
one tenth of an inch of rain today in most places as short
range/high res models indicate that there will be a shallow dry
layer between the southward advancing stratus and stratocu... And
the alto CU and cirrus deck. Sref's prob for lifr stratus
ceilings behind the front will be limited to primarily the
mountains to the north and northeast of kipt. Areas farther
south stand to see the least cloud cover.

Temps around sunrise today should range from the upper 30s to
mid 40s in the east, to the very mild mid 50s to lower 60s
across the region near and to the west of the rt 99 corridor.

Short term /6 pm this evening through 6 pm Sunday/
Frontal boundary sags back against the alleghenies of western
pa, pushed by a high pressure area sliding SE across S ontario
on Sunday as a low approaches from the ohio valley. This will
advect cooler and more moist llvl air into the region. Light
showers... With areas of drizzle/ridge top fog are likely
through much of the day Sunday.

Local experience causes us to lean greatly away from blended
model guidance for MAX temps in such llvl cold air damming
situations, as warmer outliers and the mean temp displayed by
such blends/ensembles typically masks the amount of shallow
cold air that gets funneled southwestward through the deep
valleys of central pa.

Went primarily with the latest... 25/06z NAM blended about 25
percent of the way with the nat'l blend of models. Forecast ndfd
temps Sunday will be on average about 8-10 deg f below nbm
guidance (which also collaborates well with neighboring offices
and continuity).

Long term /Sunday night through Friday/
The main precip event impacts central pa Sun night into early
mon as low moves through. QPF looks to be around 0.50 inch.

Above average temperatures (especially nighttime) appear very
likely through early next week, as GEFS indicates pa remains
beneath a mean upper level ridge and plume of anomalous pwats.

The chance of showers again spikes with passage of next
shortwave Tuesday into Wednesday and another one to start the
weekend.

U.S. 25/00z and 06z GFS and GEFS differs drastically with the
25/00z ec and its ensembles during the second half of the week,
as the ec guidance is dominated by stronger southern stream
troughs and associated northward advection of warmer air and
higher 500 mb heights. In contrast, the GFS and its ensemble
mean appears to maintain a several decameter deeper and more
persistent upper low over NRN new england and the canadian
maritimes, while also latching onto a piece of northern stream
energy that breaks away from a potent upper low that will be
digging SE across the four corners area Tuesday, before heading
east across the high plains of E new mexico and west texas
later Wednesday and Wed evening.

The presence of this aforementioned northern stream short wave
has big implications for maintaining/reinforcing colder NW flow
aloft across southern canada and the NE u.S., while shearing its
initially potent southern stream "parent" low harmlessly east
(for us here in central pa) across the carolinas.

Considering the several-run persistence in the gfs, along with
the amount of snow cover across intact parts of the NRN mid
atlantic and new england states, (not to mention the persistence
of cold air there and points north across ont and quebec), i
slightly favor the gfs/gefs solution at this point in time with
a more extended period of drier and cooler conditions for wed-
sat. The northern edge of the precip shield associated with the
shearing SRN stream wave and mdtly strong forcing via the r.E.

Region of a 100-120 kt upper jet across the lower great lakes
and mid atlantic region may support a period of cold
rain... Mix... Or even a light accumulation of snow across the
southern half of pa late in the week.

The "less likely" ec solution (at this point) would help to
develop a stronger upper ridge across the eastern u.S. For the
second half of the week with the upper low lifting nne to the
upper midwest by 00z Sat with warmer air at the surface and
aloft surging northward through the ohio river valley and
appalacians.

Aviation /10z Saturday through Wednesday/
Frontal boundary just north of the pa/ny border early this
morning will be pushed southward through the airspace toward the
pa/md line by 25/00z as strong high pressure builds over eastern
canada. Increasing low level moisture and wind shift to the east
should translate into a lower trend in flying conditions from
north to south with widespread MVFR to ifr restrictions likely
by later tonight into Sunday. Areas of light rain will be
possible today especially near the southward-moving frontal
zone with fog/drizzle overnight into early Sunday morning. The
front should lift back to the north on Sunday which should allow
for at least some marginal improvement especially over portions
of the southern airspace.

Outlook...

sun... Low risk for isolated thunderstorms in western 1/4
airspace.

Mon-tue... Sub-vfr with periods of rain.

Wed... BecomingVFR. No sig wx.

Ctp watches/warnings/advisories
None.

Synopsis... Lambert
near term... Lambert
short term... Lambert
long term... Lambert/rxr
aviation... Steinbugl


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
BLTM2 - 8574680 - Baltimore, MD 80 mi48 min Calm G 0 54°F 45°F1020.9 hPa
WASD2 - 8594900 - Washington, DC 80 mi48 min S 1.9 G 2.9 56°F 47°F1021.4 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 84 mi48 min SSW 1 G 1.9 58°F 1021.3 hPa

Wind History for Baltimore, MD
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Hagerstown, Washington County Regional Airport, MD12 mi43 minS 810.00 miA Few Clouds56°F46°F70%1021.6 hPa

Wind History from HGR (wind in knots)
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Last 24hrS6S11S8S7S10S11S9S9S12S12S11S9S5S7S7S9S7S8S7S6S7S9S8S8
1 day agoCalmN7NE6Calm3SW83E3S5S5S8S7SE5SE4E5SE7SE9S6S9S10S8S8S10S11
2 days agoNW17
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N13NW6NW8NE34NW5NE4E3N4CalmCalmN4N5

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
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Sat -- 01:34 AM EDT     0.30 feet Low Tide
Sat -- 05:41 AM EDT     Moonrise
Sat -- 07:03 AM EDT     Sunrise
Sat -- 07:18 AM EDT     2.99 feet High Tide
Sat -- 01:51 PM EDT     0.25 feet Low Tide
Sat -- 04:54 PM EDT     Moonset
Sat -- 07:25 PM EDT     Sunset
Sat -- 07:35 PM EDT     3.08 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
0.60.40.30.71.52.22.832.92.51.81.20.70.40.30.51.222.7332.72.11.5

Tide / Current Tables for Chain Bridge, Washington, D.C.
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Chain Bridge
Click for Map
Sat -- 01:35 AM EDT     0.33 feet Low Tide
Sat -- 05:41 AM EDT     Moonrise
Sat -- 07:03 AM EDT     Sunrise
Sat -- 07:18 AM EDT     2.94 feet High Tide
Sat -- 01:53 PM EDT     0.27 feet Low Tide
Sat -- 04:54 PM EDT     Moonset
Sat -- 07:25 PM EDT     Sunset
Sat -- 07:36 PM EDT     3.02 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
0.60.40.40.71.52.22.72.92.82.41.81.20.70.40.30.51.222.6332.72.11.5

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 State College, PA (7,2,3,4)
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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.