Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 240801

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
401 AM EDT TUE MAY 24 2016

Low pressure off the Mid-Atlantic coast this morning will move
northeastward towards New England today and then toward the
Canadian Maritimes tonight. High pressure over the southern
Appalachians this morning will settle off the southeastern coast
by Wednesday and generally persist through the weekend.


System that has been affecting our weather for the last several
days is finally shifting east of our area. Some clouds and a few
showers remain early this morning but showers should clear the
area by dawn. Where some breaks have occurred in the clouds...some
patchy dense fog has been trying to develop. Will need to closely
monitor observations through the next few hours in case a dense
fog advisory becomes necessary...most likely for inland locations
west of I-95. should turn out mostly sunny with
a warm northwest downslope flow. Threat of lingering showers
developing this afternoon over the higher terrain appears lower
than yesterday and have cut back on POPs. Highs should generally
be near 80.

Tonight high pressure shifts east but ridge with weak flow sits
overhead. This will again promote patchy fog development.
Otherwise...seasonal to a bit mild with lows in the 50s...60s in
the urban core.


Wednesday high pressure will dominate with continued warming.
Highs will reach the low to mid 80s. Southwest flow will continue
milder pattern Wednesday night...but an approaching weak system
will bring increased clouds and maybe even a stray shower late in
the mountains. This threat will spread east during the day
Thursday as weakening shortwave moves into the area. Have best
POPs west given some terrain influence likely...but advection will
likely carry activity east towards the metro. This will wane but
not completely end overnight as the shortwave drifts overhead.
Highs on Thursday will reach well into the 80s while lows Thursday
night stay well into the 60s.


An upper level northern stream ridge will persist over the eastern
CONUS Friday into Monday/Memorial Day. A southern stream low is
expected to develop off the southeastern CONUS coast per 00Z global
guidance consensus. Whether this low comes ashore or persists in the
gulf stream is yet to be determined.

Friday looks to be unstable with light sly flow and mainly terrain
driven diurnal thunderstorms.

Onshore flow and rain are possible at some point sunday into next
week from the coastal low. The 00Z GFS and ECMWF both feature
Memorial Day Monday into Tuesday as rainy. This would be a fitting
end to a rainy month.

Instability would be low in onshore flow Monday/Tuesday with
showers the expected precip.

Temperatures may be on steady cooling trend Friday into next week
due to this coastal low. Friday may yet have 90F temperatures in the
Balt-Wash metro where cloud cover should be less than farther west.


Generally VFR thru Thursday night. Fly in ointment is patchy fog
this morning which may cause a few terminals like MRB to go IFR.
Same thing Wednesday morning. Thursday/Thursday night showers and
thunderstorms may cause reductions.

Light sly flow and diurnal thunderstorms Friday. ifr conds expected
in heaviest activity.

Forecast confidence drops this weekend through Memorial Day with a
coastal low likely on SErn CONUS. Onshore flow and rain chances
increase Sunday through Tuesday.


NW flow expected to mix some gustier winds down today so issued
low end SCA for gusts up to 20 knots. Otherwise turning out sunny
today. Lighter winds Wednesday and Thursday but shower/storm
threat returns Thursday.

Light sly flow continues Friday. Flow looks to become onshore over
the weekend and persist into Tuesday.


Water levels a half foot above normal early this morning. NWly
flow should keep any rises limited. No coastal flooding is
expected today.

We put together some records (preliminary) of how this month compares
to rainy Mays on record for our area.

Washington, DC (records since 1871)
Most days in May with at least a trace: 25 (in 1952
and 1943) So far in 2016 (through 2AM EST on the 24th): 20

Most days in May with at least 0.01": 20 (in 2003)
So far in 2016 (through 2AM EST on the 24th): 18

Highest May monthly rainfall: 10.69" (in 1953 and 1889)
So far in 2016 (through 2AM EST on the 24th): 5.22"

Baltimore, MD (records since 1870)
Most days in May with at least a trace: 25 (in 2003)
So far in 2016 (through 2AM EST on the 24th): 20

Most days in May with at least 0.01": 21 (in 1882)
So far in 2016 (through 2AM EST on the 24th): 16

Highest May monthly rainfall: 8.71" (in 1989)
So far in 2016 (through 2AM EST on the 24th): 4.92"

Dulles, VA
Most days in May with at least a trace: 23 (in 2003)
So far in 2016 (through 2AM EST on the 24th): 21

Most days in May with at least 0.01": 21 (in 2003)
So far in 2016 (through 2AM EST on the 24th): 17

Highest May monthly rainfall: 10.26" (in 2009 and 1988)
So far in 2016 (through 2AM EST on the 24th): 6.07"


MARINE...Small Craft Advisory from noon today to 6 PM EDT this evening
     for ANZ530>543.


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