Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 191420
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1020 AM EDT THU MAY 19 2016

.SYNOPSIS...
High pressure will build through Friday morning. Low pressure
will approach the area Friday night from the Tennessee Valley and
track to our south Saturday. High pressure will build overhead
early next week...but an upper-level low will remain close by just
off the Mid-Atlantic coast.

&&

.NEAR TERM /THROUGH TONIGHT/...
Stratus across the southeastern 4/5 of the CWA with cu developing
in the nwrn sector that has cleared this morning. mixing across
the area reduces cloud cover, but stratocu will develop in its
place under subsidence. expect mostly cloudy to cloudy skies
through the rest of the day. Conditions tonight will be favorable
for fog development due to moist ground, light winds and clear
skies. will continue to monitor areas that may see dense fog,
continued patchy fog for now.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Dense high clouds will start advancing northeastward rather
quickly ahead of low pressure over the TN valley Fri. Combo of
height falls, moisture advection over cool air mass will lead to
rain Fri night into Sat. Models continue to show a faster and
weaker trend of upper trough crossing the area Sat. This leads to
an earlier end of the steady rains Sat with lighter amounts of 1
to 1.5 inches total with heaviest over the southern portions of
the CWA. At this time, flooding appears unlikely. Low pressure
exits the area Sat night with mid-levels drying out, but
additional shortwave-energy moving across the area as longwave
pattern amplifies will keep the chance of showers in the fcst.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The long term forecast will largely be influenced by a closed
upper low. This low will form Sunday as a shortwave trough rotates
into the mean troughing along the east coast after the departing
coastal low on Saturday. Therefore expect a chance of showers on
Sunday, particularly during the afternoon. Shower chances are a
little more uncertain for Monday and Tuesday, depending on the
location of the upper low and the placement of embedded vorticity
maxima. The 00Z operational guidance doesn`t suggest any
additional surface low development, which would point to light,
showery activity focused on diurnal heating. Wednesday will have
the best chance of being dry as the upper low pulls away far
enough to have high pressure from the west to be the dominant
influence.

While temperatures (especially highs) will likely remain below
normal due to the upper low, current layer RH forecasts suggest some
breaks in the clouds will be possible. Thus temperatures should be
closer to the 70F mark than some of our recent unsettled periods.
Will have to watch Monday though, as low level flow will be from the
NE. Assuming the low can move to the east by Wednesday, there is
plenty of warm air available to spread eastward from the Plains.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
vfr conds through this evening with light north winds becoming
variable this afternoon. Skies clear tonight which may cause fog
development given wet soils and light winds...will continue to
monitor this threat. Rain moves in after 00Z Sat and spreads
northeast by 12z Sat. Mvfr/ifr cigs expected Fri night through
Sat. Improving cigs Sat night.

Widespread aviation impacts are not expected Sunday into Monday,
although scattered showers will be possible at times due to upper
level low pressure (highest chance Sunday). There is a chance sub-
VFR clouds could develop Monday in NE flow.

&&

.MARINE...
North winds 5-10 kt expected rest of the morning. Variable flow
less than 10 kt through Fri night. Winds strengthen Sat through
Sun with small craft advisory conditions likely. Gusts to 30 kt
possible.

A trough axis will pass through on Sunday, and northerly winds may
reach SCA criteria. The pressure gradient should relax enough Sunday
night into Monday to keep NE winds in the 10-15 kt range.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...BAJ/LFR
NEAR TERM...BAJ/LFR
SHORT TERM...LFR
LONG TERM...ADS
AVIATION...BAJ/ADS/LFR
MARINE...BAJ/ADS/LFR



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