Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 110800

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Fri Aug 11 2017


High pressure has moved offshore. A warm front will lift north
towards the region today. A cold front will approach the region
from the northwest Saturday, then stall south of the area Sunday.
A wave of low pressure may move along the stalled front early
next week.



As of 3am, a 1013mb surface low pressure is centered over northern
Lake Michigan with the associated cold front stretching southwest
from WI to IA and 1023mb surface high pressure over the Jersey
shore. The Great Lakes low will drift east through Saturday with the
cold front crossing the central Mid-Atlantic Saturday night.

Just a few showers in the area through sunrise with a diurnal
increase in showers and thunderstorms over the area as moist
southwesterly low level flow persists. Dewpoints are currently in
the mid 60s, but will increase to around 70F through midday. MLCAPE
around 500 j/kg this afternoon allows up to scattered coverage of
thunderstorms. Theta-E ridge generally west of I-95 where
categorical PoPs are. Thick clouds make for max temps in the low 80s
for all lower elevations today.

Nocturnal decrease in precip is slowed by continued moist
southwesterly flow. Min temps upper 60s inland to around 70F



Cold front approaches Saturday warranting categorical PoPs across
much of the area. MLCAPE up to 1000 j/kg with chances for thunder
across the area. Dewpoints low 70s make for a much more humid day
than today.

Latest consensus of GFS/NAM/ECMWF is for the cold front to cross the
area Saturday night and cutoff PoPs by midnight. Cold front persists
south of the area through Sunday night with PoPs removed accordingly
through this time.



We will be into the mid part of August during the extended part
of this forecast. The high heat remains at bay for next week -
80s for high temperatures all week. The upper level air flow
will be in a general zonal pattern. A short wave is expected to
push through the northeastern US Tuesday night. This will give
Tuesday/into the overnight hours the best potential time for
precipitation, although 30-40 PoP is all that can be warranted
for now.

Wednesday/Thursday look dry as weak ridging moves over the Mid



Rain with embedded scattered thunderstorms today and Saturday across
the DC metros before a cold front crosses Saturday night.

Tranquil/VFR behind the cold front Sunday.

VFR conditions expected Monday. There will be a potential for
degraded ceilings Tuesday.



South flow generally 15 knots today and Saturday ahead of a cold
front that crosses Saturday night. Will need to look out for SCA
NWly gusts Saturday night into Sunday.

Winds are expected to remain below SCA values Monday.
Showers/thunderstorms possible Tuesday.



LWX 88D went down around 1030 pm. As there was no
threat of hazardous weather it was determined that El Techs
would wait until this morning to look at it.



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