Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 210756
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
356 AM EDT Sun Aug 21 2016

.SYNOPSIS...A cold front over Ohio will move through the
Mid-Atlantic this afternoon into the evening. High pressure then
builds over the area into Tuesday before persisting offshore
through the rest of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...Moisture will continue to increase
this morning with showers expected to become more numerous after
daybreak as a cdfnt extending from southwest Ontario swwd through
Toledo and St. Louis moves ewd. Cdfnt will then enter the fcst
area by late morning with widespread showers and scattered
thunderstorms expected. Best chance of t-storms east of the Blue
Ridge mtns based on HRRR 1-hr Max Lightning product. Storms may
pose a threat of isolated damaging wind gusts due to fast storm
motion of 20kt, moderate instability, and bulk shear values around
30kt. Rainfall amounts of half inch to inch and a quarter are
expected from far northern VA to northeast MD which may result in
isolated runoff issues particularly over the Baltimore metro area
and northeast MD. WPC PQPF shows 10-40% chance of 0.5 inches in
6-hr with highest probs over far northeast MD. Overall, flash
flood threat remains marginal attm due to fast storm motion of
20-kt and FFG of 2+in/6hr needed to bring streams to bankfull
stage. Cdfnt exits the area quickly during the early evening with
showers ending by 03z if not sooner.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...High pressure builds
Mon and holds through Wed with temperatures returning to more
typical values for late Aug.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...High pressure will begin to
move off the Mid-Atlantic coast on Wednesday and Thursday,
leading to a gradual warming trend to above normal temperatures.
Most of the area should remain dry, although moisture return may
allow for stray diurnal terrain convection on Thursday.

A cold front is still projected to approach on Friday. Mid/upper
level support is weak given a strong ridge over the SE CONUS.
However, there may be enough low level convergence for at least some
scattered showers and storms. ECMWF indicates highs may again exceed
90F ahead of the front.

The front will begin to stall and weaken as it becomes parallel to
the zonal flow around the SE ridge. However, 00Z guidance indicates
Great Lakes high pressure will provide enough of a push for the
front to drift south of the area on Saturday, resulting in little
chance of rain. Thermal differences will be small on Saturday
though, with temperatures remaining above normal.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...Widespread showers
expected with scattered thunderstorms mainly BWI, DCA, IAD and
MTN. Brief MVFR/IFR restrictions possible with t-storms. Cdfnt
moves east of terminals by 00Z Mon with showers ending quickly and
winds shifting to the NW.

No significant weather expected Wednesday and Thursday as high
pressure moves offshore.

&&

.MARINE...Widespread showers and scattered thunderstorms expected
this afternoon into early evening may pose a threat of strong
gusty winds which may require SMWs. Small craft advisory
conditions expected late tonight through Mon afternoon with NW
winds. High pressure then builds Mon through the middle of the
week with winds gradually diminishing.

Southerly flow of 5-10 kt expected Wednesday and Thursday as high
pressure moves offshore. A cold front will approach Friday, and
winds may increase slightly. Thunderstorms may accompany the front
as well.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT Monday
     for ANZ530>543.

&&

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



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