Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 201432
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1032 AM EDT Sat Aug 20 2016

.SYNOPSIS...
Weak high pressure will drift offshore today. A cold front will
move through the area Sunday afternoon. High pressure then builds
over the area into Tuesday before persisting offshore through the
rest of the week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 10am...1030mb surface high is along the Mid-Atlantic coast.
An east wind this morning will shift south through the rest of the
day. Dewpoints are around 70F, but subsidence will suppress cu
and thunderstorm development east of the Blue Ridge. A few
isolated showers t-storms possible along and west of the Blue
Ridge this afternoon with peak heating and marginal moisture
dissipating in the early evening. Otherwise, very warm with
temperatures to around 90F.

Deeper moisture begins to overspread the area late tonight and
early Sun morning as deep layered flow becomes from the SW. Sct
showers are possible by daybreak, but most of the activity is
likely to hold off until after 12z. PWs rise over 2 inches and
showers become more widespread as convergence increases along
approaching cdfnt. Threat for heavy rainfall and flash flooding
still exists mainly over northeast MD due to very high PWATs close
to 200% of normal. However, threat will be mitigated by fast
storm motion of 20-25 kt. Latest WPC PQPF guidance is showing
10-40% chance of exceeding 0.5 inches in 6-hrs which could be
enough for some flooding in highly vulnerable area of Baltimore.
There will also be a threat of 30-50 mph wind gusts with the
t-storms given fast storm motion, moderate instability and
marginal shear. Special marine warnings are likely to be required.
SPC Day 2 Otlk has area under marginal risk and this looks very
reasonable.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Cdfnt clears the area early Sun evening with showers ending
quickly. High pressure then builds through the first half of next
week with temps cooling down to the low and mid 80s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Surface high pressure will be
centered over the Mid-Atlantic on Tuesday. The seasonably
pleasant weather will continue with slightly below normal
temperatures and dew points remaining in the 50s. The high will
move offshore on Wednesday and Thursday as heights build aloft.
This will lead to a gradual warming trend as well as slightly more
humid conditions. There may be enough moisture return into the
western mountains on Thursday for a few showers and storms to
develop. Computer guidance is in fairly good agreement of a cold
front approaching Friday, which will bring the next notable chance
of showers and storms. However, the front will be slowing, and
there will be minimal upper level forcing, so it does not appear
like a widespread rain threat at this time.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
VFR prevails across the area into late tonight. Isolated
afternoon t-storms possible invof KMRB and KCHO. Cdfnt to move
through the terminals late Sun with showers and sct t-storms with
gusty winds and heavy rainfall with possible brief IFR conditions.

No significant weather expected through mid-week under high
pressure.

&&

.MARINE...
East wind less than 10 kt with high pressure along the Mid-
Atlantic coast this morning will shift south through the day.

Small craft advisory conditions possible late Sun night
through Mon as cdfnt moves through the waters and winds
strengthen. Also, t-storms Sun afternoon may be capable of
producing strong wind gusts and may require SMWs.

Northerly winds may continue up to 15 kt early Tuesday, but will
become light and variable as high pressure moves overhead late
Tuesday into Wednesday. Light southerly flow will develop by
Thursday as the high moves offshore.

&&

.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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