Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 200752
AFDLWX

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

.SYNOPSIS...Weak high pressure will move offshore today. A cold
front will move through the area late Sunday. High pressure
returns for the first half of next week.

&&

.NEAR TERM /THROUGH SUNDAY/...A few isolated 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 at or above 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 /07Z SATURDAY THROUGH WEDNESDAY/...MVFR VSBYs at KCHO
this morning, otherwise VFR. Isolated afternoon t-storms possible
at 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...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...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...ADS
AVIATION...ADS/LFR
MARINE...ADS/LFR



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