Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 130746
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
346 AM EDT Wed Sep 13 2017

.SYNOPSIS...
High pressure over eastern New York will move offshore today. The
remnants of Irma will move across the Ohio Valley today and into
Pennsylvania Thursday. High pressure will return to our region
during the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Radar is showing a couple of light showers moving up from the
south along I-95 and areas to the west into north-central
Virginia. These showers could produce a few hundredths of an
inch at best through daybreak. Additional rain showers are
expected to develop between Richmond and Virginia Beach and
move north into our region closer to Washington D.C. and
toward Baltimore and northeast Maryland by morning rush hour.
Elsewhere there will be some low stratus clouds or patchy fog
in spots.

As the rain showers move to the northeast and east out of our region
during the morning and midday, we will encounter a few peeks of
sunshine with high temperatures climbing up to near 80 or lower
80s.

This evening will be predominantly dry with weak high pressure
in control ahead of the last stage of the remnants of Irma.
Models are indicating increasing clouds and chances of rain
showers in the Potomac Highlands, mainly after midnight. These
chances will proceed eastward to the I-81 corridor and the
Shenandoah Valley by daybreak Thursday. Rain amounts would be
generally between one tenth to one quarter of an inch and would
be mainly in the northern Potomac Highlands, along the Mason-
Dixon region.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The chance for rain showers persists from west to east on Thursday
with an introduction of a few thunderstorms along the Mason-Dixon
region from around central Maryland east to the northern Chesapeake
Bay and south to around the I-66 corridor. These thunderstorms
should be isolated and pop-up Thursday afternoon due to daytime
heating underneath a cool-core remnant low of Irma. Once evening
approaches, any thunderstorms will lose their punch. High
temperatures Thursday will be lower 80s mainly east of I-95,
near 80 along and just east of the Blue Ridge, and middle to
upper 70s to the west.

The chance for lingering rain showers exist Thursday evening before
a quiet period Thursday overnight arrives as the main cool-core
remnant low slides to the east. Lows Thursday night will be cooler
than Wednesday night.

Models are indicating that a small piece of energy could wrap around
the departing remnant low Friday and approach us from the north
before departing to the east as well. For this reason, as well as
our high temperatures reaching around 80 once again, we will allow
for a chance of a few rain showers in parts of the region.

Dry conditions should arrive once again Friday night as this final
piece of energy slides to the south and east. Lows will be in middle
60s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Extended forecast hinges on the fate of Jose. There is limited
skill at track/intensity forecasts at this timeframe, which is
only magnified by lack of run-to-run forecast consistency
amongst model guidance. Latest official NHC forecast calls for
this cyclone to loop toward coast but stay offshore through
Sunday, which is what the local extended forecast will be based
upon. That still wouldn`t preclude occasional 20-30% PoPs this
weekend into early next week due to onshore flow, vort lobes
and/or an approaching cold front.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
IFR conditions at the CHO terminal due to a few rain showers and low
clouds through daybreak. A couple of rain showers, approaching the
MRB, IAD, and DCA terminals through daybreak, could drop conditions
down IFR, as well. Winds east less than 5 knots through daybreak.

IFR or perhaps MVFR conditions could persist through mid-
morning due to lingering rain showers and low stratus clouds at the
same terminals. BWI and MTN could encounter IFR conditions around
mid-morning if rain showers pivot north into these areas. VFR
condtions expected at all terminals this afternoon, tonight and
into Thursday morning. Winds becoming south 5 to 10 knots
today, then southwest around 5 knots tonight.

MVFR or brief IFR conditions possible at MRB, IAD, DCA, BWI, and/or
MTN Thursday afternoon due to isolated thunderstorms that could
develop due to daytime heating under the remnant low of Irma. VFR
conditions at all terminals Thursday night. Winds shifting northwest
5 to 10 knots Thursday, becoming light and variable Thursday night.

VFR conditions for the most part on Friday at all terminals. There
could be a shower around, but don`t anticipate too much in the way
of IFR conditions. VFR conditions Friday night. Winds northwest
around 5 knots Friday into Friday night.

At this time, VFR conditions likely to prevail. However, would
not rule out clouds coming onshore; there is low confidence in a
stratus deck.

&&

.MARINE...
No marine hazards expected today through Friday night. Winds east 5
to 10 knots today, becoming southwest 10 knots tonight. Winds
shifting to the northwest around 10 knots Thursday through
Friday.

Winds should be mainly 10 kt or less this weekend due to a ridge
of high pressure located near the waters. Clouds may be
prevalent, and flow likely to be off the Atlantic. Some of these
details still need to be determined.

&&

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

&&

$$
SYNOPSIS...KLW
NEAR TERM...KLW
SHORT TERM...KLW
LONG TERM...HTS
AVIATION...KLW/HTS
MARINE...KLW/HTS



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