Area Forecast Discussion
Issued by NWS Sterling, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KLWX 300739
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
339 AM EDT Thu Mar 30 2017
High pressure will move offshore today through tonight. Low
pressure will pass through the area Friday. High pressure will
gradually return Saturday and Sunday before another low pressure
possibly impacts the area Monday and Tuesday next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Ridge of surface high pressure has wedged itself down the
eastern US seaboard and will remain in place for much of
today. This has led to the development of low level easterly
flow, and this in turn has promoted the formation of stratus
clouds across central and western Virginia. These will slowly
grow in coverage through the morning and advect northeastward as
southwesterly flow develops a few thousand feet above the
surface. At the same time, a low pressure system centered over
Missouri this morning will move northeastward and into Illinois
by this evening. Warm and moist air advection will increase
aloft, leading to high clouds which will also stream aloft
overhead through the day. Most of the shower activity should
remain north/west of the region today towards the area of
greater forcing, however, some showers may make their way into
parts of eastern West Virginia and western Maryland during the
day. Highs today will be in the 50s.
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
Warm and moist air advection continues tonight and with that
we`ll see increasing chances for rain, especially towards
morning. Model guidance in good agreement that the low pressure
system will track east-northeastward from over Illinois this
evening to Ohio by Friday afternoon, before redeveloping near or
over the area late Friday and Friday night. Most widespread and
steady rain is expected Friday morning, and rain could be heavy
at times. Lows tonight mainly in the 40s. With the low expected
to track near the region, will continue to monitor trends as to
how far north the warm sector can make it Friday afternoon
following initial surge of rain. Best chances for thunder will
be south of DC, and the Storm Prediction Center has placed
portions of the region in a Marginal Risk for severe
High temperatures will be very dependent on initial rain and
progress of warm sector, but will show low 50s north to mid 60s
Showers will begin to taper off Friday night as low pulls away
and northwest flow develops. Lows in the 40s.
High pressure will begin to build in during the day Saturday. A
lingering shower or two will be possible in northwest flow, but
most places will likely remain dry. Highs should be near
normal for the first day of April, from the upper 50s to mid
60s. High pressure then moves overhead Saturday night, with
mostly clear skies and lows in the 40s.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
High pressure will build overhead for Sunday...bringing dry
conditions along with sunshine and a seasonably mild afternoon.
High pressure will move offshore Sunday night and low pressure
will track into the Tennessee Valley Monday before passing
through our area Tuesday. The exact track of the low is a bit
uncertain at this time...but a soaking rain is likely Monday
into Tuesday. Should the low track farther north...then a few
thunderstorms would be possible. Confidence for thunderstorms is
low at this point.
High pressure will return during the middle portion of next
.AVIATION /07Z THURSDAY THROUGH MONDAY/...
VFR expected through today, although with multiple decks of
increasing clouds. Light northeast winds this morning will turn
southeast through today and increase up to about 10 knots.
Ceilings will lower and rain will overspread the region later
tonight and into Friday morning. Widespread IFR/sub-IFR
conditions likely, especially during the 06z-18z time period.
Some improvement possible after 18z Friday as steady rain ends,
especially CHO. The northern TAF sites, MTN/BWI/MRB likely to
remain locked into IFR/sub-IFR. IAD/DCA a bit more questionable.
A few thunderstorms are also possible Friday afternoon, with
highest chance at CHO.
Improvement back to VFR will take place Friday night, with VFR
area-wide expected Saturday and Saturday night. Winds will turn
northwesterly Saturday as well.
High pressure will build over the terminals Sunday. VFR
conditions are expected. High pressure will move offshore Sunday
night and low pressure will approach from the west on Monday.
Clouds and chances for rain will increase during this time.
SubVFR conditions are possible.
Sub-SCA northeasterly winds this morning will turn southeasterly
this afternoon and strengthen this evening. A SCA goes into
effect at 6 PM for portions of the central Chesapeake and lower
Tidal Potomac and continues through Friday where highest risk of
20 knot gusts lies.
Winds will turn northwesterly behind the departing frontal system
Friday night and on Saturday, and additional SCA winds are
possible. Winds will decrease Saturday night as high pressure
High pressure will build over the waters Sunday before moving
offshore Sunday night through Monday. Low pressure may impact
the waters Monday night into Tuesday.
An onshore flow will increase tonight into Friday as high
pressure continues to move offshore. Low pressure will pass
through the area Friday night. The onshore may increase ahead of
Elevated water levels are expected tonight through Friday night
and minor tidal flooding is possible near times of high tide.
MARINE...Small Craft Advisory until 6 AM EDT early this morning for
Small Craft Advisory from 6 PM this evening to 6 PM EDT Friday