Area Forecast Discussion
Issued by NWS Sterling, VA
FXUS61 KLWX 291435
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1035 AM EDT Wed Mar 29 2017
High pressure will build overhead through tonight before moving
off the coast Thursday. Low pressure will pass through the area
Thursday night through Friday night and the cold front
associated with the low will pass through Saturday. High
pressure will return for Sunday before low pressure possibly
impacts the area Monday and Tuesday of next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Ridge of high pressure will build into the region through the day
today behind the departing frontal system that brought the showers
and thunderstorms yesterday. Clouds have been slowly but surely
breaking up as cool and dry air advection takes hold. Overall a
nice early spring day with a northerly breeze from about 5 to
15 mph gusting up to 20 mph. Highs 60-70F.
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
As ridge builds from central Canada and into the northeastern
states, we`ll see it wedge down the eastern US coastline tonight and
through Thursday, promoting northeasterly flow and cooler
temperatures. Main surge of this appears to occur overnight tonight
with shift to northeast winds and noticeable drop/gradient of 925mb
temperatures. Therefore while tonight will start mostly clear for
most locations, developing easterly flow may lead to the development
of a stratus deck of clouds, especially along the easterly upslope
favored locations across the highlands and Blue Ridge. Could even
see some light rain or drizzle develop towards morning in those
locations. Lows tonight 35-42F.
CAD will more or less remain in place in the low levels Thursday. At
the same time, low pressure system will be ejecting out of the
plains with warm/moist air advection. This will lead to clouds and
perhaps some showers by later in the day across western areas,
although the best forcing on Thursday will remain to the northwest.
Highs Thursday will remain in the 50s under the clouds/easterly
Warm and moist air advection continues Thursday night and with that
we`ll see increasing chances for rain showers. Lows mainly in the
40s. Model guidance in good agreement that the low pressure system
will track east-northeastward from near St. Louis Thursday evening
to Ohio by Friday afternoon, before redeveloping near the DelMarVa
late Friday and Friday night. Thus, most widespread coverage of rain
expected from Friday and into the first half of Friday night. We`ll
also have to monitor how far north the warm sector can make it
Friday afternoon. Latest GFS indicates it may approach portions of
central VA and southern MD, so have introduced a chance of tstorms
there Friday afternoon. Highs on Friday 50-60F. Showers will
continue Friday night, but gradually begin to taper off as the low
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Low pressure will move away from the area Saturday...but a weak
cold front associated with the low will pass through during the
afternoon and evening hours. A few showers cannot be ruled
out...but much of the time should turn out dry due to a
northwest flow and subsidence behind the departing low.
High pressure will build overhead for later Saturday night
through Sunday...bringing dry and cool conditions.
High pressure will move offshore Monday and low pressure may
impact the area Monday night and Tuesday with unsettled
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
VFR as drier air works into the region today. VFR will continue
through at least the first half of tonight. Northerly winds
from 5- 10 knots with gusts 15-18 knots expected through today.
Winds will turn northeasterly later tonight, and east-southeasterly
on Thursday. This will help usher in additional clouds, although
ceilings still expected to remain VFR. Highest chances for some MVFR
ceilings will be at CHO and MRB.
Greater chances for sub-VFR conditions will occur Thursday night
through Friday night with widespread rainfall. IFR conditions
A northwest flow will allow for cigs/vsbys to improve Saturday
behind departing low pressure...but a few showers cannot be
ruled out. High pressure will build overhead for Saturday night
Small Craft Advisory remains in effect for all of the waters.
Gusts will be 20-25 knots much of today, then taper off later
this afternoon and SCA expires at 6 PM for some of the waters. A
second surge of northeasterly winds is expected later tonight,
and a SCA will continue for the Chesapeake Bay and lower Tidal
Potomac until 6 AM Thursday.
Sub-SCA winds then expected Thursday, with next potential for
increasing winds on Thursday night/Friday ahead of our next
system, especially across our southern waters.
Low pressure will move away from the waters Saturday and
northwest flow will develop. A Small Craft Advisory may be
needed for portions of the waters during this time. High
pressure will build overhead Saturday night into Sunday before
moving offshore Monday.
Low pressure will pass through the area Friday night. An
onshore flow will develop ahead of the low and this will cause
elevated water levels Friday into Friday night. Minor tidal
flooding near high tide is possible during this time.
MARINE...Small Craft Advisory until 6 AM EDT Thursday for ANZ530>534-
Small Craft Advisory until 6 PM EDT this evening for ANZ535-