Area Forecast Discussion
Issued by NWS Sterling, VA
FXUS61 KLWX 171955
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
255 PM EST Tue Jan 17 2017
A stationary front over the Carolinas will move north as a warm
front this evening. A weak cold front will push through the area
early Wednesday. High pressure returns Thursday followed by an
approaching warm front Friday. High pressure returns again for
Saturday. Low pressure will affect the area to start the new week.
.NEAR TERM /THROUGH TONIGHT/...
Latest batch of organized steady light warm air advection showers
continues to progress eastward across the area...with radar
imagery showing the back edge just to the west of our office
(Sterling, VA) as of 250 PM. In total...generally a tenth or two
tenths of an inch of rainfall through this entire event...though
up to a quarter of an inch along the Allegheny Front. Visible
satellite imagery continues to show periodic clearing across the
Shenandoah Valley...though, any clearing should be short-lived.
Forcing will weaken by late afternoon, although spotty showers
will still be possible until cold front passes through the area
Could also be some patchy fog around before cold front passes
through near/around midnight...though increasing low-level wind
field should mitigate this in most locations.
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Compact area of upper-level energy passes over the area
tomorrow...with spotty light rain chances mainly across the
Allegheny Front and along the Mason Dixon line. Elsewhere...expect
drying/warming conditions as high pressure builds into the region
through Thursday. Next system approaches late Thursday with
showers approaching our SW zones by early Friday. Highs Wednesday
and Thursday in the 50s.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
A storm system over the western Ohio Valley will pivot northeastward
into the Lower Great Lakes region Friday into Friday night. Some
energy associated with this main low will push across our region
during the same time. Light to moderate rain will gradually spread
northeastward across the Shenandoah Valley early Friday. Rain should
reach the District of Columbia and surrounding areas by Friday
afternoon. Temperatures will remain mild with high temperatures
about 10 degrees above normal. Drier air will work its way into our
region from the west behind this wave low pressure energy and
escorted by high pressure building in from the Ohio Valley.
Weak high pressure will be overhead Saturday into Saturday night.
Temperatures will stay mild throughout the period. A separate area
of high pressure over New England could aid in some cloud cover
with an upslope flow.
A storm system will develop over the Mississippi Valley and deepen
as it pivots northward Sunday and Sunday night. This low could send
additional energy into our region Sunday into Sunday night, bringing
the chance of rain showers once again.
On Monday, the main low will move northward into the eastern Great
Lakes. The threat for showers and perhaps a rumble of thunder exist
Monday. Temperatures will remain mild. Drier air will push in
behind the departing storm system Monday night.
High pressure will usher in cooler and dry air on Tuesday. Clouds
will breaking for sunshine, except for clouds and upslope rain
and/or snow showers in the Potomac Highlands possible.
.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
IFR...to at times LIFR...conditions continue over the next few
hours as the last batch of rainfall moves across the terminals.
MVFR (to locally IFR) conditions then possible until cold front
crosses the region overnight. Mainly VFR tomorrow...though gusty
NW winds up to 25 mph possible in the wake of cold front.
Ifr to lifr conditions Friday with rain showers. Mvfr
conditions Friday night. Winds southeast around 5 knots
Friday. Winds light and variable Friday night.
Primarily southerly sub-SCA winds expected through tonight.
However, with strong low-level wind field, may see some gusts
approach SCA-criteria this evening and tonight. However, confidence
Winds will then turn to the northwest on Wednesday following cold
frontal passage. Gusts up to about 20 knots expected...a Small
Craft Advisory is in effect. Winds will then subside for
Wednesday night through Thursday night.
No marine hazards Friday through Friday night. Winds southeast
becoming light and variable 5 to 10 knots Friday through Friday
MARINE...Small Craft Advisory from 7 AM to 6 PM EST Wednesday for