Area Forecast Discussion
Issued by NWS Sterling, VA
FXUS61 KLWX 171339
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
939 AM EDT Fri Mar 17 2017
A warm front will move into the area late tonight
into early Saturday before a cold front passes through Saturday
afternoon. High pressure builds over the area early next week.
Another cold front will cross the area on Tuesday.
.NEAR TERM /THROUGH TONIGHT/...
High pressure will move offshore today and a return flow will
develop. Low pressure will move into the western Great Lakes
this afternoon and the warm front associated with the low will
approach our area from the south and west during this time.
Clouds will increase late this morning into this afternoon...and
overrunning will lead to a period of rain and snow that will
move into the Potomac Highlands this afternoon and through the
rest of the area this evening.
Despite warmer conditions due to the southeast flow this
afternoon...there will be plenty of dry air in place. This will
cause evaporative cooling when precipitation moves in...and
this will cause rain to mix with and perhaps even start as snow
late this afternoon into this evening. The best chance for snow
will be across the Potomac Highlands...northern
Maryland...eastern West Virginia and extreme northern Virginia.
Snow may coat the ground across these areas...but most paved
surfaces will be wet due to the higher march sun angle warming
those surfaces. The one exception will be for locations along
and west of the Allegheny Front...where 1-3" inches of snow are
most likely. A period of snow/sleet is possible farther south
and east toward the Washington and Baltimore Metropolitan
areas...but temps should remain well above freezing during this
Temps are going to stay steady if not rise overnight as the warm
front pushes through the Mid-Atlantic region. Precipitation will
change to all rain by Saturday morning however favorable areas
where cold air can get trapped mainly across western Maryland
may result in fzra. Confidence is low and any icing would most
likely be confined to elevated surfaces. No advisory issued
during this time due to low confidence.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Low pressure along a cold front will move through the region
Saturday morning. A strong shortwave trough will lag behind the
sfc feature and move overhead Saturday afternoon/evening.
Pressure falls and mid- level forcing will likely lead to
scattered rain showers across the region. Activity will move
eastward by Saturday evening. Snow showers expected along and
west of the Allegheny Front through Saturday night.
Accumulations of 1-3 inches are possible during this time.
The shortwave trough will move eastward Sunday and snow showers will
come to an end in the mtns.
.LONG TERM /MONDAY THROUGH THURSDAY/...
Rain showers expected late Monday and Mon night into early Tue
as a cdfnt crosses the area. High pressure builds over the area
during the middle of next week leading to cool and dry
conditions. A developing storm system over the mid section of
the country will draw milder air into the area for next weekend
with a chance of showers for next weekend.
.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
VFR conditions expected through mid-afternoon. A period of rain
and snow is likely late this afternoon and evening. Best chance
for snow will be across KMRB. MVFR conditions are possible
during this time. Low clouds and areas of fog are possible
overnight as precipitation dissipates. IFR conditions are
possible during this time. A cold front will cross the terminals
Saturday. Scattered rain showers are possible Saturday
afternoon. NW winds will increase behind the front.
Rain showers late Mon and Mon night. Cdfnt crosses the area
around 12Z Tue with shifting winds. High pressure then builds
during the middle of next week.
High pressure moves off the east coast this afternoon. S winds
will increase by this evening and SCA conditions are expected
for portions of the waters through Saturday morning. A cold
front will pass through Saturday and high pressure will approach
Saturday night. A Small Craft Advisory may be needed for
portions of the waters during this time.
Cold and breezy conditions Sunday, some showers possible as front
SCA conditions possible Mon night through Wed.
MARINE...Small Craft Advisory from 8 PM this evening to 8 AM EDT
Saturday for ANZ532>534-537-540-541-543.