Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
322 PM EDT Friday Mar 14 2014
a cold front will pass through the area late tonight into early
Saturday. High pressure will build overhead late Saturday into early
Sunday while low pressure tracks through the central United States.
The low will pass by to our south Sunday night into Monday and high
pressure will return by the middle portion of next week.
Near term /through Saturday/...
a strong pressure gradient between high pressure off the coast and
an approaching cold front has allowed for gusty southwest winds this
afternoon. The southwest winds along with sunshine will allow for
mild conditions...with maximum temperatures raising from the 50s in
northeastern Maryland to the middle and upper 60s in central Virginia
and the valleys of eastern West Virginia.
Low pressure will track through the Hudson Bay tonight and a weak
cold front associated with this system will move through our area
late tonight. Plenty of clouds are expected with the frontal
passage...but any precipitation will be light and confined to the
Potomac Highlands and northern Maryland since little moisture is
associated with the boundary.
Despite weak cold advection...a downsloping west wind and full
sunshine will cause mild conditions. Maximum temperatures will be in the middle to
upper 60s across most locations Saturday with some areas approaching
70 in the Virginia Piedmont. The forecast is a few degrees higher
than guidance due to the westerly downsloping flow along with
Short term /Saturday night through Sunday/...
Arctic high pressure will build overhead Saturday night from the
Great Lakes while low pressure develops over the Southern Plains and
tracks into the Gulf Coast states.
Dry and colder conditions are expected as northerly winds develop
ahead of the building high. High and middle-level clouds will begin to
move into the area well ahead of the low.
Low pressure will track through the Gulf Coast states Sunday.
Despite the low not being too strong and far to the south...plenty
of warm and moist air from the Gulf of Mexico is expected to begin
overrunning the low-level cold air in place. This will result in
increasing clouds Sunday morning and precipitation is expected to
begin overspreading the area from southwest to northeast Sunday
afternoon. Despite cold conditions...there should be enough warm air
near the surface during the day for precipitation to fall in the
form of rain or a rain/snow mix. Snow accumulations will be confined
mainly to the higher elevations of the Blue Ridge mountains and the
Potomac Highlands where surface temperatures will be colder.
Long term /Sunday night through Friday/...
highest impact time of the low pressure system will be Sunday
night into the morning morning commute. Models have come into
better agreement today with the GFS and European model (ecmwf) trending colder and
a tad further south with the track of the low which would be
favorable for accumulating snowfall especially from about 03z
through 12z Monday as temperatures fall into the 20s for most
areas. Boundary layer temperatures may hold in a bit warmer over southern
portions of the forecast area...especially southern Maryland where
mixing with rain and sleet may be possible before the changeover
occurs. Morning runs of the sref and NAM continue to show more
p-type concerns east of the Blue Ridge but given cold high
pressure locked to the north and winds backing around to the
north...tough to see how bl temperatures stay above freezing as long as
they have shown. Highest confidence for moderate to perhaps
significant snowfall is north and west of I-95/metropolitan areas...more
so north along I-81 as precipitation should be mostly snow for the entire
event. A bit concerned with the continued southward shift and a
precipitation gradient developing as occurred during a similar event a
couple weeks ago. Either way...situation is trending toward a more
significant event and watches may need to be considered during the
The Post 12z Monday time frame is a bit more uncertain with
potential for a dry slot/lull in the precipitation or tapering off
all together. Will continue at least likely probability of precipitation through
midday/afternoon then tapering off. Temperatures will remain well
below normal Monday.
There is a chance that some light snow may still linger Monday
night. Later Monday night into Tuesday...a low pressure system could
form near the middle Atlantic coast. Model agreement indicate any low
that does form would be well offshore and stay offshore.
High pressure will build into the region Wednesday. The Euro and GFS
both want to bring in milder air Wednesday and Thursday...as well as
bring a cold front across the region sometime Wednesday night and
Thursday. With limited moisture...only a chance of rain or snow is
expected Thursday into Friday.
Aviation /19z Friday through Wednesday/...
VFR conditions are expected through Saturday night.
Southwest winds will gust around 20 to 25 knots this afternoon into
tonight. Winds will shift to the west behind a cold front Saturday
morning with gusts around 20 to 25 knots expected later Saturday
morning and afternoon. Winds will decrease around sunset Saturday
and shift toward the north for Saturday night.
Low pressure will impact the area Sunday with increasing clouds and
wintry precipitation moving in from southwest to northeast during
the afternoon. Ceilings/visibilities will deteriorate toward evening.
IFR ceilings and visibilities expected Sunday night and Monday with mixed
precipitation changing to snow. Improving conditions expected later
Monday into Monday night.
MVFR conditions may linger Monday night with precipitation.
Improving conditions to VFR expected Tuesday through Wednesday
night. MVFR conditions may develop Thursday into Friday with an
approaching cold front.
gusty southerly winds are expected through tonight ahead of a cold
front. The cold front will pass through early Saturday and gusty
westerly winds are expected behind the front. A Small Craft Advisory
is in effect for the waters through Saturday. Winds will diminish
Saturday night as they shift to the north ahead of building high
pressure. Low pressure will approach the waters Sunday. Northeast
winds will increase during the day.
Small craft conditions will be possible over a portion of the
waters Monday morning into the afternoon.
No marine hazards Monday night through Wednesday.
Small craft advisories may be possible Wednesday night into early
Thursday with a cold front approaching the region and southwest
winds developing ahead of the front.
southwest winds will be sustained around 15 miles per hour with frequent gusts
around 25 miles per hour through late this afternoon. The relative humidity
will will be between 15 and 25 percent and fuel moisture will remain
low due to the recent dry conditions. This will cause an enhanced
threat for the spread of wildfires.
More breezy and dry conditions are expected Saturday along with
minimum relative humidity values near or below 30 percent across most locations. An
enhanced threat for the spread of wildfires is possible Saturday.
southerly winds will cause tidal anomalies to increase to around
one foot above normal late this afternoon and tonight.
However...low astronomical norms should keep water levels below
minor flooding thresholds. Westerly winds Saturday will cause
tidal anomalies to decrease.
District of Columbia...none.
Marine...Small Craft Advisory until 7 PM EDT Saturday for anz530>543.