Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
938 PM EDT Friday Mar 14 2014
a cold front will pass through the area late tonight and Saturday
morning. High pressure builds 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/...
mild conditions reside across the middle-Atlantic region this evening under
the influence of southerly flow in advance of a cold front. This cold
front extends to the southwest of a southern Ontario lopres system and is
analyzed over the Great Lakes and Midwest states as of 01z. With the
front not expected to reach the Allegheny and Potomac Highlands
until the early morning...southerly winds and cloud cover will limit
radiational cooling. Raised overnight temperatures by several degrees from previous
forecast...yielding forecast lows in the 40s across most of the area.
Showers will likely reach the Allegheny Front overnight. This activity
should break apart farther east due to downsloping flow...especially
given how weak the synoptic lift is with this system.
The cold front will move through the County Warning Area during the morning. Cold air advection near the
surface is very weak. Latest rap soundings show deep mixing potential on
Sat with strong daytime heating and downsloping winds. Am
concerned about a brief Post-frontal surge of winds gusting to to
near Wind Advisory levels along the higher elevation ridge lines Sat
morning...but confidence in this happening so early in the day is low.
Despite weak cold advection...a downsloping west wind and full
sunshine will cause mild conditions. Maximum temperatures will be in the low to
middle 60s across most locations.
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 /02z Saturday through Wednesday/...
VFR conditions through Sat night. Southerly winds have subsided a bit after
dark but still remain in the 10-15 knots range. Winds will shift to
the west behind a cold front Saturday morning with gusts around 20
to 30 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 will continue tonight ahead of a cold front.
Current marine observation show gusts 15-25 knots are occurring across all of
the waters. 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.
breezy and dry conditions are expected again Saturday with
minimum relative humidity values near or just below 30 percent across most
locations. Conditions not expected to reach red flag warning
criteria Saturday but an enhanced threat for the spread of
wildfires is certainly possible. Will coordinate with fire
officials Sat morning before deciding on issuing any Special
southerly winds will cause tidal anomalies to increase to around
one foot above normal 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.