Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
1012 am EDT Friday Aug 1 2014
a frontal boundary will remain near the coast through the
weekend. A trough is expected to move through Monday. Weak high
pressure builds in Tuesday.
Near term /through Saturday/...
analysis late this morning shows a coastal front along the middle-
Atlantic coast and an upper-level disturbance moving through North
Carolina and southern Virginia. Surface high pressure remains
along the New England coast and it extends toward the middle-Atlantic
The upper-level disturbance will move through the area this
afternoon while the coastal front slowly tracks north and west
toward the middle-Atlantic coast. Warm and moist air will overrun the
relatively cooler air in place. The combination of isentropic lift
and forcing from the upper-level disturbance should cause the rain
over central Virginia to spread northward into the rest of the
County Warning Area. Maximum temperatures will be quite cool for this time of year due to the
rain and extensive cloud cover. Maximum temperatures will range from the 60s
in the mountains to the upper 70s and lower 80s in Washington and
There may be a lull in the precipitation this evening as the
disturbance moves off to north...but pockets of light rain are
still possible as warm and moist air continues to overrun the
cooler air in place. Another disturbance will pass through the
region later tonight...bringing a better chance for rain. The best
chance for rain will be near and east of Interstate 95 closer to
the coastal front.
The stationary front will remain near the Delaware-Maryland-Virginia peninsula
Saturday and showers are expected across southern Maryland through the day.
Cloudy conditions will continue elsewhere Saturday as high pressure
noses into the middle Atlantic and moisture lingers ahead of the
trough. Although showers will be likely near the stationary front
all day...iso-sct showers will be possible across the region
Saturday as SW flow moves across cooler air. Temperatures will stay well
below normal and similar to today...upper 70s to near 80 and low 70s
in the mountains
Short term /Saturday night through Sunday night/...
boundary is forecast to remain nearly stationary along the coast
through the weekend...as an upper trough approaches from the west.
Combination of a wave of low pressure along the front and also
positive vorticity advection/shortwave energy ahead of the trough will keep unsettled
conditions during this time along with below climatology maxima and near
Long term /Monday through Thursday/...
uncertainty exists with the timing of the trough. GFS suggests
slower and thus a chance of showers/thunderstorms Monday. European model (ecmwf) is a
little faster with much of the precipitation offshore. Ensemble approach is
somewhere in between and reflected in the forecast.
Trough is forecast to have exited by Tuesday for dry conditions.
We/ll be keeping an eye on Tropical Storm Bertha which is forecast
to be across the western Atlantic by Tuesday evening. Models also
show a front diving south Wednesday into Thursday for another
chance of showers.
Aviation /14z Friday through Tuesday/...
rain will overspread the terminals this afternoon. The most
widespread precipitation will be across kcho and the eastern
terminals. Subvfr conditions are possible in periods of rain. Rain showers
possible tonight and through Saturday...at this time confidence is
low on timing as showers should be isolated-scattered at the terminals
Saturday. IFR ceilings expected at cho/mrb by early Sat morning and
MVFR at iad.
Potential exists for low ceilings to develop Saturday night into
Sunday. Unsettled conditions could continue into Monday until a
trough moves by and pushes a front near the coast further
winds will become southeast this afternoon...but remain below Small Craft Advisory
criteria. Winds become easterly tonight and wind gusts may
approach 20 knots as a front approaches the waters. Rain is
expected today and more showers will continue through Saturday
especially for the lower tidal Potomac and Maryland Chesapeake Bay south
of Sandy Point.
Southeast winds Saturday night into Sunday may turn more northeast
early next week. Gradient mainly light through then...but southeast
winds may be 10 to 15 knots up the Bay.
District of Columbia...none.