Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
757 PM EDT Monday Sep 1 2014
a Bermuda high will persist through Tuesday. A cold front will
cross the area Tuesday night...followed by high pressure through
the rest of the week.
Near term /through Tuesday/...
surface high pressure persists offshore. Water vapor imagery
indicates a disturbance moving across WV...and some associated
shower activity approaching eastern WV. This activity has weakened
somewhat in the early evening. Loss of sunlight will Foster a
gradual decrease in instability this evening...but with moist air
in place...dew points in the upper 60s to low 70s...forecast
soundings indicate it will take several hours for surface based
cape to drop below 1000 j/kg...along with elevated instability
above the nocturnal inversion that will set up. Scattered showers
and possibly thunderstorms remain in the forecast for eastern WV
and portions of western Maryland this evening...along with potential for
isolated activity over portions of western Virginia. Will continue with
potential for isolated activity over The Highlands overnight as
the upper disturbance and a vorticity maximum approach from the west.
Will have potential for fog tonight with moist airmass in
place...but it may be inhibited in some spots with approaching
clouds from the disturbance to our west.
Lows generally in the upper 60s to low 70s tonight...and slightly
cooler in elevated areas.
Short term /Tuesday night through Thursday/...
cold front will still be located across the Ohio Valley at 12z Tuesday.
But front will March eastward through the day...making it to the
Potomac Highlands by late afternoon. Pre-frontal environment will be
warm and moist...but convection likely waits until the front gets
closer to the County Warning Area and have probability of precipitation expanding eastward with time highest
in the evening across the Interstate 95 corridor.
There is the risk for a few storms to become severe /damaging wind
gusts/ Tuesday...especially before dark due to the combination of
instability and increased shear. Confidence is lower further
downstream once the sun sets. Front moves through at night. Probability of precipitation
lower from west to east.
Drier air moves in for Wednesday with the return of sunshine. While
dewpoints are lower...downsloping will support above normal
temperatures which still may be near 90. Same type of scenario on
Long term /Thursday night through Monday/...
weak surface trough...moisture and weak positive vorticity advection may be enough to supply
a slight chance of showers/thunderstorms Friday. Increased moisture
and the passage of cold front will support development of stronger
activity over the weekend and into Monday.
Aviation /00z Tuesday through Saturday/...
primarily VFR conditions expected this evening into the overnight
hours...although a brief shower is possible at kcho. Fog may develop
late tonight with a moist airmass in place.
Thunderstorms and rain possible again Tuesday afternoon/evening ahead of a cold
No significant weather expected middle to late week.
some wind gusts to 15-17kt noted near Tangier Sound this evening.
There is a little bit of a pressure gradient in this area...but it
is expected to relax overnight. Forecast soundings indicate
winds in the upper teens around 1-2kft. Not expecting this to mix
down over the open cooler waters...and nearshore gusts should
decrease as instability over land decreases. Isolated shower or
thunderstorm possible this evening.
Approaching cold front will likely produce scattered thunderstorms
late Tuesday afternoon and evening as well...with gusty winds
possible. Front moves through Tuesday night with high pressure
building in for Wednesday.
Southerly channelling/Small Craft Advisory conditions could be possible late
Friday. Cold front expected to move through over the weekend.
District of Columbia...none.