Scientific Forecaster Discussion
fxus61 klwx 220801
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
401 am EDT Thu Aug 22 2019
Synopsis...a cold front will cross the area late tonight or
early Friday, then move into the Carolinas over the weekend.
Canadian high pressure will build north of the region over the
weekend and hold through early next week.
Near term /through tonight/...
One last hot humid day in store before significant cool down
takes place for the weekend. A sfc trof will be in place this
afternoon to help focus scattered showers and thunderstorms
while actual cdfnt lags behind over PA. Hi-res convective models
show scattered convection developing late in the day (after 20z)
south of US-50 down into central Virginia with the strongest
convection over central and eastern Virginia. A few severe storms will
be possible given ample cape and marginal shear values.
Convection should exit the area by 03z tonight, but a few
showers will remain possible as cdfnt will be crossing the area
late tonight into early Fri morning.
Short term /Friday through Saturday night/...
Showers and perhaps a few thunderstorms will remain possible
Friday especially in the morning as cdfnt sags southward. Severe
wx, if any, would be confined to eastern Virginia and far southern Maryland
Chesapeake Bay waters. Most of the showers should be gone by
midnight Fri night if nor earlier. Dry and much cooler weather
will establish for the weekend as high pressure builds from the
Long term /Sunday through Wednesday/...
High pressure will build into the region Sunday and linger
through Tuesday. Dry conditions and near average temperatures
are expected each day for most of our region. An onshore flow from
the western Atlantic could spawn a few showers or a thunderstorm
Monday afternoon and again Tuesday afternoon, mainly in the upslope
areas and along the Chesapeake Bay.
The high pressure will move to the northeast Tuesday night and
Wednesday. A cold front will approach the region from the west. The
approaching front will allow for a southerly return flow to develop
and bring in more humid conditions and warmer temperatures.
Showers and thunderstorms will become more widespread, or at
least the chances will increase going into Wednesday.
One caveat to the extended forecast that could make or break our
region with a lot of showers and thunderstorms or dry through a
long stretch will be the possible coastal low, sub-tropical low,
or perhaps tropical low along the East Coast Monday night through
Wednesday. Placement and intensity and timing are low confidence
factors so far with the possible low pressure system. Both the
European and GFS models hint of this low along the East Coast and
mid-Atlantic coast, but neither model has a direct impact on our
County Warning Area. We will have to see what, if any, low develops and where it
moves over the next two to three days.
Aviation /08z Thursday through Monday/...
Scattered afternoon and early evening T-storms expected. Cdfnt
crosses the area late tonight or early Fri. High pressure builds
for the weekend.
VFR conditions for all terminals Sunday through Monday night. We
can't rule out a shower or thunderstorm near cho late Sunday
into Sunday night, or a shower or thunderstorm at any terminal
Monday afternoon. Winds northeast to east 5 to 10 knots
Sunday through Monday, becoming southeast 5 to 10 knots
Gusty T-storms possible late today or this evening may require
smws. Showers may linger across the southern waters all day Fri.
No marine hazards expected Sunday through Monday night. Winds
northeast 10 knots Sunday through Monday, becoming east 10
knots Monday night.
District of Columbia...none.