Area Forecast Discussion
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FXUS61 KLWX 010121
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
921 PM EDT TUE MAY 31 2016
Several weak frontal boundaries will be in the area through
Thursday. A stronger cold front will pass through from the west
later Friday into Friday night. High pressure may briefly build
into the area Saturday before another cold front approaches Sunday
and passes through Sunday night into Monday.
.NEAR TERM /THROUGH WEDNESDAY/...
Rather weak surface pressure pattern across the area this evening
with shortwave ridging aloft. The small showers that developed to
the south and east of DC due to mesoscale boundaries have all but
dissipated, and it looks like we should have a dry rest of the
night. A prominent feature during the early evening was a dew
point boundary, located between IAD and DCA, roughly oriented NNE
to SSW...with dew points in the mid to upper 60s to the east, and
in the 50s to the west (before rising due to decoupling).
Temperatures which rose into the 80s for most of the area will
drop into the 60s tonight...with some 50s in the cool spots and
near 70F in the urban centers. Adjusted temps up a couple degrees
where dew points are currently higher. With light winds and partly
to mostly clear skies...potential for fog exists...though with
lower dew points to start we might not get as widespread or dense
as last night, especially in the western areas. Cloud cover and
dew point trends will play an important role.
Any fog will break early Wednesday. However...back
door cold front will approach the area from the north and could
spawn a stray shower or t-storm. Forcing and moisture is
weak...mainly due to convergence in onshore flow between the
front and remnants of Bonnie. Most hi-res models simulate widely
scattered, light reflectivity. Have POPs trend east to west
through the day as stable air pushes onshore. Temps may also be a
little cooler with more clouds but generally still a decent day.
Highs again mostly in the 80s.
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Back door cold front appears to regain some strength and push
southwest into the area Wednesday night into Thursday...with
further modest decrease in temperatures. This may try to keep
north and east portions of CWA dry...while further SW spotty
showers/storms will again be possible though with low coverage
Stronger cold front will approach from the west on Thursday night
and cross the area Friday. This system will bring better
concentration and coverage of rain and storms. However...forcing
aloft is not great even if CAPE looks decent...so probably looking
at marginal severe if any. Highs again in the vicinity of 80.
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Weak high pressure briefly builds in Friday night-Saturday,
keeping most of the area dry through the day.
Attention then turns to upper trough digging into the NE Sunday.
Guidance still differs with respect to
amplitude/positioning/timing, which will have a big influence on
impacts for our area. Depending on evolution, shear/thermo
profiles could be favorable for severe thunderstorms.
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
With light winds and partly to mostly clear skies, areas of fog
possible again later tonight into Wednesday morning. Have
introduced IFR vsby at MRB (climo) and CHO (where higher dew
points currently reside, and have MVFR at the rest of the
terminals except DCA. Like last night, not out of question IAD
could drop lower right around dawn. On the whole, fog is not
looking as dense as last night.
Weak boundary pushes toward area on Wednesday and may spark an
isolated shower or perhaps a thunderstorm, likely moving roughly east
to west. Predicted coverage and intensity preclude TAF mention
ATTM. IFR or lower conditions possible Wednesday night into
Thursday morning with onshore marine layer...then more
isolated/scattered showers/t-storms Thursday afternoon mainly
Winds generally less than 10 knots through Thursday, ranging from
Better coverage of showers/t-storms late Thursday night and Friday
with stronger front. Winds become more SW for a time.
Another stronger cold front approaches Sunday with another chance
of thunderstorms across the area.
Sub-SCA winds expected through at least Wednesday with surface
flow changing from roughly southerly this evening to a more
easterly component less than 15 knots on Wednesday. Near-SCA
conditions possible Wednesday night into Thursday behind a back
door cold front. Another cold front passing through the waters
Friday into Friday night will bring better coverage of showers and
Showers and thunderstorms are possible Sunday with another
stronger cold front. Gradient winds also increase near SCA
conditions Sunday near and behind frontal passage.