Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
911 PM EDT Monday Aug 31 2015
high pressure will remain offshore through Tuesday. An upper-
level disturbance along with its associated surface trough will
pass through the region Wednesday. Weak high pressure will build
overhead Thursday before a backdoor cold front moves into the area
late Friday into the weekend.
Near term /through Tuesday/...
precipitation chances have dissipated this evening. Skies will likely
become mostly clear across the majority of the area...although
some clouds could linger in the short wave. With winds calm and elevated
dew points...some patchy fog could develop dependent on cloud
cover. Favored areas would be inland and away from the metros...
particularly to the short wave. Lows in the 60s with lower 70s along and
east of I-95.
Broad surface ridging remains in place on Tuesday. Middle and upper level
ridging will also build...and a closed low over the Ohio Valley will
remain to the west. Atmosphere will likely be capped over most of
the area...so have left the small chance of diurnal convection
limited to the western terrain. With mostly sunny skies east of the
mountains...highs should be able to near or exceed 90 in many
locations. Heat indices should remain below 100 though since dew
points should stay in the 60s.
Short term /Tuesday night through Thursday/...
any mountain convection will wane during the evening. Otherwise
continued muggy conditions are expected as weather pattern changes
very little. Lows could even be a degree or two higher...with more
locations in the upper 60s to lower 70s. Patchy fog is again a
concern away from the coastal waters and the metros.
An upper-level disturbance and its associated surface trough will
pass through the region Wednesday into Wednesday evening. More
unusually warm and humid conditions will continue...but there will
be an increased chance for a shower or thunderstorm. The best
chance for convection will be across the Potomac Highlands into
central Virginia...closer to track of the upper-level disturbance.
Most convection should dissipate Wednesday evening as the upper-
level disturbance and surface trough move off to our south and
east. A northwest flow is expected behind the trough...but with no
temperature or dewpoint gradient more warm and humid conditions
Weak high pressure will build toward the area Thursday. A
northwest flow will continue...but again more hot and humid
conditions are expected due to sunshine and a downsloping flow. An
isolated shower or thunderstorm may pop up across the higher
terrain...but most of the time will be dry.
Long term /Thursday night through Monday/...
warm and humid conditions will continue Thursday night...but most
areas will turn out dry. A backdoor cold front will approach the
region Friday before moving into the area Saturday. The boundary
may trigger a few showers and thunderstorms. Cooler and less humid
conditions are possible behind the boundary later this weekend.
There is still some uncertainty though as to how far south and
west the boundary will make it. High press builds in sun through
Monday bringing drier conditions.
Aviation /01z Tuesday through Saturday/...
all showers and thunderstorms have dissipated. Some clearing
later tonight should help br develop at mrb/cho. Confidence a bit
higher for iad so included MVFR br in taf there as well. For
Tuesday...storms should remain west of the terminals. Winds remain
under 10 knots through the taf period. Some br will again be a
concern on Tuesday night.
VFR conditions are expected most of the time Wednesday and
Thursday. A popup thunderstorm is possible Wednesday afternoon and
evening. Patchy br may briefly reduce visibilities early Wednesday
morning and again early Thursday morning. VFR conditions expected
Thursday night. Sub VFR conditions possible due to showers and thunderstorms on
southwest flow will continue across the waters through tonight.
A few gusts flirted with 20 knots this evening so issued a
statement for the Middle Bay. This expires at midnight and wind
should not be any concern after that point. High pressure becomes
reestablished by Tuesday and flow will be variable and under 10
Winds should remain below Small Craft Advisory criteria Wednesday and Thursday. A
backdoor cold front will pass through the waters late Friday into
Saturday. A Small Craft Advisory may be needed for portions of the
waters during this time. High pressure will return for early next
District of Columbia...none.