Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
353 am EDT Tue Jul 26 2016
Synopsis...a front will become stationary across the area today,
then drift southward on Wednesday. Another cold front is expected
early next week.
Near term /through tonight/...a cold front has stalled across the
mid-Atlantic region this morning. Winds have become variable in
most places and dewpts are in the 70s. Patchy fog is possible this
morning mainly in areas that received rainfall Monday and Monday
Little change in the surface pattern across the eastern Continental U.S. Today.
The frontal boundary will stay stalled across the region and warm
and humid conditions are expected again. There will be some relief
across the nrn mid-Atlantic as light northerly winds should bring
dewpts down into the 60s. Further south...dewpts will likely stay in
the low to mid 70s. Due to the heat and moisture heat indices will
climb into the low 100s east of the Blue Ridge and south of
Interstate 66 and around 105 across the central foothills, Tidewater
region and southern Maryland. A heat advisory is in effect for
these areas this afternoon.
Showers and thunderstorms are expected to develop this afternoon.
Coverage will range from isolated near the Maryland/PA border to scattered
across central Virginia. A few storms may become strong to severe across
the central Shenandoah Valley, central foothills and southern
Maryland where instability is higher. Weak shear profiles will keep
strong storms isolated. Coverage will diminish into the evening
however any ongoing thunderstorms will likely continue as little
change is airmass is expected.
Short term /Wednesday through Thursday night/...zonal flow continues
across the region Wednesday. The cold front is expected to move
south Wednesday and into central and southern Virginia. There is some
guidance that keeps the front northward along the East Coast and
therefore dewpts may not drop as much across central Virginia and
southern Maryland. Thunderstorm coverage is expected to be less on
Wednesday with a few forming across the higher terrain. If dewpts
do not drop across the East Coast a few thunderstorms will be
possible in the afternoon. Activity will diminish into Thursday.
The front lingers near the region Thursday and isolated showers and
thunderstorms are possible in the afternoon and evening. A shortwave
trough will approach the area Thursday night and coverage will
likely become more widespread and heavy rain is possible.
Long term /Friday through Monday/...guidance shows heights
falling across the region through the end of the week especially
in the Thu-Fri evening time frame as a shortwave-trough digs
across the ern great lks. Both the European model (ecmwf) and GFS show a low pres
center tracking from the Carolinas newd to south of Long Island
during the weekend with periods of rain affecting the area Fri
into Mon. Widespread total rainfall amounts of an inch or more
are likely during this period. Ignoring the GFS precip output
which appear spurious generating a large area of 1-3 inches in a
6-hr period over northern Virginia and Maryland. Based on ensembles, the
period of best rainfall potential appears to be in the Fri-Sat
time frame. By Mon night, most guidance show a front clearing the
area with enough dry air to suppress precip chances and enough cooler
air to keep temps below 90f at least in northern areas.
Aviation /07z Tuesday through Saturday/... VFR conditions expected
this morning. Rain showers/thunderstorms in the vicinity expected this afternoon and evening with
higher chance at cho. Coverage will be isolated further north and
confidence is low to put in tafs at this time. Activity will
likely diminish tonight and VFR conditions are expected. Isolated
rain showers/thunderstorms in the vicinity expected Wednesday and Thursday afternoon. Sub-VFR
conditions possible in activity.
Risk of showers and T-storms will likely continue into the weekend
as area remains under a very warm and moist air mass. Drier air
not likely to make into the area until early next week.
Marine...a cold front has stalled across the waters this morning. Winds will
likely become southerly today and remain below 15kts. Showers and
thunderstorms possible today mainly across the southern half of the
waters. Gusty winds are possible and smw may be issued. Winds become
nrly tonight and Wednesday. Isolated showers and thunderstorms
possible Wednesday and Thursday afternoons.
Sub-Small Craft Advisory conditions expected Fri through Mon, but higher winds and
waves can be expected near thunderstorms.
Climate...records were either broken or tied at all three main
A record high temperature of 100f degs was set yesterday at Dulles
breaking the old record of 98f set in 2010.
A record high temperature of 100f degs was set yesterday at
BWI Airport tying the old record of 100 set in 2010.
A record high and a record high minimum were set at dca
yesterday. A record high of 100f was set tying the old record of
100f degs set in 1930. A record high minimum of 81f degs was set
breaking the old record of 79f set in 1965.
District of Columbia...none.
Maryland...heat advisory from noon today to 8 PM EDT this evening for
Virginia...heat advisory from noon today to 8 PM EDT this evening for