Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 180028

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
828 PM EDT Sat Jun 17 2017

A very warm and moist air mass will remain in place
through Monday until a cold front clears the area Monday night.
Weak high pressure will build over the area for the middle of
next week.


A few showers and thunderstorms left out there this evening but
coverage is considerably less than on previous nights. These
should weaken/dissipate over the next several hours. Overnight,
there will be a mix of clearing and debris clouds leftover from
the day`s convection. There may also be some lower stratus that
tries to develop overnight, with the highest chances over
northern/central Maryland as well as the Potomac
Highlands/Shenandoah Valley. In areas that see some clearing,
there may also be some fog development, especially any location
that saw rain today. However continued light southerly flow
should preclude a more widespread dense fog. Otherwise a warm
and muggy night with lows from the mid 60s to mid 70s.


A cold front will move through the Midwest and into the Ohio
Valley Sunday. Somewhat drier air aloft and a stronger capping
inversion will allow for more sunshine Sunday after low clouds
and fog burn off. A south to southwest flow along with more
sunshine will cause hot and humid conditions with max temps in
the upper 80s and lower 90s across most locations. The hot and
humid conditions will lead to an unstable atmosphere. The heat
and humidity should be enough to break the capping inversion
during the afternoon and evening hours. Isolated to scattered
thunderstorms are expected. Coverage may not be as widespread as
recent days...but shear profiles will be noticeably stronger.
Therefore...a few thunderstorms may become severe especially
west of the Blue Ridge Mountains where 500mb heights will be a
bit lower and shear will be strongest.

The cold front over the Ohio Valley will approach western
portions of the CWA Sunday night. Additional showers and
thunderstorms are possible ahead of the boundary...especially
across western portions of the CWA. More warm and humid
conditions are expected Sunday night ahead of the boundary.

The cold front will slowly pass through the area Monday into
Monday night. Shear profiles will continue to strengthen as the
upper-level trough associated with the cold front digs over the
Ohio Valley and Midwest. A south to southwest flow ahead of the
cold front will continue to usher in very warm and humid
conditions. The unstable atmosphere...along with forcing from
the cold front will lead to showers and thunderstorms. Strong
shear profiles suggest that there is an enhanced threat for
severe thunderstorms with damaging winds being the primary
threats due to unidirectional winds with height. Copious amounts
of moisture will also cause thunderstorms to contain heavy
rainfall. A shear vector nearly parallel to the cold front
suggests that training convection is possible. This elevates the
threat for flash flooding despite the faster storm motion
expected. The best chance for severe storms with heavy rain will
be during the afternoon and evening hours east of the Allegheny
and Potomac Highlands.

The cold front will move off to the east by Tuesday morning and
convection should dissipate overnight behind the boundary.


Weak high pressure will build toward the region Tuesday and
Wednesday while an upper-level trough builds overhead. Drier and
less humid conditions are expected along with seasonably warm
temperatures. A couple popup showers and thunderstorms cannot be
ruled out though due to the upper-level trough overhead.

A nearly zonal flow aloft develops Thursday through Saturday.
Most of the jet energy should remain to our north...which puts
our area on the warm side of a nearly stationary to our north.
More hot and humid conditions are possible along with increasing
chances for showers and thunderstorms.


A few showers and thunderstorms this evening will dissipate
overnight. Coverage is isolated to scattered and most sites will
not see any impacts. Overnight, VFR at all sites to start,
however, there may be a low stratus deck that develops late
tonight and lasts into Sunday morning. This has the potential to
bring MVFR ceilings for about a 3-6 hour period. There may also
be some patchy fog around which may bring visibility reductions.

A cold front will then approach from the west Sunday. A few
showers and thunderstorms are possible during the afternoon
hours into Sunday night. The cold front will pass through Monday
and there is a better chance for showers and thunderstorms.
Some thunderstorms may be severe. Weak high pressure will build
over the terminals during the middle portion of next week.


A southerly flow will continue through tonight. A Small Craft
Advisory is in effect for the Chesapeake Bay and middle/lower
Tidal Potomac River for gusts up to about 20 knots.

A cold front will approach the waters Sunday and Monday before
passing through Monday night. South to southwest winds will
increase during this time. A Small Craft Advisory is in effect
for all the waters Sunday and Sunday night and will likely need
to be extended into Monday and Monday night.

Popup showers and thunderstorms are expected Sunday afternoon
and evening. Locally gusty winds are possible in stronger
thunderstorms. More widespread thunderstorms are expected later
Monday into Monday night. Severe thunderstorms are possible
during this time with damaging winds being the primary threat.

Weak high pressure may build over the waters behind the boundary
for the the middle portion of next week...but the boundary will
stall out nearby.


A southerly flow has developed over the waters today. Tidal
anomalies are around one foot above astronomical norms. The
southerly flow is expected to strengthen through tonight and the
southerly flow is expected to continue through Monday. Tidal
anomalies will likely increase a bit in response to the
strengthening flow.

Minor tidal flooding is likely for Straits Point and Annapolis
with the high tide cycle tonight. A Coastal Flood Advisory is
in effect for St Marys County and Anne Arundel Counties. Minor
tidal flooding is possible with the high tide cycle tonight for
other sensitive locations...but confidence is too low for an
advisory at this time. Minor flooding is also possible Sunday
and Monday as the southerly flow continues.


MD...Coastal Flood Advisory until 3 AM EDT Sunday for MDZ014.
     Coastal Flood Advisory until 11 PM EDT this evening for MDZ017.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ530>534-
     Small Craft Advisory from noon Sunday to 6 AM EDT Monday for


TIDES/COASTAL FLOODING...BJL is the U.S. government's official web portal to all federal, state and local government web resources and services.