Scientific Forecaster Discussion
fxus61 klwx 141839
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
239 PM EDT Mon Oct 14 2019
high pressure will build from the Tennessee Valley toward New
England through Tuesday while a secondary cold front approaches from
the Great Lakes and weakens. A strong area of low pressure will move
across the Ohio Valley Wednesday, then re-develop over southeastern
Virginia and move up the coast toward New England Wednesday night
into Thursday. High pressure will follow Friday into the weekend.
Near term /through tonight/...
high pressure building east from the Tennessee Valley this
afternoon and tonight. Dewpoints have dropped into the 30s due
to west winds near 10kt. Winds will diminish tonight, setting up
another favorable radiational cooling night. Have undercut the
guidance mean, with forecast lows in the upper 30s-lower 40s
outside of the urban centers/next to the Bay.
Short term /Tuesday through Wednesday night/...
expect another sunny day Tuesday under the firm control of high
pressure. Clouds will spread into the area Tuesday night in
advance of dual-stream low pressure. As for the precipitation
itself, though, guidance continues to delay onset. Have backed
off a little more Tuesday night, keeping forecast essentially
dry except for the Charlottesville/Staunton/Waynesboro area.
A sharp trough axis across the Great Lakes Wednesday will sweep
across the mid Atlantic, supporting the passage of a surface
cold front. Meanwhile, a second area of low pressure will cross
the southern conus, strengthening as the low reaches the coast
and interacts with northern stream energy. Have categorical
pops across the board, but the focus will be more on the coastal
during the afternoon hours. Have decent shear and minimal cape,
so have included a slight chance of thunder across the entire
forecast area as well.
Winds will increase (a core of 40 kt winds likely below 5000 ft
behind the front) and skies will clear Wednesday night as
deepening low pressure ejects northeast. Upslope showers likely.
These should be rain showers, but the peaks will drop close to
freezing by Thursday morning.
Long term /Thursday through Monday/...
low pressure will be pulling northeastward away from the region on
Thursday as high pressure builds eastward into the Ohio Valley. The
pressure gradient between these two features will lead to blustery
northwest flow and cool temperatures, with highs only in the 50s to
High pressure will then build overhead Friday and Saturday leading
to sunny skies and dry conditions. Temperatures will be chilly at
night with lows in the 30s/40s, and near to slightly below normal
during the day, with highs in the 60s.
The surface high will then slide offshore on Sunday with
southwesterly return flow developing. This will usher in increasing
warmth, to be followed by increasing moisture Sunday night and
Monday as a low organizes in the central US. Rain chances will then
increase Sunday night and Monday. Highs Sunday and Monday will
rebound back into the 70s, with lows in the 40s/50s.
Aviation /18z Monday through Saturday/...
VFR conditions should prevail through Tuesday. May have some
patchy River Valley fog tonight, but do not believe it will
impact the terminals.
Clouds will increase Tuesday night in advance of a cold front
Wednesday. A short period of flight restrictions near the time
of the frontal passage possible...likely during the midday
hours. Would not rule out a rumble of thunder either. Otherwise,
VFR will prevail through Wednesday night. Winds will increase
Wednesday night as well. If the core of the winds do not mix to
the surface, then a low level wind shear set-up would be
Predominantly VFR conditions are expected Thursday through Saturday
as high pressure builds eastward and into the region. Main aviation
weather concern will be gusty northwest winds Thursday.
winds will be light through Tuesday and then increase from the
south (10-15 kt) Tuesday night. Low pressure/cold front crosses
the waters Wednesday. Could be convective gusts near the front;
marine warnings possible. Then, in northwest flow behind the
front, small craft advisories highly likely and gales possible.
Small Craft Advisory conditions are likely Thursday with gale
conditions continuing to be possible behind a low pressure
system that will be exiting to the northeast. Small Craft
Advisory conditions may linger into Friday before slackening
Saturday as high pressure crests.
water levels under a foot above astronomical normals this
afternoon. Should be little change through Tuesday. Expect some
caution stages to be reached but no inundation. There is a
window for tides to increase Wednesday before a strong cold
front crosses the area. Would not rule out minor flooding at
sensitive locations prior to the frontal passage Wednesday
District of Columbia...none.