Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 170731

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
331 AM EDT Mon Oct 17 2016

High pressure over the Mid-Atlantic will shift southward Monday
and remain to our south through midweek. A cold front will cross
the Thursday night into Friday. High pressure will return for the


Surface high pressure has shifted south of the region and this will
allow for the development of southerly flow and warming temperatures
today. The area also lies on the northeastern extent of a building
upper level ridge with several pieces of energy moving around the
ridge. Thus, some mid/high clouds as well as some cumulus will be
around today. Also seeing some patchy fog early this morning but
this should improve shortly after sunrise. With warming both in the
low levels and aloft, will see temperatures significantly warmer
than yesterday, with highs in the low 80s for most locations. This
will be near-record warmth today for IAD (Dulles), see climate
section below.


Sprawling upper level ridge will build further northeastward
tonight and Tuesday, with a continued warming trend expected.
Near-record or record highs and high-mins are possible. Lows
tonight in the 50s and 60s with highs Tuesday in the mid to upper
80s. These high temperatures will be 15 to 20 degrees above the
climatological normals.

A weak boundary will try to push southeastward towards the region
Wednesday before lifting back northward Wednesday night. There are
some discrepancies as to the southern extent of its progression.
Will lean towards the ECMWF solution which keeps it mainly north
of the area. Could see a few isolated showers near the boundary,
mainly northern areas, although dependent on actual location of
the boundary. Very warm temperatures continue with record or near-
record warmth. Lows Tuesday night and Wednesday night in the 50s
and 60s, with highs Wednesday well into the 80s again.


A cold front will pass through the Ohio Valley Thursday while high
pressure remains over the Atlantic. A southerly flow will continue
to usher in unusually warm conditions for this time of year.

The cold front will pass through late Thursday night into
Friday...bringing some showers with it. High pressure will build
overhead late Friday through the weekend...ushering more
seasonably cool conditions.


Patchy fog with areas of MVFR expected early this morning, mainly
BWI/CHO/MRB, and possibly IAD. There may also be a brief period of
IFR. Conditions improve shortly after sunrise with VFR expected area-
wide with some mid/high clouds as well as some cumulus this
afternoon. Winds light and variable this morning will become light
south/southwest this afternoon.

Mainly VFR expected tonight through Wednesday night, however there
may be intervals of patchy fog each night/early morning with
reductions to MVFR/IFR. MRB/CHO will be most susceptible. Winds
generally south/southwesterly less than 10 knots.

Patchy low clouds and fog may impact the terminals Thursday
morning. A cold front will pass through late Thursday night into
Friday...bringing the chance for showers and subvfr conditions.


Winds will be primarily out of the south and sub-SCA through
Wednesday night. With high pressure located south of the region, a
nocturnal low level jet is likely each night, however mixing
will be limited and a SCA is not currently expected to be needed.

High pressure will remain off the coast for Thursday and a
southerly flow will continue over the waters. A cold front will
pass through Friday and high pressure will build toward the waters
during the weekend. A small craft advisory may be needed for
portions of the waters Friday and Saturday.


A southwest flow will continue over the waters through Tuesday.
Elevated water levels are expected during this time. Some
thresholds may be threatened...but only by an inch or so at times.
Elevated water levels will likely continue through Thursday into
early Friday before an offshore flow develops behind a cold front.


Below is a list of record daily warm temperatures for
October 17th through 20th.

Record daily high temperatures
Site  10/17       10/18       10/19       10/20
DCA   86 (1938)*  85 (1938)*  88 (1938)   86 (1969)
BWI   90 (1938)   82 (1945)*  82 (1947)*  87 (1969)
IAD   83 (1963)   82 (2007)*  83 (1991)*  83 (1969)
*also occurred in previous years

Record daily warm low temperatures
Site  10/17       10/18       10/19       10/20
DCA   68 (1928)   68 (1947)*  65 (1905)   64 (1885)*
BWI   67 (1928)   69 (1928)   67 (1905)   65 (1910)
IAD   62 (1989)   60 (1968)   60 (2011)   59 (1993)
*also occurred in previous years




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