Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
410 am EDT Fri Aug 26 2016
high pressure remains off the coast through tonight. A weak cold
front will cross the region this morning. High pressure will
return for the weekend. Another front may slowly slide southward
into the area by the middle of next week.
Near term /through tonight/...
at present...a large ridge of upper-level high pressure is centered
over the southern Appalachians. Over the course of today and tnoight
the ridge will slowly slide east-northeast and end up centered
directly over Virginia by late tnoight. At the surface...a cold
front is stretched from near St. Louis to the Adirondacks and is
slowly pushing southeast. The front will gradually slide southward
into our area today but there just does not appear to be enough of a
trigger to cause any thunderstorms to develop for most of the
region...with the possible exception of west-central Virginia...and
in fact the northwest flow developing today will likely suppress
convection despite the higher humidity now in place. This humidity
has allowed patchy fog to develop but it should not become dense
enough to warrant any advisories early this morning. By this
afternoon...warm air surging north ahead of the front combined with
the high humidity will allow temps to sruge to the mid-upper 90s
with heat indices in the low 100s. However...most of the moisture is
at the surface and stong mixing should allow dew pionts to lower a
bit later today...so think we should stay just below heat advisory
criteria. Nevertheless...it will be substantially hotter and more
humid than yesterday so anyone outdoors should use caution. This
part of August has relatively weak record highs...and those records
may topple...see climate section below for details.
Tonight...drier air will gradually slide southward from the north as
high pressure builds in. There may still be a little patchy fog in
the favored spots. Lows will not be quite as warm as this
morning's...but it will still be warm for this time of year.
Short term /Saturday through Sunday night/...
upper level ridge basically sits over Virginia through Sunday
night. Surface high pressure gradually shifts eastward to our
north allowing winds to shift to northeast...then southeast by the
end of the weekend. This may bring some low clouds into the area
but not sure of this at all. Otherwise...the front will dissipate
just to our south over the weekend and only slight cooling and
drying of the air mass is expected. Basically...not as bad as
today...but still hotter than normal. Thunderstorms look to be
suppressed by the ridge and lack of a trigger...with any risk
confined to the highest ridges to our west.
Long term /Monday through Thursday/...
continued warmth expected for much of next week as high pressure
remains over the East Coast to end the month of August. Highs
should be in the upper 80s/around 90. Precipitation chances look
to be in the chance range at best for much of the week - things
will primarily be dry.
But as September begins it does appear that a change will be in
store..actually beyond the scope of this forecast. Both Euro and
GFS show and upper level low deepening near Nova Scotia next
Friday which would bring a halt to the above average temperatures.
In addition a cold front would likely be moving through the mid
Atlantic next Thursday or Friday...giving region a better chance
Aviation /08z Friday through Tuesday/...
patchy fog possible early this morning mainly cho and mrb. Could
be a little around iad as well but think it should stay VFR with
just some patchy ground fog. VFR today with only a slight risk of
a T-storm down near cho. More of the same fog-wise tonight and
Saturday night. Otherwise VFR thru the weekend with no significant
T-storm risk. Winds mainly light with gusts mostly 15 knots or
less...starting west to west-northwest today...then NE Saturday..and shifting to
the southeast Sunday.
VFR conditions expected during the first part of next week.
Isolated thunderstorms will be possible in the afternoon/evening.
southerly channelling is diminishing as the front approaches so
current Small Craft Advisory drops off soon. Front sliding southward into the area
today may bring af ew northwest gusts close to 20 knots. However...am not
confident about Small Craft Advisory conditions occurring so have held off on Small Craft Advisory
for later today. Should be relatively light winds over the weekend
as high pressure slides past to the north...with winds mostly NE
on Saturday shifting more southeast by later Sunday. No significan risk
of T-storms thru Sunday night.
Winds expected to remain below Small Craft Advisory values Monday and Tuesday.
record highs are not out of the question today. Here are the
records for today:
Site record date(s)
Washington (reagan national) 97 1948
Baltimore (bwi/marshall) 101 1948
Washington (dulles) 95 1998/1993/1975
Ranking of Summer 2016 in terms of average temperature (jun 1 - Aug 25)
Site rankaverage temperature
District of Columbia 3 (tie with 2012)80.4
balt 19 (tie with 2 other years) 77.2
iad 3 77.2
District of Columbia...none.
Marine...Small Craft Advisory until 6 am EDT early this morning for