Area Forecast Discussion
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FXUS61 KLWX 230117
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
917 PM EDT Thu Sep 22 2016
Low pressure remains off the Carolina coast while high pressure
is centered over New England. A backdoor cold front will move
through the area Saturday. High pressure returns to the region
Sunday through early next week.
.NEAR TERM /THROUGH FRIDAY NIGHT/...
There has been little change in the synoptic setup this
evening...and for that matter, since yesterday evening. Clouds
have been southeast of a CHO-EZF-NAK line. No precipitation has
been detected, and don`t believe any will tonight. Therefore, will
be running with a dry forecast.
Elsewhere, mostly clear skies overnight might allow for some
patchy radiational fog to develop across the typically favored
valley locations. See no reason to make many changes to going
Remaining warm Friday with warm air advection ahead of cold front.
Limited cloud cover should allow for nearly full insulation...with
high temperatures a few degrees warmer than today and nearly 10F
above climatological normals.
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
Backdoor cold front pushes through the area Saturday morning. Models
often have a difficult time capturing sensible weather trends
(e.g., sky cover, temperature, winds) with backdoor cold fronts...so
have nudged these elements accordingly. Front is moisture starved,
so most areas will remain dry...though maintained slight chance PoPs
for a spotty shower over the higher terrain. Cloud cover will keep
temperatures cooler then previous days. Though, highs near 80s still
appear possible as cooler/drier air remains displaced further north
behind frontal boundary and doesn`t move in till later Saturday. Low
dewpoints will allow overnight low temperatures to fall into the L60s
across much of the area (50s across the north) Saturday into
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Deep ridging will traverse the region during the second half of the
weekend into early next week. The center of surface high pressure
will pass to the north and east of the region, so although high
pressure will be in control onshore flow will likely lead to
increasing low-level moisture and clouds.
An upper-trough will cut off over the upper Midwest and try to move
towards the area during the middle of next week, but the blocking
high pressure over the northwestern Atlantic will likely slow its
forward progress. The blocky/cutoff nature of the pattern lends to
greater than normal uncertainty in the forecast during this time.
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
VFR conditions expected tonight in the metros. Potentially there
could be patchy fog, but confidence remains quite low so have
kept it out of TAFs. At the typically favored locations (e.g.,
CHO and MRB) it`s a different story. Flight restrictions seem
likely with IFR conditions possible. Generally have preserved the
VFR expected Friday through Saturday night. Expect a sudden wind
shift to northerly as front moves through Saturday morning.
Sub-VFR possible Sunday into Monday as low clouds may develop in
onshore/easterly flow around 10 knots.
Winds remain below SCA values this afternoon through Friday night
with high pressure building into the area.
Small Craft Advisories are possible Saturday and Saturday
night with increased northerly flow behind frontal passage.
Easterly flow around 10 knots around high pressure over the
northwestern Atlantic should stay below Small Craft Advisory levels
Sunday into Monday.
Although higher than normal, water levels haven`t been high
enough to achieve minor flood thus far. Annapolis on track to
reach caution. No issues elsewhere on the Bay/lower Potomac.
Washington DC and Alexandria at low tide right now, with levels
below the previous HEC-RAS forecast. A rerun of the model this
evening suggests the same result as in Annapolis-- both sites
should reach caution but not minor flood.
Elevated tidal levels remain after tonights cycle...though
current forecast keeps levels below minor flood stage.
Unusually warm weather has persisted over the area for
quite some time. Autumn-like temperatures will finally make an
appearance over the weekend likely bringing low temperatures at DCA
below 60 degrees for the first time since June 9th, or 104 days ago.
The record most consecutive days at or above 60 degrees in the
Washington DC area is 112 set in 2012.