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fxus61 klwx 140221 
afdlwx

Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
921 PM EST Wed Nov 13 2019

Synopsis...
Arctic high pressure overhead will move offshore later tonight
and during the day Thursday. A weak cold front will cross the
area Thursday night with high pressure returning through Friday
night. Coastal low pressure will intensify off the southeast
coast Saturday before moving northeast off the mid- Atlantic
coast Sunday. High pressure will build over New England during
this time. Another low may impact the area early next week.

&&

Near term /through Thursday/...
Arctic high pressure overhead will move offshore through
Thursday, leading to dry conditions and light winds. High clouds
continue across the region overnight but radiational cooling is
still expected to be noticed as low temperatures fall into the
upper teens to lower 20s. Likely only to see BWI challenged for
a record low (18f), as iad/dca records are a bit chillier
(13f/19f).

We start to slowly moderate with our temperatures Thursday and
Thursday night as the high shifts offshore and winds turn
southerly. Partly to mostly sunny skies are expected on
Thursday, with temperatures topping out in the 40s areawide.

&&

Short term /Thursday night through Friday night/...
a weak cold front will cross the area Thursday night as low
pressure emerges off the southeast coastline. These features
will bring a chance for light rain to portions of southern
Maryland and the Virginia Piedmont late Thursday night into
Friday morning. Guidance is in decent agreement with the precip
remaining south and east of the Washington Metro as the
northern/southern stream interact and an upper low migrates off
the southeast coast. If this plays out as model consensus
currently indicates, ptype will remain plain rain over the above
mentioned areas. If the precip makes a more northward extent
into the colder air at the surface, there would be the potential
for freezing rain, but confidence in this occurrence at this
time is low.

High pressure over the Great Lakes builds eastward into New
England on Friday as precip is shunted to our south and east and
dry conditions prevail for the entire area. Temperatures
moderate further Friday and Friday night, but remain slightly
below normal.

&&

Long term /Saturday through Wednesday/...
a somewhat active pattern over the long term with multiple
shortwaves passing overhead inducing two main surfaces lows off the
East Coast through early next week.

Saturday, throughout the day, looks to remain dry as a large area of
high pressure centered over New England suppresses a developing
coastal low off the Carolina coast. A relatively tight pressure
gradient between the two systems will induce gusty winds (perhaps
gusts as high as 30-40 mph near/east of the Blue Ridge where the
pressure gradient will be the strongest). The combination of
temperatures (struggling to get out of the 40's) and gusty winds
will create wind chill values in the upper 20's. The low begins
departing off the Carolina coast late Saturday/early Sunday morning.
While the heaviest precipitation will remain east of the Delmarva, a
few spotty showers are possible early Sunday morning for westernmost
Metro areas. However, conditions look to remain dry through the
weekend at this time.

By early next week, an amplified trough digs southeastward, catching
whatever vorticity/shortwave energy is left near the southeastern
U.S. On Tuesday, a second, more potent, coastal low once again
develops off the Carolina coast. However, timing and placement of
the trough moving through the southeast will dictate the exact
placement of any associated precipitation. The trend of the U.S
models has kept most of the precipitation offshore while the Euro
has the low developing closer to the coast which would bring the
precipitation shield more west. In any case, any storm system
that develops should be lifting northeastward, away from the
region on Wednesday. Overall, temperatures should be on a slight
warming trend through early next week. However the question
becomes how quickly, especially for mountainous areas and
perhaps near the PA border.

&&

Aviation /02z Thursday through Monday/...
VFR conditions at the terminals overnight and Thursday as high
pressure overhead moves offshore during the day Thursday. Winds
will become light and variable to perhaps southerly at cho.
Similar southerly winds expected at the other terminals late
Thursday into Thursday evening. A weak cold front will cross
the terminals Thursday night, with a northerly flow prevailing
through Friday night. With dry conditions forecast at the
terminals, VFR conditions will win out.

VFR conditions are expected on Saturday and the early part of
Sunday. A strengthening area of low pressure off the Carolina coast
will bring some low to mid level clouds into the area throughout the
day on Sunday, primarily affecting BWI, mountain and dca. Could see some
sub-VFR conditions at these taf sites on Sunday. Precipitation
chances begin to increase late Sunday as low pressure rides up the
East Coast, but remains pretty far offshore. Could see some gusty
winds both days, depending on how close the low gets to the coast,
so something to watch. Winds will generally be out of the north-northeast.

&&

Marine...
winds will be light and variable overnight into Thursday as high
pressure moves east to the East Coast. Winds will veer around to
a southerly direction late Thursday ahead of a cold front which
should turn the winds more northwesterly.

Low pressure will intensify near the southeast coast Friday
through Friday night. An Small Craft Advisory will likely be needed for portions
of the waters during this time. A Gale Warning may also be
needed for portions of the waters late Friday night.

Small craft advisories will be needed Saturday and Sunday, as an
area of low pressure strengthens off the Carolina coast and drifts
northeast. Gale conditions also appear possible, especially late
Saturday.

&&

Tides/coastal flooding...
an improvement from blowout tides this afternoon to a slight but
gradual rise in tide levels this evening has been noted.

&&

Climate...
with the Arctic airmass over the region, record low temperatures
were set this morning at iad (19f), and tied at BWI (22f). Here
are additional record lows and record cold highs.

Site low 11/13 high 11/13 low 11/14
dca 22/1911 31/1911 19/1920
BWI 22/2019 32/1911 18/1986
iad 19/2019 38/1996 13/1986

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...none.

&&

$$
Synopsis...bkf
near term...bkf/klw
short term...bkf

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