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Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
936 PM EDT Fri Apr 28 2017

high pressure will persist over Bermuda into Tuesday. A
stationary front will linger over southern Pennsylvania late
tonight through Saturday before lifting north Sunday. A
stronger cold front will move across the region from the west
Monday night. Canadian high pressure will then build over the
area through the midweek.


Near term /until 6 am Saturday morning/...
as of 9pm, low pressure is over The Big Bend region of Texas
with a warm/stationary front extending NE across the Ohio Valley
and reaching the eastern West Virginia Panhandle. Severe
convective storms have developed on the north side of this front
along the Ohio River valley and will move northeast through the
night. Instability increases and bulk shear remains high through
the night. This should allow strong to possibly locally severe
thunderstorms to move along this front late tonight. This puts
the northern third of the County Warning Area at risk. Height rises associated
with warm air advection should make the activity elevated with
hail as the primary threat.

Storm Prediction Center has expanded the marginal risk for this area and our
hazardous weather outlook mentions this threat for this area as
well. This will continue to be monitored through the night. 00z
hrrr continues recent trend of perhaps two rounds of convection,
one late tonight and the second toward daybreak. This is
climatologically the minimum in thunderstorm activity, but not
unheard of.

Lows primarily in the 60s, but the cities may not drop below 70.
This has never happened before in District of Columbia (in april) - record high
min is 69 set in 1896.

The year 1896 holds the record high min for Baltimore for five
consecutive nights in April. They dropped only to 70 on April
19, 1896.

See climate section for more information.


Short term /6 am Saturday morning through Sunday night/...
"hot" will be the operative word for Saturday as high pressure
moves off the southeast coast and pumps warm air into the mid
Atlantic. Again, see the climate section below for high
temperature records - these will definitely be in jeopardy. Heat
indices will be in the low/mid 90s in the I-95 corridor, nowhere
near heat advisory levels but notable for April.

Continued warm temperatures Saturday night/Sunday. There is not
any real trigger for organized convection approaching, but this
is somewhat of a summertime pattern. Hence it is not out of line
to see orographically driven storms develop Sunday afternoon.

The best thunderstorm chances hold off until Monday.


Long term /Monday through Friday/...
a cold front over the eastern Ohio Valley early Monday will move
across the region Monday into Monday night. Showers and
thunderstorms, some strong, will develop ahead of and along the cold
front Monday afternoon and evening. Temperatures will be about 15
degrees above normal.

Weak high pressure will build in behind the cold front Tuesday. A
gusty westerly breeze will usher in drier air. Temperatures will not
be as warm as Monday, but could still be 5 to 10 degrees above

As the high moves east, a secondary cold front will move across the
region from the northwest Tuesday night. This front should be a dry
front. The front could sag into the Carolinas Tuesday night before
starting to move northward as a warm front on Wednesday.

A low pressure system is expected to develop along the western end
of the warm front over the lower Mississippi Valley Wednesday night
and early Thursday. We introduce a slight chance of showers or a
rumble of thunder Wednesday night with a higher chance to likelihood
of encountering showers and thunderstorm Thursday through
early Friday.

At the tail-end of an associated cold front with the storm system,
another storm system could develop and deepen over the interior
southeast U.S. Friday and Friday night. The chance of showers and
thunderstorms will linger during the period. Temperatures will also
be closer to normal Friday and Friday night.


Aviation /01z Saturday through Wednesday/...
VFR conditions prevail tonight through Sunday night. A few
thunderstorms possible overnight with mrb being the main
consideration though thunderstorms in the vicinity for iad and BWI/mountain were also

IFR to LIFR conditions possible Monday and Monday night from
thunderstorms associated with a strong cold front moving through.
VFR conditions Tuesday and Tuesday night. Winds south-
southwest 10 to 15 knots Monday, becoming southwest around 10
knots Monday night, then west- southwest 10 to 15 knots Tuesday,
and west 5 to 10 knots Tuesday night.


light southerly flow, below Small Craft Advisory values, tonight through
Saturday night. Isolated thunderstorms possible on the northern
part of the Bay late tonight into Saturday and on all of the
waters Sunday.

Small craft advisories likely Monday as south winds increase
ahead of a cold front Monday night. Small craft advisories
possible Monday night and Tuesday with the frontal passage. No
marine hazards Tuesday night. Winds south 10 to 20 knots gusts
25 knots Monday, becoming southwest 10 knots Monday night, then
west- southwest 10 to 15 knots Tuesday, and west 10 knots
Tuesday night.


Tides/coastal flooding...
tidal anamolies are expected to decrease slightly over the next
several days as wind flow decreases. However, return of southerly
flow later today into the weekend will keep anamolies elevated.


record highs/warm lows through the weekend:

Washington District of Columbia...

Saturday 29 April...91 (in 1974)/68 (in 1956)
Sunday 30 April...92 (in 1942)/67 (in 1983)

BWI Airport...

Saturday 29 April...91 (in 1974)/67 (in 1956)
Sunday 30 April...92 (in 1910)/63 (in 1983)

Dulles Airport..

Saturday 29 April...87 (in 1996)/62 (in 1996)
Sunday 30 April...86 (in 2007)/64 (in 1983)


Lwx watches/warnings/advisories...
District of Columbia...none.

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