Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 180038
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
838 PM EDT Tue Oct 17 2017

.SYNOPSIS...
High pressure will remain across the Mid Atlantic through the
rest of the week and this weekend. A low pressure system may
affect the region early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
High pressure will remain overhead tonight. Mainly clear
skies...light winds and dry air will provide an excellent setup
for radiational cooling. Lows will be in the 30s for much of
the area, except in the 40s in the immediate urban centers and
along the shorelines of the Chesapeake and tidal Potomac. The
growing season ended last night for western Allegheny, Mineral,
Grant, Pendleton, and Highland counties, so no frost/freeze
headlines there. Otherwise we have issued Freeze Warnings in the
Shenandoah Valley for lows 30-32F, and Frost Advisories for
much of the rest of the area, except the zones along the western
shore of the Chesapeake Bay. The coldest readings will be in
sheltered valleys away from large bodies of water and away from
urban areas.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Surface high pressure will remain in control Wednesday, although
will gradually shift southward by Wednesday night as a weak
system moves into New England Wednesday night into Thursday. We
may see an increase in some high clouds Wednesday night into
Thursday morning as the system passes by to the north, but
otherwise no sensible impacts. High pressure will then expand
back northward Thursday night.

Temperatures will be moderating through the week, with highs
Wednesday in the upper 60s to around 70F, and reaching the low
to mid 70s on Thursday. Low temperatures will be a bit milder
than tonight, generally from 35-45F Wednesday night and 40-50F
Thursday night, with 50s in the urban centers and along the
Chesapeake and tidal Potomac shorelines. There may be some areas
of frost again Wednesday night given these temperatures,
although not as widespread as tonight.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
High pressure system centered near or over our area
will keep dry condition on Friday as it slowly moves offshore on
Saturday. Condtions will continue to be dry on Sunday as it moves
away from the coast.

A cold front will approach from the west on Monday with a wave
of low pressure tracking through it as an upper level trough
amplifies over eastern CONUS. Guidance suggest precipitation
associated with the cold front could start as early as Monday
afternoon and last into Tuesday with periods of heavy rain at
times.

High temperatures will be between the low to mid 70s on Friday to
the mid to upper 70s on Monday. High temperature decreases on
Tuesday into the 60s.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
High pressure will provide mostly clear skies and light winds
through Sunday.

&&

.MARINE...
High pressure will crest overhead tonight and remain nearby
through Saturday, before moving offshore Sunday. A weak system
will pass by to the north Thursday night. Winds will be 10 kt
or less for much of the time, with the exception of Thursday
night when gusts may approach Small Craft Advisory criteria.

&&

.TIDES/COASTAL FLOODING...
Anomalies have risen to around one-half foot above normal this
evening. The anomalies should end up around one-half to three
quarters of a foot above normal for the high tide cycle later
tonight into early Wednesday based on the anomalies upstream
across the southern portions of the Bay. This should keep water
levels below minor flood thresholds but it will be close for the
sensitive sites of Straits Point, Annapolis, and Washington DC.
Water levels will need to be monitored.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Frost Advisory from 1 AM to 9 AM EDT Wednesday for DCZ001.
MD...Frost Advisory from 1 AM to 9 AM EDT Wednesday for MDZ003>006-
     013-016-017-502>507.
VA...Frost Advisory from 1 AM to 9 AM EDT Wednesday for VAZ028>031-
     036>040-050>057-501-502-505-506.
     Freeze Warning from 1 AM to 9 AM EDT Wednesday for VAZ025>027.
WV...Frost Advisory from 1 AM to 9 AM EDT Wednesday for WVZ050>053-
     055.
MARINE...None.

&&

$$
SYNOPSIS...MM
NEAR TERM...BJL/MM
SHORT TERM...MM
LONG TERM...IMR
AVIATION...MM/IMR
MARINE...MM/IMR
TIDES/COASTAL FLOODING...BJL/MM



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