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Area Forecast Discussion (AFD)

Issued by Sterling, VA (LWX)

                            
661 
FXUS61 KLWX 250033
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
833 PM EDT Sat Jun 24 2017

.SYNOPSIS...
High pressure will build west of the area through the rest of
the weekend and into next week as a series of weak cold fronts 
cross the region. These fronts will bring with them little if
any precipitation. The sprawling surface ridge will then cross 
the region Wednesday and settle over the western Atlantic Ocean
late in the week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
A couple showers have popped up over West Virginia this evening.
An isolated shower cannot be ruled out in the Allegheny and
Potomac Highlands this evening...but most places will end up
dry. Latest mesoanalysis shows little to no instability east of
the Allegheny Highlands. 

High pressure will continue to build from the west tonight. A
west to northwest flow ahead of the high will usher in dry and
comfortable conditions for this time of year. Min temps will
range from the 50s in the Allgheny and Potomac Highlands...to
the 60s across most other locations...to the low 70s in downtown
Washington and Baltimore.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Upper level troughing over the northeastern US will define the 
rest of the weekend and early week period, with a sprawling
surface high developing over the Midwest and Ohio Valley. This
will allow several weak frontal features to drop through the
northeast states during this time.

The first will cross portions of the northeast on Sunday. For
the most part this will remain off to our northeast, with
westerly flow and a mix of sun and clouds. Highs from 75-85F.
Fair weather continues Sunday night, with temperatures cooling
off into the 50s/60s.

The next weak frontal passage will occur on Monday, bringing
with it additional cumulus and perhaps a few isolated showers.
Highs Monday in the 70s to around 80F, dropping off at night 
into the 50s to around 60F.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Upper level trough and its associated surface reflection will 
slide east, and its axis will move across our area Tuesday. This
trough could create enough instability to allow for some 
showers and thunderstorms mainly Tuesday afternoon. Temperatures
will be below normal with highs in the 60s and 70s, and lows in
the 40s and 50s.

Surface high pressure builds east Tuesday night, then moves offshore 
late Wednesday, settling as a Bermuda high into Thursday as 
flow becomes more southerly. Temperatures will be on the rise 
and dry conditions continue into Thursday night. Guidance 
suggest that upper level energy could bring showers and 
thunderstorms over parts of our area Friday into Saturday. Cold 
front approaches from west on Saturday.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR expected through the forecast period. Gusts out of the 
west/northwest to around 20 knots likely Sunday and Monday. An 
isolated shower could also occur Monday with a weak cold front, 
but coverage will be extremely limited. 

Scattered showers and thunderstorms possible Tuesday as upper 
air disturbance moves through, which could cause periods of sub-
VFR conditions. VFR conditions return Tuesday night into 
Thursday with high pressure building in.

&&

.MARINE...
Winds have diminished this evening. A pressure surge behind a
trough is expected late tonight. Northwest winds may approach
SCA criteria along the Bay and lower Tidal Potomac River.
However...confidence is too low for an SCA at this time since
the surge will be weak. Will continue to monitor overnight. 

Additional gusts up to about 20 knots likely Sunday
afternoon/evening across the northern Chesapeake Bay, so have 
issued a Small Craft Advisory from 1 PM through 10 PM. As cooler
air moves in over warmer water temperatures Sunday night,
increased mixing may lead to these winds persisting through
Sunday night...but confidence for an advisory is too low at this
time since the pressure gradient will be weak.

Additional gusts near SCA criteria may occur Monday and Monday
night with persistent west-northwest flow and weak frontal
passages.

Scattered showers and thunderstorms possible Tuesday 
as upper air disturbance moves through. Conditions improve Tuesday 
night with high pressure building in and weather remaining dry into 
Thursday. Winds gusts will be below the small craft advisory 
criteria Tuesday through early Thursday. Wind gusts will increase 
Thursday afternoon.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 1 PM to 10 PM EDT Sunday for 
     ANZ530>532-538>540.

&&

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