Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 181840
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
240 PM EDT Mon Sep 18 2017

.SYNOPSIS...
Warm high pressure will remain over the eastern United States
this week. Meanwhile, Hurricane Jose is expected to track
north off the Mid Atlantic coast tonight through Wednesday.
Refer to the National Hurricane Center`s website hurricanes.gov
for the latest on Jose.

&&

.NEAR TERM /THROUGH TONIGHT/...
An upper-level ridge will remain over the eastern United States
through tonight while surface high pressure over New England
wedges down into the Mid-Atlantic.

Breaks of sunshine has allowed for another warm afternoon...but
low-level moisture has also cause limited instability underneath
the subsidence inversion. An isolated shower cannot be ruled out
this afternoon but much of the time should turn out dry.

A north to northeast flow is expected tonight as Jose moves
north well offshore. The onshore flow will continue to cause
high amounts of low-level moisture...which means areas of low
clouds and fog are likely overnight as the moisture gets trapped
underneath the subsidence inversion. There is a better chance
for fog in sheltered valleys west of the Blue Ridge Mountains
and there is a better chance for low clouds east of the Blue
Ridge Mountains where the onshore flow will be stronger. A few
bands of showers from Jose will approach areas near the Bay
tonight while other locations remain dry. However...Jose should
remain far enough for the steadier rain to remain to our east.
Min temps will range from the mid to upper 50s in the colder
valleys of the Potomac Highlands to the mid and upper 60s in
downtown Washington and Baltimore.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Jose will pass by well to our east Tuesday before moving well
off to our north and east Tuesday night through Wednesday night.
Outer bands of showers from Jose will approach areas near and
east of Interstate 95 into portions of north-central Maryland
Tuesday. The best chance for showers will be near the Bay. Any
rain amounts will be light across these areas.
Elsewhere...subsidence from a large scale upper-level ridge
overhead and behind the tropical system will allow for dry
conditions along with some sunshine. Max temps will range from
the mid to upper 70s near the Bay where more clouds and possible
showers are expected to the lower 80s across most other
locations where more breaks of sunshine are expected.

Jose will move well off to the north and east Tuesday night
while surface high pressure builds overhead. Dry conditions are
expected during this time.

Another upper-level disturbance will build in from the west
later Wednesday into Wednesday night while weak surface high
pressure remains overhead. There may be a couple showers across
central Virginia into the Potomac Highlands later Wednesday into
Wednesday evening...but any instability will be limited so much
of the time will be dry. Elsewhere...dry conditions are
expected along with more warm conditions.


&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Benign conditions expected in the long term period
as upper level ridge/surface high pressure builds over our area
Thursday into Monday. Maybe some showers over the ridges, but
looking minimal. So, looking at an extended period of dry
conditions and high temperatures near 80 of in the low to mid
80s. Remnants of Jose might be lingering off of the Mid-
Atlantic/New England coast, away from us, and Maria could be
somewhere in the west Atlantic, but it is too early to tell.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
A band of MVFR cigs and isolated showers are expected through
21z across the eastern terminals. Cigs should lift to VFR levels
across these areas late this afternoon. Elsewhere...VFR
conditions are expected. An onshore flow will lead to more areas
of low clouds and fog late tonight into Tuesday morning. An
increasing flow may allow for more MVFR conditions vs. IFR
conditions across the eastern terminals and that is reflected in
the forecast...but confidence is low and IFR conditions are
possible. Low clouds and fog will dissipate later Tuesday
morning...but a few showers are possible across the eastern
terminals. Even across these areas much of the time should turn
out dry with the steadier rain remaining off to the east.

High pressure will build overhead for Tuesday night through
Wednesday night. Patchy fog cannot be ruled out during the
overnight and early morning hours.

VFR conditions expected Thursday into Saturday with high
pressure built into our area.


&&

.MARINE...
Jose will move north offshore tonight and pass by well to our
east Tuesday before moving off to the north and east Tuesday
night through Wednesday. A strengthening gradient will allow for
winds to strengthen through tonight into Tuesday. Will continue
with the Small Craft Advisory for the middle portion of the
Maryland Chesapeake Bay and lower Tidal Potomac River
tonight...and all of the waters Tuesday into Tuesday evening.
The strongest winds will be across the southern Maryland
Chesapeake Bay Tuesday with gusts around 30 knots likely.

A Small Craft Advisory remains in effect for the middle portion
of the Bay and lower Tidal Potomac River Tuesday night and it
may need to be extended Wednesday for portions of the waters.
High pressure will build overhead Wednesday night.

No small craft advisory expected between Thursday and
Saturday due to low wind speeds over our area.

&&

.TIDES/COASTAL FLOODING...
An onshore flow has led to elevated water levels around one half
to three quarters of a foot above normal. The elevated water
levels will continue through Tuesday morning as the onshore flow
strengthens. A Coastal Flood Advisory remains in effect for
Straits Point in St. Marys county during this time. Water levels
will be close to minor flood thresholds in Annapolis and
Washington DC during the high tide cycle late tonight into
Tuesday morning.

Model spread remains high for later Tuesday and Wednesday. Water
may be piled up near the Bay from Jose...but a northerly flow
should push water out of the Bay. Will continue with elevated
water levels in the forecast with caution stages being met...but
confidence in forecast is low and minor flooding cannot be ruled
out.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory until 4 PM EDT Tuesday for MDZ017.
VA...None.
WV...None.
MARINE...Small Craft Advisory from midnight tonight to 8 PM EDT Tuesday
     for ANZ531-539.
     Small Craft Advisory from 6 AM to 8 PM EDT Tuesday for ANZ530-
     535-536-538.
     Small Craft Advisory until 8 PM EDT Tuesday for ANZ542.
     Small Craft Advisory until 6 AM EDT Wednesday for ANZ532>534-
     537-540-541-543.

&&

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



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