Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 161845
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
245 PM EDT Sat Sep 16 2017

.SYNOPSIS...
High pressure will dominate the region through Sunday. Hurricane
Jose is forecast to move north along...but well offshore of...
the Atlantic coast early next week. See the National Hurricane
Center bulletins for the latest information on Jose. High
pressure over New England may extend into our area late next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A ridge of high pressure will remain over the eastern United
States through tonight. A small weakness in the ridge remains
over our area in the form of an upper-level low. The upper-level
low is weak...but there are enough height falls for limited
instability this afternoon and early evening.

An easterly flow will usher in moisture from the Atlantic as
well...and that can be seen currently with dewpoints in the 60s
for most locations. Unseasonably warm conditions will continue
through late this afternoon with max temps in the lower to
middle 80s across most locations.

Isolated to widely scattered popup showers are expected through
early this evening due to daytime heating and limited
instability. Latest forecast soundings show that convection will
be low topped due to the large scale subsidence from the upper-
level ridge. Therefore...left lightning out of the forecast at
this time and any showers that do occur are expected to be
brief.

Any showers should diminish around sunset. Plenty of moisture
underneath the nocturnal inversion will result in some fog
tonight. Fog may be dense...especially in rural areas and
sheltered valleys.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Surface high pressure will wedge into the area from the New
England Coast Sunday while a weak upper-level trough remains
overhead within the longwave upper-level ridge. More warm
conditions are expected for this time of year with isolated to
widely scattered popup showers. The best chance for showers will
be near and west of the Blue Ridge and Catoctin Mountains where
terrain circulation may serve as a lifting mechanism.

Jose will track north off the Mid-Atlantic Coast Sunday night
through Monday night. This system is most likely to stay far
enough offshore to prevent any significant impact on our
weather. However...an east to northeast flow around this system
will continue to usher in more moisture across our area. A few
outer band of showers cannot be ruled out...but much of the time
is likely to turn out dry. Please refer to the National
Hurricane Center for updates on the forecast regarding Jose.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Hurricane Jose will be moving north on Tuesday, well
east of the Mid-Atlantic coast. Confidence has increased in its
track, which currently keep its center well offshore with
minimal impacts to our CWA. Current concerns are minor coastal
flooding and/or wind gusts between 30 to 40 mph over the
Chesapeake Bay. The National Hurricane Center is issuing
advisories on Hurricane Jose and can be found at the following
website: http:/www.nhc.noaa.gov.

Jose will continue to track north and then northeast away from
our region Wednesday into Saturday as high pressure builds
into our area. Some afternoon showers possible Wednesday into
Friday due to upper level energy.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VFR conditions are expected through this evening. A popup shower
cannot be ruled out through sunset. Areas of fog are expected
overnight into Sunday morning. Fog may be locally dense with IFR
or subIFR conditions possible. The best chance for dense fog
will be across KCHO and KMRB...but it is possible across the
other terminals as well. Kept the lowest vsbys forecasted in the
western terminals for now where confidence is highest.

A weak onshore flow will continue through Monday night. Areas of
low clouds and/or fog are possible during the overnight and
morning hours each day.

Tuesday maybe periods of sub-VFR conditions at times
due to showers and/or thunderstorms, with maybe an increase in
winds as Jose moves away from us. Wednesday into Thursday
mostly VFR conditions expected with high pressure building in.

&&

.MARINE...
An onshore flow will continue through Monday...but wind speeds
should remain below SCA criteria. Jose is most likely to pass by
well offshore Monday night through Tuesday night. A Small Craft
Advisory will likely be needed for portions of the waters during
this time. Will have to watch Jose...any shift in the track will
have a significant impact on wind speeds. See the National
Hurricane Center for the latest on the forecast of Jose.

Weak high pressure may return for late next week.

&&

.TIDES/COASTAL FLOODING...
A light onshore flow will continue through tonight. Elevated
water levels are expected. Most areas should have water levels
just below minor thresholds during the preferred high tide cycle
tonight. However...latest forecast has minor flooding at Straits
Point so a Coastal Flood Advisory has been issued.

Later Sunday and especially Monday, the approach of Jose may
further elevate water levels, resulting in minor flooding at
sensitive sites. The nighttime tide cycle is astronomically
preferred. Depending on how close the storm gets, moderate is
not impossible, but uncertainty on this is very high at the
moment.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory from 10 PM this evening to 3 AM EDT
     Sunday for MDZ017.
VA...None.
WV...None.
MARINE...None.

&&

$$
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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