Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 250800
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Thu Aug 25 2016

.SYNOPSIS...
High pressure remains over the region today. A cold front will
cross the region on Friday. High pressure will return for the
weekend. Another front may slowly slide southward into the area
by the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure is offshore this morning, extending to the southern
Appalachians. Decaying convection is moving into the upper Ohio
Valley. The remnants of the convection and associated vort max has
led to some timing changes in the forecast, albeit minor due to high
uncertainty. Some showers may reach the northern Potomac Highlands
shortly after daybreak, generally dissipating as they continue
eastward. Despite the diurnal minimum, some showers may survive in
an environment of theta-e advection/isentropic lift. Diurnal
convection along the terrain which was originally forecast, may be
minimized in the wake of the vort max, which will skim the northern
part of the area. It may be difficult for much to develop toward the
I-95 corridor due to lessening instability and the building upper
level ridge. Decaying convection originating from near Lake Erie may
make a run at the northern Potomac Highlands late this evening, but
should have a difficult time making it into our area. In summary,
convection may have more of a nowcasting component today, but
definitely lowering chances with SE extent across the area.

Otherwise, expect a good bit of cirrus originating from the
convection, at least for the first part of the day. This may take a
slight edge off temperatures, but locations from DC/CHO east have a
reasonable shot at 90F. Dew points will also be rising into the
lower 70s. For tonight, those higher dew points will prevent many
from falling below 70F.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
High pressure is offshore this morning, extending to the southern
Appalachians. Decaying convection is moving into the upper Ohio
Valley. The remnants of the convection and associated vort max has
led to some timing changes in the forecast, albeit minor due to high
uncertainty. Some showers may reach the northern Potomac Highlands
shortly after daybreak, generally dissipating as they continue
eastward. Despite the diurnal minimum, some showers may survive in
an environment of theta-e advection/isentropic lift. Diurnal
convection along the terrain which was originally forecast, may be
minimized in the wake of the vort max, which will skim the northern
part of the area. It may be difficult for much to develop toward the
I-95 corridor due to lessening instability and the building upper
level ridge. Decaying convection originating from near Lake Erie may
make a run at the northern Potomac Highlands late this evening, but
should have a difficult time making it into our area. In summary,
convection may have more of a nowcasting component today, but
definitely lowering chances with SE extent across the area.

Otherwise, expect a good bit of cirrus originating from the
convection, at least for the first part of the day. This may take a
slight edge off temperatures, but locations from DC/CHO east have a
reasonable shot at 90F. Dew points will also be rising into the
lower 70s. For tonight, those higher dew points will prevent many
from falling below 70F.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Guidance remains in relatively good agreement in the long term.
Sunday morning a ridge of high pressure aloft will be sitting
squarely over the region. A weak shortwave passing to the north
will weaken the high a bit on Monday but it will remain over the
region. Another shortwave may then slowly slide southward into the
area by Wednesday...possibly accompanied by a weak cold front.
While we will start mostly dry early Sunday with the surface high
sliding to the northeast...increasingly southerly flow will
promote moisture advection which will help some terrain convection
going. This will be aided by the weak disturbance and front by
Wednesday. This so far ignores any potential impacts of any
tropical systems which various pieces of guidance are depicting
impacting the United States. Uncertainty becomes very high as we
head into the middle of next week.


&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
Increasing high clouds this morning, which should put a damper on
fog, although MRB is nearing its dew point. Today`s forecast is
somewhat uncertain in regards to convection, as activity currently
over Ohio should diminish as it crosses the mountains, although a
few showers could survive, especially to MRB. Very little storms may
redevelop however, and ones that do should be isolated. Mention will
not be included in the TAFs at this time. Due to possibility of
cloud cover and a light wind, fog formation for tonight is also in
question.

A weak front will slip through the area on Friday, with little more
than a wind shift. While a rogue storm can`t be ruled out, it`s a
very low probability. VFR conditions expected Saturday with high
pressure to the north.

Mainly VFR in the long term.

&&

.MARINE...
Increasing high clouds this morning, which should put a damper on
fog, although MRB is nearing its dew point. Today`s forecast is
somewhat uncertain in regards to convection, as activity currently
over Ohio should diminish as it crosses the mountains, although a
few showers could survive, especially to MRB. Very little storms may
redevelop however, and ones that do should be isolated. Mention will
not be included in the TAFs at this time. Due to possibility of
cloud cover and a light wind, fog formation for tonight is also in
question.

A weak front will slip through the area on Friday, with little more
than a wind shift. While a rogue storm can`t be ruled out, it`s a
very low probability. VFR conditions expected Saturday with high
pressure to the north.

Winds mainly sub SCA in long term.


&&

.TIDES/COASTAL FLOODING...
Increased southerly flow will cause water levels to rise today.
By tonight, caution stage will be reached at several sites on the
Bay. Annapolis could approach minor flood, although not all
guidance sources support that solution.

Winds will become west on Friday, so there should not be a concern
beyond the Thursday night cycle.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 2 AM EDT Friday for ANZ531>533-
     539>541.
     Small Craft Advisory until 6 AM EDT Friday for ANZ534-543.
     Small Craft Advisory until 6 AM EDT early this morning for
     ANZ536-537.

&&

$$
SYNOPSIS...RCM
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...RCM
AVIATION...ADS/RCM
MARINE...ADS/RCM
TIDES/COASTAL FLOODING...HTS/RCM



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