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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 011842
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
242 PM EDT Wed Jul 1 2020

.SYNOPSIS...
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An upper-level low will slowly move offshore from New England
tonight through Friday. A weak backdoor boundary may approach
the area during the weekend before dissipating early next week
as high pressure strengthens over the Atlantic.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Shortwave energy around an upper-level low over New England will
pass through our area this afternoon into early this evening while
a surface trough remains near central Virginia and southern
Maryland.

Daytime heating has led to an unstable atmosphere, with most of
the instability east of the Blue Ridge Mountains, and the
highest instability over southern MD into the VA Piedmont
(latest mesoanalysis shows 1500-2500 J/KG of MLCAPE across
these areas). The unstable atmosphere has led to popup showers
and thunderstorms, and this will continue into this evening. The
most widespread convection is expected over central Virginia
into southern Maryland where low-level forcing will be a little
stronger near the surface trough, and instability will be
highest as well.

A few severe storms are possible, with locally
damaging winds and large hail being the primary threats. The
best chance for a severe storm will be over southern Maryland
into central Virginia where instability is highest. A strong to
severe storm cannot be ruled out around the I-95 corridor near
Washington and Baltimore, but confidence is lower due to less
low-level forcing and slightly less instability. Farther
northwest, coverage will be more isolated due to even less
instability and no forcing.

Convection will dissipate after sunset with the loss of daytime
heating and subsidence behind departing shortwave energy. Patchy
dense fog is possible late tonight with clearing skies and light
winds.
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&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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The upper-level low will continue to move offshore while upper-
level ridging builds overhead for Thursday through Friday. A
warming trend is expected during this time, with highs into the
upper 80s to lower 90s Thursday for most areas and the lower to
middle 90s for most areas Friday. Most of the time will be dry
due to a capping inversion associated with the building upper-
level ridge.

A weak backdoor cold front may drop into the area late Friday
or Friday night, and this may trigger a shower or thunderstorm.
However, confidence is low at this time.
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&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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A weak backdoor cold front will stall out nearby Saturday and
Sunday, but there will be little in the way of a temperature
gradient with any marine air likely staying well off to the
northeast. Therefore, more hot and humid conditions are expected
with max temps in the lower to middle 90s each day. A weak wind
shift from the boundary may be enough to trigger isolated to
scattered showers and thunderstorms during the afternoon and
evening hours from daytime heating. Forecast confidence in
regards to exact location and timing of convection remains low
at this time. We will continue to monitor forecast trends as we
move closer to the weekend.

A southerly flow will develop and bring higher humidity conditions
into the region Monday and Tuesday. Threats for showers and
thunderstorms will be focused moreso in the mountains and along the
Blue Ridge. Highs will linger in the lower 90s.

High pressure will be weak to approach on Wednesday. This day may be
our drier day as we head into a more unsettled late week and weekend
period.
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&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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Scattered showers and thunderstorms are expected into this
evening. Brief IFR conditions are possible in convection along
with gusty winds. The best chance for a storm will be across
DCA, BWI, and CHO. Patchy fog is possible overnight into early
Thursday, especially across KMRB and KCHO.

VFR conditions are expected for Thursday and Friday along with
light north to northwest winds.

VFR conditions expected most of the time for Saturday through
Monday. A few popup showers and thunderstorms are possible each
day, especially during the afternoon and evening hours.
Cigs/vsbys could briefly be reduced during times of convection.
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&&

.MARINE...
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Sct-nmrs t-storms are expected into this evening. Storms may
produce isolated strong wind gusts that require SMWs.
Otherwise, onshore winds will be around 10 kt or less during
this time. A north to northwest flow is most likely for
Thursday and Friday, and winds should remain below SCA criteria
for most of the time.


No marine hazards expected Saturday through Monday. Winds
generally north 5 to 10 knots through the period. Winds could
become gusty in thunderstorms.
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&&

.TIDES/COASTAL FLOODING...
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A light onshore flow has caused elevated water levels this
afternoon. These levels will continue through tonight before an
offshore flow develops for Thursday.

Minor flooding is possible for sensitive areas around the
preferred high tide late tonight into early Thursday morning.
Confidence is too low at this time for advisories, but this will
have to be monitored throughout the evening.
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

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