637
FXUS61 KLWX 090801
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
401 AM EDT Thu May 9 2024

.SYNOPSIS...
A stationary boundary will reside across the area today. Troughing
will dig across the eastern US this weekend. High pressure will
build offshore early next week, with low pressure approaching
from the middle of the country during the middle of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM, current radar imagery shows a large complex of
thunderstorms tracking to our south across southern VA and the
Carolinas, with just a few showers moving into the central
Shenandoah Valley and central VA. An additional area of
thunderstorms is situated off to our west extending from
eastern OH across northern WV. These storms are forming along a
stationary boundary which extends eastward into our forecast
area. A few additional showers and storms may try to develop
eastward along this boundary across far western MD and the WV
Panhandle over the coming hours. The light area of showers
across the central Shenandoah Valley and central VA may also
start to expand in coverage as it spreads northeastward during
the pre-dawn hours.

Chances for showers will continue through much of the morning
into the early afternoon, although coverage of these showers
should be rather low. Thick overcast will persist across the
northern half of the area through the day to the north of a
stationary boundary that stretch from west to east across the
central Shenandoah Valley and central Virginia. Less low cloud
cover is expected to the south of the boundary, which will allow
temperatures to climb into the upper 70s to near 80. Further
north, high temperatures in the 60s are forecast to the north
of roughly I-66/US-50.

A surface low will track from the mid-Mississippi Valley this
morning toward WV this evening. As this surface low approaches,
low-level forcing ascent in the vicinity of the surface boundary
will gradually increase, leading to increasing chances for
showers and thunderstorms. Model guidance shows that surface
based instability should remain confined to near/south of this
boundary across the central Shenandoah Valley/central VA.
Further north, no instability is expected through much of the
day, with only elevated instability developing after dark as the
surface low approaches from the west. As a result, the greatest
chance for strong to severe thunderstorms is expected to reside
in the vicinity of the boundary across the central Shenandoah
Valley and central Virginia. In those locations, model soundings
show around 1000 J/kg of MLCAPE and 50 knots of effective bulk
shear, with some limited low-level curvature in hodographs. As a
result, supercell, and all severe hazards appear possible in
that area. However, the tornado threat does appear minimal. In
terms of timing, storms may develop as early as mid-afternoon,
but the threat may persist through the evening as the surface
low and better forcing approaches from the west. Further north,
an elevated thunderstorm can`t be ruled out during the evening,
but the threat for severe thunderstorms appears to be low.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
A potent shortwave trough will track from the Ohio Valley
eastward toward the crest of the Appalachians during the day
Friday. Large scale ascent downstream of the trough axis will
lead to continued chances for showers across much of the
forecast area, with the most frequent showers expected to the
north of I-66/US-50. Temperatures will remain cool, with highs
in the upper 50s and lower 60s for most. Temperatures may be a
bit warmer across central Virginia (highs near 70), where
they`ll receive less in the way of rain.

The aforementioned shortwave trough will pass to our east
Friday night, but another shortwave will follow on its heels,
tracking into the Ohio Valley late Friday night. While showers
may linger through a portion of the night, a brief period of
clearing may move in between the two systems. If skies are able
to clear out for a time, some patchy fog may be possible in more
sheltered valleys. Overnight lows Friday night should be in the
40s for most.

Saturday should start out dry, but chances for showers will
increase during the afternoon once again as the next shortwave
disturbance approaches from the west. Chances for showers will
linger into the overnight as upper troughing builds overhead.
High temperatures on Saturday are generally expected to be in
the 60s, with overnight lows Saturday night in the 40s to lower
50s.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Upper trough axis will begin to move further north of the area
during the day on Sunday. Some showers and isolated thunderstorms
will be possible, mainly north of I-66/US-50. This will be where
the better forcing is. Severe chances are limited at this time
for this particular event. Highs will be in the upper 60s to low
70s for most lower elevations, with 50s across the higher
terrain.

Drier air works in for the start of the workweek with high pressure
nearby. A mix of sun and clouds is expected with highs climbing back
up into the low to mid 70s for most areas. Moisture returns on
Tuesday and Wednesday ahead of an approaching low pressure system
from the south slowly moving further northeast. Expect on and off
periods of rain both days with isolated to scattered chances of
thunderstorms in the afternoon and early evening. Cannot rule out an
isolated severe thunderstorm with these systems, especially
Wednesday as the associated warm front continues to move further
north. Highs will continue to be in the low to mid 70s for areas
east of the Allegheny Front (60s). Lows will drop down mostly in the
60s during the middle part of the week.


&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
Conditions are currently VFR at all terminals, but ceilings
should gradually drop throughout the day, becoming MVFR this
afternoon, and then IFR tonight. The exception will be CHO,
which should stay VFR through the day, before dropping to MVFR
and then IFR tonight. Showers will be possible on and off
throughout the day, and a thunderstorm may be possible at CHO
later this afternoon. VCTS has been introduced there to account
for that possibility. A rumble of thunder can`t be ruled out
elsewhere this evening, but the chance is far too low to
mention directly in the TAFs. IFR ceilings and chances for
showers will linger through the day tomorrow. Improvement back
to VFR conditions is expected on Saturday, but additional
chances for showers will move back in late Saturday afternoon
into Saturday night.

Winds will be out of the east today, northeast tomorrow, north
tomorrow night, and then south on Saturday.

Occasional sub- VFR ceilings will be possible on
Sunday, especially for the northernmost terminals. Otherwise,
VFR conditions will persist with northwest winds gusting 15 to
20 knots at times during the afternoon. Winds turn more
southerly with VFR conditions in place for Monday.

&&

.MARINE...
Sub-SCA easterly winds are expected during the day today. These
easterly winds may near low-end SCA values for a time this
evening as low pressure passes to our south. Wind turn
northeasterly tomorrow, northerly tomorrow night, and then
southerly by Saturday afternoon.

SCAs may be needed Sunday into early Monday as a result of
strengthening pressure gradient near the waters. No other marine
hazards are expected during the long-term period.

&&

.TIDES/COASTAL FLOODING...
Southerly winds will allow for minor flooding across some sensitive
locations this morning. These levels will likely drop later today.
Additional minor flooding will be possible late tonight into Friday
morning for the high tide cycle. Levels should drop well off by
Sunday when offshore northwest flow kicks in across the area.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory until 9 AM EDT this morning for MDZ014.
     Coastal Flood Advisory until 5 AM EDT early this morning for
     MDZ017.
VA...None.
WV...None.
MARINE...None.

&&

$$

SYNOPSIS...KJP
NEAR TERM...KJP
SHORT TERM...KJP
LONG TERM...ADM
AVIATION...KJP/ADM
MARINE...KJP/ADM
TIDES/COASTAL FLOODING...ADM