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000
FXUS61 KLWX 111419
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1019 AM EDT Thu Apr 11 2024

.SYNOPSIS...
Low pressure will track into the Great Lakes today, with an
associated cold front moving through tonight. Upper troughing
will linger overhead tomorrow, with a reinforcing cold front
moving through tomorrow evening. High pressure will build to our
south this weekend. A weak area of low pressure will track to
our north late Sunday night into early Monday, before high
pressure regains control early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
1030 AM Update: Showers are starting to approach the area late
this morning with some partial clearing happening across
western portions of MD and the eastern WV panhandle.
Temperatures are already climbing into the mid to upper 60s
across the lower elevations. It is worth noting a dry slot
building in behind the initial cold front passage affecting
areas further south of our CWA. Discrete cells and clouds should
begin building back in through the early afternoon with
increasing rain chances.

Previous Discussion Follows:
Broad troughing is situated from central Canada southward
through the Mississippi Valley to the Gulf Coast. A prominent
shortwave is located within the base of the much larger trough
over the Lower Mississippi/Arkansas Valleys, while another
shortwave descends down the backside of the trough through the
Plains states. As we move forward in time, the two shortwaves
will interact, causing the broader longwave trough to deepen and
eventually take on a negative tilt by later tonight.

Skies are currently cloudy, but most locations remain dry, with
just a few sprinkles and light showers scattered about the
forecast area. As we progress through the day, large scale
ascent will increase ahead of the approaching upper trough,
causing showers to gradually break out from south to north
through the morning. Scattered showers will continue through
much of the afternoon, with winds gradually picking up out of
the south, and temperatures making it into the 60s to near 70.
Wind Advisories are in effect for far western portions of the
forecast area starting this morning, and then for the Blue Ridge
this afternoon through the first half of the overnight as a
strong low-level jet moves overhead.

The upper trough will take on a negative tilt as it moves
overhead tonight. At the surface, low pressure will deepen as it
tracks into the Ohio Valley. Thunderstorms are expected to form
within the zone of strong forcing for ascent ahead of the
negatively tilted trough across OH/WV/SW VA late this afternoon
into early this evening. These storms should initially reach
far southwestern portions of the forecast area during the late
evening, before progressing northeastward across the remainder
of the forecast area between 10 PM and 4 AM.

Instability will increase through the evening as a low level
mass response occurs ahead of the approaching trough. CAPE
values are expected to increase to around 300-600 J/kg across
much of the area. When coupled with an impressive low- level jet
and ample deep layer shear present, some of the storms this
evening into the overnight may be on the strong to severe side.
Damaging winds should be the primary threat, but a brief tornado
can`t be ruled out given the strong low-level jet, 0-1 km SRH
values increasing to around 200-300 m2/s2, and STP values
climbing above 1. Weak stabilization evident on forecast
soundings right near the surface may potentially serve as a
limiting factor for both the damaging wind and tornado
potential. SPC currently has locations to the west of the Blue
Ridge outlooked in a Slight Risk for severe thunderstorms, while
locations to the east of the Blue Ridge are in a Marginal Risk.

A few heavier downpours may also be possible given the
instability present and highly anomalous PWAT values (near 1.5
inches). However, widespread flooding isn`t anticipated with
storm total rainfall values generally forecast to be under an
inch in most locations. Thunderstorm activity should be on the
decrease during the second half of the night, but a few showers
may linger through daybreak.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Low pressure will continue to deepen and track northeastward
from the Great Lakes into southern Canada on Friday as upper
troughing moves in aloft. Upslope showers will continue in the
mountains, with a few showers and potentially even a
thunderstorm or two possible to the east of the mountains Friday
afternoon. The majority of the day Friday will remain dry, and
temperatures should run above normal, with highs in the 60s to
near 70 for most. Winds will remain gusty out of the southwest.

A reinforcing cold front will move through Friday evening,
with winds increasing out of the west behind the front. Gusts
may near Wind Advisory levels, particularly over the higher
terrain Friday night. Low temperatures will range from the 30s
in the mountains, to near 50 along the I-95 corridor.

Troughing will progress off to our east on Saturday, as heights
rapidly rise aloft. Winds will remain gusty out of the west-
northwest, and high temperatures are forecast to reach into the
mid-upper 60s for most.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
On Sunday, a surface low will move through the Great Lakes region
with the associated warm front draping across the forecast area.
Aloft, an upper level trough will be eroding and pivoting towards
New England. Light rain showers are possible in the afternoon,
mainly in the northern portions of the forecast area. Generally, low
end PoPs (<30%) are expected all day with a slight uptick between
8PM and 2AM as the GFS and Canadian hint at shortwave energy passing
overhead. During this time, PoPs increase to 50% in the Alleghenies
and stay between 30-40% along the MD/PA border. Elsewhere, low end
PoPs remain. In the wake of the warm front passing through, high
temperatures will be in the upper 60s to upper 70s with metro
regions possibly reaching 80. Overnight low temperatures will be in
the 50s for most.

As we head into the workweek, a stalled frontal boundary just to the
north of the area will continue low end PoPs for the northern half
of the forecast area. The frontal boundary will slowly move towards
the area, with the warm front dipping into NE Maryland by Wednesday.
This will lead to slightly increase PoPs (30-40%) Tuesday night into
early Wednesday morning. Temperatures gradually warm each day with
highs in the 70s to low 80s for most(upper 60s in the mountains).
Overnight lows will be in the 50s to low 60s.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
Showers will overspread the area from south to north this
morning and continue through the afternoon. Southerly winds will
gradually pick up through the day.

Thunderstorms may move in from the southwest during the first
half of the overnight. VCTS has been introduced at all terminals
during that time. LLWS also appears possible late this afternoon
through the evening as a strong low-level jet moves overhead. A
few showers may linger through the remainder of the overnight
as ceilings start to gradually improve. Winds will turn
southwesterly behind a cold front on Friday, and ceilings will
improve back to VFR. A stray shower or thunderstorm may be
possible Friday afternoon. A reinforcing cold front will move
through Friday evening, bringing another surge in winds. Gusts
of 30-40 knots may be possible at the terminals overnight Friday
night. VFR conditions and continued gusty winds are expected on
Saturday.

Gusty southwest winds are expected at all terminals on Sunday with
wind gusts of 15-20 knots expected. Overnight, winds shift to
west/northwest and diminish. Winds remain out of the west/northwest
on Monday before becoming light and variable overnight.

&&

.MARINE...
Southerly flow will gradually increase today over the waters as
low pressure deepens to our west and the pressure gradient
tightens. Small Craft Advisories are in effect for all waters
in southerly flow today with Gale Warnings going into effect
late this evening through the overnight hours. Winds turn west-
southwesterly behind a cold front late tonight into tomorrow.
SCAs remain in effect through the day tomorrow. A reinforcing
cold front will cross over the waters Friday evening. Winds will
turn westerly behind that front, and may potentially pick up a
bit in magnitude as well. A Gale Watch is in effect for all
waters Friday night through the daylight hours on Saturday.
Winds should drop back to SCA and potentially even sub-SCA
levels Saturday night.

Gusty winds remain on Sunday with southwest winds gusting 15-20
knots across the waters. Small Craft Advisories are possible across
all waters for Sunday. Winds shift to west/northwest on Monday and
diminish to below Small Craft Advisory criteria.

&&

.TIDES/COASTAL FLOODING...
Southerly flow will increase through tonight. Light flow will
lead to a gradual increase in tide levels through the remainder
of the overnight, then stronger flow and approaching strong low
pressure will result in a more significant increase later today
into tonight. The highest tides are expected late tonight
through Friday morning, and this is when widespread minor to
localized moderate tidal flooding would be most likely. However,
if onshore flow is a bit stronger, tides could easily end up a
foot or so higher than currently forecast. This would result in
more widespread moderate tidal flooding (perhaps as early as
late tonight, with near major for the most vulnerable areas).

Westerly flow should cause a decrease in tide levels Friday
afternoon into Saturday, though the flow is west instead of
northwest which may result in some residual elevated water
levels sloshing around the Chesapeake Bay and tidal Potomac
River a little longer than is typical behind a front.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 8 AM EDT Friday for DCZ001.
     Coastal Flood Watch from Friday morning through Friday
     afternoon for DCZ001.
MD...Wind Advisory until 11 PM EDT this evening for MDZ001.
     Coastal Flood Advisory from 10 PM this evening to 4 AM EDT
     Friday for MDZ008.
     Coastal Flood Advisory from 7 PM this evening to 4 AM EDT
     Friday for MDZ011.
     Coastal Flood Watch from late tonight through Friday afternoon
     for MDZ011.
     Coastal Flood Advisory until 4 PM EDT this afternoon for
     MDZ014.
     Coastal Flood Warning from 4 PM this afternoon to 2 PM EDT
     Friday for MDZ014.
     Coastal Flood Advisory from 4 PM this afternoon to 10 AM EDT
     Friday for MDZ016.
     Coastal Flood Advisory until 2 PM EDT this afternoon for
     MDZ017.
     Coastal Flood Warning from 2 PM this afternoon to 10 AM EDT
     Friday for MDZ017.
     Coastal Flood Advisory from 1 AM to 10 AM EDT Friday for
     MDZ018.
     Coastal Flood Advisory until 4 AM EDT Friday for MDZ508.
     Coastal Flood Watch from Friday morning through Friday
     afternoon for MDZ508.
VA...Coastal Flood Advisory until 8 AM EDT Friday for VAZ054.
     Coastal Flood Watch from Friday morning through Friday
     afternoon for VAZ054.
     Coastal Flood Advisory from 4 PM this afternoon to 10 AM EDT
     Friday for VAZ057.
     Wind Advisory until 8 PM EDT this evening for VAZ503.
     Wind Advisory from 2 PM this afternoon to 2 AM EDT Friday for
     VAZ507-508.
WV...Wind Advisory until 11 PM EDT this evening for WVZ501.
     Wind Advisory until 8 PM EDT this evening for WVZ505.
MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ530-535-536.
     Gale Watch from Friday evening through Saturday afternoon for
     ANZ530>543.
     Small Craft Advisory until 6 PM EDT this evening for
     ANZ531>534-537>543.
     Small Craft Advisory from 6 AM to 6 PM EDT Friday for
     ANZ531>534-537>543.
     Gale Warning from 6 PM this evening to 6 AM EDT Friday for
     ANZ531>534-537>543.

&&

$$

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