744
FXUS61 KLWX 171329
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
929 AM EDT Tue Jun 17 2025

.SYNOPSIS...
A warm front will slowly lift through the area this afternoon
bringing the return of warm temperatures and thunderstorm
chances to the region. Temperatures continue to climb Wednesday
with additional shower and thunderstorm chances as a trough of
low pressure passes through. The heat and humidity remain
Thursday along with the risk of severe weather as a strong cold
front crosses the region. Drier and less humid Friday as hot
high pressure builds for the upcoming weekend and into the
middle part of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Low clouds, fog, and drizzle continue across Northeast MD,
northeastern VA and Washington DC with a few showers developing
in the central Appalachians. A ripple of shortwave energy looks
to push toward the region from West Virginia later this morning;
thus, aiding to additional showers and a few thunderstorms once
the energy sends a stalled boundary northward as a warm front
through this afternoon. Some uncertainty remain in regards to
the placement of the warm front later this afternoon given the
influence of high pressure off the northern New England coast.
With the high up to the north the current cold air wedge will
be hard to erode especially over central and northern MD this
afternoon and even into the early evening hours. Areas further
south toward northern and central VA, and the Alleghenies will
likely see the wedge erode away during the midday hours with a
few filtered breaks of sunshine poking through. Areas that do
see the sunshine will see an increased chance for thunderstorm
development this afternoon as instability increases (i.e CAPE
values of 500-1500 j/kg). 0-6 km shear values look to increase
as well between 30-40 kts favoring progressive multicellular
clusters and line segments heading into the afternoon/evening
especially in locations along and west of the Blue Ridge. PWATS
unfortunately will remain anomalously high with values running
anywhere between 1.8-2.1 inches. Even with progressive storm
motions current antecedent conditions and efficient warm rain
processes (i.e rain rates 1-2"+/hr) will yield continued
concerns for localized flash flooding. With all that said, a
Flood Watch has been issued from 11am today through 10pm this
evening for locations along and west of the Blue Ridge.

00z CAM guidance shows convective initiation over the mountains
around midday before bringing everything east toward I-81/US-15
around 2-5pm and toward the metros shortly thereafter between 4-7pm.
The highest flood concerns appear to be across northern VA, the
Shenandoah Valley, and the Alleghenies where repetitive flash flood
warnings/flood warnings have taken place over recent days. Rain
totals of 0.5-2" are possible in the watch area with localized
totals up to 5 inches under heavier storms. Current 3-6 hr FFG
guidance remains less than 1 inch over a large chunk of the area, so
it won`t take much for instances of flash flooding to occur. The
risk for severe weather is low, though non-zero as SPC maintains a
Marginal Risk (Level 1 out 5) much of the area outside of northeast
MD this afternoon and evening. Damaging winds and wet microbursts
look to be the main threat with storms today.

After several days of well below normal temps we finally return
close to normal temps for mid June with highs in the low to mid 80s
this afternoon. Locations along the MD/PA line (i.e northeast and
central MD) may run a touch cooler in the upper 70s as the wedge
will hold on through mid-afternoon. Lows will fall back into the
upper 60s and low 70s tonight as the warm front lifts through the
area. Any residual thunderstorm activity will come to an end
although low and mid level clouds will remain especially along and
north of I-66/US-50. Fog will also be concern with the moist airmass
overhead.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Previous discussion...
More of the same can be expected Wednesday as the warm front
lifts further north of the area. This will allow hotter
temperatures to move in along with slightly drier conditions
under the influence of west to southwest downsloping flow.
Current 00z CAMS and synoptic guidance still hint on the threat
of a few showers and thunderstorms during the afternoon and
evening hours Wednesday as an upper level trough passes through.
Highest probability of severe thunderstorms looks to be west of
the Alleghenies due the proximity of an encroaching cold front
and east of US-15 where subtle lift from the departing
trough/bay breeze interaction could take place. Elsewhere, pop
showers and thunderstorms are likely given the hot and humid
airmass in place. Damaging winds will once again be the primary
threat with any storms that form along with localized concerns
for flash flooding. Highs Wednesday will push into the upper 80s
and low 90s outside the mountains. Heat index values Wednesday
afternoon will make it feel like the mid to upper 90s,
especially east US-15 as humidity continues to increase across
the region.

The lead shortwave trough works east Wednesday night into Thursday
as the cold front approaches form the Ohio River Valley. Convection
over the mountains will work east as well before slowly dissipating
given the lack of instability during the overnight hours. Lows
Wednesday night will fall back into the low to mid 70s.

An upper level trough pivoting across the Great Lakes region will
push a strong cold front through the area Thursday. High
temperatures will rise into the low to mid 90s Thursday afternoon
with heat index values in the metros near 100 degrees. CAPE values
will increase to around 1500-2000 j/kg with steep low-level lapse
rates (7+ C/Km) and moderate bulk shear values of (30-50 kts). This
will lead to progressive multicellular clusters and line segments
across the region. Damaging wind gusts will be the main hazard with
any storms that form. The Storm Prediction Center has the forecast
area east of the Allegheny front in a 15% risk for severe weather on
Thursday afternoon. One wildcard will be westerly flow aloft. This
could disturb the coverage of storms especially as they push east of
the mountains. We`ll continue to monitor this threat as it evolves.

Any convection will come to an end Thursday night with lowering
humidity in the wake of the frontal passage. Lows Thursday night
will fall back into the low to mid 60s. Areas of fog will remain
possible near the water and in the valleys.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The main theme of the Long Term period will be increasing heat.
Medium range model progs indicate a likelihood of several days of
90+ degree high temperatures, with some low end potential of hitting
100 particularly early next week. This is thanks to a large ridge
that will be building over the eastern CONUS. Although no large
scale troughs or fronts are expected to cross the region, small
disturbances rounding the ridge in the hot and increasingly humid
airmass could result in a risk for showers and thunderstorms late in
the weekend into early next week. Heat indices will be on the rise
as well during this time, with at least a small chance of the first
round of heat headlines for the season.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Widespread IFR to LIFR conditions continue across the terminals
through midday as a maritime airmass remains in place. Low
clouds continue to prevail along with passing showers and areas
of drizzle. CIGS range between 400-900 feet within the corridor
with vsbys bouncing between 2-6SM. These vsby reductions are due
largely in part to drizzle/showers compared to fog. Passing
showers and drizzle will remain within the corridor through at
least 14-15z/10-11am as a warm front lifts northward through the
region. This boundary should erode away the residual maritime
airmass in place resulting in a lifting cloud deck heading in
the afternoon, especially at terminals along and south of a line
from KMRB to KIAD/KDCA. Areas further north toward KBWI and
KMTN will likely hang in the maritime air longer with subtle
improvements after 17-18z/1-2pm this afternoon. MVFR to VFR
conditions are expected this afternoon and evening although
renewed shower and thunderstorm chances look to impact the
terminals. Have PROB30 groups in for the corridor terminals with
a focus on thunderstorm development between 20-24z/4-8pm.
Temporary sub-VFR reductions are likely during this time. Storms
will pack a punch with damaging winds and localized flash
flooding as the primary concerns. Periods of sub-VFR conditions
are likely again overnight with low and mid level clouds
sticking around and areas of fog. This is especially true in
areas that do see the rain and locations north of I-676/US-50
which will be closer to the warm front as it slowly jogs north
of the area. Winds today will switch from east this morning to
the south and southeast this afternoon at less than 15 kts.

After a brief period of sub-VFR Wednesday morning, VFR conditions
look to prevail. Additional showers and thunderstorms during the
afternoon and evening hours will lead to temporary sub-VFR drops
especially at terminals east of the Blue Ridge. Overall coverage
will be limited with damaging winds and localized flash flooding
once again as the primary concerns.

Prevailing VFR conditions are expected Thursday. Temporary drops to
sub-VFR conditions may be possible in thunderstorms especially
Thursday afternoon and evening. VFR conditions are expected Friday
into Saturday with west to northwest winds 5-10 knots becoming
south.

&&

.MARINE...
Low clouds will be slow to lift this afternoon as a warm front
lifts through the region. Sub- SCA level southerly winds are
expected over the waters on both this afternoon and Wednesday.
An SMW or two cannot be ruled out with scattered showers and
thunderstorms during the afternoon and evening hours. Highest
coverage for storms both days will be between 3-8pm.

SMWs are possible given thermodynamic and kinematic environment for
Thursday in any thunderstorm. SCA conditions likely return with cold
frontal passage Thursday into Friday. West to northwest winds are
expected Friday into Saturday, becoming southerly Saturday afternoon
at generally 10 knots or less.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch from 5 PM EDT this afternoon through this evening
     for DCZ001.
MD...Flood Watch from 5 PM EDT this afternoon through this evening
     for MDZ004-013-503-504.
     Flood Watch through this evening for MDZ003-501-502-509-510.
VA...Flood Watch from 5 PM EDT this afternoon through this evening
     for VAZ054.
     Flood Watch through this evening for VAZ025>031-036>040-050-
     051-053-501>508-526-527.
WV...Flood Watch through this evening for WVZ050>053-055-501>506.
MARINE...None.

&&

$$

SYNOPSIS...EST
NEAR TERM...KLW/EST
SHORT TERM...EST
LONG TERM...DHOF
AVIATION...KLW/DHOF/EST
MARINE...KLW/DHOF/EST