719
FXUS61 KLWX 131952
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
352 PM EDT Sun Jul 13 2025

.SYNOPSIS...
High pressure will remain in place offshore over the course of
the week. A weakening cold front will approach from the
northwest tomorrow, before ultimately stalling out and
dissipating overhead by mid-week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Two areas of showers and thunderstorms are ongoing across the
area early this afternoon. The first area is located across the
DC and Baltimore Metros, and extends southward to near
Fredericksburg. Much of this activity has trended weaker,
especially with northward extent, following numerous showers
that caused flash flooding in the DC/Baltimore Metros. A strong
outflow has formed as a result of this activity and is rapidly
moving westward toward the Blue Ridge. Another area of showers
and storms is present in the Shenandoah Valley, and is slowly
spreading eastward. Outflow from these two areas of storms
should collide shortly, potentially sparking another round of
thunderstorms extending from Central Virginia northward to the
vicinity of HGR/MRB.

Additional cumulus is deepening along the spine of the
Alleghenies, and could potentially result in a fourth area of
thunderstorms that should gradually spread eastward later this
afternoon into this evening. This is likely the activity
depicted in several of the recent HRRR runs that could
potentially linger through the first half of the overnight.

Several factors point toward storms today being very efficient
heavy rainfall producers. SPC Mesoanalysis and model soundings
show around 2000-3000 J/kg of MLCAPE, precipitable water values
near or in excess of two inches, and very deep warm cloud
layers. Background steering flow is also very light (around
5-15 knots through the depth of the troposphere), which should
result in slow storm motions. A few instances of flash flooding
have already occurred, and more instances may be possible
through the remainder of the afternoon and into the first half
of the night. A Flood Watch for flash flooding remains in effect
for the bulk of the forecast area until 2 AM. A severe storm or
two can`t be ruled out, given high CAPE and respectable DCAPE
(around 700-900 J/kg) in place. Activity should wind down prior
to midnight across the majority of the area, but could linger
in a few spots until the end of the Watch. Dry conditions are
expected during the last few hours of the night, and some patchy
fog could be possible, especially to the west of the Blue
Ridge. Overnight low temperatures should be in the upper 60s
and low 70s for most.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Another active day is expected tomorrow as a shortwave and
associated cold front approach from the northwest. Differential
cyclonic vorticity advection ahead of the aforementioned
shortwave will provide synoptic scale forcing that has been
lacking on previous days, within what will be a very similar
thermodynamic environment. A much higher areal coverage of
storms is expected as a result. With the increased organization
and slightly stronger mid-level flow (around 15 knots), storms
may be be slightly more progressive compared to preceding days,
but will likely pose an even greater threat for flash flooding,
given the higher areal coverage and a thermodynamic environment
that will still be very favorable for producing heavy rainfall.
Forecast soundings still show 2000-3000 J/kg of MLCAPE, deep
saturated profiles, PWATs near or in excess of 2 inches, and
high freezing levels. A Flood Watch for flash flooding will
likely be needed for much of the area once again. Storms may
fire over the higher elevations of western MD and the WV
Panhandle, as well as along the Bay Breeze further east. Much
like today, outflows from these areas of storms may eventually
meet up.

The aforementioned cold front will stall out overhead on
Tuesday, with slightly drier air filtering in behind the front,
especially in the mid-upper levels. The drier air moving in
aloft and lack of large scale forcing may limit thunderstorm
development across northwestern portions of the forecast area on
Tuesday. Better chances for showers and thunderstorms will
reside further southeast, where they`ll hang on to deeper
moisture.


&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
On Wednesday, a southeastern U.S. upper ridge will continue to bulge
northward into the Mid-Atlantic region. Eventually the northern
extent of this ridge axis erodes in response to amplification in the
northern branch of the jet. As this occurs, shortwave intrusions
over subsequent days will augment convective chances, particularly
in light of the continued warm and humid conditions in place.
Although these impulses should only offer a grazing blow to the
region, even subtle height falls can still have notable effects on
the quality of the forcing. Given the unpredictability of such
shortwaves, plus any storm-scale features which are unknown at this
time, will contribute to a low confidence convective forecast. By
late next weekend into the following week, a few deterministic
solutions attempt to show a deeper trough on the horizon. However,
as expected, global ensembles favor a more conservative elongated
longwave trough over much of eastern North America. The
aforementioned cold front will stall out overhead on Tuesday

Looking at the surface pattern, the early week boundary which stalls
nearby is expected to return northward as a warm front on Wednesday.
This returns the area into the broadening warm/moist sector and more
90 degree temperatures. The next frontal system of interest enters
the picture by Friday into Saturday. While daily afternoon/evening
thunderstorm chances are possible through the period, they will
likely further increase with the approach of this cold front. At
this point, like typical summertime boundaries, this system may
stall nearby toward the end of next weekend.

Daily high temperatures through the period will mainly rise into the
upper 80s to low 90s (70s to mid 80s across the mountains). For low
temperatures, expect readings in the upper 60s to mid 70s (low/mid
60s for mountain locations). Global ensembles are fairly consistent
in this signal with some downtick next weekend as the trough/front
moves through.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Prevailing VFR conditions are expected through the remainder of
the afternoon, but showers and thunderstorms may cause temporary
restrictions at some of the terminals. We`ve tried to highlight
the time period of greatest risk at each of the terminals in
TEMPOs, with the exception of MTN, where the threat for a
thunderstorm looks to be low. Thunderstorms could linger through
the first half of the overnight as they gradually drift
eastward, before eventually dissipating. A few low clouds may
also be possible overnight, but confidence wasn`t high enough to
include it in the TAFs yet.

Additional thunderstorms are expected tomorrow afternoon as a
cold front approaches from the north and west. Coverage of the
storms should be higher tomorrow afternoon into tomorrow
evening. Storms may be possible again on Tuesday afternoon, but
the highest coverage will likely be further south (in the
vicinity of CHO).

With convection perpetually in the forecast, restrictions are
possible each afternoon/evening from Wednesday through Friday. Each
day carries a 50 to 70 percent chance of showers and thunderstorms.
Thus, it is difficult to say which day will be more active than the
other. However, outside of these thunderstorms, VFR conditions
should be anticipated. Given the warm/moist conditions in place,
patchy fog cannot be ruled out at night, particularly for areas
which see appreciable rainfall. Winds through the period meander
between south to southwesterly before turning more westerly in
nature by Friday. Afternoon gusts could push into the 10 to 15 knot
range.

&&

.MARINE...
Sub-SCA level winds are expected over the waters through
Tuesday. Winds will be out of the southeast today, and then
south both tomorrow and Tuesday. SMWs may be needed as a result
of thunderstorms any of the next couple days, but most storms
are expected to stay off to the west of the waters this
afternoon.

A stalled frontal zone is expected to lift north of the waters on
Wednesday. As this occurs, south to southwesterly winds pick up in
strength Wednesday evening into much of Thursday. Wind gusts across
the southernmost waters could near 20 knots at times which would
warrant Small Craft Advisories. Elsewhere, gusts of 10 to 15 knots
are expected. The threat for convection increases through the period
with a 40 to 60 percent chance of showers and thunderstorms on both
Wednesday and Thursday afternoon/evening. Special Marine Warnings
may be needed for some of the stronger storms.

&&

.TIDES/COASTAL FLOODING...
A prolonged period of southeasterly winds will lead to elevated
tidal anomalies today and into early next week. This carries
most of the tidal locations into Action stage, particularly
during the higher of the two astronomical high tide cycles.
Sensitive locations, such as Annapolis, are forecast to stay
just below Minor stage during the high tide cycles Sunday and
Monday morning.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch until 2 AM EDT Monday for DCZ001.
MD...Flood Watch until 2 AM EDT Monday for MDZ003>006-011-013-014-
     016-501>510.
VA...Flood Watch until 2 AM EDT Monday for VAZ025>031-036>040-050-
     051-053>057-501>508-526-527.
WV...Flood Watch until 2 AM EDT Monday for WVZ050>053-055-501>506.
MARINE...None.

&&

$$

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