FXUS61 KLWX 080800
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Tue Jul 8 2025
.SYNOPSIS...
A cold front will drop closer to the area by this afternoon and
will then stall and waver nearby through the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
There's a lull in the active weather to start the day, with just
some patches of clouds and fog. Ridging at the surface and aloft
remains offshore, while a cold front lurks across central PA
into central OH. The front will slowly sag toward the area this
afternoon, while ripples in the WSW flow aloft will provide
additional lift and enhance mid level winds slightly. Expect
convection to rapidly develop over the mountains between noon
and 2 PM and then progress eastward through the remainder of the
afternoon and evening. Moderate to strong instability in the hot
and humid airmass will support strong updrafts. While the
airmass will be fairly moist with weaker lapse rates, the
favorably-oriented 20-25 kt of shear will help organize the
storms into clusters, and there will likely be sufficient DCAPE
for strong to severe downbursts. This threat is greatest as
storms intensify near and east of the Blue Ridge, where SPC has
a Slight Risk. Precipitable water values will be around 2 inches
east of the Blue Ridge as well, supporting heavy rain rates.
While average storm motion should limit residence time of the
thunderstorms, there is potential for mergers and backbuilding
along outflows. There are also some indications the storms
could get "strung out" for a time across southern Maryland,
which has had above normal rainfall over the past week. Combined
with the more sensitive urban areas, a Flood Watch for flash
flooding has been issued from 2 PM until midnight for this area.
Today will be the hottest day of the week for a large part of
the area with highs in the lower to mid 90s east of I-81. Have
expanded the Heat Advisory to include Washington DC and the VA
I-95 corridor, as it appears dew points will pool along and east
of a subtle surface trough near the fall line. This area will
also see the longest period of sunshine before storms arrive, so
feel there is a reasonable chance to reach 105 heat index.
Elsewhere, heat indices will be in the upper 90s to lower 100s.
The second half of tonight will bring the opportunity for fog
and/or low clouds in the saturated low level airmass. Lows will
range from the upper 60s to mid 70s.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The weather pattern will get stagnant moving forward as the
frontal zone gets stuck between the ridge to the southeast and
stronger troughing in Canada. The theme for each day will be
similar, with exact details unfolding as the airmass boundary
between the warm and humid air to the south and slightly drier
air to the north wavers about the Mid Atlantic. Showers and
thunderstorms will primarily focus on the afternoon and evening
hours each day, with some attendant threat of localized flooding
and damaging winds.
Of Wednesday and Thursday, Wednesday may be a bit more active as
a notable shortwave is forecast to traverse the area during peak
heating. Shear may increase with this wave, though there are
indications the greatest instability will favor the southern
half of the area. We are currently outlooked for Marginal Severe
and Slight Excessive Rainfall. CAMS indicate there may be
opportunities for greater rainfall totals compared to Tuesday due
to the boundary being situated nearby which could promote
training. Temperatures may be a few degrees cooler as the ridge
is suppressed, but still likely reach the upper 80s and lower
90s. Deep southwest flow looks to bring more cloud cover
Thursday, which may keep temperatures a bit cooler and limit
instability. Therefore showers and storms may not be quite as
intense, but will have to continue to monitor the threats as
mentioned above. Overnights will be muggy with some potential
for fog and/or low clouds.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
A front is expected to stall across the region late in the week and
through much of the weekend. Upper level energy will ride along the
stalled front and be fueled by rich humidity to create several
rounds of showers and thunderstorms. Most of the convection will
occur during the afternoon and early evening hours. Temperatures
will be near average with highs in the middle 80s.
&&
.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
The day will start out mostly clear and calm, but expect
thunderstorms to erupt this afternoon with fairly widespread
coverage. The bigger time window appears to be between 1 and 9
PM from west to east, but tried to keep a 3 hour TEMPO window
in the TAF. If storms can organize into clusters, impacts should
be less than an hour, but there is some potential for more
complicated and erratic storm evolution. Threats will include
very heavy rain, frequent lightning, and potential downbursts
to 50 kt. Somewhat lower coverage around MRB and CHO makes
impacts less certain there, but intense storms are highly likely
in the metros. S to SW winds will remain less than 10 kt
otherwise. After storms depart, there are indications fog
and/or low clouds may form the second half of the night,
especially west of the metros.
There will be another opportunity for strong to severe
thunderstorms with heavy rain Wednesday afternoon and evening.
While not totally certain, the more intense storms may be near
IAD/DCA and to the south. The pattern remains fairly stagnant
the remainder of the week with daily opportunities of mainly
afternoon and evening thunderstorms and patchy fog and/or low
clouds overnight. Outside of storms, winds generally remain less
than 10 kt.
&&
.MARINE...
As a cold front approaches today, more widespread coverage of
thunderstorms is expected during the afternoon and evening hours
today with potential severe downburst winds. This will likely
repeat Wednesday, though the highest coverage may be focused
across southern Maryland as the front shifts a bit to the south
and stalls. Winds should be fairly light out of the south
outside of thunderstorms, with outflows likely disrupting
opportunities for southerly channeling.
Sub-advisory caliber winds are expected for Thursday through
Saturday. Gradients remain rather weak with wind direction
being dictated by the position of the front and any convective-
scale processes. The main hazard will come from gusty
thunderstorm winds possible each afternoon and evening.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from 1 PM this afternoon to 7 PM EDT this
evening for DCZ001.
Flood Watch from 2 PM EDT this afternoon through this evening
for DCZ001.
MD...Heat Advisory from 1 PM this afternoon to 7 PM EDT this
evening for MDZ008-011-013-014-016>018-508.
Flood Watch from 2 PM EDT this afternoon through this evening
for MDZ005-006-008-011-013-014-016>018-503>508.
VA...Heat Advisory from 1 PM this afternoon to 7 PM EDT this
evening for VAZ053>057-527.
Flood Watch from 2 PM EDT this afternoon through this evening
for VAZ053-054-506-526-527.
WV...None.
MARINE...Heat Advisory from 1 PM this afternoon to 7 PM EDT this
evening for ANZ530.
Flood Watch from 2 PM EDT this afternoon through this evening
for ANZ530.
&&
$$
SYNOPSIS...ADS
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...KLW
AVIATION...ADS
MARINE...ADS