916
FXUS61 KLWX 211359 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
959 AM EDT Tue Jul 21 2026

.WHAT HAS CHANGED...
Severe weather probabilities have increased Wednesday for the
I-95 corridor, though much uncertainty remains. Small Craft
Advisories were extended into Wednesday for portions of the
waters. The overall message for today`s severe weather remains
the same, with specifics depending on mesoscale evolution.

&&

.KEY MESSAGES...
- 1) Strong to severe thunderstorms are still possible today,
  with some thunderstorm risk lingering into Wednesday.

- 2) Below average temps Thursday through the weekend with only
  small rain chances.

&&

.DISCUSSION...
KEY MESSAGE 1...Strong to severe thunderstorms are still
possible today, with some thunderstorm risk lingering into
Wednesday.

Today`s forecast has become very complicated/uncertain due to
extensive high dense overcast moving in from the northwest
associated with thunderstorm complex over eastern OH and
northwest PA. This will likely cut down on heating, especially
across northern areas with temperatures struggling to reach 90F
based on current trends. Central and southern VA seems like it
will see the most heating and the highest probabilities of
severe weather. Many CAMs show a minima in QPF between the
Alleghenies and the Blue Ridge Mountains. Also, HRRR forecasts
are likely overdone as it has temperatures reaching into the mid
and upper 90s, which ain`t happening based on 24-hr model and
current trends. While the potential still exists for severe wx,
there are still many unknowns at this time.

Previous afd...

A seasonably strong trough will be approaching from the west,
providing forcing and anywhere between 30 and 50 kt of flow in
the cloud bearing layer. This will provide a favorable
environment for severe thunderstorms, with supercells and
clusters both possible. One initiation region will likely be
along the prefrontal/lee trough near or just east of the Blue
Ridge. These storms will likely affect the I-95 corridor between
mid afternoon and early evening. While these storms will
certainly carry severe potential, it is interesting to note on
average the 850-700 mb wind fields will be greater to our south
and west until late afternoon or early evening. Other details
remain unresolved, especially the effects of upstream convection
that moved through the upper Great Lakes and mid Mississippi
Valley. This could have some impact on how thunderstorms develop
across the Ohio Valley this afternoon and what subsequently
moves into western areas. If stronger/more widespread
convection does not move in from the Ohio Valley, there is some
potential there is a relative minimum in coverage between the
Blue Ridge and Alleghenies.

The coverage of afternoon storms and upstream effects will
determine what happens this evening as the strongest forcing
overspread the area along with increasing low level wind fields.
A second round of showers and thunderstorms will be possible for
some areas, though increasing low level stability may limit the
severe weather threat. It appears the evening/overnight coverage
could gradually shift to southern parts of the forecast area, or
even mostly to our south, potentially focusing on outflow from
earlier activity.

Damaging winds will be the primary severe hazard, although
large hail and a tornado or two are possible if supercells
develop. Some localized swaths of more considerable wind damage
are possible. Relatively speaking, the tornado threat is higher
to the north (and north of the CWA) closer to the warm front
and possibly closer to the Chesapeake Bay where low level winds
could be backed. With that said, forecast hodographs vary quite
a bit between models and also throughout time, so any relatively
higher threat will depend on the mesoscale details.

With precipitable water values increasing (over 2 inches east of
the Blue Ridge), any storm mergers and training along mesoscale
boundaries could result in localized flash flooding. Overall
storm motions will be progressive though, so this threat
appears too localized for a Flood Watch at the moment and will
continue to be evaluated. Additional areas to monitor will be
the Ohio Valley low level jet potentially leading to training
(looks to be mostly west of the area), and the evening low level
jet leading to backbuilding along any residual
outflow/convergence feature (best QPF signal is currently mostly
south of the forecast area).

Dry air should start working in from the northwest during the
second half of the night, and the surface cold front should
reach the Appalachians by 8 AM Wednesday. There is still plenty
of uncertainty regarding the front`s progress by afternoon, and
more specifically, how far south and east the deeper moisture
and instability reach. Some models do show convection firing
east of the Blue Ridge mountains in the afternoon, with shear
sufficient for severe thunderstorms. SPC has expanded severe
weather probabilities farther north and west compared to the
previous outlook. However, it`s also still possible most storms
are across SE Virginia. Western parts of the CWA will start
feeling post frontal effects with falling dew points and highs
in the upper 70s/lower 80s.


KEY MESSAGE 2...Below average temps Thursday through the weekend
with only small rain chances.

UL trofing will prevail over NE US with sfc high pressure building
in settling overhead Fri into Sat. Canadian high pressure will
result in lower Tds, allowing for a pleasant airmass in the Mid
Atlantic for late July. Overnight lows in the 50 for most, low 60s
metros and near waters. Would not be surprised with a few pockets of
mid to upper 40s Thu and Fri night in sheltered valleys. Daily highs
only 60s in higher terrain, 70s to low 80s elsewhere. Rain chances
possible Sat into Sun from either the stalled front over the SE
state buckling northward or a cold front approaching from the
NW. Confidence remains low.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...

Multiple rounds of showers and thunderstorms are likely, one
between 18Z-00Z, and the other one coming (or lingering) into
the evening. Right now, the greatest evening precipitation
chances are from IAD/DCA to the south. Only included PROB30s for
thunder since coverage and timing becomes much more uncertain.
Especially with the afternoon storms, severe wind gusts are
possible, along with the potential for some large hail and very
heavy rain. Some low clouds could try to form overnight, but
confidence is low.

More storms are possible Wed, particularly eastern terminals,
though the initiation point could be mostly south/east. Any
storms could be strong to severe again though. Winds will then
shift to the northwest as a cold front passes through.

Prevailing VFR Thu through Sun. Light NE winds become S`ly Sat
night.

&&

.MARINE...
SCA continues along the bay through this morning, though
channeling effects likely decrease for a time. Gusty SSW winds
expected by this afternoon for all waters, which will linger
into the night. Some gusts around 30 kt are possible on the bay.
Strong to severe thunderstorms are also likely this afternoon
and evening, so Special Marine Warnings are likely. Winds will
gradually taper off from north to south late tonight into
Wednesday. Have extended SCAs to account for this timing. However,
a cold front will quickly follow Wednesday afternoon, shifting
winds to the NW, then a N surge will push across the area
Wednesday night. This will likely warrant additional SCAs
through early Thursday. Another round of strong to severe
thunderstorms are possible Wednesday afternoon as the front
crosses.

Winds expected to remain below SCA levels Thu aftn through
Sun. NE winds become S`ly Sat night.

&&

.TIDES/COASTAL FLOODING...
Elevated southerly flow continues through this evening, pushing
anomalies close to one foot. No tidal flooding is forecast at
this time, but Annapolis and Havre de Grace will be close. Water
levels will drop as a cold front passes Wednesday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 8 AM EDT Wednesday for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ530-531-
     538-539.
     Small Craft Advisory until noon EDT Wednesday for ANZ532-533-
     540>542.
     Small Craft Advisory until 6 PM EDT Wednesday for ANZ534-537-
     543.
     Small Craft Advisory until 4 AM EDT Wednesday for ANZ535-536.

&&

$$

DISCUSSION...ADS/LFR/CPB
AVIATION...ADS/LFR/CPB
MARINE...ADS/LFR/CPB