644
FXUS61 KLWX 071906
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
306 PM EDT Fri Aug 7 2026

.WHAT HAS CHANGED...
A Severe Thunderstorm Watch was issued until 9 PM this evening
for areas generally along/east of I-81 and north of US-50. The
forecast remains unchanged, with things panning out as expected
thus far.

Also, a Marginal Risk for severe weather was added for Saturday
afternoon across much of the region, with damaging wind gusts
being the primary threat.

&&

.KEY MESSAGES...
- 1) Severe thunderstorms expected this afternoon through this
  evening across portions of the area.

- 2) Patchy morning fog, high humidity, hot temperatures, and
  daily thunderstorm chances continue through early next week.

- 3) A cold front could arrive late next week and into the
  weekend bringing relief from the heat and humidity.

&&

.DISCUSSION...
KEY MESSAGE 1...Severe thunderstorms expected this afternoon through
this evening across portions of the area.

Shower and thunderstorms are beginning to develop over the
higher terrain and in the lee of the Blue Ridge as of 2 PM EDT.
Not seeing much of anything developing on the Bay/River breezes,
so seems like the main threat will be with storms along the
lee trough and leading edge of the incoming shortwave this
afternoon/evening. Mostly sunny to partly cloudy skies
throughout the day have lead to MLCAPE values on the order of
1500-3000 J/kg with lowest amounts SW and higher amounts towards
the Chesapeake Bay into northeast MD. DCAPE values range from
500-800 J/kg, which is sufficient to produce some damaging wind
gusts with the strongest storms. The highest shear is along the
MD/PA border, with values around 20-25 knots. As a result of all
of this, a Severe Thunderstorm Watch was issued from areas
along/east of I-81 and north of US-50. Storms thus far have had
trouble really getting organized, which is likely due to weaker
lapse rates out west, and not quite having the strongest shear
we expect later in the afternoon. As storms move east, as well
as the subsequent outflows from said storms, expect them to grow
upscale and become stronger the closer we get to the I-95
corridor into northeast MD. This is where it seems like all of
the ingredients have the best chance of coming together for the
highest severe weather threat. That being said, any storms in
this environment could become severe and produce locally
damaging winds even outside of more organized clusters. Frequent
cloud-to-ground lightning can be expected with storms today,
likely well ahead of and behind storms. Use extreme caution if
outdoors later this afternoon and remember that when thunder
roars to head indoors!

The severe threat should wane into the evening as we lose
daytime heating. However, storms today will produce very heavy
rainfall rates, perhaps as high as 3-4 inches/hour for short
periods. Should this find the wrong area, and/or if an area sees
a couple back-to-back, a flash flooding threat isn`t out of the
question. This threat is highest in northeast MD, which is
where the best chance for colliding outflow boundaries and/or
Bay Breeze interactions is. This could cause some localized
training effects, which brought a few areas a quick 3 to 4
inches yesterday, so can`t completely rule that out. WPC has
this area in a SLGT risk excessive rainfall outlook as a result.



KEY MESSAGE 2... Patchy morning fog, high humidity, hot
temperatures, and daily thunderstorm chances continue through early
next week.

Somewhat similar conditions are expected Saturday as another
potent shortwave passes through. The main difference is that
mid-level flow turns a bit more W to WSW versus the SW`ly flow
we have had in recent days. As a result, coverage of storms is
likely to be less than what we see today. However, shear values
increase a bit, reaching 30 to 35 kts as the subtropical jet
stream begins to strengthen. Mid-level lapse rates are also
impressive, similar to today`s event. Instability will be a bit
less tomorrow, owing to the westerly mid-level flow.
Thermodynamic profiles depict skinnier CAPE profiles, but
inverted-V signatures towards the surface. Our thoughts are
that the coverage should be less tomorrow, but the ceiling could
be higher in terms of damaging wind potential, should storms be
able to develop and get organized. The Storm Prediction Center
has added a Marginal Risk for severe weather tomorrow as a
result that encompasses much of the forecast area, further
reinforcing our thoughts.

Convection begins to wane a bit Sunday into Monday given quasi-zonal
flow aloft. A few storms may develop over the higher elevations,
but coverage will be much less than in recent days. This will
be short-lived however, with storm chances increasing once
again Tuesday through the end of the week as a series of
shortwave disturbances passing through.

Outside of the storm chances expect highs in the upper 80s and low
90s with heat indices east of the BLue Ridge up around 100 degrees.
The hottest days look to be Sunday through Tuesday given the
strengthened subtropical ridge over the region.


KEY MESSAGE 3...A cold front could arrive late next week and
into the weekend bringing relief from the heat and humidity.

While this is very far out in the forecast period, there is some
signal that a more potent frontal system could push through the
region late in the week. The details are murky at this stage of the
forecast, with timing very uncertain, as well as potential impacts.
Deterministic and ensemble guidance is generally between
Thursday/Friday right now, with improvement in the weather pattern
possible into the upcoming weekend. Any decent frontal passage in
the summertime should be watched closely for potential severe
weather, so we will keep monitoring this in the coming days to see
if that potential is there, and try to narrow down the timeframe a
bit more.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Prevailing VFR conditions are expected across the terminals
through the middle of next week given subtropical high pressure
offshore and the lack of any real front passing through. Brief
periods of sub-VFR are likely during the afternoon and evening
hours due to thunderstorms, though Sunday and Monday look to
have the lowest chances, and primarily at MRB and CHO.

For today, storms are already developing west of MRB. These will
gradually advance east. Not expecting more than 1-1.5 hrs of
significant restrictions for most sites within the 3 hour time
windows given. However, uncertainty remains with exact start
time at this point. For the metro terminals especially, will be
watching to see if any additional storms form east of the Blue
Ridge, which would probably put arrival times towards the early
end of the given ranges in the TAFs. Any storms today could
bring wind gusts of 60 mph, as well as frequent lightning and
torrential rainfall rates.

A similar set up is expected Saturday afternoon and evening, but
with less coverage. Added a 3 hour PROB30 for now, as the
likelihood of storms tomorrow is less than today, and there is a
lot more uncertainty with convective initiation than we have
today. As we get closer, will refine that forecast and add
TEMPOs or FM groups as necessary.

Outside of the thunderstorms expect patchy fog between the
terminals each morning through early next week. Winds will
remain light out of the south and southeast at less than 15 kts.

&&

.MARINE...
SCA is in effect for portions of the Chesapeake Bay today due to
southerly channeling. However the bigger threat will be with
storms this afternoon/evening, which will likely necessitate
some SMWs. Damaging wind gusts and frequent cloud-to-ground
lightning will be the main threats.

Small Craft Advisories may be needed again on Saturday due to
southerly channeling mainly in the afternoon and evening.
Another chance for storms Saturday afternoon, which could again
bring damaging winds and frequent lightning. However, a bit more
uncertainty with tomorrow`s event in terms of coverage.

A break from showers and storms is expected on Sunday and Monday
with winds generally gusting 10-15 knots at most during the
afternoon/evening hours.

&&

.TIDES/COASTAL FLOODING...
Tidal anomalies climb through the weekend in response to return
southerly flow. Periods of coastal flooding are possible at times of
high tide at sensitive locations.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ534-
     537-543.

&&

$$

DISCUSSION...CJL
AVIATION...CJL
MARINE...CJL

NWS LWX Office Area Forecast Discussion