377
FXUS61 KLWX 311904
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
304 PM EDT Mon Aug 31 2026
.WHAT HAS CHANGED...
The potential for thunderstorms has significantly decreased
today, so have trimmed back rain and thunder chances in the
forecast.
&&
.KEY MESSAGES...
- 1) Thunderstorm chances increase this week, but timing and
intensity remain uncertain.
- 2) Near-record early September heat expected.
&&
.DISCUSSION...
KEY MESSAGE 1...Thunderstorm chances increase this week, but timing
and intensity remain uncertain.
The focus of showers and thunderstorms today has now trended south
of our area. Abundant mid-level cloud cover really prevented a lot
of instability from developing and temperatures have been several
degrees below forecast. The warmest conditions in Central VA where
temps are near 90F. The forecast was updated to lower rain chances,
with coverage of thunderstorms now expected to be low and focused in
Central VA to southern MD. Any lingering showers dissipate this
evening, with muggy and mostly cloudy skies tonight.
Looking at the rest of this week, the strong mid-level ridge
positioned over the Mid-South will slowly push east toward the TN
Valley. Numerous shortwave troughs / disturbances will round the top
of the ridge, traversing the Great Lakes to Mid-Atlantic. This is
going to bring us several rounds of thunderstorms, some of which
could be strong to severe. The presence of strong lift and
increasing shear, along with a hot and unstable airmass will produce
an environment supporting of significant severe thunderstorms. The
big caveat is timing. This setup can be very tricky to forecast
exactly when these complexes of storms develop, and exactly where
they track. The next shortwave is forecast to arrive Tuesday
afternoon/evening. SPC has the northeast part of the forecast area
in a Slight Risk (level 2 of 5), and a Marginal Risk (level 1 of 5)
down into central VA. The latest 12Z guidance today has pushed back
convection to Tuesday evening, and by that time we may avoid the
worst of the severe weather impacts as storms arrive after peak
daytime heating.
SPC also has a Slight Risk across the area Wednesday through Friday
as several additional shortwave troughs are expected to traverse the
region. At some point this week, most likely toward the end when a
strong upper trough digs south from Canada, we will be in a much
more favorable position for the upper forcing, instability, and
daytime heating to align. The latest AI/ML guidance indicates the
highest chance for this is now on Thursday, but I would not discount
any day for potentially strong to severe thunderstorms at this time.
A cold front begins to slide south through the area Friday night
into Saturday, bringing drier conditions and seasonal temperatures.
Some thunderstorm chances linger south of I-66 on Saturday, then
most of the area is dry and cooler come Sunday.
KEY MESSAGE 2...Near-record early September heat expected.
A strong ridge of high pressure over the southern Plains will
build toward the Mid-South throughout this week. While humidity
will be up to support several rounds of showers and thunderstorms,
the heat will be up as well, especially Tuesday through Thursday.
High temperatures are expected to reach the lower to middle 90s
Tuesday and Wednesday, while making a possible run at 100 degrees in
a few spots in parts of eastern and northeastern Virginia, near the
metros, and along the eastern areas of the Blue Ridge Mountains on
Thursday. Heat indices, because of the humidity, will be high as
well. Heat indices should reach 100 to 103 degrees in scattered
places in interior parts of our region on Tuesday. Expect more
widespread 100 to 105 degree heat indices on Wednesday. To round it
off, Thursday will have heat indices readings more so in the 103 to
105 degree ranges. These ranges can obviously change some by a few
degrees warmer or a few degrees cooler. Either way, the point we
want to make is it is going to be hot and humid through much of the
week. Heat headlines could be issued soon regarding this 3-day
stretch of heat and humidity. For the moment, monitor information at
www.weather.gov. Even Friday, although may be cooler in terms of
temperatures because of convection with a front, heat indices could
still reach the 95 to 100 degree range in many places.
&&
.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Not much in the way of convection is expected now this afternoon as
a thick deck of mid-level clouds have kept conditions stable. A few
showers or storms possible around CHO, otherwise other terminals
could see a few light showers through this evening. Some patch fog
or low clouds possible tonight, but not enough confidence to include
in the TAFs.
Looking at the rest of this week, while VFR conditions are expected
to prevail there could be periods of sub-VFR conditions. Each
morning, low clouds could develop due to a very moist environment,
then lift by late morning as daytime heating strengthens. There will
be complexes of thunderstorms moving across the region, but timing
is uncertain. The next one could arrive Tuesday evening into Tuesday
night, then several more rounds possible again sometime Wednesday
through Friday. Conditions improve this weekend as cold front moves
through the region.
&&
.MARINE...
Favorable marine conditions are expected through the week.
Thunderstorm complexes are forecast to move from the Great Lakes to
the Mid-Atlantic and Northeast at times this week. While the timing
of exactly when this will occur remains uncertain, it is likely that
Special Marine Warnings will be needed. Wind gusts in excess of 35-
40 knots and lightning strikes are going to be the main threats to
mariners.
&&
.CLIMATE...
Near-record heat is possible, peaking Tuesday through Thursday.
Below is a list of record warm temperatures for September 1, 2, and 3.
(A `+` indicates the record also occurred in previous years).
The period of record for most sites dates back to the late 1800s,
except for Sterling-Dulles Airport which dates back to 1960.
====================================================================
SEPTEMBER 1
====================================================================
Site Record Daily High Record Daily Warm Low
Baltimore (BWI) MD 99 (1962) 78 (1932+)
Washington DC 99 (1980+) 77 (1980)
Sterling-Dulles Airport VA 98 (1980) 73 (2000)
Baltimore (Downtown) MD 99 (1973) 80 (2012)
Annapolis MD 95 (1962) 78 (2018+)
Hagerstown MD 101 (1902) 72 (2018+)
Martinsburg WV 103 (1932) 73 (2000+)
Charlottesville VA 105 (1932) 78 (1932)
====================================================================
SEPTEMBER 2
====================================================================
Site Record Daily High Record Daily Warm Low
Baltimore (BWI) MD 99 (1953) 75 (1932+)
Washington DC 101 (1980) 78 (1980)
Sterling-Dulles Airport VA 99 (1980) 72 (2020+)
Baltimore (Downtown) MD 98 (1980+) 80 (1980)
Annapolis MD 97 (1998) 79 (2018+)
Hagerstown MD 100 (1953) 73 (2018+)
Martinsburg WV 103 (1932) 72 (2000+)
Charlottesville VA 105 (1953) 80 (1930)
====================================================================
SEPTEMBER 3
====================================================================
Site Record Daily High Record Daily Warm Low
Baltimore (BWI) MD 98 (2023) 79 (1993)
Washington DC 98 (1953) 79 (1993)
Sterling-Dulles Airport VA 99 (2023) 77 (1993)
Baltimore (Downtown) MD 98 (2023) 82 (1993)
Annapolis MD 99 (1993) 79 (2018)
Hagerstown MD 100 (1953) 72 (2018+)
Martinsburg WV 102 (1953) 71 (1957)
Charlottesville VA 104 (1953) 75 (1930)
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
DISCUSSION...KLW/KRR
AVIATION...KRR
MARINE...KRR
NWS LWX Office Area Forecast Discussion