023
FXUS61 KLWX 011921
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
321 PM EDT Tue Sep 1 2026
.WHAT HAS CHANGED...
Severe weather threat continues through the end of the week.
While heat indices remain below criteria on Wednesday, heat
headlines remain possible on Thursday.
&&
.KEY MESSAGES...
- 1) Daily severe weather threat through the end of the week.
- 2) Hot and humid conditions yield possible record high
minimum temperatures this week
- 3) Decreasing heat & thunderstorm chances heading into Labor
Day weekend.
&&
.DISCUSSION...
KEY MESSAGE 1...Daily severe weather threat through the end of
the week.
Aloft, upper level ridging over the Ohio River Valley slowly
shifts eastward this afternoon as a shortwave trough pivots
over the forecast area. At the surface, a strong low pressure
system tracks east across Canada through the end of the week
with the associated fronts lingering near the forecast area. On
Friday, the associated cold front tracks across the forecast
area. Daily shower and thunderstorm chances continue through
the end of the week across the forecast area with a hot and
humid airmass yielding ample CAPE (1500-2500 J/kg)each
afternoon.
For this afternoon, highest chances remain in NE
Maryland where the Storm Prediction Center has a slight risk for
severe weather. Primary hazard types are damaging wind gusts
and large hail. The forecast for Wednesday through Friday
remains uncertain regarding timing and thunderstorm coverage.
Should thunderstorm development coincide with peak daytime
heating, instability will yield strong to severe thunderstorms
across the forecast area. The best chance for severe weather is
on Thursday as the aforementioned cold front approaches the
forecast area.
KEY MESSAGE 2...Hot and humid conditions yield possible record high
minimum temperatures this week
A hot and humid airmass builds overhead this week with heat
indices soaring into the upper 90s to low 100s each afternoon.
Heat indices remain below criteria today and Wednesday, maxing
out at around 100-103 along the metros. Coverage of heat indices
exceeding criteria remains isolated and brief for tomorrow, so
refrained from issuing a Heat Advisory for Wednesday. However,
Thursday has the potential to be the warmest day of the week
with heat indices forecast to exceed 100 in the valleys west of
the Blue Ridge and 105 along the I-95 corridor. There remains
some uncertainty regarding cloud coverage and convection on
Thursday and how that effects the high temperatures. Should
severe weather occur during the day, heat indices will struggle
to reach criteria in the afternoon. However, if severe weather
occurs later in the afternoon/evening, peak daytime heating will
have high temperatures nearing the mid to upper 90s. Humid
conditions continue overnight, with near record high minimum
temperatures possible.
KEY MESSAGE 3...Decreasing heat & thunderstorm chances leading
into Labor Day weekend.
On Saturday, high pressure builds at the surface over the Great
Lakes further advancing a cold front south across our region. Drier
air trailing behind this boundary will stabilize conditions and
reduce thunderstorm chances through the weekend. Brief showers or
thunderstorms remain possible as a few disturbances round the base
of the upper-level trough, but overall, no hazardous weather is
expected through the beginning of next week. Through the long
weekend, day time temperatures continue to drop back into seasonable
conditions for early September. With dew-points in the low to mid
60s, seasonable temperatures, and relatively low precipitation
chances, Labor Day weekend is shaping up to be a pleasant September
weekend.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Light winds and prevailing VFR conditions are expected across
the terminals through Thursday. Showers and thunderstorms are
possible in NE Maryland this evening, so have a PROB30 for KMTN
and KBWI. For Wednesday and Thursday, daily shower and
thunderstorm chances yield periods of sub-VFR conditions.
Currently have a PROB30 for KIAD and KDCA for tomorrow evening
for -TSRA. Convection will move into the TAF periods this
evening and will be added at surrounding terminals.
Periods of sub-VFR conditions could persist Friday as showers and
thunderstorms track across the area primarily in the afternoon &
evening hours. Some of these storms could become severe. On Saturday
afternoon and evening, terminals west of I-95 could experience sub-
VFR conditions as thunderstorm and shower chances return in the
afternoon and evening. Westerly winds shift north to northeasterly on
Saturday with gusts below 20 kts.
&&
.MARINE...
Light winds are expected over the waters through Thursday.
Chances for strong to severe storms over the waters increases
each day with SMWs possible. For today, the best chances for
SMWs is in the upper portions of the Chesapeake Bay. For
Wednesday and Thursday, convection chances cover all waters.
On Friday and Saturday, winds below 15kts most of the time, but
higher winds and waves could during afternoon and evening showers
or thunderstorms. Westerly winds shift north to northeasterly on
Saturday.
&&
.CLIMATE...
Given slightly cooler trends seen in the guidance for daytime
highs, record high maximum temperatures seem unlikely. However,
record high minimum temperatures are possible.
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...AVS/KVH
AVIATION...AVS/KVH
MARINE...AVS/KVH
NWS LWX Office Area Forecast Discussion