480
FXUS61 KLWX 161305
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
905 AM EDT Thu Jul 16 2026

.WHAT HAS CHANGED...
Added in low probabilities for thunderstorms late this afternoon
into this evening for the I-70/I-68 corridor down into central
MD as a weak front drops south.

&&

.KEY MESSAGES...
- 1) High heat and hazy skies look to continue through Friday.

- 2) Thunderstorm chances increase this weekend and could
  potentially linger into Sunday as a stronger cold front drops
  into the region.

&&

.DISCUSSION...
KEY MESSAGE 1...High heat and hazy skies look to continue through
Friday.

Opted not to issue any HYY today in coordination with
neighboring WFOs. Still hot, but likely short of criteria for
most of a given zone. Main reasoning was thickness of the
Canadian wildfire smoke limits mixing. Similar conditions are
expected Friday making the temp/heat index forecast more
complex as an even thicker plume of Canadian wildfire smoke
descends upon the region.

Smoke concentrations will continue to increase as an additional
wave of smoke is sent southward from fires raging over Quebec
and western Ontario. With that said, hi-res guidance (such as
the RRFS-A and HRRR) hint at some slightly lower air temps and
higher Tds today and Fri which could negate the need for heat
headlines. This will be something that will need to be monitored
given what played out yesterday with the smoke aloft and
subdued mixing. With the smoke will come a few more days of
poor air quality. The respective air quality agencies in MD, DC
and VA have issued Code Orange Air Quality Alerts for the
DC/Baltimore metros today with additional alerts likely Fri as
air quality worsens. Latest: airnow.gov.

In addition to the heat and smoke/poor air quality will be the
concern for a few isolated showers/strong thunderstorms. SPC
has a Marginal Risk (Level 1 out of 5) for northern into central
MD. Height falls/PVA will be negligible as most forcing for
ascent will be associated with shortwaves in cyclonic flow
passing to the N/NE. However, a halt in height rises paired with
a slowly southward sagging cold front and potentially bay
breezes in areas where low-level flow goes weak in the vicinity
of the front (NE MD), may be enough when coupled with heating to
result in a few thunderstorms. There is further uncertainty
given continued smoke aloft, as that could hamper heating and
instability/convective initiation. However, the gradient between
thicker smoke to the north and less to the south could actually
enhance the differential heating/frontal zone, similar to upstream
over NE PA into NJ and the NYC tri-state area yesterday. Any
storms that manage to develop will have ample MLCAPE (2000-3000
J/kg) and DCAPE (1000-1500 J/kg) to work with, as well as
notable flow in the mid and upper levels for mid July (40-50+
kts). 12Z KIAD RAOB shows mid-level lapse rates near 7 C/km
resulting in 2200+ J/kg MUCAPE with ~35 kts effective bulk
shear. DCAPE is elevated (1000+ J/kg) with mid-level dry air and
PWs near 1.5". If any storms manage to develop by late
afternoon, they could at least briefly congeal into a small
cluster and propagate south/southeast toward and across the
Chesapeake Bay during the evening hours. Damaging winds would be
the primary (conditional) risk, but large hail is also possible
given ample CAPE, shear, and seasonably low wet-bulb zero
heights around 12 kft. Any storms that we do see will help
briefly scrub out some of the smoke and improve air quality.

KEY MESSAGE 2...Thunderstorm chances increase this weekend and
could potentially linger into Sunday as a stronger cold front
drops into the region.

The surface front will drop further southward Fri. Additional
smoke likely mixes into the region. Any convection on Fri will
likely be limited to the higher terrain as the front washes out
and pairs with orographic lift. Again, any storm that does form
could be on the strong side.

Fri night, the aforementioned front will begin to lift north
ahead of a wave of low pressure and stout shortwave approaching
from the Upper Midwest/Great Lakes. Increasing MLCAPE late at
night with some moisture advection and modest low-level flow
overtop the front may result in a few t-storms heading into
early Sat morning, especially east of the Blue Ridge where a
bit richer low-level theta-e ridge looks to pivot through, as
well as across northern MD just north of the low-level front.

Forcing and shear will be ample on Sat, but the amount of
instability is in question due to potential morning precip.
Should enough instability develop, svr wx is possible with all
hazards (damaging straight-line winds, large hail, a few
tornadoes, and isolated instances of flash flooding) on the
table. This aligns with high probabilities in ML/AI guidance.
After morning storms, convection may re-develop in association
with a surface trough during the afternoon, then another round
of storms may approach from the north/northwest along a synoptic
cold front. If the front does not make it entirely through the
area, repeated strong storms will be possible on Sun, with
highest chances south toward I-64.

After a brief lull possible on Mon, another strong wave may
approach Tue.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
VFR and mostly dry conditions will likely continue through Fri.
Smoke aloft will result in a hazy appearance of the sky through
Fri. Vsby reductions of 5-6 SM are possible for the metros
(especially Baltimore TAF sites) today and Fri with lower vsbys
(2-4 SM) tonight into Fri as smoke mixes south and closer to
the sfc behind a weak front. Winds will vary between N/NW and SW
over the next few days as that front sits nearby. A t-storm
can`t be ruled out this late afternoon and evening, mainly east
of the Blue Ridge and in nrn MD but confidence is very low. Did
maintain a PROB30 between 20-24z at both BWI/MTN where the
confidence seems the highest for storm development off the bay
breeze. Can`t rule out a t-stprm near the mtns Fri afternoon.

Periods of sub-VFR restrictions can be expected this weekend
in any t-storms. The greatest coverage of storms likely Sat,
potentially lingering into Sun. Possible early morning low CIGS
or patchy fog with afternoon/evening convection. Winds will
remain light overall with chaotic motions in/around t-storms.

&&

.MARINE...
Winds will waver between N/NW and SW over the next few days as a
cold front dangles near the waters. Depending on the strength of the
front and how far N or S it pushes, there may be brief/marginal
periods of SCA level gusts (late tonight in N flow, late Fri in
S flow). A couple of t-storms can`t be ruled out along the cold
front this late afternoon and evening, and anything that does
manage to form could produce rather gusty winds.

More widespread t-storm activity and the need for Special Marine
Warnings are probable over the weekend as a cold front
approaches. Southerly channeling also lingers Sat into Sun.

&&

.CLIMATE...
Well above normal temperatures will persist through Thursday.

Below is a list of record daily high and warm low temperatures for
July 16 (Thursday).

=================================================================
July 16 Record Daily High/Warm Low Temperatures
=================================================================
Baltimore MD 104 (2024, 1988) 78 (1879) Washington DC 104
(2024, 1988) 84 (1983) Sterling-Dulles Airport VA 104 (1988) 74
(2013) Baltimore (Downtown) MD 105 (2024) 85 (2013) Annapolis MD
98 (1997, 1900) 79 (2024, 2013, 1955) Hagerstown MD 104 (1988)
76 (2024) Martinsburg WV 107 (1988) 77 (1983) Charlottesville VA
102 (1988) 82 (1983)

Period of Record (POR) information (records since):
Baltimore MD - July 1872
Washington DC - January 1872
Sterling - Dulles Airport VA - January 1960
Baltimore (Downtown) MD - July 1950
Annapolis MD - January 1894
Hagerstown MD - January 1899
Martinsburg WV - January 1891
Charlottesville VA - January 1893

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$

DISCUSSION...DHOF/CPB/EST
AVIATION...DHOF/CPB/EST
MARINE...DHOF/CPB/EST
CLIMATE...LWX

NWS LWX Office Area Forecast Discussion