171
FXUS61 KLWX 212216
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
616 PM EDT Tue Jul 21 2026

.WHAT HAS CHANGED...
A Flood Watch has been issued for north-central to northeast
Maryland. Repeated rounds of very heavy rain (3 inches per hour)
are evolving in this area, with additional activity likely
through the evening as a cold front approaches from the west.
Considerable flash flooding is possible.

&&

.KEY MESSAGES...
- Severe weather risk will continue through this evening with
  the greatest risk across central VA, southern MD, and the
  Appalachian region.

- Below average temperatures and mainly dry conditions
  are expected Thursday through the weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...Severe weather risk will continue through this evening with
the greatest risk across central VA, southern MD, and the Appalachian
region.

KEY MESSAGE 1 DESCRIPTION...

18Z RAOB plots along with WV imagery show an unusually deep
trough across the Great Lks into the OH Valley with an 85-kt 250
mb jet streak measured at Davenport, IA and Wilmington, OH and
55-kt 500 mb wind speeds measured at ILN and IAD. 18Z NUCAPS
data showed the greatest instability and moisture axis resides
along the AKQ and LWX borders. This looks like it will be
battleground zone for the most severe wx and flash flood risk
through this evening into the early morning hours. Multiple
rounds of thunderstorms are expected, particularly across the
south where training convection is most likely. Convection
across OH and southwest PA will have less instability to work
with, but stronger shear which may still pose a severe wind
risk. Convection will gradually sink through the evening
tapering from northwest to southeast, but convection will likely
linger along the AKQ and LWX borders well through the night.

Still a risk of severe wx Wed, but likely for areas south of the
Capital Beltway and southern MD.

KEY MESSAGE 2...Below average temperatures and mainly dry conditions
are expected Thursday through the weekend.

KEY MESSAGE 2 DESCRIPTION...

A sprawling area of high pressure will build to our north for
Thursday and Friday, before shifting off the New England Coastline
on Saturday. Northerly flow ahead of the approaching high will
advect a much cooler and drier airmass into the region for Thursday.
Well below normal temperatures and dewpoints are forecast for late
July, with high temperatures only in the upper 70s/low 80s. Dewpoints
in the 50s will also make it feel much less humid than is typical
for July. Mostly sunny skies will accompany the well below normal
temperatures/dewpoints. Temperatures will stay well below normal for
Friday and Saturday within easterly flow. Both temperatures and
dewpoints begin to rise again on Sunday as flow turns southerly,
with highs in the mid to upper 80s and dewpoints in the 60s. The
return of higher dewpoint air should lead to slightly greater
chances for afternoon/evening showers and thunderstorms, but most
locations will likely still stay dry.

Forecast confidence decreases substantially by Monday and Tuesday,
but chances for showers and thunderstorms may further increase as
multiple shortwave disturbances move through in northwesterly flow
aloft. Depending on how the forecast details evolve, there could be
a conditional threat for severe thunderstorms on either Monday or
Tuesday.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
Widespread showers and thunderstorms expected through mid
evening with the risk of some severe wx. Thunderstorm risk Wed
will likely stay south of the main terminals.

Prevailing VFR condtions are expected Thursday through Saturday.
Winds will generally be out of the north on Thursday, east on
Friday, and east to southeast on Sunday.

&&

.MARINE...
Numerous to widespread showers and thunderstorms expected, some
of which may require SMWs this afternoon and this evening and
again Wednesday.

SCA conditions may linger in northerly flow into Thursday morning.
Thereafter, sub-SCA level winds are expected Thursday afternoon
through Saturday. Winds will generally be out of the north on
Thursday, east on Friday, and east to southeast on Saturday.

&&

.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.
     Flood Watch through late Saturday night for MDZ004>006-008-011-
     503>508.
VA...Flood Watch until 2 AM EDT Wednesday for VAZ025-026-036-037-
     503-504-508.
WV...Flood Watch until 2 AM EDT Wednesday for WVZ505-506.
MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ530-531-
     538-539.
     Flood Watch through late Saturday night for ANZ530.
     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/DHOF
AVIATION...ADS/LFR/DHOF
MARINE...ADS/LFR/DHOF