477
FXUS61 KLWX 281420
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1020 AM EDT Tue Jul 28 2026

.WHAT HAS CHANGED...
Monitoring the evolution and subsequent effects of morning
showers and clouds. SPC expanded the 30 percent damaging wind
contour to include the I-95 corridor.

&&

.KEY MESSAGES...
- 1) Slight Risk of severe thunderstorms today as a strong cold
 front impacts the forecast area.

- 2) A few chances for rain through the weekend, but no
 hazardous weather expected between Wednesday and Sunday at this
 time.

&&

.DISCUSSION...
KEY MESSAGE 1...Slight Risk of severe thunderstorms today as a
strong cold front impacts the forecast area.

Mid morning regional radar shows stratified and weakening
rainfall affecting the southern tier of the forecast area. A
northern segment extending from PA toward the Potomac River has
held its structure a little better and has had occasional
lightning strikes. With elevated instability existing down
stream, at least some showers and a few embedded thunderstorms
could continue eastward over the next few hours. In the
subsidence in the wake of this convection, some breaks in the
clouds are already occurring in the Allegheny and Potomac
Highlands. Such breaks may prove to be sufficient to allow
instability to build as we move toward peak heating. On a large
scale, however, there is still a fair amount of regional cloud
cover, and 12Z soundings locally and upstream at PIT and ILN
show multiple stable layers through the mid levels. So there
remains some uncertainty with how the threat will evolve this
afternoon, although recent CAMs continue to develop a decent
coverage of thunderstorms. The coverage of the Flood Watch still
looks good at this time with more potential for storms to get
hung up as they interact with the bay breeze.

Previous discussion:

A potent surface low pressure system tracks east from the Great
Lakes region towards New England today with the associated cold
front pushing across the forecast area later today. This strong cold
front, combined with a deep upper level trough digging across
eastern CONUS, leads to an increased chance of scattered severe
thunderstorms this afternoon and into the evening. Showers and
thunderstorms increase in coverage between 2PM and 8PM with storms
lingering later in the southeastern portions of the forecast area.
Multiple bowing and linear segments are possible with damaging wind
gusts as the primary hazard type. That being said, cooling mid-level
temperatures contributes to a threat of large hail and a brief
tornado is possible due to low-level shear. The Storm Prediction
Center has the majority of the forecast area (with the exception of
western Maryland being in a marginal risk) in a slight risk for
severe weather.

In addition to the severe weather threat, a moist airmass with PWATS
exceeding 1.7 inches makes strong thunderstorms capable of producing
torrential downpours. Where PWATS and ensemble QPF
probabilities are highest, a Flood Watch is in effect from 8AM
this morning to 2AM early Wednesday morning in northeast
Maryland. The most vulnerable locations would be urbanized areas
along I-95 as well as areas which have experienced heavy
rainfall in recent days. Recent HREF probabilities have slightly
shifted the bullseye of QPF maxima eastward, so kept the Flood
Watch northeast of the DC metros although an expansion may be
needed later should future guidance indicate an increased risk.

In the wake of the frontal system, surface high pressure builds over
the area from the west with slightly cooler and drier conditions
expected Wednesday and Thursday.

KEY MESSAGE 2...A few chances for rain through the weekend, but no
 hazardous weather expected between Wednesday and Sunday at this
 time.

The upper-low over the northeast CONUS will linger through Friday
before finally pulling off to the northeast. As a result, there will
be non-zero rain chances each day, primarily areas further north and
east. Friday could be dry for all, but still a bit of uncertainty
regarding exactly when the upper low departs.

A broad upper-level trough will begin to form over the Ohio River
Valley over the weekend. As this trough tracks east, cloud cover &
precipitation chances will begin to increase, particularly between
Saturday evening and Sunday as the low tracks offshore and towards
the northeast. Severe probabilities look low at this time, with a
pretty weak wind field aloft. Nonetheless, weekend showers are
possible with this system should the synoptic setup continue to
trend toward development over the Midwest.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
A strong frontal system brings showers and thunderstorms to the
terminals on today. Some decaying showers are crossing the area
this morning. While a few lightning strikes were observed
earlier near MRB, overall impacts with this round appear to be
limited. More notable impacts are expected later in the
afternoon as strong to severe thunderstorms track across the
forecast area. Strong wind gusts, low ceilings, reduced
visibilities, heavy rain, and frequent lightning are all
possible in the afternoon to perhaps early evening at
DCA/BWI/MTN. Timing remains a bit uncertain. Outside of
thunderstorms, southerly winds may gust 15-20 kt.

Sub-VFR conditions continue into Wednesday morning depending on
how slowly the front tracks offshore. Winds gust 15 to 25 knots
out of the northwest. Prevailing VFR conditions are expected
across terminals Thursday with 10-15 knot winds gusting up to 20
knots before diminishing overnight.

VFR conditions are expected on Friday. However, an upper-low to our
northeast could bring some showers close to BWI/MTN. This is a very
low likelihood scenario at this time, but can`t completely rule it
out. Either way, no significant reductions appear likely at this
time.

Saturday and Sunday appear to be days with occasional showers
possible, but VFR conditions otherwise.

&&

.MARINE...
Winds increase through this morning with Small Craft Advisories in
effect through tonight. Active convection will also make for
hazardous conditions across the waterways with SMWs likely this
afternoon and evening. This may include strong winds, abrupt
wind shifts, and frequent lightning. Winds shift to
northwesterly overnight into Wednesday with SCA criteria winds
likely throughout the day. Small Craft Advisory conditions
continue through Friday morning.

Winds will drop below SCA criteria for Friday and continue for much
of Saturday. However, as winds turn southerly late Saturday
afternoon/evening, winds could approach SCA criteria as they channel
up the Chesapeake Bay.

&&

.TIDES/COASTAL FLOODING...
Southerly winds combined with a full moon keep tidal anomalies
elevated today. Annapolis is forecast to reach minor flood
stage late tonight, although it`s possible northwest winds could
lead to water levels declining enough to keep it short. Many
tidal locations are forecast to reach action stage through
Thursday morning before tidal anomalies slowly decrease.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Flood Watch through late tonight for MDZ006-008-011-014-
     506>508.
     Small Craft Advisory until 8 PM EDT this evening for MDZ008.
VA...None.
WV...None.
MARINE...Flood Watch through late tonight for ANZ530.
     Small Craft Advisory until 8 PM EDT this evening for
     ANZ530>533-537>542.
     Small Craft Advisory until 6 AM EDT Wednesday for ANZ534-543.
     Small Craft Advisory from 1 PM this afternoon to 8 PM EDT this
     evening for ANZ535-536.

&&

$$

DISCUSSION...ADS/AVS/CJL
AVIATION...ADS/AVS/CJL
MARINE...ADS/AVS/KLW/CJL

NWS LWX Office Area Forecast Discussion