051
FXUS61 KLWX 091426 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
1026 AM EDT Thu Jul 9 2026

.WHAT HAS CHANGED...
The Slight Risk from the Storm Prediction Center has been
expanded westward to include western VA and areas along I-81.

&&

.KEY MESSAGES...
- 1) Thunderstorms, some of which may produce damaging winds and
  heavy rain, are possible through Friday.

- 2) Turning cooler this weekend into Monday, with renewed heat
  by mid-week.

&&

.DISCUSSION...
KEY MESSAGE 1...Thunderstorms, some of which may produce
damaging winds and heavy rain, are possible through Friday.

A surface front to the south will surge poleward as a warm
front later today. The other key player is a seasonably strong
shortwave currently over the OH River Valley down into the
Tennessee Valley.

This trough is forecast to move toward the Mid-Atlantic states
which is accompanied by increasing mid-level winds to around 30
to 35 knots. Ultimately this bolters 0-6 km vertical shear to 30
knots which is plenty sufficient for early/mid July standards.
The Storm Prediction Center Slight Risk has been expanded
westward to include areas to the west of I-81 likely due to more
sunshine this morning. While instability is not off the charts,
mixed-layer CAPE values rise to around 1,500 to 2,000 J/kg. The
tropical air mass featuring 2 to 2.25 inch precipitable water
values will lower lifted condensation levels (LCLs). This
ultimately puts a cap on the amount of downdraft CAPE (DCAPE),
generally averaging around 600 to 800 J/kg. The 00Z high-
resolution model suite indicates convective initation off the
higher terrain during the early afternoon hours. High-
resolution ensembles depict 40 dbZ paintballs which track toward
the I-95 corridor during the late afternoon/early evening
hours. Ample vertical shear will aid in decent storm
organization, particularly for developing line segments. As
usual, damaging wind gusts should be the primary severe hazard,
but with frequent lightning and torrential downpours possible in
any storm. The primary threat for severe thunderstorms ends by
the mid-evening hours as convection pushes out to the Eastern
Shore.

With only modest DCAPE values on forecast soundings, the forward
acceleration of storms via cold pools/gust fronts may not offset
a possible flash flood threat. In particular, locations recently
hit by recent heavy rainfall along with the more vulnerable I-95
urban areas will see an elevated flood risk. The Weather
Prediction Center has placed a Slight Risk across all areas
north of I-64. Given a decent signal for heavy rainfall along
the I-95 corridor, have opted for a Flood Watch given the
threat of flash flooding. This covers the 2 PM through 11 PM
timeframe while spanning north-central Maryland down to northern
Virginia and points eastward. While convection should be
progressive in nature, intense rainfall rates on the order of 2
to 3 inches per hour could aid in some hydrologic response. Will
continue to monitor for any necessary westward/southward
expansions.

Some degree of convective threat likely continues into Friday
given ample moisture in the atmosphere. However, a primarily
westerly flow often is known to negate the development of more
organized thunderstorm activity. Friday does mark the warmest
day of the remainder of the week with highs in the upper 80s to
low 90s. Depending on how much rainfall occurs during the
previous day, some level of flash flood risk may take place
again on Friday afternoon/evening.


KEY MESSAGE 2...Turning cooler this weekend into Monday, with
renewed heat by mid-week.

As an upper ridge builds across the Desert Southwest into the
central Rockies, this will lend itself to longwave troughing
across far eastern Canada into the northeastern U.S. Weak height
falls accompanying this trough will push a cold front through
the area on Saturday morning. This boundary sags southward in
time as broad high pressure over the Great Lakes and New England
approaches from the north. Some lingering showers are possible
over the weekend given the close proximity of the frontal zone
to the area. Temperatures drop over the weekend with initial
post-frontal northwesterlies giving way to easterlies by Sunday.

The true drop in humidity levels does not take place until late
in the weekend into Monday. This should offer a dry start to the
upcoming work week. Eventually above average temperatures return
to the picture toward the middle of next week. Building heights
across the central U.S. should eventually spread eastward into
the Great Lakes and Ohio Valley. Low to mid 90s become more
likely as this occurs, but with less humidity than the last bout
of excessive heat. Forecast dew points are in the 60s with upper
ridging generally limiting convective chances.

&&

.AVIATION /13Z THURSDAY THROUGH MONDAY/...

As a seasonably strong shortwave moves through this afternoon,
the models agree on numerous showers and thunderstorms pushing
eastward across the area. Have maintained a TEMPO group in the 3
to 7 PM timeframe, slightly earlier for the western terminals.
Restrictions are likely as these storms roll through, some of
which could be severe in nature. In the wake of these storms,
initial southerly winds turn more southwest to westerly tonight.
Low ceilings are again possible, particularly in areas which
saw heavier rainfall. Westerly winds on Friday may offset some
of the convective threat on Friday. However, some afternoon to
evening restrictions will again be possible.

A cold front moves through on Saturday which yields a shift to
northwesterly winds. These eventually turn more easterly on
Sunday into Monday as the boundary slides farther to the south.
Despite some weekend shower chances, mainly VFR conditions are
expected.

&&

.MARINE...
With summertime gradients in place, any potential for Small
Craft Advisories appears low through the weekend and into early
next week. Any hazardous conditions over the waterways will
again be tied to thunderstorms, lightning, and any gust
fronts/outflows. Special Marine Warnings may be needed for this
afternoon and evening as strong convection pushes eastward to
the I-95 metro areas. While westerly winds should offset some
of Friday`s convective threat, some storms could impact the
waters during the core heating hours.

&&

.TIDES/COASTAL FLOODING...
Anomalies are around 1 to 1.25 feet early this morning as winds
have shifted over to southerly. This will likely result in near
minor flooding of vulnerable shoreline through the end of the
week. Annapolis is most likely to reach the minor flood
threshold, and a Coastal Flood Advisory has been issued for
the early morning high tide. Havre de Grace will also be close.
A gradual decline in water levels is expected this weekend.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch from 2 PM EDT this afternoon through this evening
     for DCZ001.
MD...Flood Watch from 2 PM EDT this afternoon through this evening
     for MDZ004>006-008-011-013-014-503>508.
VA...Flood Watch from 2 PM EDT this afternoon through this evening
     for VAZ053-054-505-506-526-527.
WV...None.
MARINE...Flood Watch from 2 PM EDT this afternoon through this evening
     for ANZ530.

&&

$$

DISCUSSION...LFR/BRO
AVIATION...LFR/BRO
MARINE...LFR/BRO

NWS LWX Office Area Forecast Discussion