FOUS30 KWBC 200827
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
427 AM EDT Mon Jul 20 2026

Day 3  Valid 12Z Wed Jul 22 2026 - 12Z Thu Jul 23 2026

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR THE CAROLINAS,
PORTIONS OF THE INTERMOUNTAIN WEST, AND THE CENTRAL GULF COAST...

...Carolinas into Southeastern Virginia...

A strong cold front that impacted much of the Mid-Atlantic on
Tuesday will stall out over central Virginia on Wednesday. Ahead of
the front, abundant Gulf moisture will continue streaming
northeastward from Tropical Depression 2, likely to be centered
south of the Mississippi Delta. Since the front will remain strong,
and the moisture will remain well above normal for the Carolinas,
as PWATs spike above 2.25 inches at times, the front will act as a
train track for numerous training and backbuilding thunderstorms.
The focus for these storms will be where the front interacts with
the deepest moisture, which is expected from central North Carolina
northeast through the Tidewater of Virginia.

This area should get a break in the rain on Day 2/Tuesday, such
that by the time the heaviest rains impact NC and VA on Wednesday,
some draining from prior days' storms should work to limit the
flash flooding risk somewhat. Thus, for now the area remains in a
higher end Slight. The forecast rainfall will continue to be
monitored as a Moderate Risk upgrade remains a possibility.

...Central Gulf Coast...

Tropical Depression 2 is expected to be drifting west to the south
of Louisiana on Wednesday. The conditions impacting the system will
remain much the same on Wednesday as on prior days. Northerly shear
will remain in place, pushing most of the associated convection
south of the circulation center, keeping nearly all of the heaviest
rains over the Gulf. Only a tiny fraction of the storm's overall
rainfall will impact land areas, with the best chance expected
along the immediate Gulf Coast of southeastern Louisiana. The
inherited Slight Risk was trimmed to just the immediate coast,
dropping the threat for metro New Orleans, in coordination with
LIX/Slidell, LA forecast office. Of course, trends in the storm
will continue to be monitored, as subtle changes in the environment
around the storm could result in large changes in the rainfall forecast.

...Intermountain West...

The combination of well above normal moisture across much of the
intermountain West on Wednesday, strong upper level disturbances
tracking northeastward ahead of a longwave trough over the Pacific
Northwest, and numerous mountain ranges will all work to promote a
much higher than normal flash flooding potential over the area from
the 4 Corners north through much of southeastern Idaho. The Slight
Risk for Idaho and Wyoming was expanded south due to yet another
day of expected showers and thunderstorms impacting the highly
flash flooding prone areas of Utah and western Colorado. The
greatest rainfall totals are likely into northwestern Wyoming, from
Yellowstone south. Few changes were needed north of Wyoming's southern border.

Wegman
 

Day 4 and Day 5  Valid 12Z Thu Jul 23 2026 - 12Z Sat Jul 25 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
CENTRAL PLAINS TO LOWER MISSOURI VALLEY, THE CENTRAL TO WESTERN
GULF COAST, AND THE EASTERN CAROLINAS ON DAY 4...

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
LOWER MISSOURI AND MID MISSISSIPPI VALLEYS, AND THE EASTERN
CAROLINAS ON DAY 5...

...Southeast...
A moisture-laden front will continue to sink slowly south across
the region. While the overnight guidance continues to present
differences on the timing of the front and corresponding
precipitation, there remains a strong signal for additional heavy
amounts impacting parts of the region, especially for portions of
the Carolinas. PWs remaining around 2.25 inches along with periods
of enhanced ascent will raise the threat for additional heavy
amounts most likely centered over eastern North Carolina into
northeast South Carolina Thursday into early Friday. Due in part to
model differences and forecast uncertainty, maintained a Slight
Risk. However, this has the potential to be a second day in-a-row,
and the fourth day this week for heavy rains impacting parts of
the region. Therefore, if forecast confidence increases and the
signal for a multi-day heavy rainfall event holds, future upgrades
may be required.

For Friday into early Saturday, it remains a question
whether the front will continue to push south, bringing drier
conditions into the Carolinas as the GFS/UKMET indicate, or
continue to hang up well to the north as shown by the ECMWF and
Canadian. Opted for a Slight Risk on for the Day 5, centered
similar to the Day 4 area, which presents a compromise between the
two camps and lined up with the higher probabilities from the most
recent ECENS.

...Gulf Coast...
Shear across Tropical Depression Two is expected to keep the
heaviest rainfall amounts associated with the system mostly south
of the center and offshore. However, cannot rule out the threat for
onshore flow supporting some locally heavy amounts along the coast,
especially if the trends support a stronger system and more
northerly track. Therefore, the a Slight Risk was maintained along
the Louisiana to the upper Texas Coast on Day 4.

A Marginal Risk was drawn for Day 5 from the upper Texas Coast
inland toward south-central Texas, where heavy amounts are
possible if the storm remains organized and continues to track west.

...Central Plains to the Mid Mississippi Valley...
Models continue to show a well-defined shortwave sliding southeast
off of the top of the western U.S. ridge through the northern
Plains and into the mid Mississippi Valley on Day 4. Organized
heavy rain may develop late Thursday into early Friday as this
energy interacts with a deepening moisture pool fed by a
strengthening southwesterly jet. A Slight Risk was maintained on
Day 4 over parts of southeastern Nebraska into adjacent parts of
Kansas, Iowa, and Missouri, where models indicate the deepest
moisture, better forcing and greater potential for localized
training will center. Storms continuing through Friday morning and
possibly redeveloping later in the day downstream will extend the
threat across across a greater part of the mid Mississippi Valley on Day 5.

...Southwest/Great Basin/Central and Southern Rockies...
Monsoon moisture will continue to fuel diurnal activity, however
the footprint is expected to diminish especially by Day 5 as
moisture anomalies drop off and heights build across the Southwest.

Pereira
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