Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1155 AM EDT Wed Jul 22 2026
Day 1
Valid 16Z Wed Jul 22 2026 - 12Z Thu Jul 23 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR SOUTHEASTERN
VIRGINIA AND EXTREME NORTHEASTERN NORTH CAROLINA...
...Southeast...
16Z UPDATE: No major changes were made to the outlook with this
update, other than small tweaks to account for the latest
observational trends and new 12Z hi-res model runs. A slow-moving
front will continue to act as a focus for training convective rain
bands and thunderstorms from the Upper Tennessee Valley into North
Carolina, southeast Virginia, and the far southern Delmarva
Peninsula. Although hi-res guidance now indicates less persistence
and focus to the convective activity overnight, with somewhat lower
rain threshold and FFG exceedance probabilities, the Moderate Risk
was maintained for continuity and a favorable pattern for training
convection. Within the Moderate Risk area, signals remain strongest
in the Hampton Roads area.
Meanwhile, the level of concern is increasing for later tonight for
the southern Appalachians, in particular the mountainous areas of
eastern Tennessee and western North Carolina, and perhaps far
northern Georgia. Deep moisture is expected to increase over the
next 12 hours as a more direct connection is made with some of the
low-mid level moisture associated with Bertha along the Gulf Coast.
This can be seen in the CIRA layer precipitable water products from
the Surface to 850mb, as well as 850-700mb. There has already been
a concerted northward push of anomalous moisture, and the PWAT at
BMX increased from 1.86 inches to 2.10 inches between the 06 UTC
and 12 UTC balloon launches. As this reaches the stalling front
tonight, with increasing westerly low-level flow parallel to that
front, ingredients will become favorable for reinvigoration of a
training and backbuilding convective band in the vicinity of the
southern Appalachians. QPF signals in the hi-res models have
increased, with some chances of rain rates reaching 2 inches per
hour if organized thunderstorms can become established. Therefore,
although the risk level is being held at Slight, this area will be
monitored closely in case a targeted upgrade is needed.
...Intermountain West...
16Z UPDATE: The risk areas were not changed appreciably with this
update. Within the Slight Risk area, there may be a greater
concentration of convection and flash flood potential in portions
of western Colorado, northeast Utah, and southern Wyoming. A well-
defined mid-upper level vorticity maximum is pushing into southeast
Utah, evident on GOES-West water vapor channels. To the north and
northeast of this feature, an area of enhanced upper level
divergence would be favored. This also overlaps with an area of
weak winds (and thus slow storm motions), moderate instability, and
anomalously high moisture, even for July. Given there is much less
cloud debris in these areas to restrict destabilization, the chance
of flash flooding may be considered to be at the higher end of the
Slight Risk range.
PREVIOUS DISCUSSION: In coordination with the Albuquerque forecast
office, the Slight Risk area was expanded south along the AZ/NM
state line. Plentiful burn scars, relatively little amounts of
rain it's taken in some areas to cause flash flooding, and many
areas not seeing recent flooding at all are all contributing
factors to the Slight Risk upgrade. Meanwhile further north, the
heaviest rainfall totals will be tied to the topography in many
areas from the Bitterroots through Yellowstone, much of Utah and
western Colorado. With sufficient upper level forcing helping the
storms to form and cause flash flooding, it's probable in many
instances that any storms that start along the topography will move
off the mountains towards the northeast, so lower elevation
valleys in between also remain in the Slight Risk for flooding.
...Gulf Coast/Tropical Storm Bertha...
PREVIOUS DISCUSSION: T.S. Bertha will continue to struggle from
strong northeasterly shear pulling nearly all of the significant
associated rainfall south over the open waters of the Gulf. With
little rain expected along the Gulf Coast, the inherited Marginal
remains little changed. The Marginal mostly covers the fact that
any significant tropical cyclone carries inordinate amounts of
atmospheric moisture, even when being sheared. That moisture can
easily support heavy rainfall, even if isolated, so the Marginal
threat remains.
Lamers/Wegman
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1155 AM EDT Wed Jul 22 2026
Day 2
Valid 12Z Thu Jul 23 2026 - 12Z Fri Jul 24 2026
...THERE'S A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN NORTH CAROLINA...
...Southeast...
A strong and very slow moving cold front draped across portions of
the Mid-Atlantic on Wednesday makes only very slow progress through
the day Thursday across far southern Virginia and northwestern
North Carolina. A second day of intense rainfall in the form of
seemingly endless trains of storms will impact much of the
Carolinas on Thursday. The good news is the southward progress of
the front on the order of about 50 miles or so will spare most of
Virginia much heavy rainfall for yet another day. However, this
means the heavy rain simply impacts areas further south across much
of North Carolina and northern South Carolina. Unfortunately there
looks to be some overlap in the heavy rainfall footprints from
Wednesday into Thursday, particularly in northeastern North
Carolina, likely extending from Norfolk south and east. Once again
the heaviest rainfall amounts will likely concentrate along the
coast. As such the Moderate Risk for this period was also
unchanged, focused from I-95 east and from I-40 north and east.
Further west, a similar situation remains as on Wednesday.
Painfully slow southward movement means many of the same areas get
hit with heavy rains again on Thursday as on Wednesday. The Slight
Risk was expanded west along the front due to the large amounts of
atmospheric moisture in place immediately ahead of the front. Many
areas have PWATs above 2 inches. The Slight Risk area includes
metros Birmingham, AL, Atlanta, and into Charlotte, NC. All 3 of
these metros have some risk of training storms, with Charlotte the
highest of those 3.
...Central Plains...
A pair of nocturnal MCSs, one Wednesday night into Thursday
morning, and a second much stronger one Thursday night into Friday,
will impact portions of southeastern Nebraska, northeastern Kansas,
and into small portions of Iowa and Missouri through the period.
These back-to-back MCSs will sufficiently soak the soils such that
the heavy rain with Thursday Night's MCS will cause widely
scattered instances of flash flooding, especially where urban areas
such as Lincoln, Topeka, St. Joseph, and possibly Omaha and Kansas
City are impacted. The area of the Slight was adjusted, but remains
little changed with this update. The isolated flash flooding threat
represented by the Marginal extends well west of there through
nearly all of Wyoming and Colorado. While the flooding threat
diminishes considerably in these states compared with Wednesday,
the leftover saturated soils and still likely formation of showers
and storms will keep an isolated flash flooding threat going.
...Bertha/South Texas...
Latest CAMs guidance are starting to come into agreement on a
solution that keeps the circulation of Bertha intact over the
northwestern Gulf before the westward moving storm moves inland in
Texas near or south of Houston. As such, the persistent convection
that continues to focus south/southwest of the center eventually
impacts land areas, in this case in south Texas. A Marginal Risk
covering much of South Texas was introduced with this update. It's
likely that a Slight Risk upgrade will be needed with future
updates, short of a northward jog in the guidance that kills off
the rain much earlier, as the guidance had been showing in recent
days. The area most likely to see that upgrade is around Corpus
Christi through Victoria.
Wegman
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1155 AM EDT Wed Jul 22 2026
Day 3
Valid 12Z Fri Jul 24 2026 - 12Z Sat Jul 25 2026
..THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHEAST AS WELL AS FOR MUCH OF MISSOURI...
...Southeast...
The front that has been causing heavy rain across portions of the
Southeast through Thursday continues on into Friday, though begins
to weaken and in some areas lift back to the north as a warm front.
Due to this weakening forcing, the rainfall forecast footprint over
the Carolinas diminishes substantially (by about half) as compared
with prior days' rains. While many areas continue to see periods of
heavy rain, which may overlap with heavy rainfall from prior days,
the much lower rainfall forecast over North Carolina did allow for
the risk level to drop back into the Slight category for the Friday
period. That said, any increase in rainfall, especially for areas
hit hard on Wednesday and Thursday, could easily necessitate
another upgrade to a Moderate for portions of eastern North
Carolina with future updates.
The rainfall forecast increases from prior days further west into
northern Alabama and Georgia. The inherited Slight risk, as on past
days, was expanded west. In this case, the expansion went all the
way to the Mississippi state line with Alabama, as Alabama in
particular looks to have its wettest day of the week on Friday.
Considering prior days rains forecast for this same area, more
favorable hydrology and further increases in expected rainfall in
northern Alabama and Georgia could mean a Moderate Risk upgrade
with future updates isn't entirely out of the question. Certainly
eastern NC has a much higher chance of this happening.
...Missouri...
An MCS over the area Friday morning diminishes in intensity with
differential heating over the Plains and Ozarks on Friday. However,
guidance is not in good agreement as to whether or not the rainfall
dissipates entirely. Peak heating could provide enough instability
that the convective organization changes, but not its coverage.
Thus, A Slight Risk for a large portion of Missouri remains in
place. Any rain will continue in this area into Friday night.
...Texas..
Regardless of whether Bertha does better at maintaining its
intensity on Thursday, or if it dies earlier by taking a more
northerly track, by Friday the rainfall associated with the storm
will be long dissipated or diminished to nuisance showers. As
such, all flooding risks directly associated with Bertha will be
ended by Friday.
Wegman
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1155 AM EDT Wed Jul 22 2026
Day 4 and Day 5
Valid 12Z Sat Jul 25 2026 - 12Z Mon Jul 27 2026
...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE MID
MISSISSIPPI VALLEY TO THE SOUTHEAST DAY 4 AND ACROSS PORTIONS OF
THE WESTERN U.S. DAYS 4 AND 5...
...Mid Mississippi Valley to the Southeast...
The overall trend in the overnight guidance was to shift the slow-
moving surface front and associated axis of deeper moisture farther
east and off of the Southeast Coast on Saturday, diminishing the
threat for widespread additional heavy rains across the Carolinas.
Therefore, the Slight Risk was removed from the eastern Carolinas.
However, cannot rule out an isolated threat for localized heavy
rains and an isolated flash flood threat. Therefore, the Marginal
Risk was maintained for the Day 4 period from eastern North
Carolina into the Southeast before notably drier air begins to
spread across much of the region on Sunday.
The Marginal Risk was also maintained farther northwest back across
the Tennessee Valley into the mid Mississippi Valley. Some models,
more notably the ECMWF and UKMET, show elevated storms that are
expected to develop Friday night continuing to propagate southeast
from the mid Mississippi into the Mid South, with deepening
moisture and training storms raising the potential for heavy
accumulations. As the associated mid level energy continues to drop
southeast, there is the potential for at least locally heavy
amounts and isolated flash flooding concerns as it interacts with
lingering deep moisture from the Tennessee Valley into Alabama and
Georgia on Saturday.
...Southwest to the northern Rockies...
After a dropoff late in the week, the footprint for diurnal
showers and storms is expected to expand once again by Saturday as
high moisture anomalies (+2 sigma) return to parts of Arizona and
New Mexico. This moisture along with mid-level energy moving
around the southern periphery of the high will raise the threat for
efficient-rainfall producers, raising flash flooding concerns
across parts of the Southwest both days. This elevated moisture and
enhanced forcing may support the need for an upgrade to a Slight
Risk in future updates.
Meanwhile deeper moisture and energy lifting along the northwest
side of the high will extend the threat into parts of the northern
Intermountain West and Rockies on Day 4, before moisture anomalies
drop off on Day 5.
Pereira
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1155 AM EDT Wed Jul 22 2026
Day 4 and Day 5
Valid 12Z Sat Jul 25 2026 - 12Z Mon Jul 27 2026
...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE MID
MISSISSIPPI VALLEY TO THE SOUTHEAST DAY 4 AND ACROSS PORTIONS OF
THE WESTERN U.S. DAYS 4 AND 5...
...Mid Mississippi Valley to the Southeast...
The overall trend in the overnight guidance was to shift the slow-
moving surface front and associated axis of deeper moisture farther
east and off of the Southeast Coast on Saturday, diminishing the
threat for widespread additional heavy rains across the Carolinas.
Therefore, the Slight Risk was removed from the eastern Carolinas.
However, cannot rule out an isolated threat for localized heavy
rains and an isolated flash flood threat. Therefore, the Marginal
Risk was maintained for the Day 4 period from eastern North
Carolina into the Southeast before notably drier air begins to
spread across much of the region on Sunday.
The Marginal Risk was also maintained farther northwest back across
the Tennessee Valley into the mid Mississippi Valley. Some models,
more notably the ECMWF and UKMET, show elevated storms that are
expected to develop Friday night continuing to propagate southeast
from the mid Mississippi into the Mid South, with deepening
moisture and training storms raising the potential for heavy
accumulations. As the associated mid level energy continues to drop
southeast, there is the potential for at least locally heavy
amounts and isolated flash flooding concerns as it interacts with
lingering deep moisture from the Tennessee Valley into Alabama and
Georgia on Saturday.
...Southwest to the northern Rockies...
After a dropoff late in the week, the footprint for diurnal
showers and storms is expected to expand once again by Saturday as
high moisture anomalies (+2 sigma) return to parts of Arizona and
New Mexico. This moisture along with mid-level energy moving
around the southern periphery of the high will raise the threat for
efficient-rainfall producers, raising flash flooding concerns
across parts of the Southwest both days. This elevated moisture and
enhanced forcing may support the need for an upgrade to a Slight
Risk in future updates.
Meanwhile deeper moisture and energy lifting along the northwest
side of the high will extend the threat into parts of the northern
Intermountain West and Rockies on Day 4, before moisture anomalies
drop off on Day 5.
Pereira
