567
FOUS30 KWBC 031913
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Thu Jul 3 2025

Day 1
Valid 16Z Thu Jul 03 2025 - 12Z Fri Jul 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS WESTERN
PORTIONS WEST TEXAS AND NEW MEXICO...

...Southwest to the Southern Plains...

16Z Update: The threat for heavy rainfall across much of West TX
and New Mexico remains with ongoing flash flood threats extending
from the Permian Basin over into Southwest TX. The threat will grow
across areas of TX east of the Permian Basin with the Concho Valley
and adjacent Hill Country getting more into the mix as we move
later in the day and overnight hours. The SLGT risk was adjusted a
bit more to the east to account for trends in the heavier QPF
signals via CAMs. Coincidentally, the CAMs are now in agreement
with the heavy rain axis noted via ECMWF AIFS ML and other ML tools
allowing for a greater confidence in the threat. This was enough
for the small adjustment and general maintenance for the threat.
Look for pockets of 2-4" with locally up to 6" possible over any
area encompassed by the SLGT risk from Southeast NM over into West
TX.

New Mexico will see less in terms of maxima, but still looks like
conditions will improve with diurnal heating this afternoon
allowing for another round of convection to fire in-of the terrain
between the Sacramento`s up into the southern portion of the Sangre
de Cristos. Greatest threat for flash flooding will occur within
the remnant burn scars and adjacent valley towns that are impacted
by heavy thunderstorms. This threat will begin to dissipate
overnight with decoupling processes, but any outflow generation
could maintain convection a little longer over Eastern NM before it
completely ceases. The SLGT risk was maintained over the area with
no changes from previous forecast.

Kleebauer

..Previous Discussion..

A mid-to-upper level shortwave moving into southern
California this morning will move into the Four Corners region by
this evening and then the central and southern Rockies overnight.
The large scale lift associated with the wave, along with ample
moisture remaining in place, are expected to produce widespread
showers and thunderstorms across Arizona and New Mexico. A Slight
Risk was maintained across the eastern New Mexico and West Texas
mountains into the High Plains, where additional storms are
expected to develop across the same areas that have received
several rounds of storms and periods of flash flooding over the
past several days. A Marginal Risk was maintained farther to the
north into the central Rockies, extending into parts of southern
Wyoming, where the overnight guidance continues to indicate the
potential for localized heavy amounts as the deeper moisture is
drawn northward ahead of the advancing shortwave.

While differing in the details, the models continue to show a
notable signal for more widespread heavy amounts developing further
east into parts of central Texas. Continued to extend the Slight
Risk from eastern New Mexico and West Texas out into parts of
Northwest Texas and the Hill Country. Persistent southerly flow
will support a widespread area of PWs AOA 2 inches (+3 std dev),
supporting the potential for heavy amounts. The Slight Risk was
drawn to include areas where the 00Z HREF showed high neighborhood
probabilities for amounts of over 2 inches, with notable
probabilities for amounts of 3 inches as well.

Pereira

...Eastern Oklahoma to central Louisiana...

16Z Update: Multiple flash flood warnings were issued this AM for
the threat as a focused area of convergence within the boundary
referenced in previous discussion allowed for a pocket of
training/redevelopment over parts of Eastern OK. Rainfall rates
were noted ~3"/hr at times which coincides with the anomalous
moisture presence (12z KOUN sounding depicted 2.01" PWATs), so any
stronger convective cores will be capable of locally enhanced rates
and flash flood concerns. The boundary slopes southeastward into
Northern LA with the cu field bubbling over the area and other
cells pulsing up near the ArkLaTex. The threat will linger through
the afternoon with the activity waning after sunset with
traditional diurnal heat loss. Until this occurs, isolated flash
flood prospects will remain with the best threat likely over
Southeast OK through the ArkLaTex towards I-20 in Northern LA. The
MRGL risk was maintained with no deviation from previous forecast.

Kleebauer

..Previous Discussion..

A slow-moving returning boundary is expected to become the focus
for deeper moisture (PWs ~2 inches), which along with daytime
heating and modest mid-to-upper level forcing, is expected to
produce a swath of slow-moving storms later today, capable of
producing heavy rainfall rates and accumulations. The overnight
HREF shows a decent signal for some locally heavy amounts,
especially from central/southeastern Oklahoma through the ArkLaTex
into central Louisiana. Neighborhood probabilities for amounts
over 2 inches are above 50 percent across this region. Given the
relatively high FFGs covering much of this area, opted to introduce
just a Marginal Risk area at this time.

Pereira

...Southeast...

The previous SLGT risk was removed in this update as trends for
scattered to widespread coverage of heavy rainfall have all but
deteriorated on the latest guidance across FL. Latest ASCAT pass
across the Gulf signaled very little in the way of an organized
area of low pressure meaning the entire setup is being driven by
frontal convergence and mean troughing positioned across the
Northeastern Gulf. The best signal of convergence remains over
Southwest FL leading to some amounts exceeding 1-2" over places
like Ft. Myers down into Naples. The rates are still lacking
however, as the expected convergent pattern is just not sufficient
for those enhanced rates that were expected previously and
necessary for flash flood concerns in this part of the CONUS. There
are still inferences within the CAMs on pockets of heavier rainfall
materializing through the period, but the coverage is less than
optimal for a higher risk. 12z KTBW sounding came with a solid warm
cloud layer and PWATs running ~2.2" meaning the environment is
capable, but missing that ascent pattern necessary to access the
potential. Still, any convective cores will be capable of 2-3"/hr
rates with the best threat over any urbanized zones.

The threat for isolated flash flooding extends up the GA/SC coastal
areas where elevated PWATs and differential heating will likely
spark another round of slow-moving convection capable of locally
heavy rainfall and isolated flash flooding with 2-4" of rain
plausible in any stronger cell development. The MRGL risk was
maintained for these areas, along with the extension into the
Southeast FL metro.

Kleebauer

...North Dakota/Northwest Minnesota...

16Z Update: The setup for strong nocturnal thunderstorms to impact
ND into Northwest MN remains with a consistent signature of heavy
rain encroaching Northwest ND with cell propagation to the
northeast as we move through the period. This threat remains within
the lower threshold for the MRGL risk, however the anomalous
moisture presence allows for a bit of a better threat locally
compared to normal. HREF neighborhood probs are privy to at least
1" falling over the area north of Bismarck with upwards of 2" still
within reason. The signals were basically similar to last nights
update, so didn`t feel a need to change course, so maintained
general continuity in the MRGL risk.

Kleebauer

..Previous Discussion..

Storms are expected to develop later this evening across North
Dakota along a slow-moving warm front and ahead of a subtle
shortwave moving into the High Plains. Southerly flow is expected
to support an uptick in PWs (~1.5 inches). While widespread heavy
amounts are not expected, models do show some potential for locally
heavy amounts, bolstered by a period of slow-movement followed by
training cells. A Marginal Risk was introduced for the area where
the HREF showed high neighborhood probabilities for amounts over an
inch. The HREF indicates the greater threat for heavier amounts
centers over northwestern North Dakota, where slow-moving storms at
the onset may produce locally heavy amounts. The HREF shows some
modest probabilities for amounts over 2 inches across this area.

Pereira

...Wisconsin...

16Z Update: The overall synoptic pattern and general convective
expectation has not changed since the previous forecast. The one
shift was the orientation of the heavier QPF a bit more to the
southwest when assessing the differences fields in the CAMs. The
HREF blended mean shifted approx 25-50 miles further west and
southwest from the 00z suite, so the adjustment was made to reflect
the change. Otherwise, the probability signals are actually more
robust for >2" with the 12z HREF neighborhood probs now upwards of
50-80% extending from Eau Claire down through the Milwaukee metro.
This is more than enough confidence to maintain the risk area in
place with only that minor adjustment necessary to reflect the
latest QPF alignment.

Kleebauer

..Previous Discussion..

A Marginal Risk was also added over portions of Wisconsin, where a
downstream portion of the previously noted front will become a
focus for deeper moisture and slow-moving storms tonight. The
signal for heavy amounts and potential flash flooding is a little
greater across this area. Amplifying southwesterly low level inflow
will support PWs climbing to ~1.5-1.75 inches, which along with a
weak shortwave moving across the top of an upper ridge, will
support storm development. Guidance indicates slow storm movement,
with some backbuilding, supporting the potential for locally heavy
amounts. The HREF shows neighborhood probabilities as high as 50
percent for amounts over 2 inches centered over northwestern
Wisconsin.

Pereira


Day 2
Valid 12Z Fri Jul 04 2025 - 12Z Sat Jul 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
EASTERN NORTH DAKOTA AND NORTHWESTERN MINNESOTA...

...Northern/Central Plains and Upper Midwest...

20Z Update: The SLGT risk across the Northern Plains and Upper
Midwest was maintained, but adjusted a bit further to the east to
account for relevant trends in heavier QPF now positioned a bit
more across North-Central MN. Highest neighborhood probs for >3"
(40-80%) lies on a southwest to northeast orientation from the
ND/SD line between BIS/ABR up through the International border of
MN. Convective scheme is historically proven to skew a bit further
east with cold pool advancement which is one reason we are likely
seeing some adjustment in the CAMs already and is outlined in some
of the ML output. Will keep a close eye on the forecast as some
further adjustments east are plausible, but the consensus should
keep the maxima over the Dakotas and Minnesota pretty similar.

Across NE/KS, another shortwave will eject out of the Front Range
with thunderstorm genesis within the Sandhills of NE. The trend is
for heavy rainfall likely to occur over North Platte to Grand
Island with a trend in convection further east towards the
Missouri River as we step into the back end of the forecast period.
12z HREF EAS probs for >1" are running high between the two urban
centers in NE referenced above with a pretty good signature of
50-70% for at least 1" over the general area northeast of Goodland
through that zone between LBF/GID. This correlates to growing
consensus on heavy rain with prospects for local totals between
2-4" when assessing the deterministic CAMs output and some of the
bias corrected ensemble. The MRGL remains due to higher FFG`s and
some questions on the specifics of the evolution of the
convection, but odds for a targeted SLGT have increased and could
be a focus as we move into the D1.

Kleebauer

..Previous Discussion..

A much stronger signal for heavy amounts and possible flash
flooding is expected to unfold across parts of eastern North Dakota
and northwestern Minnesota late Friday into early Saturday.
Southerly winds ahead of a shortwave trough lifting northeast into
the Northern Plains will support PWs climbing to ~2 inches (+2 to
3 std dev). Storms are expected to develop by late afternoon and
train southwest to northeast ahead of a slowly advancing cold
front. With the HREF indicating that 12-hr amounts (ending 00Z Sat)
are likely to exceed 2 inches in some locations, a Slight Risk was
introduced across parts of eastern North Dakota and northwestern
Minnesota. A Marginal Risk was maintained farther to the south into
parts of the Central Plains where convection developing over the
High Plains during the afternoon is expected to advance more
steadily east, limiting the heavy rainfall/flooding threat.

Pereira

...Southern Plains...

Impacts from the previous period coupled with elevated PWATs
reaching between 2-3 deviations above normal and general diurnal
destabilization will likely lead to another round of scattered
convection capable of at least some localized flash flood prospects
across the Permian Basin over into the Concho Valley and adjacent
Hill Country. Modest probs for locally >2" (40-60%) exist over the
aforementioned areas with the recent hi-res ensemble depicting a
greater threat further west than previously forecast. With the
pattern so meridional, the setup will be harder to break down as it
customary for these regimes this time of the year. The previous
MRGL risk was expanded longitudinally in either direction to
account for the threat.

Kleebauer

...Northern Rockies...

20Z Update: Only minor adjustments were made to the MRGL risk
centered over Big Sky country in MT down through ID/WY. Isolated
heavy thunderstorms could cause some issues within more urbanized
zones and complex terrain aligned over the Northern Rockies. Pretty
solid agreement on guidance with the maxima hovering between 1-2"
with a sharp drop off in neighborhood probabilities for >2"
compared to fairly elevated probs for >1". This is generally
coincident with a MRGL risk for these setups and this is no
different, so maintained relevant continuity given the signals.

Kleebauer

..Previous Discussion..

A Marginal Risk was maintained across parts of Idaho, western
Montana, and northwestern Wyoming, where widespread light to
moderate, with embedded locally heavy amounts are expected. A well-
defined shortwave trough along with fairly anomalous PWs (+1 to 2
std dev) are expected to support locally heavy amounts and an
isolated flash flooding threat.

Pereira

...Florida...

Scattered to widespread thunderstorms will form across the
Peninsula on the 4th leading to fireworks likely from Mother Nature
before we kick off the evening festivities. Some of the heavy
rainfall could be pretty efficient with the environment generally
favorable for local 2-4"/hr rates as PWATs reside between 2-2.4"
along the front hung-up over the Central FL Peninsula. Flow will
run relatively parallel to the stationary front leading to some
storms training over the same areas within proxy to the boundary.
Local totals between 3-6" with max to 8" are possible over the area
generally north of Lake Okeechobee up to about Gainsville. This
includes the Orlando metro, so will be monitoring closely for a
possible risk upgrade, but with guidance struggling mightily to
resolve the pattern and potential for surface low generation near
the FL coast, did not want to upgrade too early and will assess
further. For now, the MRGL risk remains.

Kleebauer


Day 3
Valid 12Z Sat Jul 05 2025 - 12Z Sun Jul 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE UPPER MIDWEST AND THE SOUTHEAST...

20Z Update: Little change was necessary for any of the MRGL risk
areas in place across the Upper Midwest and Great Lakes, and across
the Southeast U.S. The Southeast MRGL`s will be contingent on
potential surface low development and/or maturation as that could
allow for focused convergence near the coastal areas of FL/GA/SC
which would enhance the threat of heavier rainfall. This is
depicted within a few of the deterministic, but most of the 12z
suite remains just offshore with the heaviest precip. Until we have
a better consensus, the threat is deemed more MRGL with potential
for upgrades if the synoptic threat materializes and model output
increases in magnitude.

Kleebauer

..Previous Discussions..

...Upper Midwest...
Heavy rain developing Day 2 will continue well into Saturday as the
previously noted shortwave and preceding axis of deep moisture
advance from the Northern Plains into the upper Great Lakes. Model
show PWs at or above 2 inches extending as far north as the
Minnesota Arrowhead and the Michigan U.P. With some signal for
training storms to continue, an upgrade to a Slight across some
parts of the region may be forthcoming if the signal persists and
the models start to show greater agreement.

...Southeast...
With the aforementioned wave expected to move out along the
Southeast Coast, a Marginal Risk was maintained from coastal
Georgia to southeastern North Carolina, where the threat for heavy
rains is expected to increase. A Magical Risk was also maintained
along the west coast of Florida along the trailing inflow and axis
of high PWs.

Pereira


Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt