FOUS30 KWBC 050817
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
417 AM EDT Fri Jun 5 2026

Day 1
Valid 12Z Fri Jun 05 2026 - 12Z Sat Jun 06 2026

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
EASTERN NEBRASKA/KANSAS INTO THE MID-MISSISSIPPI VALLEY AS WELL AS
MUCH OF TEXAS/SOUTHERN OKLAHOMA...

...Eastern Nebraska/Kansas to Mid-MS Valley...

A northern stream shortwave with multiple embedded vort maxes will
move through the Midwest Friday and provide lift for convection.
First, convection and potential for flash flooding looks to be
ongoing as the period begins 12Z Friday morning generally near the
Iowa/Missouri and Iowa/Illinois border. This also sends
precipitation into Wisconsin and Lower Michigan in the morning to
early afternoon, but ahead of the influx of instability, so this is
a more Marginal flood threat. The next and likely stronger energy
in the shortwave, along with a cold front slowly shifting
southward, will help develop another round of storms beginning in
the afternoon and likely becoming enhanced in the evening and
overnight hours. The HREF and its members as well as the REFS show
this should be centered in southeastern Nebraska and northeastern
Kansas to southern Iowa, with periods of QPF exceeding FFG (HREF
and REFS probabilities 20-50% for FFG exceedance). A Slight Risk
remains reasonable for this activity, but upgrades are not out of
the question if training looks to overlap with the currently
ongoing (Thursday night) convection.

...Texas to Southern Oklahoma...

A compact southern stream upper low is forecast to drift from 
northern Mexico across Texas during the Day 1 period. This lifting 
mechanism will be paired with precipitable water anomalies in the 
90-95th percentile in the southern Plains. There is some 
uncertainty in magnitude of instability due to cloud cover, but 
models show CAPE being sufficient at generally 1000-3000 J/kg, with
the low aloft helping steepen lapse rates. Scattered convection 
that has the ingredients for flash flooding is likely to occur, so 
went with an upgrade to a broad Slight Risk in this issuance. The 
exact focus for the heaviest rain remains somewhat elusive, but 
there is some signal in the CAMs for east-central Texas. Also 
included areas to the west in the Slight, to include some of the 
typically more sensitive/lower FFG areas in the Hill Country to 
Concho Valley and Permian Basin. The Marginal Risk stretches back 
into New Mexico where there are some sensitive areas like burn scars.

...Central Gulf Coast...

A disturbance likely in the form of a trough at low levels is
forecast to drift slowly toward the central Gulf Coast,
specifically southeastern Louisiana and southern Mississippi. With
moisture anomalies over the 90th if not the 95th percentile and
sufficient instability, intense rain rates could lead to a flooding
threat in the form of a Marginal Risk. Though typically not a very
sensitive area to flash flooding, antecedent wet conditions could
enhance the potential. The back end of the trough could also lead
to heavy rain in the Florida Keys, with the HREF and REFS
neighborhood probabilities of reaching over 5 inches of rain
greater than 60 percent, but considering the possibility the
heaviest rain could be offshore and how much rain the Keys can
handle with the sandy soils, held off on any risk area.

Tate


Day 2
Valid 12Z Sat Jun 06 2026 - 12Z Sun Jun 07 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHERN PLAINS TO MISSISSIPPI VALLEY...

...Southern Plains/Mississippi Valley...

The meteorological setup on Saturday across the south-central U.S.
will be similar to Friday, through with the compact upper low
gradually tracking north across the southern half of the Plains.
The continued enhanced moisture and instability will yield an
environment favorable for convection with intense rain rates
causing flash flooding concerns. Areas farther north into Oklahoma
should see stronger forcing, while the low level jet could be
maximized farther south into Texas. Thus covered all this area with
a Slight Risk. REFS probabilities (which extend through the Day 2
period) show scattered instances of QPF potentially exceeding FFG.
Smaller scale boundaries leftover from thunderstorms on previous 
days could provide areas of focus that would likely be unclear 
before the near term.

...Central Gulf Coast...

By Saturday the surface/low level trough mentioned in the Day 1
discussion should reach the central Gulf Coast during the day, and
produce heavier QPF on land compared to Friday. Once again,
antecedent conditions in the region are not typically sensitive,
but are wetter than normal. REFS probabilities of exceeding FFG are
20-40% in southeast Louisiana, so will continue to monitor if slow
storms/training are likely to cause more Slight Risk level impacts
and need an upgrade.

...Ohio Valley...

The northern stream shortwave is forecast to push through the Great
Lakes/Ohio Valley and Northeast on Saturday, with a frontal system
ahead of it. The front should lay west to east across the Ohio
Valley, so scattered storms could train and cause isolated flash
flooding. The Northeast can also expect some convection, but likely
progressive enough to limit flash flood potential to below a
Marginal. In this ERO issuance, connected the Plains and Ohio
Valley Marginal Risks together. There is some potential for storms
back into northern Missouri and vicinity, which could be very wet
after multiple rounds of convection, so wanted to cover that area.

Tate


Day 3
Valid 12Z Sun Jun 07 2026 - 12Z Mon Jun 08 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHERN/CENTRAL PLAINS TO LOWER/MIDDLE MISSISSIPPI VALLEY...

Into Sunday, southern stream energy will continue to push north 
through the central/northern Plains and Midwest while opening up 
into a trough. This will once again provide forcing for 
thunderstorms in the Plains and Mississippi Valley. A low level jet
of 30-40 kt should bring instability and moisture into the region.
The best overlap of ingredients for flash flooding, supported by 
GEFS/ECens probabilities for over an inch of rain, will likely be 
centered over Missouri south into Arkansas and west into eastern 
parts of Kansas and Oklahoma, so this is where the Slight Risk is 
drawn for Day 3. Some convection could linger farther south toward 
the Gulf Coast, which the Marginal covers. By Sunday night, a 
northern stream trough with a strong vort max is forecast to push 
into the northern High Plains, bringing enhanced QPF ahead of it 
for a Marginal Risk stretching through portions of the Dakotas and 
western Minnesota.

Tate
$$
--- SBBSecho 3.28-Linux
 * Origin: Capitol City Online (618:250/10)