FOUS30 KWBC 310825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Sun May 31 2026

Day 1
Valid 12Z Sun May 31 2026 - 12Z Mon Jun 01 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN ROCKIES AND THE SOUTHEAST UNITED STATES...

Northern Rockies...
With rainfall on-going from Saturday due to a slow moving mid- and
upper-level system over the northern Rockies...opted to keep 
portions of Montana and nearby Wyoming and the far western Dakotas 
in a Slight Risk area during the new Day 1 period. The expectation 
is that rainfall intensities will not be as high as they were on 
Saturday but the cumulative effect of an additional 1+ inch amounts
on top of what has already fallen has the potential to produce 
flooding concerns today. The Slight risk area was extended into far
western South Dakota where MRMS showed 3+ inches having fallen on 
Saturday evening and was susceptible to flooding from even modest 
rainfall amounts.

Southeast US...
Also introduced a Slight Risk area over portions of the Southeast
US where some model agreement has developed...although the
agreement was far from unanimous. Neither the HREF or RRFS showed 
a strong signal for exceedance of flash flood guidance but showed 
about 20 percent neighborhood probabilities of rainfall exceeding 2
inches. At the same time...a spaghetti plot of SREF QPF showed 
decent amount of ARW members with QPF at 2 inch and 3 inch amounts.
That was largely supported by the GEFS. Given the 2 to 2.25 inch 
precipitable water values and the amount of instability in the area
that could support intense rainfall rates...opted to include a 
Slight Risk at this point.

Elsewhere...maintained the broad and largely unfocused Marginal
Risk area in between given the lack of clear forcing mechanism, the
light flow aloft and the broad pool of instability along and south
of a quasi-stationary boundary.  

Bann


Day 2
Valid 12Z Mon Jun 01 2026 - 12Z Tue Jun 02 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN ROCKIES AND PARTS OF THE PLAINS...

Northern Rockies... 
Introduced a Marginal Risk area in the northern Rockies where
moisture/precipitation lingers as a slow moving mid- and upper- 
level system pulls away. The concern is not so much for rainfall 
intensity at this point but for the cumulative effect of the 
additional rain on top of what has fallen in the previous few days.
The concern is also fairly limited in terms of duration as 
rainfall does come to an end during the middle- to latter-part of the period.

Western High Plains...
Also introduced a Marginal Risk area mainly in the western portion
of Kansas/Nebraska as an axis of low level moisture begins to 
return northward during the day. Placement of the QPF and any 
associated risk of excessive rainfall remains somewhat tenuous. 
Concern is that the instability should be enough that the QPF 
amounts approaching or exceeding 2 inches from the UKMET/NAM and 
GFS would be delivered quickly. A

Southeast US...
Portions of the Mid-South/Southeast may also be at-risk for 
Excessive Rainfall, but guidance remains murky on where storms will
initiate. Given these reasons, the Day 2 ERO remains free of risk 
areas for the time being.

Mullinax/Bann


Day 3
Valid 12Z Tue Jun 02 2026 - 12Z Wed Jun 03 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
NEW MEXICO AND A SMALL PORTION OF WEST TEXAS...

A plume of Gulf-sourced moisture will be drawn northward into the 
southern Rockies/drifting east over the southern High Plains/west 
Texas to maintain a Slight Risk area for excessive rainfall on
Tuesday into Tuesday night from portions of New Mexico into west 
Texas. Farther north...warm moist air will advect along a low 
level convergence zone with early June heating that has the 
potential for locally heavy rainfall over portions of the western
High Plains into the Dakotas.

Bann
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