Subj : HVYRAIN: Excessive Rainfa
To   : All
From : Mike Powell
Date : Tue Apr 18 2023 17:19:00

FOUS30 KWBC 182004
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
402 PM EDT Tue Apr 18 2023

Day 1
Valid 16Z Tue Apr 18 2023 - 12Z Wed Apr 19 2023

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Jackson


Day 2
Valid 12Z Wed Apr 19 2023 - 12Z Thu Apr 20 2023

....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE
CENTRAL PLAINS TO THE UPPER MISSISSIPPI VALLEY...

Showers and thunderstorms are expected to develop ahead of a cold
front over eastern portions of the Central Plains early Wednesday
evening before expanding southwest to northeast through the night
from eastern Kansas through Wisconsin. Higher QPF is forecast to
setup over eastern Kansas through southern Iowa where there is
better alignment of deep layer flow with the slow moving cold
front with instability (CAPE values of 1000-1500 J/kg). There is a
risk for rainfall rates over 1"/hr per the 12Z HREF. While KS will
have the most instability, antecedent conditions are most
favorable for flash flooding in Wisconsin due to added snowmelt
from the recent winter storm over the western half of the state.
Furthermore, some rainfall is expected tonight over southeast Neb
and IA which could aid preconditioning. The Marginal Risk was
refined just a bit from eastern Kansas through Wisconsin based on
the 12Z model consensus.


Jackson

Day 3
Valid 12Z Thu Apr 20 2023 - 12Z Fri Apr 21 2023

....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FROM NORTHEAST
TEXAS TO THE MID-SOUTH...

Gulf moisture will continue to advect northward and pool ahead of
a cold front pushing southeast from the central Plains. PW values
of 1 to 1.75 inches (1.5 to 2 sigma) will in place ahead of the
frontal boundary as it approaches the Mid-South and eastern Texas
Thursday afternoon. Continued southwesterly deep layer flow, which
will be nearly parallel to the front will be conducive for storms
repeating with some backbuilding of convection. Based on the 12Z
guidance consensus, the Slight Risk area was maintained/focused a
bit from northeast Texas to the Mid-Mississippi Valley where areal
averages of 1 to 3 inches are forecast. QPF across the Upper
Mississippi Valley/Great Lakes region are closer to the 1 inch
range, but FFG will remain lower due to recent rains (and snowmelt
in the Upper Midwest), thus keeping an elevated threat for
flooding concerns. The Marginal Risk continues to span from
eastern Texas to the Upper Peninsula of Michigan.

Jackson

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