Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Thu Mar 30 2023

Day 1
Valid 12Z Thu Mar 30 2023 - 12Z Fri Mar 31 2023

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PARTS OF
THE UPPER MIDWEST...

A vigorous deep-layer trough traversing the Great Basin and
Southwest today will lift across the central-southern Rockies and
High Plains tonight and early Friday. Increasingly difluent
upper-levels across the Upper Midwest will make for a more
favorable environment for deep-layer ascent, particularly later
tonight as the the models depict an enhanced right-entrance region
of a departing northern stream jet streak (of 130+ kts). A rapid
increase in low- to mid-layer moisture transport from the western
Gulf of Mexico is expected, as 850-700 mb moisture flux anomalies
climb quickly to between 4 and 5 standard deviations above normal
tonight into early Friday (on the heels of robust SSW 850 mb flow
of 50-60 kts). On the nose of that strong flow, enough instability
(500-1000 J/kg of MUCAPE) and convergence will materialize to
support deep convection that may become surface-based along the
warm front across northeastern Nebraska and vicinity this evening
before migrating east-northeastward into a slightly more stable
airmass. The orientation of convection could allow for spotty
areas of convective training, with FFG thresholds generally around
1"/hr supporting isolated potential for excessive runoff. The main
limitation to a higher excessive rainfall threat is the transient
upper flow pattern, with the progressive closed 500 mb low and
associated surface frontal features (along with relatively dry
antecedent conditions, per NASA SPoRT-LIS 0-40 cm soil moisture
anomalies at or below the 10th percentile for much of the region).
Such a pattern, one without the benefit of more prolonged low-mid
level frontogenesis, would limit the risk of cell training (though
that starts to become more of a factor going into Day 2).

Churchill/Hurley/Cook


Day 2

The Day 2 outlook will be updated by 0830Z.


Day 3

The Day 3 outlook will be updated by 0830Z.


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