MESO: Heavy rain - AR/MO
From
Weather Alert@454:1/105 to
All on Sat Sep 3 09:30:00 2022
AWUS01 KWNH 030938
FFGMPD
MOZ000-ARZ000-031535-
Mesoscale Precipitation Discussion 0926
NWS Weather Prediction Center College Park MD
537 AM EDT Sat Sep 03 2022
Areas affected...Northeastern AR...Southeastern MO
Concerning...Heavy rainfall...Flash flooding likely
Valid 030935Z - 031535Z
Summary...Training showers and thunderstorms with 1-2"+/hr
rainfall rates will likely support localized streaks of 2-3"+
accumulations, isolated to widely scattered instances of flash
flooding.
Discussion...Convection has been gradually organizing and
strengthening this morning near the base of a stalling shortwave trough/upper-level low along the MO/AR border region. As this
synoptic scale feature becomes wedged between two large scale
ridges situated over both the western CONUS and Eastern Seaboard,
a mesoscale region of persistent low-level moisture
transport/convergence seems to be developing near the base of the aforementioned trough (spcifically over portions of northeastern
AR and southeastern MO). The environment in this area is currently characterized by 500-1000 J/kg of MU CAPE, precipitable water
values of 1.8-2.0 inches (near or above the 90th percentile per
LZK sounding climatology), and effective bulk shear of 20-25 kts.
This anomalously moist air mass is supporting rainfall rates of
1-2"+/hr in the heaviest showers and thunderstorms, as SW to NE
training near the border region is allowing for localized 2"/hr
exceedance.
Hi-res model guidance from overnight suggests that the threat for
localized training of heavy showers and thunderstorms will persist
for much of the morning across portions of northeastern AR and
southeastern MO. 00z HREF 2" neighborhood exceedance probabilities
(over 3-hr) are as high as 40-60%, with more recent HRRR runs also
consistently depicting streaky localized totals of 2-3"+ (though
15z). With the expectation for 1-2"+/hr rainfall rates to
continue, much of the expected rainfall will occur in as little as
1-2 hours. As 1-3 hr flash flood guidance locally is as low
1.5-2.0", isolated to widely scattered instances of flash flooding
are considered likely.
Churchill
ATTN...WFO...LSX...LZK...MEG...PAH...SGF...
ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC...
LAT...LON 37649053 37258991 36668986 36079009 35649043
35139121 35089241 35749242 36439189 36719176
37149195 37569163
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