Mesoscale Precipitation Discussion 1281
NWS Weather Prediction Center College Park MD
502 AM EST Sun Dec 28 2025

Areas affected...northern MO/southeastern IA/north-central
IL/northwestern IN

Concerning...Heavy rainfall...Flash flooding possible

Valid 281000Z - 281600Z

SUMMARY...Isolated flash flooding will be possible from portions
of northern MO, southeastern IA into north-central IL and
northwestern IN through 16Z (10 AM CST). Rainfall of 1 to 2 inches
in an hour will be possible with isolated 3 to 6 hour totals of
2-3 inches.

DISCUSSION...0945Z radar imagery Midwest showed scattered showers
and embedded thunderstorms from northern MO, southern IA and
central IL, located north of a quasi-stationary front that
extended eastward from a 998 mb low just west of Salina, KS. SW to
WSW 850 mb winds of 30-50 kt were in place to the east of the
surface low with overrunning occurring atop the frontal boundary.
OSPO ALPW imagery showed low level moisture rapidly advecting
northward into the central U.S. beneath a plume of mid to upper
level moisture with origins in the tropical eastern Pacific. Total
PW values were estimated to be between 1.1 and 1.4 inches (SPC
mesoanalysis) from eastern KS into western IN, which equate to +4
to +5 standardized anomalies. The low level moisture return was
allowing for the northward advection of instability and erosion of
low level CINH amid 700-500 mb lapse rates of 7.0 to 7.5 C/km,
supporting MUCAPE of 500-1500 J/kg from eastern KS into
western/central MO via 09Z SPC mesoanalysis data. This change in
the thermodynamic environment has been reflected in recent
infrared satellite imagery showing bursts of colder cloud tops
over northern MO and far southern IA.

As the surface low over central KS moves eastward early this
morning, strengthening low level flow will translate into MO and
IL with 850 mb speeds locally exceeding 50 kt. Convergence at the
nose of 925-850 mb moisture transport will align WSW to ENE or
parallel to the mean steering flow. This will set up narrow axes
of heavy rainfall with training and potential for hourly rainfall
between 1 and 2 inches. The best overlap of low level convergence
with moisture/instability will be from northern MO into
north-central IL and northwestern IN through 16Z. Isolated
flash/urban flooding may result from 2-3 inches of rain in 2-3
hours. However, a lack of precipitation for this region of the
U.S. over the past couple of weeks (lower than average soil
moisture) and warmer than average temperatures (no/negligible
frost depth) should limit runoff. Therefore, any flash flood
concerns will likely be minor and remain limited to urban or
sensitive low lying areas.

Otto

ATTN...WFO...DMX...DVN...EAX...ILX...IND...IWX...LOT...LSX...

ATTN...RFC...KRF...MSR...TIR...NWC...

LAT...LON   42178726 41658634 40918612 40448688 40038825
            39629015 39199219 39289312 39699398 40409379
            41329161 42118904