448
AWUS01 KWNH 090007
FFGMPD
KSZ000-COZ000-090600-

Mesoscale Precipitation Discussion 0410
NWS Weather Prediction Center College Park MD
806 PM EDT Sat Jun 08 2024

Areas affected...far Eastern Colorado, much of Kansas

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

Valid 090004Z - 090600Z

Summary...Widespread thunderstorms in eastern Colorado will likely
merge into an MCS this evening and move west to east across
Kansas. Rainfall rates of 2-3"/hr are likely, which could produce
2-4" of rain with locally higher amounts. Flash flooding is
possible.

Discussion...The regional radar mosaic this afternoon shows
widespread thunderstorms moving across eastern Colorado with
embedded supercells containing radar-estimated rain rates of 1.5
to 2 inches per hour. These thunderstorms are expanding in a
region of ascent forced via easterly upslope flow and through
low-level convergence along a stationary front. A convectively
enhanced shortwave racing through the flow from the west is also
contributing ascent to the area. This resulting impressive lift is
occurring into robust thermodynamics to support heavy rainfall,
with PWs reaching 1.3 to 1.5 inches, overlapping a ribbon of
MLCAPE of 2000-3000 J/kg. The greatest instability and moisture is
currently pooled over central/eastern KS, but persistent E/SE flow
between 925-850mb will draw these more elevated thermodynamics to
the west to support intensification and expansion of thunderstorms
as they emerge from CO.

As convection pushes east this evening, it will encounter bulk
shear above 50 kts, supporting MCS development as storms move
across Kansas. There is good model and ingredient support for this
evolution, so confidence is high in this progression, and rainfall
rates within this MCS will likely (40-60% chance) exceed 2"/hr,
with short term rates of 3+"/hr possible. This MCS may become
forward propagating as it tracks to the east, so rainfall duration
may be somewhat muted. However, downstream of this MCS an
increasing LLJ reaching 25-30 kts from the S/SW will efficiently
merge into a convergence axis along the nose draped west to east
across KS. With this LLJ resupplying ample moisture and
instability into the region, additional thunderstorm development
along this axis and ahead of the MCS is likely as shown by most
available high res CAMs. Thunderstorms that develop along the LLJ
will feature repeating rounds, and with rain rates here also
likely reaching 1-2"/hr, where this convection overlaps with the
MCS sweeping through later in the evening, some areas may receive
2-4" of rain with locally higher amounts.

Parts of KS have received more than 200% of rainfall the past 7
days according to AHPS, and although the coverage is variable,
this has reduced FFG to below 2"/3hrs in many areas. The HREF 3-hr
FFG exceedance probabilities peak above 40%, highest across areas
that get both LLJ thunderstorms and the MCS, but 0-10cm RSM from
NASA SPoRT is only 25-35%. This could limit the FF risk at least
somewhat, so it appears instances are possible, but additional
MPDs may be needed to address a greater FF risk later tonight.

Weiss

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...DDC...GID...GLD...ICT...PUB...TOP...

ATTN...RFC...ABRFC...MBRFC...NWC...

LAT...LON   39670153 39300028 38919855 38799696 38359569
            38049549 37789553 37559560 37299599 37179681
            37109824 37080013 37230163 37720245 38960311
            39660264