968
AWUS01 KWNH 081959
FFGMPD
KSZ000-NEZ000-COZ000-WYZ000-090000-

Mesoscale Precipitation Discussion 0408
NWS Weather Prediction Center College Park MD
358 PM EDT Sat Jun 08 2024

Areas affected...Portions of the Central High Plains

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

Valid 081957Z - 090000Z

Summary...Organizing showers and thunderstorms will move east into
the Central High Plains through this evening. Rainfall rates of
more than 2"/hr are likely, which through short-term training
could produce 2-3" of rain with locally higher amounts. Flash
flooding is possible.

Discussion...The GOES-E clean IR imagery this afternoon shows
expanding cloud tops that are cooling rapidly to nearly -60C
across eastern and central Colorado. These thunderstorms are
blossoming within favorable thermodynamics characterized by PWs of
0.8-1.0 inches and a ribbon of SBCAPE exceeding 2500 J/kg. These
thermodynamics are being acted upon by increasing ascent as a
potent shortwave noted in the WV imagery dropping out of Idaho
approaches from the west, driving downstream height falls and
divergence, which is overlapping increased upslope flow as
easterly winds advect atop a stationary front and lift into the
terrain. Together this is resulting in the expanding thunderstorm
coverage, and recent radar-estimated rain rates have already
reached 1.5"/hr according to KFTG WSR-88D.

During the next few hours, convection is expected to expand and
intensify as forcing for ascent increases and moisture/instability
continues to surge on the E/SE flow out of the Plains. This is
evident in simulated reflectivity from the available high-res
members, which is additionally supported by nearly 100%
probabilities in the SPC HREF for widespread coverage of >40dbZ
reflectivity shifting east through this evening. Additionally,
0-6km bulk shear values rise steadily to the east, reaching 40-50
kts into the northeast High Plains of CO, which will support more
rapid storm organization, and there is high confidence in MCS
development this evening. The combination of storm organization
and persistently robust thermodynamics will support rainfall rates
that have a 20-30% chance of exceeding 2"/hr according to the HREF
neighborhood probabilities. Despite propagation vectors that are
generally 30 kts to the east, some training is likely as these are
aligned to the 850-300mb mean winds, supporting the accumulation
of 2-3" of rainfall with locally higher amounts progged by HREF
3"/6hr probabilities reaching 10-20%.

Soils are generally dry across the Central High Plains at this
time, with 0-10cm RSM from NASA SPoRT being just 20-30% due to
7-day rainfall that has been only 25-50% of normal. This is
resulting in generally elevated FFG, but there still exist pockets
as low as 1-1.5"/3hrs which has a 10-20% chance of exceedance.
While the greater flash flood risk appears to be focused later
this evening and farther east, for the next several hours any
training or more intense rainfall rates could produce isolated
instances of runoff and flash flooding.

Weiss

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

ATTN...WFO...BOU...CYS...GLD...LBF...PUB...

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

LAT...LON   41610460 41480357 40990217 40910206 40430155
            39770142 39100171 38760230 38760299 38830360
            39230434 39730473 40640530 40890544 41500537