930
AWUS01 KWNH 291944
FFGMPD
COZ000-NMZ000-AZZ000-300143-

Mesoscale Precipitation Discussion 0513
NWS Weather Prediction Center College Park MD
343 PM EDT Sat Jun 29 2024

Areas affected...Portions of the Southwest U.S.

Concerning...Heavy rainfall...Flash flooding likely

Valid 291943Z - 300143Z

SUMMARY...Increasing coverage of showers and thunderstorms with
locally enhanced rainfall rates will likely result in at least
scattered instances of flash flooding this afternoon.

DISCUSSION...The midday GOES-E visible satellite imagery shows a
fair amount of cloud cover over areas of east-central AZ in
connection to a slow-moving MCV that is seen lifting north around
the western periphery of the subtropical ridge over the southern
Plains. However, convection is beginning to initiate with the aid
of differential heating boundaries and orographic ascent. As
additional boundary layer destabilization ensues via strong
diurnal heating, there will be increasing coverage of showers and
thunderstorms over the next several hours.

Already the airmass is quite unstable across areas of eastern NM
which is expected to drive concerns for more focused convective
activity by later today across the Sacramento Mountains and
especially the Sangre De Cristo Mountains farther to the north.
SBCAPE values the eastern flanks of the terrain here are already
as high as 2000 to 3000 J/kg and with rather moist upslope flow.
Areas of north-central to northeast NM in particular have added
concerns today of a cold front arriving down from the north and
northeast. Convergence along the front and moist post-frontal flow
into the terrain will be conducive for convection eventually that
is relatively focused and potentially anchored close to the
terrain.

SBCAPE values of 1000 to 2000 J/kg are seen currently over areas
of central AZ in close proximity to the aforementioned MCV, and
this instability will further drive an uptick in locally
slow-moving and rather efficient thunderstorms capable of
producing high rainfall rates. The PW anomalies over the Southwest
are greatest from southern AZ northeastward through north-central
NM, and are locally 2 to 3 standard deviations above normal.

Rainfall rates will likely reach 1 to 2 inches/hour with the
stronger storms, and with slow cell-motions and locally focused
convection near some of the higher terrain in general, there may
be some storm totals that reach 2 to 4 inches. This will likely
result in at least scattered instances of flash flooding going
through the afternoon hours. The normally dry washes and areas
that are near and adjacent to burn scars will be the most
susceptible to enhanced impacts and flash flooding which may
include debris flow activity.

Orrison

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

ATTN...WFO...ABQ...EPZ...FGZ...GJT...PSR...PUB...TWC...

ATTN...RFC...ABRFC...CBRFC...WGRFC...NWC...

LAT...LON   37310558 37130433 36260410 34960501 33500538
            32330573 32000742 32770943 33421093 34771207
            35821170 36491053 36880861 36900714