819
AWUS01 KWNH 210223
FFGMPD
AZZ000-210700-

Mesoscale Precipitation Discussion 0475
NWS Weather Prediction Center College Park MD
1023 PM EDT Thu Jun 20 2024

Areas affected...Southeast Arizona...

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

Valid 210225Z - 210700Z

SUMMARY...Developing thunderstorms with ample moisture flux may
pose quick 1-2" totals and localized possible flash flooding
conditions over the next few hours.

DISCUSSION...Surface analysis depicts strong moisture surge
continues through the desert southwest ahead of the tropical
wave/gyre associated with former Alberto. Strong 20-25kt surface
flow from the east-southeast across SW NM into SE AZ has reached a
north-south barrier from upslope flow coming out of the Sonoran
Desert upslope, resulting in strong moisture flux convergence.
Modest mid-level lapse rates support some 1000-1500 J/kg of CAPE
across the region to support/maintain stronger updrafts at the
collision region.  While moisture at the surface is in the 50s, it
is the 850-700mb layer with .6-.75" along with the stronger winds
that place the moisture flux at the 99th to maximum percentile
with respect to time of year for the CIRA ALPW suite; while totals
are in the 1.25-1.4 range.  There will be obvious sub-cloud
evaporative loss with some upslope mixing of drier air, rates of
1.5"/hr are probable given the moisture flux and updraft strength.

Duration will be key for any potential localized flash flooding
and given 20kts of south to north mean cell motions, this will
increase duration to allow for localized 1-2".  Effective bulk
shear is above 30kts and should provide some longevity to the
cells as well; and given orientation of steering flow to the
north-south convergence line there is a low to moderate potential
for some cells to cross similar paths.  As such, an isolated spot
of 2"+ remains possible before the pocket of instability wanes.
As such, a spot or two of localized flash flooding is considered
possible through the early overnight period.

Gallina

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

ATTN...WFO...FGZ...PSR...TWC...

ATTN...RFC...CBRFC...NWC...

LAT...LON   34851035 34710951 34370910 33770910 33040940
            32230990 31481017 31431073 32381118 33841146
            34571113