Mesoscale Precipitation Discussion 0074
NWS Weather Prediction Center College Park MD
510 PM EST Wed Feb 28 2024

Areas affected...South-Central to Southeast AZ...Southwest NM

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

Valid 282210Z - 290410Z

SUMMARY...Scattered bands of heavy showers and thunderstorms with
locally heavy rainfall rates may foster an isolated concern for
runoff problems and flash flooding going into the evening hours.

DISCUSSION...The latest GOES-W visible satellite imagery in
conjunction with dual-pol radar has been showing an uptick in the
coverage of convection across areas of south-central to southeast
AZ. A relatively strong and compact mid-level low center/trough is
seen gradually ejecting east-northeast out of far northwest
Mexico, and strong dynamical forcing/divergent flow aloft coupled
with the diurnal heating cycle has been favoring the expansion of
convection and increase in rainfall rates over the last couple of
hours.

MLCAPE values across southern AZ have risen to as much as 500
J/kg, and there are pockets of locally stronger moisture
convergence in place that are seen helping to facilitate some
loosely organized bands of convection around the eastern flank of
the mid-level low center. The visible satellite imagery downstream
of the current activity involving especially southeast AZ has been
reflecting an increasingly agitated CU/TCU field, and this is
reflective of the increase in diurnally enhanced boundary layer
instability.

Despite the dry boundary layer profiles, the 12Z/18Z HREF guidance
supports some localized 20 to 30 percent probabilities of seeing
1"+/hour rainfall rates with some of the stronger convective cells
going through the 00Z to 03Z timeframe. The heaviest rates should
tend gradually shift from south-central AZ into southeast AZ and
southwest NM through early this evening. Given some of the uptick
in convective organization and banded structures, some spotty
storm total amounts of 1.5 to 2.5 inches cannot be ruled out in at
little as 2 to 3 hours.

These rainfall amounts may cause some isolated concerns for runoff
problems and flash flooding, with the normally dry washes/arroyos
in this case being the more sensitive areas to closely monitor.

Orrison

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

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

LAT...LON   33760861 33240777 32530764 32010788 31530831
            31310899 31190960 31201079 31441192 31771256
            32461238 33021150 33690960