Mesoscale Precipitation Discussion 1312
NWS Weather Prediction Center College Park MD
530 AM EDT Thu Sep 17 2026

Areas affected...Eastern AZ...Central and Western NM...Southwest
CO

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

Valid 170930Z - 171530Z

SUMMARY...Areas of heavy showers and thunderstorms will continue
to lift northward this morning across the Southwest. Rainfall
rates as high as 1.5 inches/hour and localized cell-training will
maintain a regional threat for flash flooding.

DISCUSSION...The latest GOES-W IR satellite imagery shows a
well-defined and increasingly elongated shortwave trough lifting
north across eastern AZ. This energy along with deep layer
southerly moisture transport and modest instability continues to
focus broken coverage of heavy showers and thunderstorms.

MUCAPE values are as high as 500 to 1000 J/kg, but the moisture is
particularly impressive with values running 2 to 3 standard
deviations above normal and generally in the 95th+ percentile of
climatology. High WBZ heights along with the transport of tropical
moisture northward from mainland Mexico is fostering very
efficient rainfall across the broader Southwest U.S., with locally
enhanced rainfall rates where areas of deeper convection are
situated. Radar and satellite data shows the strongest areas of
convection generally over central NM, but some dynamically
enhanced convection is seen over eastern AZ in closer proximity
the shortwave energy.

The latest guidance lifts the shortwave energy northward toward
the Intermountain West this morning which will bring much of the
broken convective activity northward along with it. Upslope flow
and related orographic ascent over the higher terrain, and
especially into southwest CO, will bring areas of heavy rainfall
that may result in flash flooding. Rainfall rates with any of the
stronger convective elements may reach 1.5 inches/hour, with some
localized additional rainfall totals through mid-morning of 2 to 3
inches given concerns for some cell-training.

A regional threat for flash flooding will continue as a result,
and this will again include the highly sensitive dry wash areas,
along with burn scar locations and slot/box canyons.

Orrison

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

ATTN...RFC...FWR...STR...TUA...NWC...

LAT...LON   38710671 38600544 37340481 35200492 32600555
            31830659 31810780 32670844 32900933 32631062
            33511138 34551139 35811081 36620950 38020818