899
AWUS01 KWNH 141759
FFGMPD
COZ000-NMZ000-AZZ000-UTZ000-150000-

Mesoscale Precipitation Discussion 1282
NWS Weather Prediction Center College Park MD
158 PM EDT Mon Sep 14 2026

Areas affected...Eastern AZ..Western & Central NM...Southwest
CO...Far Southeast UT...

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

Valid 141800Z - 150000Z

SUMMARY...Increased moisture within confluent low level return
flow resulting in scattered monsoon thunderstorms with rates of
1-1.5"/hr and localized spots of up to 2" totals and possible
flash flooding.

DISCUSSION...GOES-E WV suite denotes tightening of abnormal return
moisture stream from the sub-tropical Pacific and some weak Gulf
influence through northern Old Mexico becoming confluent across
the AZ/NM borderlands.   CIRA LPW and RAP analysis notes enhanced
absolute moisture values with 850-700mb moisture around and above
.75" reaching as far north as the E San Francisco Plateau, while
700-500mb, also well above normal over .5"-.6" but centered a bit
further east along and east of the SE AZ border into central NM.
With strengthening ridge to southeast and upstream jet/shortwave
energy across the Great Basin, this will further tighten
vertically as well as increase over moisture flux. Current
placement of right entrance to 70+ kt 3H jet over the Four Corner
region is providing stronger ascent for increased over coverage at
this time. CIRA LVT values are much higher in the stronger jet
further north in the Central Rockies, but with 700mb flow
increasing to 20-25kts through the moisture axis should support
more than sufficient flux near cloud base for efficient rainfall
production.

Surface observations rising into the low to mid 90s already in the
south and 70s+ over the northern Plateau, has seen a steady
increase of MLCAPEs across the region with a slow erosion of CINH
from the Four Corners southward.  MLCAPE values of 2000 J/kg still
remained a bit more capped in SE AZ and are expected to further
increase toward 2500-3000 J/kg toward peak heating.  As such,
mountain circulation convection is starting to develop (including
through the Sacramento Range at the far periphery of the best
moisture) and will slowly increasing in efficiency as initial
downdrafts saturate the sub-cloud drier air, but as secondary
development converging outflow boundaries will increase the
overall coverage and rainfall efficiency toward 21-22z.  Rates of
1"/hr will increase to 1.5"/hr and while mean flow is fairly solid
at 20-30kts toward the north-northeast, cell motions will remain
fairly parallel to the moisture and instability axis for a few
accidental/random repeats that may allow for isolated to widely
scattered incidents of up to 2"+.  Given strength of
updrafts/downdrafts and resulting rain-rates over hard/rocky
ground conditions similar widely scattered to scattered incidents
of flash flooding will be considered possible through the
afternoon into evening hours.

Gallina

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

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

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

LAT...LON   38140748 37180632 36800512 34990521 34080505
            33200493 32770542 32850584 33210665 32690724
            31710787 31280807 31200944 31251123 31611215
            32351232 33391155 34121173 35111192 35951157
            36791093 36990997 37700976