Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Sep 19 2025 07:24:09

AWUS01 KWNH 190724
FFGMPD
AZZ000-191200-

Mesoscale Precipitation Discussion 1105
NWS Weather Prediction Center College Park MD
323 AM EDT Fri Sep 19 2025

Areas affected...Central Arizona...

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

Valid 190720Z - 191200Z

SUMMARY...Increasing convective development within some
WAA/upslope out of weakly capped conditionally unstable airmass in
the Sun Valley.

DISCUSSION...GOES-E WV suite depicts a convectively enhanced
shortwave feature along the SE Mohave/W Yavapai county line still
with fairly symmetric outflow and shortwave trough extending
southeastward within the left exit of the strengthening WSW
upper-level jet that is cutting across the Lower Colorado River
Valley and southern Arizona into SW NM.  Lingering surface heating
in proximity to the Phoenix Metro heat island and still enhanced
deeper layer moisture through the valley with some steepening
lapse rates aloft, has maintained a small pocket of 1500-2000 J/kg
of MUCAPE.  The combination of the left exit ascent and DPVA from
the NNE advancing shortwave and trough axis has allowed for veered
700mb flow to ascend isentropically to destabilize into steepening
terrain.

The 925-850mb 15-20kt of ESE to SE flow has maintained the ample
moisture in the lower levels and contributed to the deeper layer
moisture flux convergence to help support the expanding convective
development noted with a few rapidly cooling CBs on 10.3um EIR and
scattered updrafts in the KIWA RADAR domain.  Nose of the deeper
layer moisture in the sfc to 700mb layers on CIRA combined with
the 20-30kts of flow support flux for moisture loading through the
thunderstorms with limited sub-cloud evaporation expected.

As such, localized rates of 1.25-1.5"/hr are possible, though
steering flow is fairly strong even in the diffluent left exit of
the jet, limiting individual cell's residency.  Yet, the upstream
environment and general upslope flow for the passing wave/upper
level divergence should maintain a modest probability for upstream
regeneration to allow for some localized repeating over the next
few hours.  As such spots of 1-2" totals may induce localized
flash flooding concerns particularly near steeper terrain in the
lower slopes of the Mogollon Rim or near any burn scars that dot
the area of concern.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!--W3iV5M4FZouwYySjHKU6ZDNK82yAOMwPoClkgJR6gZafLjH21XCVYhU8ZuEVMGCbl2=
jBmEhjNWUdH4hMTPGHWMXr8$  for graphic product...

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

ATTN...RFC...STR...NWC...

LAT...LON   35001160 34981079 34421008 33530971 32880979=20
            32641024 32631110 33001168 33591217 34371218=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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