Graphic for MPD #0053

Mesoscale Precipitation Discussion 0053
NWS Weather Prediction Center College Park MD
408 PM EST Tue Feb 06 2024

Areas affected...lower CO River Valley into western AZ

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

Valid 062106Z - 070300Z

Summary...Areas of flash flooding may develop across western AZ
back to far southeastern CA through 03Z. Shallow convective cells
are expected to develop later this afternoon with areas of
training after 00Z. Rainfall rates of 0.5 to 1.0 in/hr will be
possible within areas of training but may locally exceed 1 in/hr.

Discussion...2030Z GOES West water vapor imagery showed a
neutrally oriented and elongated mid to upper level trough
extending from northern CA into the eastern Pacific, just west of
120W. The trough was moving east with a dry slot noted from
northern Baja California into eastern CA/western AZ and southern
NV. Low level moisture advection was occurring just ahead of the
dry slot a seen on layered PW imagery from the lower CO River
Valley into western AZ. However, an 18Z sounding from Yuma showed
zero instability despite a precipitable water value just over 1
inch, due to a relatively warm 700-500 mb layer.

Forcing for ascent will increase as the upper trough axis to the
west continues to push eastward over the next 6 hours. Cooling of
the 700-500 mb layer should allow instability to increase with
recent forecasts from the RAP/HRRR showing up to ~500 J/kg MLCAPE
developing through 00Z over western AZ. Aloft, the left exit
region of a strong upper level jet max (~150 kt at 250 mb) is
forecast to maintain favorable lift over western AZ. An increase
in shallow convective cells is anticipated to occur near 00Z in
the vicinity of the lower CO River Valley, with expansion into
western AZ through 03Z. While steering flow should keep individual
elements moving along at 3o to 40+ kt toward the NNE, this
orientation is expected to align with a slow moving axis of
similarly oriented convergence in the 850-700 mb layer over
western AZ, allowing for training. In addition, roughly 30 kt of
700 mb flow will focus an upslope component to the flow into the
Mogollon Rim, supporting enhancement of rainfall below ~7000 ft.
While precipitable water values are forecast to decrease beyond
00Z with the eastward translation of the low level moisture axis,
a brief window of overlap with higher instability/moisture could
allow for 0.5 to 1.0 in/hr rates (perhaps locally higher) to
support some 1 to 2+ inch totals through 03Z and possible flash
flooding from the lower CO River Valley into western AZ.

Otto

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

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

LAT...LON   35861385 35721317 35331278 35021227 34941182
            34511177 33831221 32771288 32031353 32101427
            32531504 33491513 34091493 34901458 35701453
            35851419
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Last Updated: 408 PM EST Tue Feb 06 2024