Mesoscale Precipitation Discussion 0914
NWS Weather Prediction Center College Park MD
1110 PM EDT Mon Oct 01 2018

Areas affected...Southern Arizona

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

Valid 020309Z - 020839Z

Summary...Moisture associated with TS Rosa lifting north-northeast
into southern Arizona through tonight will bring locally heavy
rain and intense rainfall rates which may lead to localized flash
flooding.

Discussion...KYUX radar returns show an uptick in reflectivity
along and south of the US/Mexico border. While some cloud tops
have warmed, there remains a pocket of cooling per latest GOES IR
imagery. While the center of TS Rosa remains southwest of the rain
shield, moisture lifting within broad southwesterly flow will
continue streaming north-northeast over the next several hours.

A recent mesoanalysis shows PWATs locally 2" near Yuma, which
matches well with GPS TPW product. The highest SBCAPE is centered
south of the area but the 500-1000 J/kg line does extend northward
into southern and south central AZ. 700 mb flow is impressive with
25 to 30 kts and is expected to increase to over 35 kts within the
the next several hours.

There is decent agreement in the hi-res models of convection
pushing slowly northward into southern Arizona. How far north is
more uncertain with recent runs of the HRRR holding back and
keeping the highest rainfall amounts near the border. This is a
trend seen in the ARW and NMM as well. Given this, it is believed
that the highest flash flood threat will be confined to extreme
southern Arizona with a more localized threat further north into
portions of central AZ overnight. Given the past 24 hours of
rainfall (pockets of 1-2" already) and low FFG, flash flooding
will become possible across the area.

Taylor

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

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

LAT...LON   33821427 33661234 32581192 31671207 31411278
            31751397 32101485 32341489 32721472 33181461