Mesoscale Precipitation Discussion 0996
NWS Weather Prediction Center College Park MD
1202 PM EDT Tue Oct 23 2018

Areas affected...Southeast Arizona...Southwest New Mexico

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

Valid 231600Z - 232200Z

Summary...As instability builds across the region through the
afternoon, convection is expected to increase in coverage and
intensity. This will pose a localized flash flood threat with
maximum totals of 1-2" possible through 22z.

Discussion...Recent water vapor imagery and 500 mb heights showed
a well-defined shortwave across far southern California and
southwest Arizona with broad diffluent flow ahead of it across
much of AZ and NM. The 12z EPZ and TUS soundings showed PWATs of
around 1.1", which is roughly 2-3 SD above the mean for this time
of year. Finally, a recent mesosanalysis showed MLCAPE of
1000-1500 J/kg where scattered convection has been ongoing since
earlier this morning. Recent observations show a few locations
have received around 0.5" in about an hour.

Through this afternoon convection is expected to increase in
coverage and intensity as instability builds further across the
region. This will coincide with the approach of the mid/upper
level shortwave trough, enhancing the forcing for ascent. The
850-300 mb flow is unidirectional which combined with an increase
in moisture will allow the potential for training convection
across the area. 

12z HREF probabilities for exceeding 1" are maximized across far
southeastern Arizona and southwest into south-central New Mexico.
Totals 1-2" (with locally higher amounts) will be possible by
early afternoon. Given wet antecedent conditions (parts of AZ/NM
running 200-300 percent of normal last 7 days) and lower FFG (1-hr
1-1.5"), there is increased confidence for localized flash flood
threats across the area.   

Taylor

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

ATTN...RFC...CBRFC...WGRFC...

LAT...LON   35260799 34180606 32880580 31570639 30961094
            32961167 35091123