U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 221250 
Storm Prediction Center ac 221249 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0749 am CDT Mon Oct 22 2018 

Valid 221300z - 231200z 

..there is a marginal risk of severe thunderstorms this afternoon 
for parts of eastern and northern Arizona... 

Isolated large hail will be possible, mainly later this afternoon 
across parts of eastern and northern Arizona. 

A relatively dry/stable Continental air mass will dominate much of 
the conus, while a slow-moving midlevel trough persists over the 
southwest. One embedded shortwave trough is now rotating 
northeastward over the lower Colorado River valley, and should reach Utah 
later this afternoon into tonight. 

..parts of eastern and northern Arizona mainly 20z to 00z... 
Ongoing elevated convection in clusters from southeastern 
Nevada/southwestern Utah to southeastern Arizona is related to ascent with the 
shortwave trough over the lower Colorado River valley. There have been 
only minor changes in low-midlevel moisture and midlevel lapse rates 
across Arizona (at tus and fgz) compared to yesterday morning, though 
slight midlevel warming in the wake of this morning's wave will tend 
to reduce midlevel lapse rates a little from the rim southward 
compared to Sunday. The storm environment will be characterized by 
sufficient buoyancy (mlcape of 500-1000 j/kg with afternoon surface 
heating) and vertical shear (effective bulk shear of 30-35 kt) for 
organized storms and isolated supercells/storm splits. Despite some 
weakening of ascent by this afternoon south of the rim, at least 
isolated storm coverage is still expected where buoyancy will be 
larger. The strongest storms could produce isolated large hail and 
gusty outflow winds. 

.Thompson/Peters.. 10/22/2018 


Mesoscale Discussion

acus11 kwns 212027 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 212026 

Mesoscale discussion 1589 
National Weather Service Storm Prediction Center Norman OK 
0326 PM CDT sun Oct 21 2018 

Areas affected...Southeast Arizona 

Concerning...severe potential...watch unlikely 

Valid 212026z - 212200z 

Probability of watch issuance...5 percent 

Summary...a few strong thunderstorms are possible into the evening 
hours across Southeast Arizona. Gusty winds and marginally severe 
hail are the primary threats. 

Discussion...northern extent of higher moisture plume (pw values 
around 1") currently extends across northern Mexico into Southeast 
Arizona. Cu field is deepening within this plume where strong 
boundary-layer heating has has allowed surface temperatures to warm 
into the mid 80s. Forecast soundings suggest as readings rise 
another degree or so, and boundary layer deepens, low-level flow 
should veer across western Pima County which may enhance convergence 
near this deepening cu field. Latest cams suggest a few strong 
thunderstorms could evolve over eastern Pima and Cochise counties 
where current thermodynamic profiles are supportive of robust 
updrafts. Given the modest shear observed across this region a few 
storms could exhibit weak rotation as they propagate east. 
Marginally severe hail and gusty winds are the primary threats. 

.Darrow/Kerr.. 10/21/2018 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 30991114 32251205 32741073 31300983 30991114