U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 201616 
Storm Prediction Center ac 201614 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1114 am CDT Fri Oct 20 2017 

Valid 201630z - 211200z 

..no severe thunderstorm areas forecast... 

scattered thunderstorms are possible today over eastern Texas, with 
more isolated activity overnight into parts of the Central Plains 
and Midwest. A few strong storms are possible, but the severe 
thunderstorm risk is expected to be low. 

Downstream from a progressive midlevel trough now moving over the 
Pacific northwest and northern Great Basin, Lee cyclogenesis across 
the northern High Plains will begin to draw low-level moisture 
northward from Texas across the plains. Isolated lightning strikes 
will be possible today from the Pacific northwest into parts of the 
northern rockies with the midlevel thermal trough and associated 
steep lapse rates. Otherwise, a lead shortwave trough over the 
Southern Plains has interacted with the primary moisture return 
corridor/weakening frontal zone across the Upper Texas coast, where 
thunderstorms have persisted through the overnight hours into this 
morning. A minor boost to storm coverage could occur inland with 
the diurnal heating cycle, but overall storm coverage should still 
decrease later this afternoon/evening as the lead shortwave trough 
ejects north-northeastward ahead of the moisture plume. Later 
tonight, some elevated convection will be possible from NE/South Dakota to Minnesota 
within the warm advection regime on the north edge of the returning 

.Thompson/leitman.. 10/20/2017 


Mesoscale Discussion

acus11 kwns 192021 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 192020 

Mesoscale discussion 1720 
National Weather Service Storm Prediction Center Norman OK 
0320 PM CDT Thu Oct 19 2017 

Areas affected...southwest New Mexico into a portion of far western 

Concerning...severe potential...watch unlikely 

Valid 192020z - 192245z 

Probability of watch issuance...5 percent 

Summary...stronger storms will remain capable of producing a few 
instances of downburst winds and hail through early evening. Overall 
threat is marginal, and coverage of severe events is not expected to 
become sufficient for a ww. 

Discussion...surface temperatures have climbed to near 80f with 
dewpoints in the mid to upper 40s in the presence of boundary-layer 
mixing, boosting MLCAPE to 400-800 j/kg. Storms over southern nm 
have increased in overall intensity during the last hour, and 
further increase in coverage may occur as forcing for ascent 
attendant to a progressive shortwave trough over Arizona spreads into 
western nm. No substantial increase in winds aloft is expected with 
the approach of the impulse, and vertical shear will remain weak and 
supportive of multicells. Nevertheless, the thermodynamic 
environment with steep lapse rates and inverted-v boundary layers 
will continue to promote a risk for a few instances of downburst 
winds and hail through early evening. 

.Dial.. 10/19/2017 

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


Latitude...Lon 31800602 31970707 32370817 33530845 33830682 33460584 
32500539 31800602