SPC AC 011703

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1203 PM CDT Thu Jun 01 2017

   Valid 021200Z - 031200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE NORTHERN PLAINS TO THE UPPER MISSISSIPPI VALLEY...

   ...SUMMARY...
   Marginally severe thunderstorms with strong wind gusts and hail will
   be possible Friday afternoon and evening across parts of the
   northern Plains and upper Mississippi Valley.

   ...Northern Plains to the Upper MS Valley...

   An upper ridge will reside over the Plains Friday morning. Beneath
   the ridge, southerly low level flow will maintain low to mid 60s
   dewpoints across portions of the Dakotas and the upper MS Valley
   vicinity. A shortwave trough over the northern Rockies will shift
   northeast through the day and traverse the northern Plains after
   00z. Meanwhile, a surface cold front associated with a low over the
   Canadian prairie provinces will shift east across the northern
   Plains during the afternoon and evening hours. Strong heating ahead
   of this boundary will result in moderate to strong instability and
   thunderstorms are expected to develop across the western/central
   Dakotas by mid to late afternoon. Deep layer shear will be rather
   weak, on the order of 20-30 kts, and this will limit overall storm
   organization. However, steep midlevel lapse rates and SBCAPE values
   greater than 2000 J/kg should be sufficient for isolated strong to
   marginally severe storms through the evening hours. Hail will be the
   main concern, though if storms can organize into any linear/bowing
   segments along the front or through outflow interactions, a wind
   threat could temporarily increase. 

   Further east, additional strong to marginally severe thunderstorms
   will be possible across portions of MN, WI, IA and IL. Isolated
   diurnally driven storms will be possible, though weak forcing
   beneath the eastward progressing upper ridge and weak vertical wind
   profiles should limit intensity/coverage of any afternoon storms.
   Later in the evening/overnight hours, height falls across the region
   will occur with the approach of the upper shortwave trough and 850mb
   flow will increase. Thunderstorms are then expected to develop along
   a moist axis from northern MN into WI and possible eastern IA and
   northern IL. Modest lapse rates approaching 7 deg C/km and weak to
   moderate instability could support a few marginally severe
   thunderstorms capable of mainly small hail.

   ..Leitman.. 06/01/2017

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z