Jul 22, 2018 0730 UTC Day 3 Severe Thunderstorm Outlook
Updated: Sun Jul 22 07:25:36 UTC 2018 (20180722 0730Z Day 3 shapefile | 20180722 0730Z Day 3 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
0730 UTC Day 3 Outlook Graphic
Day 3 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 81,673 450,092 Rapid City, SD...Bismarck, ND...Mandan, ND...Pierre, SD...Spearfish, SD...
Probabilistic Graphic
20180722 0730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 3 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 81,976 454,203 Rapid City, SD...Bismarck, ND...Mandan, ND...Pierre, SD...Spearfish, SD...
   SPC AC 220725

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0225 AM CDT Sun Jul 22 2018

   Valid 241200Z - 251200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE TUESDAY
   AFTERNOON AND EVENING ACROSS PARTS OF THE WESTERN INTO CENTRAL
   DAKOTAS AND WESTERN NEBRASKA...

   ...SUMMARY...
   Strong thunderstorms may impact parts of the western into central
   Dakotas and western Nebraska late Tuesday afternoon and evening,
   accompanied by at least some risk for severe wind and hail.

   ...Synopsis...
   Highest mid-level heights may gradually shift westward across
   Arizona during this period.  Otherwise, models indicate little
   appreciable change to a prominent subtropical high encompassing all
   but the northern tier of the western into central United States. 
   Downstream troughing east of the Mississippi Valley into the
   Atlantic Seaboard may also change little, with an elongated embedded
   cyclonic circulation lingering over the eastern Gulf States.  But
   guidance suggests that broad troughing within the mid-latitude
   westerlies may begin to dig across the central Canadian/U.S. border
   area.  Within seasonably strong northwesterly flow between this
   feature and the northern periphery of the subtropical high, a
   perturbation may emerge from the northern Rockies and dig across the
   northern Plains by late Tuesday night.

   ...Western/central Dakotas and western Nebraska..
   Models indicate at least modest steepening of lower/mid tropospheric
   lapse rates associated with the eastward advection of elevated mixed
   layer air into the northern High Plains by Tuesday afternoon.  In
   association with a developing surface low to the lee of the northern
   Rockies, boundary layer moistening is expected to contribute to an
   axis of weak to moderate destabilization with insolation.  This
   probably will take place beneath 30-50 kt northwesterly 700-500 mb
   flow, which may contribute to an environment conducive to organized
   convection, including supercells, posing a risk for severe wind and
   hail.  Enough spread exists within the various model output
   concerning the synoptic and sub-synoptic details and magnitude of
   destabilization to preclude a categorical slight risk at this time,
   but it is possible that this could change in subsequent outlooks for
   this time period.

   ..Kerr.. 07/22/2018

   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z