Sep 19, 2018 1730 UTC Day 2 Convective Outlook
Updated: Wed Sep 19 17:27:54 UTC 2018 (20180919 1730Z Day 2 shapefile | 20180919 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180919 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 34,981 4,528,231 Minneapolis, MN...St. Paul, MN...Rochester, MN...Bloomington, MN...Plymouth, MN...
SLIGHT 78,854 3,917,644 Des Moines, IA...Cedar Rapids, IA...Green Bay, WI...Appleton, WI...Waterloo, IA...
MARGINAL 192,497 24,324,289 Chicago, IL...Detroit, MI...Milwaukee, WI...Omaha, NE...Lincoln, NE...
Probabilistic Graphic
20180919 1730 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 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
30 % 36,452 4,647,303 Minneapolis, MN...St. Paul, MN...Rochester, MN...Bloomington, MN...Plymouth, MN...
15 % 79,151 3,835,143 Des Moines, IA...Cedar Rapids, IA...Green Bay, WI...Appleton, WI...Waterloo, IA...
5 % 192,655 24,377,721 Chicago, IL...Detroit, MI...Milwaukee, WI...Omaha, NE...Lincoln, NE...
   SPC AC 191727

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1227 PM CDT Wed Sep 19 2018

   Valid 201200Z - 211200Z


   Severe storms are expected across parts of the Upper Mississippi
   Valley and Great Lakes on Thursday, with the greatest threat from
   southeast Minnesota into central Wisconsin where damaging winds are
   most likely, along with an isolated tornado threat.

   A shortwave trough will move rapidly eastward across the northern
   Plains during the day with substantial cooling aloft while an upper
   high holds over the Southeast. The tightening height gradient
   between the two will result in strengthening winds through the
   period, with 70-80 kt midlevel winds by evening from SD into MN. At
   the surface, low pressure will begin the day over central NE, and
   will deepen with time as it approaches Lake Superior by 06Z.
   Preceding the low will be an east-west oriented baroclinic zone and
   eventual warm front, reinforced by early day precipitation, which
   will move across southern MN and WI during the afternoon. Despite
   relatively warm midlevel temperatures initially, rapid warm
   advection in the low-levels will result in a destabilizing situation
   by late afternoon and evening ahead of the surface low with storms
   focused near the surface low track and warm front. A cold front will
   also surge eastward across the upper MS Valley during the evening,
   providing an additional focus for storms.

   To the south, convergence along the trailing cold front will also
   support afternoon storms from NE into KS, with marginally severe
   hail or wind possible.

   ...MN and IA into WI and the U.P. of MI...
   An extensive area of rain and scattered thunderstorms is expected to
   be ongoing from SD into MI in association with a broad region of
   warm advection and north of the developing surface low and warm
   front. A few of the storms could contain hail early in the day. The
   warm front will then begin to move northward, with rapid
   destabilization due to a southwesterly low-level jet of 55 kt by
   00Z. Initially elevated storms are expected to focus just north of
   the warm front by early afternoon from MN into WI, and these will
   likely contain hail. With time, and as the surface low approaches,
   some of these cells may become surface based with bows and isolated
   supercells possible. The most likely area for significant wind
   damage or a tornado will be near the low as it tracks along the
   lifting warm front. Due to the expected narrow zone of greatest
   threat, and early precipitation potential, will defer any
   hatched/SIG area to later updates. Shear profiles will be quite
   strong, supporting a continued severe threat in this corridor
   perhaps into Upper Michigan. Farther south, a few severe storms may
   occur into IA along the cold front with a hail and wind threat.

   ...NE and KS...
   Strong heating will occur ahead of the cold front which will extend
   from eastern NE into north-central KS by late afternoon. The
   presence of 60s F dewpoints will lead to an axis of sufficient
   instability supporting a few strong to severe storms, and hodographs
   suggest multicellular mode with localized damaging winds or hail
   possible for a few hours before storms weaken.

   Tornado:   5%     - Slight
   Wind:     30%     - Enhanced
   Hail:     15%     - Slight

   ..Jewell.. 09/19/2018