Sep 14, 2019 2000 UTC Day 1 Convective Outlook
Updated: Sat Sep 14 19:39:22 UTC 2019 (20190914 2000Z Day 1 shapefile | 20190914 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20190914 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 11,285 4,151,312 Phoenix, AZ...Mesa, AZ...Glendale, AZ...Chandler, AZ...Scottsdale, AZ...
MARGINAL 258,466 21,396,073 Milwaukee, WI...Tucson, AZ...Omaha, NE...Minneapolis, MN...St. Paul, MN...
Probabilistic Tornado Graphic
20190914 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
2 % 36,420 2,504,827 Rochester, MN...Sioux City, IA...Bloomington, MN...Eagan, MN...Eden Prairie, MN...
Probabilistic Damaging Wind Graphic
20190914 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 11,285 4,151,312 Phoenix, AZ...Mesa, AZ...Glendale, AZ...Chandler, AZ...Scottsdale, AZ...
5 % 207,590 17,207,212 Tucson, AZ...Omaha, NE...Minneapolis, MN...St. Paul, MN...Lincoln, NE...
Probabilistic Large Hail Graphic
20190914 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 190,077 16,911,776 Milwaukee, WI...Omaha, NE...Minneapolis, MN...St. Paul, MN...Lincoln, NE...
   SPC AC 141939

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0239 PM CDT Sat Sep 14 2019

   Valid 142000Z - 151200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
   SOUTHERN ARIZONA...

   ...SUMMARY...
   Isolated to scattered severe wind gusts are possible this afternoon
   and evening across southern and central Arizona. Isolated severe
   storms with large hail and damaging wind gusts are possible from the
   Upper Midwest to the central Great Plains through tonight.

   ...Discussion...

   Only minor adjustments have been made to the previous forecast.

   ..Dial.. 09/14/2019

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Sat Sep 14 2019/

   ...Southern/central AZ...
   An MCV over western Chihuahua will drift north-northwestward across
   southeast AZ through tonight. 50s surface dew points are common
   across southern AZ amid easterly flow north of this MCV. In
   conjunction with ample heating northwest of the thicker cloud cover
   near the MCV, a modestly buoyant air mass with MLCAPE approaching
   1000 J/kg should develop by peak heating. 15-25 kt east-northeast
   700-500 mb winds around the north side of the MCV will be favorable
   for cells and semi-organized clusters to spread off the Mogollon Rim
   into the lower deserts with a threat for severe gusts. Whether more
   organized clustering can evolve is uncertain compared to the
   significant severe wind event two weeks ago, but there is at least
   sufficient damaging wind potential to warrant a Slight Risk across
   parts of the Gila Valley.

   ...Upper Midwest to the central Great Plains...
   Elevated thunderstorms are ongoing in western IA on the leading edge
   of a low-level warm theta-e advection plume. This plume and
   attendant zone of ascent will spread east-northeast across the Upper
   MS Valley into tonight in advance of a low-amplitude shortwave
   trough near the ND/MB border that will move east-southeast into Lake
   Superior. This elevated convection will pose a threat for isolated
   large hail, mainly this evening into tonight with a probable decay
   cycle this afternoon. A risk for locally damaging winds may also
   develop tonight towards the IA/IL/WI border region if a cluster can
   become semi-organized. 

   In the wake of the warm advection regime, storm initiation will
   depend on weak low-level ascent along a surface trough that extends
   southwestward across NE/KS. Stronger surface heating and deeper
   mixing is expected along the trough in KS, with lesser mixing depths
   and a greater probability of maintaining MLCIN through the afternoon
   in the warm sector farther northeast. Thus, surface-based
   thunderstorm development should be sparse and may struggle to be
   sustained during the late afternoon/early evening. If surface-based
   storms can form as far northeast as southern MN this afternoon,
   vertical shear profiles will be sufficient for supercells. Weaker
   vertical shear is expected with southwestward extent into southwest
   KS, where high-based storms would pose a threat for isolated severe
   wind and hail. 

   ...Central Appalachians...
   A narrow corridor of weak to modest buoyancy is expected with
   scattered storms along a cold front and over the higher terrain
   through early evening. Isolated strong downburst winds are possible
   on the periphery of weak to moderate mid-level southwesterlies.

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z