Sep 22, 2017 1300 UTC Day 1 Convective Outlook
Updated: Fri Sep 22 12:46:29 UTC 2017 (20170922 1300Z Day 1 shapefile | 20170922 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170922 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 16,768 189,250 Grand Forks, ND...
MARGINAL 249,259 2,830,642 Sioux Falls, SD...Fargo, ND...Duluth, MN...Roswell, NM...Clovis, NM...
Probabilistic Tornado Graphic
20170922 1300 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 % 25,814 489,011 Fargo, ND...Moorhead, MN...West Fargo, ND...West Fargo, MN...Fergus Falls, MN...
Probabilistic Damaging Wind Graphic
20170922 1300 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 % 13,653 104,306 No Major Population Center in Risk Area
5 % 195,321 2,673,502 Sioux Falls, SD...Fargo, ND...Duluth, MN...Grand Forks, ND...Roswell, NM...
Probabilistic Large Hail Graphic
20170922 1300 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
15 % 16,785 189,420 Grand Forks, ND...
5 % 222,797 2,307,278 Sioux Falls, SD...Fargo, ND...Duluth, MN...Roswell, NM...Clovis, NM...
   SPC AC 221246

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0746 AM CDT Fri Sep 22 2017

   Valid 221300Z - 231200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHWEST MN...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS UPPER MIDWEST TO
   SOUTHERN HIGH PLAINS...

   ...SUMMARY...
   Isolated severe hail and wind storms are possible from the Upper
   Midwest to the southern High Plains, mainly during the late
   afternoon and evening. The most likely corridor for severe storms,
   including a brief tornado, is across northwest Minnesota.

   ...Upper Midwest...
   Ongoing clusters of elevated storms across the MN Arrowhead into
   northwest WI will pose a risk for isolated, marginally severe hail
   and localized strong gusts this morning before activity wanes with
   diminishing low-level warm advection.

   Within a highly amplified mid-level flow pattern characterized by a
   longwave trough over the West and a ridge from the southern Great
   Plains to the Great Lakes, forcing for ascent will be tied to
   low-level warm advection and convergence along a quasi-stationary
   front. A surface cyclone over south-central SD will gradually fill
   as it tracks northeast into northwest MN by evening. The warm sector
   will become very unstable with MLCAPE reaching 2500-3500 J/kg. A
   veering wind profile with height will support a conditional
   supercell risk should a surface-based storm form. However, capping
   will likely inhibit development over the warm sector. Isolated to
   scattered storms during the late afternoon and evening should remain
   confined along and north of the front. Large hail should be the
   primary hazard, but a brief tornado and severe wind gusts are
   possible across northwest MN prior to updrafts becoming elevated.

   ...Central Great Plains to southern High Plains...
   Isolated storms should develop along the dryline in the late
   afternoon. Ample diabatic heating will yield very warm surface
   temperatures into the 90s and result in moderate buoyancy with
   MLCAPE of 1000-1500 J/kg. The region will remain on the eastern
   periphery of moderate mid-level southwesterlies associated with the
   longwave trough over the West. This should provide sufficient
   deep-layer shear for weakly organized updrafts and a risk for severe
   hail/wind. Low severe potential may continue tonight with widely
   scattered storms persisting across eastern NM and parts of NE/SD.

   ..Grams/Jewell.. 09/22/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z