Aug 27, 2022 2000 UTC Day 1 Convective Outlook
Updated: Sat Aug 27 19:56:56 UTC 2022 (20220827 2000Z Day 1 shapefile | 20220827 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20220827 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 29,954 2,914,806 St. Paul, MN...Des Moines, IA...Rochester, MN...Bloomington, MN...Eagan, MN...
MARGINAL 185,909 6,997,871 Omaha, NE...Minneapolis, MN...Lincoln, NE...Amarillo, TX...Billings, MT...
Probabilistic Tornado Graphic
20220827 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 % 16,301 3,789,130 Minneapolis, MN...St. Paul, MN...Rochester, MN...Bloomington, MN...Plymouth, MN...
Probabilistic Damaging Wind Graphic
20220827 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 % 29,826 2,896,411 St. Paul, MN...Des Moines, IA...Rochester, MN...Bloomington, MN...Eagan, MN...
5 % 186,144 7,016,503 Omaha, NE...Minneapolis, MN...Lincoln, NE...Amarillo, TX...Billings, MT...
Probabilistic Large Hail Graphic
20220827 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
15 % 23,283 1,382,308 Des Moines, IA...Rochester, MN...Ames, IA...West Des Moines, IA...Cedar Falls, IA...
5 % 114,252 7,367,308 Omaha, NE...Minneapolis, MN...St. Paul, MN...Amarillo, TX...Duluth, MN...
   SPC AC 271956

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0256 PM CDT Sat Aug 27 2022

   Valid 272000Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   IOWA...SOUTHEASTERN MINNESOTA...AND FAR WESTERN WISCONSIN...

   ...SUMMARY...
   Severe thunderstorm potential appears most concentrated today over
   parts of Iowa, southeastern Minnesota, and far western Wisconsin.

   ...20Z Update...
   The only substantial change to the outlook with this update was to
   trim the northeastern extent of the Slight Risk across western WI.
   Cloud cover has remained entrenched most of this area through the
   day, which has limited destabilization and reduced severe chances
   through this evening. Otherwise, convection is still expected to
   gradually increase in coverage and intensity across parts of IA into
   southern MN this afternoon and evening. Reference Mesoscale
   Discussion 1728 for more information on the short-term severe threat
   across these areas.

   ..Gleason.. 08/27/2022

   .PREV DISCUSSION... /ISSUED 1126 AM CDT Sat Aug 27 2022/

   ...IA/MN/WI this afternoon/evening...
   A midlevel shortwave trough over the central NE/KS border will
   continue moving northeastward to western IA by this evening and the
   upper MS Valley overnight.  Clouds and ongoing convection within a
   deep moisture plume over the central Plains will likewise spread
   northeastward through the day.  Surface heating to the east of the
   thicker cloud band and relatively steep low-midlevel lapse rates
   will contribute to MLCAPE of 1500-2500 J/kg, and the likelihood of
   additional thunderstorm development this afternoon in the zone of
   differential heating from IA into southern MN (along and south of a
   warm front).  Vertical shear profiles are forecast to be a bit
   disjointed with substantially backed/weaker flow in the mid levels
   across IA this afternoon.  Low-level shear/clockwise hodograph
   curvature will be larger this afternoon/evening closer to the warm
   front across southeast MN/western WI, with a similar weakness in the
   midlevel flow.  Thus, the environment favors a mixed/messy storm
   mode with clusters and some transient rotating updrafts, with a
   primary threat for damaging winds and isolated large hail given the
   moderately large buoyancy/precipitation loading and sufficiently
   steep low-midlevel lapse rates (DCAPE near 1000 J/kg).

   ...TX Panhandle into KS this afternoon/evening...
   Along the southern fringe of the residual monsoonal moisture plume
   and the ejecting midlevel trough over northern KS, differential
   heating and weak convergence along a lee trough will support
   scattered thunderstorm development later this afternoon.  Midlevel
   lapse rates will not be steep, but surface heating/mixing will
   steepen low-level lapse rates, and westerly flow aloft will
   contribute to modest effective bulk shear of 25-30 kt.  Somewhat
   organized cells/clusters will be capable of producing isolated
   strong-severe outflow gusts and marginally severe hail from mid
   afternoon into this evening.  

   ...Southern MT and vicinity this afternoon/evening...
   Within the primary jet, an embedded speed max/shortwave trough over
   southern BC and WA will progress eastward to MT later this afternoon
   into tonight.  An associated cold front will move into central MT by
   this evening, with strong surface heating and deep mixing in advance
   of the front.  Some high-based convection is expected to form over
   the higher terrain of southern MT later this afternoon, and storms
   will spread eastward into this evening.  Though low-level moisture
   and buoyancy will be limited, deep inverted-v profiles will support
   isolated strong-severe outflow gusts.

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