Feb 23, 2017 0600 UTC Day 1 Convective Outlook
Updated: Thu Feb 23 05:33:28 UTC 2017 (20170223 1200Z Day 1 shapefile | 20170223 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170223 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 74,477 3,870,490 Omaha, NE...Lincoln, NE...Des Moines, IA...Cedar Rapids, IA...St. Joseph, MO...
Probabilistic Tornado Graphic
20170223 1200 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
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20170223 1200 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
No Risk Areas Forecast
Probabilistic Large Hail Graphic
20170223 1200 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 % 74,477 3,870,490 Omaha, NE...Lincoln, NE...Des Moines, IA...Cedar Rapids, IA...St. Joseph, MO...
   SPC AC 230533

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1133 PM CST Wed Feb 22 2017

   Valid 231200Z - 241200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF SOUTHERN NE...NORTHERN KS...NORTHERN MO...AND IA...

   ...SUMMARY...
   Thunderstorms may produce isolated severe hail across portions of
   southern Nebraska, northern Kansas, northern Missouri, and Iowa from
   this afternoon into tonight.

   ...Synopsis...
   Deep surface low pressure will track along a curved trajectory from
   east-central CO across northern KS to IA -- in the vicinity of a
   sharpening frontal zone extending from the central Great Plains to
   the Great Lakes region. This will occur as a broadly cyclonic and
   strong midlevel wind-speed maximum emerges over the central High
   Plains, while the exit region of the speed maximum advances toward
   the middle Mississippi Valley through the period. A dryline is
   forecast to sharpen to the south of the surface low, east of which
   strengthening low-level south-southwesterly/southwesterly flow will
   encourage poleward fluxes of only weakly modified Gulf moisture. As
   the surface low deepens, a cold front trailing west/southwest of the
   low will advance southward/southeastward.

   ...Portions of southern NE, northern KS, northern MO, and IA...
   Strengthening frontogenetic circulations preceding the mobile
   surface low will support increasing ascent on the warmer side of the
   sloped frontal zone over the region. This will permit erosion of
   capping at the base of an elevated mixed layer, which will
   overspread recycled moisture embedded within the frontal zone.
   Isolated to widely scattered thunderstorm development will be
   possible within this zone during the afternoon, across portions of
   northern KS and southern NE. While low-level moisture will be scant,
   it will be sufficient for a narrow corridor of elevated buoyancy
   (rooted above the frontal zone), mainly enhanced by steep midlevel
   lapse rates accompanying the elevated mixed layer. This initial
   activity will spread east-northeastward toward the lower/middle
   Missouri Valley through the evening hours. Long hodographs in the
   mid/high levels will support convective organization with a few
   instances of severe hail possible.

   During the evening and overnight hours, the strengthening low-level
   jet will yield an increase in isentropic ascent north of the surface
   front, from parts of northern MO into IA and eastward toward
   portions of the adjacent Mississippi Valley region. Relatively
   greater convective coverage will likely exist in this regime, as
   additional (albeit modest) low-level moistening occurs. Strong deep
   shear and an influx of steepening midlevel lapse rates will support
   the risk for isolated severe hail in association with elevated
   convection. With time through the night, individual storms will tend
   to congeal into clusters, which will be associated with an overall
   lessening of the severe-hail risk.

   ..Cohen.. 02/23/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z