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    Day 2 Outlook >
Feb 21, 2024 1300 UTC Day 1 Convective Outlook
Updated: Wed Feb 21 12:45:10 UTC 2024 (Print Version | 20240221 1300Z Day 1 shapefile | 20240221 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 211245

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0645 AM CST Wed Feb 21 2024

   Valid 211300Z - 221200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE WESTERN OZARKS REGION AND OVER NORTH-CENTRAL PARTS OF ILLINOIS
   AND INDIANA...

   ...SUMMARY...
   Areas of strong thunderstorm development are possible across parts
   of the Ozark Plateau and adjacent Great Plains and across central
   Illinois to far western Indiana late Wednesday evening into early
   Thursday, with some risk for severe hail.

   ...Synopsis...
   The mid/upper-level pattern will trend more toward zonal through the
   period, as a well-developed southern-stream shortwave trough now
   near coastal southern CA moves quickly east-northeastward and
   penetrates a low-amplitude mean ridge over the central CONUS.  This
   perturbation should cross the central/southern High Plains around
   00Z, then deamplify somewhat as its northern part enters confluent
   flow and height falls ahead of a northern-stream trough crossing the
   Upper Midwest.  By 12Z, the southern perturbation should reach from
   northern parts of IL/IN to southwestern MO and northwestern AR.

   At the surface, 11Z analysis depicted a wavy, slow-moving frontal
   zone from northernmost Lower MI across southern WI, through a weak
   low near DBQ, to near MKC, EMP and through a broad area of low
   pressure over western KS.  Cyclogenesis is forecast today over the
   western KS region, shifting eastward across KS to near MKC by 06Z,
   trailing a cold front southwestward over northern OK.  The Great
   Lakes/Mississippi Valley frontal segment should move southeastward
   then stall.  A secondary low is possible along the cold front over
   northern OK by 06Z, when a  warm to stationary front should extend
   from the MKC-area low across central parts of IL/IN.

   ...Ozarks to southern Great Lakes region...
   Isolated to scattered, elevated thunderstorms are expected to
   develop across portions of IL/IN and perhaps the western Ozarks
   region overnight, shifting/expanding eastward especially across the
   IL/IN region.  Activity will attain greatest coverage after 06Z, and
   may pose a risk of marginally severe hail.

   Low-level warm/moist advection above the boundary layer is underway
   in a relatively dry, early-stage return-flow event across a broad
   corridor from the southern Plains to the Ohio Valley and southern
   Great Lakes States.  The warm-advection plume should become more
   confluent and moist through today, and especially this evening into
   tonight, as it intensifies with the approach of the southern
   shortwave trough.  Though the return-flow regime still will be far
   from mature or optimal, moist advection/transport will persist such
   that increasingly high-theta-e parcels are involved, and ultimately
   lifted to an LFC.

   The two areas with the most such progged lift are in and near the
   "marginal risk" outlooks.  The northern area should have greater
   lift and thunderstorm coverage thanks to contribution from elevated,
   low-level frontal forcing, while theta-e and midlevel lapse rates
   will be greater above a relatively stable boundary layer in the
   southern area.  Albeit with much-different vertical distributions,
   both areas should attain around 500-1200 J/kg MUCAPE, with greater
   effective shear in the northern area (35-45 kt), and a stronger
   proximate LLJ (45-55 kt) for the southern area across the Ozarks. 
   However, despite a favorable environment for severe hail, given
   thunderstorms, the southern region appears more conditional because
   of stronger CINH, imparted by the same EML that is providing the
   high lapse rate.  That implies less convective coverage, and some
   (not all) convection-allowing progs with weaker indicators of
   isentropic ascent indicate none -- despite greater moisture content
   in the potential inflow region.

   ..Edwards/Mosier.. 02/21/2024

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: February 21, 2024
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