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    Day 2 Outlook >
Jun 13, 2024 2000 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Thu Jun 13 19:44:13 UTC 2024 (Print Version | 20240613 2000Z Day 1 shapefile | 20240613 2000Z Day 1 KML)
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 Forecast Discussion
   SPC AC 131944

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0244 PM CDT Thu Jun 13 2024

   Valid 132000Z - 141200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN SOUTHERN
   IA...NORTHERN MO...AND NORTHERN/CENTRAL IL...

   ...SUMMARY...
   Severe thunderstorms are expected late this afternoon and early
   evening across parts of southern Iowa into northern Missouri and
   northern/central Illinois. Very large hail, destructive wind gusts,
   and a couple of tornadoes all appear possible. A broader corridor of
   severe hail/wind potential will extend from portions of the
   southern/central High Plains to the Great Lakes.

   ...20Z Update...
   Overall prior forecast appears reasonably on-track. Only minor
   changes were made based on latest observational trends. This was
   largely to the west/north side of ongoing convection/frontal
   placement from MI to IA and in south FL. For additional short-term
   forecast information, please see MCD 1248 regarding the
   south-central High Plains and MCD 1249 for the Mid-MS to Lower MO
   Valleys.

   ..Grams.. 06/13/2024

   .PREV DISCUSSION... /ISSUED 1128 AM CDT Thu Jun 13 2024/

   ...Great Lakes...
   A mid-level shortwave trough with associated westerly
   mid/upper-level jet will move eastward across the Upper Midwest and
   Great Lakes today. An attendant surface cold front will likewise
   sweep eastward across these regions through this evening, with the
   primary surface cyclone forecast to remain in Canada. Partly cloudy
   skies this morning should give way to better opportunity for diurnal
   heating this afternoon. Increasing low-level convergence along the
   front, along with ascent associated with shortwave trough/mid-level
   jet, should encourage convective development along/near the front by
   mid afternoon across parts of Lower MI into northern IL/IN and
   vicinity. Sufficient instability and deep-layer shear are forecast
   to support robust thunderstorms with a threat for scattered damaging
   winds and severe hail. The magnitude of the severe threat will be
   dependent on how much instability can develop, with differences
   remaining in high-resolution guidance regarding both how much
   convection develops, and how intense it will become. Regardless,
   some severe threat remains apparent, and the Marginal/Slight Risks
   have been maintained across this region with minimal changes for
   this update.

   ...Mid Mississippi Valley...
   A surface cold front is progged to sag more slowly
   south-southeastward across the mid MS Valley today, with better
   forcing aloft generally remaining to the north across the Upper
   Midwest and Great Lakes. A rather moist low-level airmass, with
   surface dewpoints generally in the upper 60s to low 70s, will remain
   along/south of this boundary across the mid MS Valley. Robust
   daytime heating of this airmass, along with steep mid-level lapse
   rates, will promote moderate to strong instability (MLCAPE 2500-3500
   J/kg) by mid/late afternoon from southeast NE/northeast KS into
   southern IA/northern MO and vicinity. Warm mid-level temperatures
   noted on area 12Z soundings (700 mb temperatures of 13+ C) will
   likely inhibit robust convective development for much of the day,
   until surface temperatures reach at least the low 90s and finally
   erode lingering MLCIN.

   Explosive thunderstorm development is likely by 20-22Z along/near
   the front, as strong instability combines with enhanced deep-layer
   shear to support an threat for multiple intense supercells. Very
   large hail of at least 2-3 inches in diameter, and perhaps a couple
   tornadoes, will be a threat with these initially discrete
   supercells. With mid-level westerly flow largely parallel to the
   surface boundary, a quick transition/upscale growth into one or more
   bowing clusters seems likely by early evening. This activity should
   tend to have a greater threat for severe/damaging winds, including
   the potential for some significant gusts of 75-80 mph. The severe
   wind/hail threat should continue in a relatively narrow corridor
   this evening across the mid MS Valley, before increasing MLCIN and
   nocturnal cooling gradually reduce the overall severe risk tonight.

   ...Kansas into the Southern/Central High Plains...
   A hot and deeply mixed airmass is anticipated along/near the front
   across KS into the southern/central High Plains. This region will
   generally be displaced to the south of stronger forcing aloft, and
   warm mid-level temperatures may inhibit convection for much of the
   day. Still, most guidance suggests isolated to scattered
   thunderstorms will develop with a very well mixed boundary layer and
   steepened low/mid-level lapse rates. Severe/damaging downdraft winds
   appear to be the main threat with this activity, although some hail
   may also occur with any marginal supercell structures that can form.
   Based on latest guidance trends, the Slight Risk has been expanded
   westward to include more of western KS and eastern CO. Isolated
   significant severe wind gusts (75+ mph) may occur with any loosely
   organized clusters across KS. But, weaker deep-layer shear compared
   with locations farther east suggests the overall severe threat will
   probably remain fairly isolated.

   ...South Florida...
   A loosely organized band of convection is ongoing across parts of
   south FL. While mid-level lapse rates are expected to remain poor,
   sufficient instability and deep-layer shear may support occasional
   strong/gusty winds with the more robust activity this afternoon and
   early evening. A brief tornado or two may also occur given modestly
   enhanced low-level flow.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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