NWS Storm Prediction Center - Day 1 Convective Outlook

Aug 18, 2022 2000 UTC Day 1 Convective Outlook
Updated: Thu Aug 18 19:49:00 UTC 2022
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Overview Overview

 Forecast Discussion - Day 1 Convective Outlook


   SPC AC 181949

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0249 PM CDT Thu Aug 18 2022

   Valid 182000Z - 191200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH-CENTRAL
   NE TO THE MID-MO VALLEY...

   ...SUMMARY...
   Isolated large hail and localized severe wind gusts are most likely
   from south-central Nebraska to the Mid-Missouri Valley through early
   evening.

   ...20z Update...

   The Marginal risk area across parts of TX/LA and across FL/GA have
   been trimmed a small amount based on the current locations of the
   quasi-stationary surface boundary and convective trends. No other
   changes have been made to the outlook, and isolated strong to severe
   storms are still expected through early evening across parts of the
   central Plains into southwest MN. For more details, see previous
   outlook discussion below. For information regarding short term
   severe potential across MN, reference MCD 1693.

   ..Leitman.. 08/18/2022

   .PREV DISCUSSION... /ISSUED 1051 AM CDT Thu Aug 18 2022/

   ...KS/NE to southwest MN...
   A shortwave trough will gradually amplify as it drifts southeast
   across the Upper Midwest through tonight. An initially weak surface
   cyclone over the Upper Red River Valley will deepen as it slowly
   moves east across northern MN. Trailing cold front to its southwest
   will sharpen towards late afternoon across the Mid-MO Valley.
   Boundary-layer moisture will be relatively modest by mid-August
   standards, but a confined plume of steep mid-level lapse rates
   sampled by the 12Z Aberdeen sounding should support a narrow
   corridor of moderate buoyancy with MLCAPE of 1000-2000 J/kg. 

   A belt of enhanced mid-level northwesterlies will overspread much of
   the Great Plains to the west and southwest of the shortwave trough.
   This will strengthen deep-layer shear, mainly across the central
   Great Plains portion of the front, yielding elongation of the
   hodograph atop weak low-level SRH. This should support potential for
   a few discrete supercells with mid-level rotation centered on the
   IA/NE/SD border area southwest into south-central NE. Isolated large
   hail and localized severe gusts should be the primary hazards before
   convection wanes rapidly after dusk. With northeast extent into MN,
   slower-moving storms and more prominent multicell clustering should
   serve to marginalize wind/hail intensities. 

   ...Central TX to southern LA and north FL to southeast GA...
   While deep-layer shear will be lacking to the south of a
   convectively reinforced surface front, very rich boundary-layer
   moisture characterized by observed PW values around 2 inches will
   support a threat for localized wet microbursts, peaking in the late
   afternoon. Extensive pulse to weakly organized multicells are
   anticipated before convection decays this evening.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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



Data courtesy the Storm Prediction Center
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