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    Day 2 Outlook >
Sep 26, 2023 0600 UTC Day 1 Convective Outlook
Updated: Tue Sep 26 05:06:18 UTC 2023 (Print Version | 20230926 1200Z Day 1 shapefile | 20230926 1200Z Day 1 KML)
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 Forecast Discussion
   SPC AC 260506

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1206 AM CDT Tue Sep 26 2023

   Valid 261200Z - 271200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   MIDWEST AND FROM CENTRAL NEW MEXICO TO SOUTHWEST TEXAS...

   ...SUMMARY...
   Thunderstorms capable of producing isolated hail and strong wind
   gusts will be possible this afternoon and tonight across parts of
   Illinois and Indiana, and also across parts of New Mexico into west
   Texas.

   ...Synopsis...
   Latest water-vapor imagery depicts an amplified upper ridge shifting
   east from the Intermountain West into the Plains over the past 12
   hours. An occluded low over the upper MS River Valley is beginning
   to shift to the southeast within the mean northwesterly flow regime,
   and is expected to reside across central IL by peak heating.
   Filtered heating of a moist airmass currently in place across the
   Midwest, combined with weak ascent in the vicinity of the low, will
   support scattered thunderstorm development this afternoon and
   evening. To the south, a weak surface high over OK is fostering
   modest moisture return flow into NM. Thunderstorm development is
   expected by mid to late afternoon within the upslope flow regime,
   and may feature a few strong/severe storms. 

   ...Midwest...
   Thunderstorms will likely be ongoing across northern IL and adjacent
   areas of IA and WI at the start of the period to the east of the
   surface low within a weak warm advection regime. A second round of
   thunderstorms is probable along the surface trough during the
   afternoon hours across IL as ascent associated with the left-exit
   region of a weak upper jet overspreads a weakly capped environment.
   Cold temperatures aloft should support SBCAPE values on the order of
   500-1000 J/kg, but values up to 1500 J/kg are possible depending on
   the degree of daytime heating and residual cloud cover. Regardless,
   deep-layer shear is forecast to be adequate (around 20-25 knots) to
   support a few stronger cells capable of large hail and damaging
   gusts. A brief/weak tornado is possible with initial cells along the
   surface trough and in the vicinity of the surface low where forecast
   soundings show some low-level veering and effective SRH values on
   the order of 100-150 m2/s2. 

   ...New Mexico and Southwest Texas...
   04 UTC surface observations show a plume of 50-60 F dewpoints
   advecting to the west/northwest into southeast NM. With no
   appreciable strengthening of the surface high expected over the next
   12 hours, further moistening into the 50s and low 60s across much of
   southern NM appears probable by mid-afternoon with MLCAPE values
   around 1500-2000 J/kg. Temperatures climbing into the 80s and low
   90s should mix through the nocturnal inversion, allowing for
   convective initiation within the upslope flow regime around peak
   heating. Despite fairly weak northwesterly flow aloft, southeasterly
   low-level winds will support straight hodographs with sufficient
   effective bulk shear (around 30 knots) for organized cells with an
   attendant large hail and severe wind risk.

   ..Moore/Leitman.. 09/26/2023

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: September 26, 2023
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