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    Day 2 Outlook >
Apr 13, 2024 2000 UTC Day 1 Convective Outlook
Updated: Sat Apr 13 19:38:12 UTC 2024 (Print Version | 20240413 2000Z Day 1 shapefile | 20240413 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
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 Forecast Discussion
   SPC AC 131938

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0238 PM CDT Sat Apr 13 2024

   Valid 132000Z - 141200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF OREGON AND ADJACENT NORTHEASTERN CALIFORNIA...

   ...SUMMARY...
   Thunderstorms with isolated severe hail and strong wind gusts remain
   possible this afternoon and early evening across parts of Oregon.

   ...Discussion...
   Current forecast reasoning, and the MRGL risk area across parts of
   the Oregon vicinity, appear to remain valid at this time, and thus
   no changes are being implemented in this forecast update.  The most
   appreciable change has been to remove the small thunder areas from
   the central U.S., as any lightning should remain sparse at best, and
   to add a small thunder area over northern Maine where sporadic
   lightning is ongoing, and may continue for a couple of hours.

   ..Goss.. 04/13/2024

   .PREV DISCUSSION... /ISSUED 1106 AM CDT Sat Apr 13 2024/

   ...Far Northeast California into Oregon...

   An upper low off the northern/central CA coast will continue to
   slowly migrate east through tonight. Deep-layer south/southeasterly
   flow on the northeast periphery of this cyclone will advect a plume
   of midlevel moisture and steep lapse rates over the area. Heating
   through broken cloud cover will allow temperatures to warm into the
   60s F by mid-afternoon and MLCAPE around 500-1000 J/kg is forecast.
   Moderate deep shear, with 0-6km effective shear magnitudes near 35
   kt will support organized clusters, or perhaps a supercell,
   developing in the 20-22z time frame. Isolated large hail around 1 to
   1.5 inches in diameter will be possible with the strongest cells
   given steep lapse rates and favorable shear in the 4-6 km layer. In
   addition to hail, a deeply-mixed sub-cloud layer will result in
   inverted-v thermodynamic profiles, and isolated strong gusts may
   occur. 

   While low-level moisture will remain a limiting factor for tornado
   potential, a brief spin-up can not be ruled out. Enlarged low-level
   hodographs are evident in forecast soundings and effective SRH will
   increase to 100-200 m2/s2 by 22-00z amid 0-3km MLCAPE near 100 J/kg.
   Have added a 2 percent tornado probability to reflect this low, but
   non-zero potential.

   Uncertainty in storm coverage will preclude an upgrade to Slight
   risk at this time.

   ...Great Lakes...

   A low-amplitude shortwave trough migrating through large-scale
   northwesterly flow regime will foster elevated thunderstorm
   development during the evening/overnight. Weak instability (MUCAPE
   generally less than 500 J/kg) will limit storm intensity, though
   steep midlevel lapse rates and cool temperatures aloft may be
   sufficient for a few instances of small hail.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: April 13, 2024
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