NWS Storm Prediction Center - Day 1 Convective Outlook

Dec 12, 2018 0100 UTC Day 1 Convective Outlook
Updated: Wed Dec 12 00:56:39 UTC 2018
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Overview Overview

 Forecast Discussion - Day 1 Convective Outlook


   SPC AC 120056

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0656 PM CST Tue Dec 11 2018

   Valid 120100Z - 121200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Isolated thunderstorms remain possible this evening through tonight
   across western Washington and northwest Oregon.

   ...Western WA/northwest OR...
   Trends in satellite imagery and objective analyses indicated a
   change in air mass will occur across western parts of WA/OR this
   evening into tonight.  A cold front (now moving into far western WA)
   will advance eastward, while cold low- to mid-tropospheric air
   (500-mb temperatures at or below -30 C) spreads across the
   post-frontal environment.  These cold midlevel temperatures are
   associated with a Pacific shortwave trough/exit region of an
   accompanying 100+ kt 500-mb jet shifting inland this forecast
   period.  Lightning data from today through this outlook issuance
   indicated sporadic thunderstorms within an area of post-frontal
   convection.  

   Steepening lapse rates are already evident in northwest WA, given
   the 00Z UIL sounding representing the leading edge of the
   post-frontal environment, with buoyancy deep enough for charge
   separation.  Sufficient destabilization, given steepening lapse
   rates, will allow for low-topped cellular convection that spreads
   inland to possibly produce isolated thunderstorms this evening into
   tonight.  Weak instability/shear will preclude a severe-weather
   threat.

   ..Peters.. 12/12/2018

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z



Data courtesy the Storm Prediction Center
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