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Feb 22, 2017 0100 UTC Day 1 Convective Outlook
Updated: Wed Feb 22 00:57:29 UTC 2017 (Print Version | 20170222 0100Z Day 1 shapefile | 20170222 0100Z Day 1 KML)
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 Forecast Discussion
   SPC AC 220057

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0657 PM CST Tue Feb 21 2017

   Valid 220100Z - 221200Z


   The risk for severe storms appears negligible across the U.S.
   through tonight.

   Despite the presence of seasonably mild conditions across much of
   the U.S., under the prominent influence of split belts of westerlies
   emanating from the mid-latitude Pacific, thermodynamic profiles
   across most areas remain largely unsupportive of appreciable
   convective potential.  However, within broader scale upper troughing
   gradually shifting across and inland of the Pacific coast, through
   the Intermountain West and Rockies, forcing for ascent and
   destabilization associated with a number of smaller scale
   perturbations have been contributing to a few areas of generally
   weak thunderstorm activity.  The most significant of these
   perturbations have been progressing east northeastward along a
   strong, but weakening cyclonic mid-level jet, across northern
   California through the northern Great Basin and northern Rockies.

   East of the Rockies, a lower/mid tropospheric closed low within the
   southern-most branch of mid-latitude westerlies has been supporting
   some thunderstorm activity across the lower Mississippi Valley late
   this afternoon.  With the unstable warm sector of the associated
   occluded surface low confined to the eastern Gulf of Mexico, this
   has largely been aided by daytime heating beneath the mid-level cool
   pool, and does not seem likely to persist beyond the 01-03z time

   ...Northern Plains...
   One of the impulses emerging from the mid-latitude Pacific now
   appears to be in the process of progressing east of the northern
   Rockies, into the crest of low amplitude ridging across the northern
   Plains.  Mid-level moisture return to an eastward developing zone of
   stronger lower/mid tropospheric warm advection appears to be
   contributing to the maintenance of ongoing thunderstorm activity
   across the western Dakotas.  This activity seems likely to persist
   and spread eastward across the Dakotas through the 03-06Z time, and
   perhaps continue into portions of the Upper Midwest overnight.

   ...North California/southern Oregon/northwestern Nevada...
   Objective analysis suggests that weak to modest boundary layer
   destabilization has taken place across the region, beneath cold
   mid-level temperatures along/north of the stronger mid-level jet
   axis.  Before this environment stabilizes appreciably with the loss
   of daytime heating this evening, forcing associated with another
   inland migrating short wave impulse may still contribute to an
   increase in scattered thunderstorm activity.

   ...Florida Peninsula...
   Latest guidance suggests that vigorous warm sector thunderstorm
   activity may at least approach Gulf coastal areas of the Florida
   Peninsula by 12Z Wednesday.  However, destabilization appears
   unlikely to become supportive of appreciable severe weather
   potential, given the weak to modest nature of the wind fields and
   vertical shear to the east of the approaching mid-level closed

   ..Kerr.. 02/22/2017



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