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Apr 25, 2018 0600 UTC Day 2 Convective Outlook
Updated: Wed Apr 25 05:41:14 UTC 2018 (Print Version | 20180425 0600Z Day 2 shapefile | 20180425 0600Z Day 2 KML)
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 Forecast Discussion

   SPC AC 250541

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1241 AM CDT Wed Apr 25 2018

   Valid 261200Z - 271200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PORTION
   OF NORTHERN CALIFORNIA INTO WESTERN OREGON...

   ...SUMMARY...
   Isolated thunderstorms with a threat for downburst winds and small
   to marginally severe hail are possible from northern California into
   western Oregon Thursday afternoon and evening.

   ...Synopsis...

   Several vorticity maxima will move through a broad synoptic trough
   situated over the eastern two thirds of the U.S. Thursday. Farther
   west a closed upper low will move into northern CA and the Pacific
   Northwest region. Shortwave trough forecast to be over the lower MS
   Valley early Thursday will continue east and northeast through the
   Southeast States, reaching the Middle Atlantic toward the end of the
   period. This feature will be accompanied by a weak surface low and
   cold front. Farther west an upstream trough will advance southeast
   through the central and southern Plains as well as the lower MS
   Valley region accompanied by another frontal surge.

   ....Northern Sierra Nevada through the Pacific Northwest...

   Steep mid-level lapse rates will reside in this region in advance of
   the approaching upper trough, promoting marginal instability.
   Isolated surface-based thunderstorms may occur over the Sierra
   Nevada and farther into a part of western OR during the afternoon
   and early evening. Deeply mixed boundary layers and very steep lapse
   rates will support a risk of isolated downburst winds with any
   storms that develop, but coverage of storms will remain somewhat
   sparse during the day. Greater thunderstorm coverage (with most
   updraft bases rooted above 700 mb)is expected overnight over western
   OR when ascent accompanying a vorticity maximum rotates through the
   upper low circulation and onshore. Some of this activity could
   produce small hail.

   ...Southeast States...

   With limited moisture return inland and weak lapse rates,
   instability will remain very marginal with MUCAPE near or below 500
   J/kg. Bands of shallow convection will likely be ongoing over the
   lower MS and TN Valley along warm conveyor belt and farther north in
   deformation region. Isolated lightning strikes will be possible with
   this activity. A narrow corridor of surface-based destabilization
   might occur in wake of warm-conveyor convection, and additional
   showers and a few thunderstorms may initiate along cold front across
   AL into GA during the afternoon. Activity will spread northeast
   through the Carolinas overnight. 

   ...Southern and central Plains through middle and lower Mississippi
   Valley...

   Have made significant revisions to previous general thunder area due
   to limited moisture and instability inland and likelihood of sparse
   thunderstorm coverage. Very limited low-level moisture will reside
   in pre-frontal warm sector, but mid-level lapse rates and
   boundary-layer warming in conjunction with frontal ascent might be
   sufficient to initiate shallow convection. Some of this activity
   might become deep enough for a few lightning strikes. Elevated
   convection will be possible into the overnight within band of ascent
   accompanying the shortwave trough, and some of this activity might
   also produce isolated lightning strikes.

   ..Dial.. 04/25/2018

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z

        
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Page last modified: April 25, 2018
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