Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS48 KWNS 200833
SWOD48
SPC AC 200833

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0333 AM CDT SUN APR 20 2014

VALID 231200Z - 281200Z

...DISCUSSION...
MODELS ARE IN SOMEWHAT BETTER AGREEMENT REGARDING THE EVOLUTION OF
LONG-WAVE TROUGH AS IT PROGRESSES ACROSS THE ROCKIES INTO THE PLAINS
WEDNESDAY.  HOWEVER...CONSIDERABLE UNCERTAINTY EXISTS BEYOND DAY4 AS
GFS IS QUITE A BIT STRONGER WITH EJECTING SHORT-WAVE TROUGH/SPEED
MAX ACROSS THE MID MS VALLEY THAN THE ECWMF.
ADDITIONALLY...MOISTURE/INSTABILITY MAY NOT INITIALLY BE OF QUALITY
THAT WILL SUPPORT SIGNIFICANT ORGANIZED SEVERE DOWNSTREAM OF THE
PLAINS.

HOWEVER...THERE IS GROWING CONFIDENCE THAT ROBUST CONVECTION WILL
DEVELOP DURING THE DAY4 PERIOD ACROSS THE CNTRL/SRN HIGH PLAINS.
LEE TROUGH WILL BE WELL ESTABLISHED BY TUESDAY ACROSS THE HIGH
PLAINS AND A NARROW CORRIDOR OF BOUNDARY LAYER MOISTURE SHOULD
ADVANCE NWD ACROSS WEST TX INTO NEB.  THERE IS REASON TO BELIEVE
NEAR 60F SFC DEW POINTS WILL RESIDE JUST EAST OF THE DRYLINE BY PEAK
HEATING AND SBCAPE ON THE ORDER OF 1500-2000 J/KG APPEARS POSSIBLE
ALONG WRN FRINGE OF THICKER LOW CLOUDS WITHIN RETURN FLOW.  WITH
40-50KT 500MB SWLY FLOW EXPECTED TO OVERSPREAD THE
DRYLINE...ENVIRONMENTAL SHEAR WILL SUPPORT ORGANIZED ROTATING
UPDRAFTS.  WILL MAINTAIN 30 PERCENT SEVERE PROBS FOR EXPECTED
SUPERCELL DEVELOPMENT.

ALTHOUGH SIGNIFICANT ORGANIZED SEVERE IS NOT CURRENTLY FORECAST
BEYOND DAY4...LATEST MEDIUM-RANGE GUIDANCE WOULD SEEM TO FAVOR
SEVERAL BOUTS OF SEVERE DURING THE DAY4-8 TIME PERIOD.  MODEL
DISCREPANCIES WILL PREVENT A MORE ACCURATE DEPICTION OF THIS
THREAT...THUS PROBABILITIES WILL REMAIN TOO LOW TO JUSTIFY AN
OUTLOOK DAY5-8.

..DARROW.. 04/20/2014


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