Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS48 KWNS 190910
SWOD48
SPC AC 190909

DAY 4-8 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0409 AM CDT SUN APR 19 2015

VALID 221200Z - 271200Z

CORRECTED FOR WORDING

...DISCUSSION...
THE MEDIUM-RANGE MODELS INCLUDING THE ECMWF AND GFS SOLUTIONS BEGIN
THE DAY 4 TO 8 PERIOD WITH AN UPPER-LEVEL RIDGE OVER THE SRN PLAINS.
THE MODELS BUILD THE UPPER-LEVEL RIDGE SLOWLY NWWD INTO THE SRN AND
CNTRL ROCKIES ON WEDNESDAY/DAY 4. AT THE SFC...A LOW IS FORECAST TO
DEVELOP IN THE SRN PLAINS WEDNESDAY AFTERNOON AHEAD OF A COLD FRONT.
A WARM SECTOR IS FORECAST ACROSS OK...AR...LA AND THE ERN HALF OF
TX. BOTH SOLUTIONS DEVELOP CONVECTION ALONG THE FRONT ACROSS
OKLAHOMA LATE WEDNESDAY AFTERNOON INTO THE EVENING WITH THE GFS ALSO
SHOWING CONVECTION ESEWD ACROSS AR. MODERATE TO STRONG DEEP-LAYER
SHEAR WOULD BE FAVORABLE FOR SEVERE STORMS WITH LARGE HAIL...WIND
DAMAGE AND POSSIBLY A FEW TORNADOES IN NRN PARTS OF THE SRN PLAINS
AND POSSIBLY IN THE OZARKS. AN ENHANCED SEVERE THREAT SEEMS POSSIBLE
ACROSS THE REGION. ON THURSDAY/DAY 5...THE ECMWF AND GFS REMAIN IN
GENERAL AGREEMENT MOVING THE UPPER-LEVEL RIDGE EWD ACROSS THE SRN
PLAINS WITH A WARM SECTOR IN PLACE ACROSS THE SERN HALF OF TX ESEWD
INTO THE LOWER MS VALLEY WHERE ISOLATED STRONG TO SEVERE
THUNDERSTORMS COULD OCCUR. AN ENHANCED SEVERE THREAT COULD ALSO
DEVELOP ACROSS PARTS OF THE WARM SECTOR THURSDAY AFTERNOON AND
EVENING. MODEL SOLUTIONS DIVERGE THURSDAY NIGHT WITH THE ECMWF
INCREASING LOW-LEVEL MOISTURE ACROSS MUCH OF THE SRN PLAINS WITH THE
GFS CONFINING THE WARM SECTOR TO SCNTRL TX AND THE IMMEDIATE GULF
COAST. FOR THIS REASON...FORECAST UNCERTAINTY INCREASES ON
FRIDAY/DAY 6 BUT THUNDERSTORMS...SOME POTENTIALLY SEVERE...WILL BE
POSSIBLE ACROSS PARTS OF THE SRN PLAINS AND OZARKS AS A SHORT-WAVE
TROUGH MOVES ENEWD OUT OF THE SRN ROCKIES. BY SATURDAY/DAY 7...THE
UPPER-LEVEL TROUGH IS FORECAST TO MOVE OVER THE MID MS VALLEY WITH
THE WARM SECTOR REMAINING OVER THE GULF COAST STATES WHERE SOME
STRONG TO POTENTIALLY SEVERE STORMS COULD OCCUR SATURDAY AFTERNOON.

ALTHOUGH AN ORGANIZED SEVERE THREAT WILL BE POSSIBLE FOR BOTH
WEDNESDAY/DAY 4 AND THURSDAY/DAY 5...THE LEAST UNCERTAINTY APPEARS
TO BE ACROSS OK WEDNESDAY AFTERNOON AND EVENING. WILL ADD A SLIGHT
RISK AREA IN THE SRN PLAINS EXTENDING SEWD INTO THE ARKLATEX ON
WEDNESDAY.

..BROYLES.. 04/19/2015



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