Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 231243
SWODY1
SPC AC 231242

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0742 AM CDT TUE SEP 23 2014

VALID 231300Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
A FEW THUNDERSTORMS ACROSS THE CENTRAL PLAINS COULD BE STRONG TO
MARGINALLY SEVERE.

...SYNOPSIS...
PROGRESSIVE UPPER-AIR PATTERN OVER CONUS WILL FEATURE AMPLIFICATION
OF RIDGING FROM GREAT BASIN ACROSS NRN ROCKIES AND NRN HIGH
PLAINS...IN ADVANCE OF LARGE CYCLONE MOVING EWD ACROSS NERN PAC.
JUST E OF THAT RIDGING...SHORTWAVE TROUGH IS MOVING EWD ACROSS
N-CENTRAL PLAINS...WITH MIDDLE-UPPER-LEVEL CIRCULATION CENTER
EVIDENT OVER BLACK HILLS ATTM.  THIS SYSTEM WILL MOVE SLOWLY EWD
ACROSS DAKOTAS AND NRN NEB...REACHING WRN MN AND NEB/IA BORDER BY
12Z.  LOOSELY ATTACHED AREA OF MIDLEVEL HEIGHT WEAKNESS WILL PERSIST
ACROSS SRN HIGH PLAINS...PARTLY RELATED TO VORTICITY RESIDUE FROM
FORMER EAST-PAC HURRICANE ODILE.

FARTHER E...STG SHORTWAVE TROUGH EXTENDING FROM ERN QUE SSWWD OVER
ERN NEW ENGLAND WILL EJECT NEWD...LEAVING BEHIND SECONDARY VORTICITY
LOBE NOW OVER GA/SC.  RESULTANT/WEAK 500-MB CYCLONE SHOULD WEAKEN
GRADUALLY THROUGH PERIOD WHILE MEANDERING ERRATICALLY OVER SRN
PIEDMONT REGION.

AT SFC...11Z ANALYSIS SHOWED COLD FRONT FROM OFFSHORE GA/CAROLINAS/
WSWWD ACROSS NRN FL AND NRN GULF TO S-CENTRAL TX...BEFORE FRONT
LOSES IDENTITY IN HIGHER TERRAIN OF NRN MEX.  MOST OF THIS FRONT
SHOULD BECOME QUASISTATIONARY ON SYNOPTIC SCALE THROUGH PERIOD.
ONLY MESOSCALE SHIFTS IN POSITION ARE LIKELY OUTSIDE POSSIBLE
WAVE-LOW DEVELOPMENT OFFSHORE GA/CAROLINAS.  LEE-SIDE TROUGHING WITH
WEAK ATTACHED LOWS WAS EVIDENT FROM MT/ND BORDER REGION SWD ACROSS
ERN CO AND ERN NM.

...CENTRAL PLAINS...
WIDELY SCATTERED TSTMS ARE EXPECTED TO DEVELOP THIS AFTN...SOME OF
WHICH MAY PERSIST INTO EARLY-MID EVENING.  ISOLATED SVR HAIL AND
STG-/DAMAGING GUSTS MAY OCCUR.

GRADUAL LOW-LEVEL THETAE ADVECTION WILL CONTINUE ACROSS SRN/CENTRAL
HIGH PLAINS E OF LEE TROUGH...WITH CONTINUING NNEWD SPREAD OF SFC
DEW POINTS MID 50S TO LOW 60S F WITHIN NARROW CORRIDOR FROM ERN NM
TO WRN NEB AND SRN SD.  THIS MOISTURE...COMBINED WITH POCKETS OF
SUSTAINED INSOLATION AND WEAK LIFT INVOF TROUGH...WILL SUPPORT
CONVECTIVE DEVELOPMENT THIS AFTN BEHIND MORNING CONVECTION NOW
MOVING EWD ACROSS CENTRAL KS AND ERN NEB.  COLDER TEMPS ALOFT ARE
EXPECTED WITH NWD EXTENT IN PROXIMITY TO SHORTWAVE TROUGH...WHILE PW
GENERALLY WILL INCREASE SWD.  WITH WWD EXTENT...LAPSE RATES ALOFT
SHOULD WEAKEN IN RELATION TO 450-500-MB STABLE LAYER EVIDENT IN
MORNING AMA/DNR RAOBS...WHILE HEIGHTS ALOFT INCREASE WITH TIME OVER
CENTRAL/SRN ROCKIES.  AS SUCH...MOST FAVORABLE PARAMETRIC OVERLAP
FOR ORGANIZED TSTMS AND MRGL-SVR WIND/HAIL PROBABILITIES APPEARS TO
BE FROM NEB SANDHILLS SWD TO W-CENTRAL/SWRN KS.  500-1500 J/KG
MLCAPE MAY DEVELOP...WITH AROUND 30-40 KT EFFECTIVE-SHEAR MAGNITUDES
INDICATING MULTICELLULAR AND AT LEAST TRANSIENT SUPERCELLULAR MODE.

RELATIVE MIN OR SMALL GAP MAY DEVELOP BETWEEN COLD-CORE-INFLUENCED
CONVECTION OVER NEB AND HIGHER-THETAE-SUPPORTED ACTIVITY IN
KS...HOWEVER MESOSCALE UNCERTAINTIES PRECLUDE BIFURCATING AREA OF 5%
PROBABILITY ATTM.  CONCERNS OVER COVERAGE...AS WELL AS LACK OF BOTH
STRONGER LAPSE RATES AND GREATER VERTICAL SHEAR IN MOST BUOYANT AIR
MASS...PRECLUDES SUFFICIENT UNCONDITIONAL PROBABILITIES FOR
CATEGORICAL OUTLOOK ATTM.

..EDWARDS/MARSH.. 09/23/2014




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