Severe Storm Outlook Narrative (AC)
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
ACUS01 KWNS 291631
SWODY1
SPC AC 291629

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT FRI MAY 29 2015

VALID 291630Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE SRN PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE UPPER GREAT LAKES TO
SRN PLAINS AND LOWER MS VALLEY...

...SUMMARY...
STRONG TO SEVERE STORMS WILL OCCUR LATER TODAY INTO TONIGHT OVER
WESTERN PORTIONS OF THE SOUTHERN PLAINS...WITH LARGE HAIL AND
LOCALLY DAMAGING WIND THE MAIN THREATS. SCATTERED THUNDERSTORMS WITH
STRONG WINDS AND PERHAPS HAIL ARE EXPECTED FROM THE GREAT LAKES
SOUTHWEST ACROSS THE MID-MISSOURI VALLEY AND OZARKS INTO THE CENTRAL
PLAINS AND LOWER MISSISSIPPI VALLEY.

...SYNOPSIS...

THE PRIMARY BELT OF POLAR WESTERLIES WILL REMAIN CONFINED TO CANADA
IN ASSOCIATION WITH A VIGOROUS SHORT-WAVE TROUGH WHICH WILL
TRANSLATE SEWD FROM MANITOBA INTO ONTARIO.  THIS SYSTEM WILL BE
LOOSELY PHASED WITH A LOWER-LATITUDE SHORT-WAVE TROUGH WHICH WILL
TRACK FROM WY/CO INTO THE MID MO VALLEY AND UPPER MIDWEST.
ELSEWHERE...A VORTICITY MAXIMUM --LARGELY OF CONVECTIVE ORIGIN--
WILL PROGRESS FROM THE SRN PLAINS INTO OZARKS AND LOWER MS VALLEY.

AT THE SURFACE...A COLD FRONT ASSOCIATED WITH THE CNTRL CANADA
UPPER-AIR SYSTEM WILL ADVANCE SEWD THROUGH THE UPPER GREAT LAKES AND
MID/LOWER MO VALLEY WITH THE WRN EXTENSION OF THE FRONT REACHING THE
SRN HIGH PLAINS LATE TONIGHT INTO EARLY SATURDAY.

...SRN HIGH PLAINS THIS AFTERNOON INTO TONIGHT...

MORNING WATER VAPOR IMAGERY IS SUGGESTIVE OF A WEAK MID-LEVEL
IMPULSE ALONG THE AZ-NM BORDER WHICH SHOULD CONTINUE ESEWD TODAY
WITHIN THE SRN PERIPHERY OF THE MORE PROMINENT WY/CO SHORT-WAVE
TROUGH MENTIONED ABOVE.  FORCING FOR ASCENT ASSOCIATED WITH THIS
FEATURE COUPLED WITH AN INCREASING LOW-LEVEL UPSLOPE WIND COMPONENT
WILL FOSTER THE DEVELOPMENT OF TSTMS THIS AFTERNOON FROM THE RATON
MESA SWD ACROSS PARTS OF ERN NM WITH ACTIVITY MOVING/DEVELOPING
ESEWD INTO WRN TX LATE THIS AFTERNOON INTO EVENING.

12Z UPPER-AIR DATA INDICATE THAT LOW-LEVEL MOISTURE QUALITY IS
POORER THAN PAST DAYS.  HOWEVER...ABUNDANT SUNSHINE IN CONCERT WITH
RELATIVELY COOL MID-LEVEL TEMPERATURES /I.E. -11 TO -13 C AT 500 MB/
SHOULD SUPPORT MODERATE AFTERNOON INSTABILITY WITH MLCAPE OF
1000-2000+ J/KG.  THIS INSTABILITY WILL ALIGN WITH A CORRIDOR OF
MODEST /30-35 KT/ DEEP-LAYER SHEAR WHICH WILL PROMOTE MULTICELL AND
SOME SUPERCELL STRUCTURES WITH THE INITIAL HAZARD BEING SEVERE HAIL.
BY THIS EVENING....STORMS MAY EVOLVE INTO A FORWARD-PROPAGATING TSTM
COMPLEX WITH THE MAIN SEVERE WEATHER RISK TRANSITIONING TO DAMAGING
OUTFLOW WINDS.

...OZARK PLATEAU EWD/NEWD INTO THE OZARKS AND LOWER MS VALLEY THIS
AFTERNOON/EVENING...

MID-MORNING SURFACE OBSERVATIONS AND MOSAIC RADAR DATA INDICATE AN
MCV OVER CNTRL OR S-CNTRL OK WITH THE LEADING EDGE OF A COLD POOL
ASSOCIATED WITH A DECAYED NOCTURNAL MCS STRETCHING FROM THE MCV
SSEWD THROUGH ERN TX.  THINNING CLOUDS AHEAD OF THE COLD POOL WILL
COMBINE WITH DEWPOINTS IN THE MID 60S TO LOWER 70S TO SUPPORT
POCKETS OF MODERATE AFTERNOON INSTABILITY WHERE MLCAPE MAY APPROACH
1000-1500 J/KG.

FORCING FOR ASCENT AHEAD OF THE MCV AND LOW-LEVEL CONVERGENCE ALONG
THE RESIDUAL COLD POOL SHOULD FOCUS RENEWED STORM DEVELOPMENT THIS
AFTERNOON FROM PARTS OF ERN OK/WRN AR SWD INTO THE SABINE RIVER
VALLEY.  ACTIVITY WILL SUBSEQUENTLY SPREAD EWD AND NEWD TOWARD THE
LOWER MS VALLEY AND OZARKS LATE THIS AFTERNOON INTO EVENING WITH A
RISK FOR MAINLY ISOLATED DAMAGING WINDS AND SOME HAIL.

12Z RAOBS AND CURRENT VAD DATA FROM NRN TX INTO ERN OK/WRN AR DO
INDICATE A CHANNEL OF STRONGER LOW TO MID-TROPOSPHERIC FLOW WHICH
HAS BEEN GENERATED BY THE NOW-DECAYED MCS.  SHOULD THIS
HIGHER-MOMENTUM FLOW BECOME FAVORABLY ALIGNED WITH CLEARING SKIES
AND RESULTING GREATER AIR MASS DESTABILIZATION...POTENTIAL WOULD
EXIST FOR A MORE ORGANIZED SEVERE WEATHER EPISODE AND AN UPGRADE TO
SLIGHT RISK AT 20Z.

...MID MO VALLEY INTO UPPER MIDWEST THIS AFTERNOON/EVENING...

LOW-LEVEL UPLIFT ALONG THE COLD FRONT WILL BE AUGMENTED BY FORCING
FOR ASCENT/DCVA ATTENDANT TO THE WY/CO IMPULSE AND AN MCV JUST E OF
FSD TO PROMOTE AN INCREASE IN STORMS THROUGH THE PEAK OF THE DIURNAL
HEATING CYCLE.  WEAK LAPSE RATES AND WIDESPREAD CLOUDS WILL LIMIT
THE POTENTIAL FOR ROBUST AIR MASS DESTABILIZATION AND A RESULTANT
RISK FOR ORGANIZED SEVERE STORMS.  NONETHELESS...A FEW STRONG TO
MARGINALLY SEVERE STORMS MAY MATERIALIZE BY AFTERNOON...NAMELY OVER
PARTS OF SERN MN/NERN IA/WRN WI IMMEDIATELY AHEAD OF A FRONTAL WAVE
WHERE FORCING FOR ASCENT AND VERTICAL SHEAR ARE LOCALLY ENHANCED.
LOCALLY GUSTY WINDS WILL BE THE PRIMARY HAZARD WITH THESE STORMS.

..MEAD/BUNTING.. 05/29/2015




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.