Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 071731
SWODY2
SPC AC 071730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT TUE JUL 07 2015

VALID 081200Z - 091200Z

...THERE IS A MRGL RISK OF SVR TSTMS OVER A PORTION OF THE MID MS
VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS OVER A PORTION OF THE SRN HIGH
PLAINS...

...SUMMARY...
A CONDITIONAL RISK WILL EXIST FOR A COUPLE OF TORNADOES OVER THE
MIDDLE MISSISSIPPI VALLEY WEDNESDAY AFTERNOON AND EVENING. A FEW
STRONG STORMS WILL ALSO BE POSSIBLE OVER A PORTION OF THE SOUTHERN
HIGH PLAINS.

...SYNOPSIS...

BELT OF STRONGER WINDS ALOFT WILL REMAIN NORTH OF THE INTERNATIONAL
BORDER WITH MODEST QUASI-ZONAL FLOW PERSISTING OVER THE REST OF THE
U.S. DOWNSTREAM FROM A CUTOFF UPPER LOW THAT WILL DRIFT SLOWLY INTO
CA. SEVERAL PERTURBATIONS EMBEDDED WITHIN THIS FLOW REGIME ARE OF
INTEREST INCLUDING ONE CURRENTLY LOCATED OVER SWRN OK/NWRN TX THAT
WILL MOVE SLOWLY ENEWD THROUGH THE MID MS VALLEY WEDNESDAY. ANOTHER
SUCH FEATURE OVER NRN AZ WILL EMERGE OVER THE SRN/CNTRL HIGH PLAINS
WEDNESDAY AFTERNOON. AT THE SFC A CONVECTIVELY ENHANCED FRONT WILL
STALL FROM THE SRN PLAINS INTO THE MID-MS VALLEY BEFORE POSSIBLY
ADVANCING SLOWLY NWD AS A WARM FRONT IN RESPONSE TO WEAK
CYCLOGENESIS.

...MID MS VALLEY REGION...

SHOWERS AND THUNDERSTORMS WILL LIKELY BE ONGOING 12Z WEDNESDAY IN
VICINITY OF STALLED FRONT FROM ERN OK INTO NRN ARK/SRN MO AND THE OH
VALLEY. A SFC LOW INDUCED BY THE SLOW...ENEWD-MOVING VORTICITY
MAXIMUM WILL DEVELOP NEWD ALONG THIS BOUNDARY THROUGH THE MID MS
VALLEY DURING THE DAY ACCOMPANIED BY A STRONG /50+ KT/ SLY LLJ. THE
INTERACTION OF THE LLJ WITH THE FRONT WILL PROBABLY MAINTAIN
CONVECTION ALONG AND NORTH OF THIS FEATURE. A VERY MOIST BOUNDARY
LAYER WITH LOW 70S F DEWPOINTS WILL RESIDE SOUTH OF CONVECTIVELY
REINFORCED FRONT WHERE POTENTIAL WILL EXIST FOR SOME WARM SECTOR
DESTABILIZATION. HOWEVER...WIDESPREAD CLOUDS AND WEAK MID-LEVEL
LAPSE RATES SUGGEST INSTABILITY WILL REMAIN MARGINAL WITH MLCAPE
PROBABLY AOB 500 J/KG. NEVERTHELESS...DEPENDING ON DEGREE OF
BOUNDARY LAYER WARMING...POTENTIAL EXISTS FOR STORMS TO INTENSIFY.
SOME OF THESE STORMS MAY POSE A RISK FOR ISOLATED TORNADOES AS THEY
MOVE ENEWD AND INTERACT WITH THE FRONT WHERE 0-1 KM HELICITY WILL BE
LOCALLY ENHANCED AT THE INTERSECTION OF THE LLJ AND BOUNDARY. THIS
REGION WILL BE MONITORED...AND A SLIGHT RISK MIGHT BE NEEDED IN DAY
1 UPDATES ONCE UNCERTAINTIES REGARDING EVOLUTION OF MESOSCALE AND
THERMODYNAMIC ENVIRONMENT HAVE BEEN MITIGATED.

...SRN HIGH PLAINS...

COLD FRONT HAS PUSHED THROUGH MUCH OF WRN TX...AND THIS BOUNDARY
WILL BEGIN TO UNDERGO FRONTOLYSIS AND MOVE SLOWLY NWD AS A WARM
FRONT AS WINDS RETURN TO SLY NORTH OF THIS FEATURE. WHILE THE RICHER
MOISTURE WILL REMAIN CONFINED TO SOUTH OF THE FRONT...AT LEAST LOW
60S F DEWPOINTS WILL RETURN NWD THROUGH THE SRN HIGH PLAINS EAST OF
DEVELOPING LEE TROUGH AND BENEATH ERN FRINGE OF STEEPER MID LEVEL
LAPSE RATES RESULTING IN 1500 J/KG MLCAPE. MEANWHILE...DIABATIC
WARMING OVER THE HIGHER TERRAIN AND FORCING FOR ASCENT ATTENDING A
SLOW MOVING SHORTWAVE TROUGH WILL PROMOTE DEVELOPMENT OF
THUNDERSTORMS ESPECIALLY FROM NERN NM INTO SERN CO DURING THE
AFTERNOON. WHILE VERTICAL SHEAR IS EXPECTED TO REMAIN RELATIVELY
MODEST...A FEW STORMS MAY BECOME CAPABLE OF PRODUCING ISOLATED
DOWNBURST WINDS AND SMALL TO MARGINALLY SEVERE HAIL AS THEY DEVELOP
EWD THROUGH THE TX PANHANDLE.

..DIAL.. 07/07/2015




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