Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 041632
SWODY1
SPC AC 041630

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT SAT JUL 04 2015

VALID 041630Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF ND AND MT...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PART OF THE NRN AND
CNTRL HIGH PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE GULF
COAST STATES...

...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN NC...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE NRN PLAINS THROUGH
GULF COAST TO ERN CAROLINAS...

...THERE IS A MRGL RISK OF SVR TSTMS OVER A PART OF THE GREAT
BASIN...

...SUMMARY...
A FEW SEVERE STORMS WITH LARGE HAIL...DAMAGING WINDS...AND POSSIBLY
A TORNADO ARE EXPECTED OVER PARTS OF THE NORTHERN AND CENTRAL PLAINS
LATE THIS AFTERNOON AND EVENING. STORMS CAPABLE OF LOCALLY DAMAGING
WIND AND HEAVY RAIN ARE EXPECTED OVER CENTRAL GULF COAST STATES.
MORE ISOLATED STRONG TO SEVERE STORMS WILL AFFECT THE SOUTHERN
PLAINS...GEORGIA...THE CAROLINAS...AND THE GREAT BASIN.

...SYNOPSIS...

A MID TO UPPER-LEVEL LOW WILL TRACK ACROSS NRN PORTIONS OF THE
CANADIAN PRAIRIE PROVINCES WHILE A RELATED VORTICITY MAXIMUM DIGS
SWD THROUGH BRITISH COLUMBIA INTO THE PACIFIC NW.  THIS PATTERN
EVOLUTION WILL DAMPEN A MID-LEVEL RIDGE PRESENT FROM THE GREAT BASIN
INTO NRN MEXICO...AND EFFECTIVELY FRACTURE THE ERN U.S. LONG-WAVE
TROUGH INTO SEPARATE AIR STREAMS WITH THE NRN BRANCH UNDERGOING
SUBSTANTIAL HEIGHT RISES OVER ONTARIO AND QUEBEC.  MEANWHILE A BELT
OF ENHANCED CYCLONIC FLOW AND COOL MID-LEVEL TEMPERATURES WILL
PERSIST WITH THE SRN PORTION OF THE RESIDUAL TROUGH OVER THE TN
VALLEY AND GULF COAST STATES INTO SERN CONUS.  AHEAD OF THE EVOLVING
CANADIAN UPPER-AIR SYSTEM...A LOW-AMPLITUDE SHORT-WAVE TROUGH WILL
TRACK FROM THE NRN PLAINS INTO THE UPPER MS VALLEY.

AT THE SURFACE...A LEE CYCLONE WILL DEEPEN TODAY OVER ERN MT ALONG A
COLD FRONT SHIFTING SWD INTO THE NRN HIGH PLAINS.  AN ASSOCIATED LEE
TROUGH WILL CORRESPONDINGLY STRENGTHEN FROM THE LOW SWD THROUGH THE
CNTRL HIGH PLAINS.  ELSEWHERE...A QUASI-STATIONARY FRONT CURRENTLY
FROM THE SRN PLAINS THROUGH LOWER OH VALLEY TO AN AREA OF LOW
PRESSURE OVER THE MID ATLANTIC WILL BECOME MORE DIFFUSE WITH TIME.

...NRN/CNTRL PLAINS THIS AFTERNOON INTO TONIGHT...

THE INFLUENCES OF THE LEAD SHORT-WAVE TROUGH MOVING THROUGH THE
DAKOTAS TODAY...AND THE LARGER-SCALE CANADIAN UPPER-AIR SYSTEM WILL
AUGMENT CIRCULATIONS ALONG THE SWD-MOVING COLD FRONT AND LEE TROUGH
TO FOSTER CORRIDORS OF STORMS BY LATE AFTERNOON/EARLY EVENING OVER
ND INTO NRN MT...AND FROM PARTS OF WRN/CNTRL SD INTO WRN NEB.  THE
AMBIENT WARM SECTOR AIR MASS WILL BE CHARACTERIZED BY STEEP LAPSE
RATES...MODEST BOUNDARY-LAYER MOISTURE CONTENT AND RESULTING MLCAPE
OF 1500-2500 J/KG.  WHEN COUPLED WITH A VERTICALLY VEERING WIND
PROFILE AND 30-35 KT OF DEEP-LAYER SHEAR THE SETUP WILL BE
SUPPORTIVE OF SUPERCELLS CAPABLE OF LARGE HAIL...LOCALLY DAMAGING
WINDS AND PERHAPS A TORNADO OR TWO.

RECENT CONVECTION-ALLOWING MODEL GUIDANCE IS SUGGESTIVE THAT THE
DIURNALLY ENHANCED STORMS OVER SD/NEB COULD EVOLVE INTO A SWD-MOVING
MCS OVER SWRN NEB/NWRN KS LATER THIS EVENING OWING THE ENHANCEMENT
OF MOIST/UNSTABLE INFLOW BY A NOCTURNALLY STRENGTHENING LLJ.  SHOULD
THIS SCENARIO UNFOLD...THE RISK FOR ISOLATED DAMAGING WINDS COULD
CONTINUE INTO TONIGHT OVER PARTS OF WRN KS.

...GULF COAST STATES THIS AFTERNOON INTO EVENING...

FORCING FOR ASCENT/DCVA RELATED TO A VORTICITY MAXIMUM PROGRESSING
SEWD INTO THE LOWER MS VALLEY COUPLED WITH LOW-LEVEL UPLIFT ALONG A
COMPOSITE OUTFLOW BOUNDARY MOVING SEWD THROUGH NRN LA AND CNTRL
PARTS OF MS AND AL WILL PROMOTE AN INCREASE IN STORM COVERAGE AND
VIGOR ACROSS THE REGION THROUGH THE PEAK OF THE DIURNAL HEATING
CYCLE.  WHILE VERTICAL SHEAR WILL WEAKEN WITH THE PROGRESSIVE SWD
DISPLACEMENT OF THE WARM SECTOR TODAY...THE PRESENCE OF A VERY MOIST
AIR MASS AND RESULTING MODERATE INSTABILITY WILL PROMOTE STRONG
UP/DOWNDRAFTS WITH THE PRIMARY HAZARD BEING WET MICROBURSTS.

...ERN CAROLINAS THIS AFTERNOON...

THE EWD PROGRESSION OF A SUBTLE MID-LEVEL IMPULSE THROUGH THE SRN
APPALACHIANS HAS GIVEN RISE TO RECENT TSTM DEVELOPMENT OVER CNTRL
NC.  DAYTIME HEATING OF A VERY MOIST AIR MASS OVER ERN NC WILL YIELD
AN AXIS OF MODERATE INSTABILITY LATER TODAY WHICH WILL COINCIDE WITH
A RESIDUAL BELT OF ENHANCED WLY FLOW IN THE 700-600-MB LAYER PER
CURRENT VAD DATA AND FORECAST SOUNDINGS.  AS SUCH...THE POTENTIAL
WILL EXIST FOR THE EVOLUTION OF BOWING STORM STRUCTURES CAPABLE OF
DAMAGING WIND GUSTS INTO EARLY EVENING.

...GREAT BASIN THIS AFTERNOON...

A SHORT-WAVE TROUGH OVER THE LOWER CO VALLEY WILL PROGRESS NNWWD
THROUGH NV TODAY...PROMOTING A GRADUAL INCREASE IN TSTM COVERAGE AND
INTENSITY.  MORNING VISIBLE SATELLITE SUGGESTS THAT STRONGER HEATING
AND RESULTANT AIR MASS DESTABILIZATION WILL REMAIN CONFINED TO NRN
NV WHERE A FEW BRIEFLY SEVERE STORMS MAY OCCUR LATER TODAY.

..MEAD/MOSIER.. 07/04/2015



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