Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 042003
SWODY1
SPC AC 042002

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0302 PM CDT SAT JUL 04 2015

VALID 042000Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN PLAINS FROM
NORTHEAST MT TO NRN ND...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN/CNTRL PLAINS
FROM SD ACROSS WRN NEB AND PARTS OF NERN CO AND NWRN KS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE DELTA REGION TO SRN
AL...

...THERE IS A MRGL RISK OF SVR TSTMS OVER NRN NV...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE NORTHERN/CENTRAL AND
SOUTHERN PLAINS TO GULF AND SOUTHEAST COASTS...

...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.

...DELTA REGION TO SOUTHERN AL/WRN FL PNHDL...
QUASI-LINEAR CONVECTIVE SYSTEM NEAR THE BASE OF A SLOW-MOVING LARGE
SCALE TROUGH SHOULD CONTINUE TO SETTLE ESEWD INTO MODERATELY
UNSTABLE AIRMASS FROM SRN LA ALONG THE GULF COAST AND ACROSS SRN AL
AND THE WRN FL PNHDL THROUGH LATE AFTERNOON. MID-LEVEL FLOW OF
25-35KT AND LIFT ASSOCIATED WITH THE MID/UPPER TROUGH WILL LIKELY
SUSTAIN MARGINALLY ORGANIZED STORMS ALONG THE LEADING EDGE OF
CONVECTIVE COLD POOLS WITH SEA-BREEZE AND OTHER BOUNDARY
INTERSECTIONS OCCASIONALLY BOOSTING WET DOWNBURST POTENTIAL.

...SOUTHEAST COAST...
A NARROW CORRIDOR OF ISOLATED DAMAGING WIND POTENTIAL ALSO APPEARS
TO BE DEVELOPING FROM NRN FL NORTHEAST ACROSS SOUTHEAST GA AND
PERHAPS SRN SC. DCAPE IN THIS AXIS WAS IN EXCESS OF 1000 J/KG WHERE
TEMPS HAVE CLIMBED INTO THE LOWER 90SF. DIFFERENTIAL HEATING AND
OUTFLOWS FROM THE POORLY ORGANIZED CLUSTER OF STORMS ACROSS SRN GA
MAY BE SUFFICIENT FOR ADDITIONAL DEVELOPMENT ACROSS THE INSTABILITY
AXIS DESPITE THE ABSENCE OF STRONGER FLOW AND ASCENT. A COUPLE TO A
FEW DOWNBURST EVENTS APPEAR POSSIBLE.

..NC..
HIGHER PROBABILITIES WERE REMOVED FROM ERN NC AS IT APPEARS STORM
COVERAGE WILL REMAIN TOO ISOLATED TO SUPPORT A CONTINUATION OF THE
SLGT RISK IN THIS AREA.

THE REMAINDER OF THE OUTLOOK WAS UNCHANGED FROM EARLIER FORECAST.

..CARBIN.. 07/04/2015

.PREV DISCUSSION... /ISSUED 1130 AM CDT SAT JUL 04 2015/

...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.



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