Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS02 KWNS 061731
SWODY2
SPC AC 061730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED MAY 06 2015

VALID 071200Z - 081200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS TO THE
UPPER MIDWEST...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PORTIONS OF NV/UT...

...SUMMARY...
SEVERE THUNDERSTORMS WILL BE POSSIBLE THURSDAY FROM PORTIONS OF THE
SOUTHERN AND CENTRAL PLAINS NORTHEASTWARD INTO THE UPPER MIDWEST.

...SYNOPSIS...
RELATIVELY LIMITED LARGE-SCALE PATTERN FLUCTUATION WILL OCCUR OVER
THE CONUS ON THURSDAY. AN INCREASINGLY CLOSED UPPER LOW OVER THE
PACIFIC NORTHWEST WILL SHIFT SOUTH-SOUTHWESTWARD OVER THE GREAT
BASIN/CA ON THURSDAY...WHILE ONE OR MORE SHORTWAVE
TROUGHS/CONVECTIVELY RELATED DISTURBANCES MOVE NORTHEASTWARD OVER
THE CENTRAL/SOUTHERN PLAINS TO UPPER MIDWEST AMID A MODERATELY
STRONG BRANCH OF SOUTHWESTERLY FLOW ALOFT. A COLD FRONT WILL SPREAD
EASTWARD OVER THE UPPER MIDWEST/MIDDLE MO VALLEY THROUGH THURSDAY
NIGHT...WHILE A DRYLINE WILL EXTEND GENERALLY SOUTHWARD ACROSS WEST
TX/FAR WESTERN OK FROM A SOUTH-CENTRAL HIGH PLAINS SURFACE LOW.

...CENTRAL/SOUTHERN PLAINS...
MORNING SHOWERS/SOME EMBEDDED THUNDERSTORMS AND RELATED CLOUD COVER
WILL LIKELY BE FACTORS THURSDAY MORNING ACROSS PORTIONS OF KS/OK
INTO NORTH TX. ON THE WESTERN FRINGE OF THIS EARLY DAY ACTIVITY...AN
ELEVATED MIXED LAYER/PLUME OF STEEP MID-LEVEL LAPSE RATES WILL
QUICKLY BECOME REESTABLISHED ATOP A RELATIVELY MOIST AIR MASS WITH
60S F SURFACE DEWPOINTS COMMON TO THE EAST OF A SOUTHERN HIGH PLAINS
DRYLINE/SURFACE TRIPLE POINT AND TO THE SOUTHEAST OF A SLOW
SOUTHEASTWARD-MOVING FRONT ACROSS NORTHERN KS/EASTERN NEB. SCENARIO
SHOULD LEAD TO AT LEAST MODERATE DESTABILIZATION WITH UPWARDS OF
2500-3500 J/KG MLCAPE PLAUSIBLE BY MID-AFTERNOON PARTICULARLY ACROSS
WEST-CENTRAL/NORTH-CENTRAL TX INTO EASTERN TX PANHANDLE/WESTERN OK
AND WESTERN/NORTHERN KS.

LARGER-SCALE FORCING FOR ASCENT WILL BE RELATIVELY MODEST...BUT THE
LEFT-EXIT REGION OF AN APPROACHING SOUTHERN STREAM JET AND THE
INFLUENCE OF MODERATELY STRONG CYCLONIC WESTERLIES...ALONG WITH
STRONG HEATING/SUFFICIENT CONVERGENCE...SHOULD CONTRIBUTE TO AT
LEAST ISOLATED DEEP CONVECTIVE INITIATION BY MID/LATE AFTERNOON.
INITIAL DEEPER CONVECTIVE DEVELOPMENT MAY OCCUR ACROSS EASTERN CO BY
MID/LATE AFTERNOON VIA A POST-FRONTAL UPSLOPE REGIME...WITH
ADDITIONAL DEVELOPMENT BY LATE AFTERNOON/EARLY EVENING NEAR THE
DRYLINE ACROSS THE TX/OX PANHANDLES AND NEAR THE TRIPLE
POINT/ADJACENT FRONT ACROSS WESTERN/NORTHERN KS.

GIVEN AFOREMENTIONED BUOYANCY...DEEP-LAYER SHEAR /GENERALLY 35-40
KT/ WILL BE SUPPORTIVE OF SUPERCELLS CAPABLE OF LARGE HAIL ALONG
WITH SOME TORNADO RISK. CURRENT THINKING IS THAT THE RELATIVELY
GREATEST TORNADO POTENTIAL WILL EXIST BY EARLY EVENING ACROSS PARTS
OF NORTHWEST TX/FAR WESTERN OK NEAR THE DRYLINE...WITH RESIDUAL
OUTFLOW/DIFFERENTIAL HEATING POTENTIALLY AN ADDITIONAL MESOSCALE
FACTOR ASIDE FROM A NOCTURNALLY STRENGTHENING LOW-LEVEL JET. STORMS
SHOULD COALESCE INTO ONE OR MORE EASTWARD-SPREADING MCS/S DURING THE
LATE EVENING/OVERNIGHT HOURS ACROSS OK/KS AS THE LOW-LEVEL JET/WARM
ADVECTION FURTHER INCREASES.

...SOUTHERN MN AND IA/NORTHWEST MO...
A NORTHEASTWARD-MOVING SHORTWAVE TROUGH WILL AT LEAST GLANCE MOST OF
THE REGION...WHILE WIDESPREAD EARLY-DAY CLOUD COVER/SCATTERED
PRECIPITATION WILL LIKELY PRECEDE AN EAST-SOUTHEASTWARD MOVING COLD
FRONT. DEEP-LAYER SHEAR WILL BE MODEST /30-35 KT AT MOST/ AND
UNCERTAINTIES EXIST REGARDING THE RESIDUAL IMPACTS OF EARLY DAY
CLOUDS/PRECIPITATION. HOWEVER...AT LEAST MODEST CLOUD BREAKS/HEATING
AND THE INFLUX OF LOWER 60S F SURFACE DEWPOINTS COULD LEAD TO
MODERATE DESTABILIZATION THROUGH THE AFTERNOON/EARLY EVENING. THIS
MAY LEAD TO AT LEAST AN ISOLATED SEVERE HAIL/WIND RISK AS STORMS
LIKELY REDEVELOP/INTENSIFY NEAR OR EAST OF THE COLD FRONT. PORTIONS
OF THE REGION COULD WARRANT A CATEGORICAL RISK UPGRADE /SLIGHT/ IN
SUBSEQUENT DAY 1 OUTLOOKS.

...NORTHERN/CENTRAL PORTIONS OF NV/UT...
A FEW STRONGER STORMS WILL BE POSSIBLE OVER THE REGION IN
ASSOCIATION WITH THE EXIT REGION OF THE
RETROGRADING/SOUTHWESTWARD-MOVING UPPER LOW OVER THE WESTERN GREAT
BASIN/CENTRAL CA. STEEP LAPSE RATES/MODEST BUOYANCY AND A SUFFICIENT
VERTICAL SHEAR COULD ALLOW FOR LOCALLY STRONGER WINDS AND POSSIBLY
SOME HAIL.

...COASTAL CAROLINAS THURSDAY NIGHT...
WHILE NOT HIGHLY CONFIDENT IN THE DETAILS...A STRENGTHENING
LOW-LEVEL WIND FIELD COULD APPROACH THE COASTAL CAROLINAS AS EARLY
AS THURSDAY NIGHT/EARLY FRIDAY IN ASSOCIATION WITH A POSSIBLE
SUBTROPICAL OR TROPICAL CYCLONE. REFERENCE THE SPECIAL TROPICAL
WEATHER OUTLOOK STATEMENT FROM NHC FOR ADDITIONAL DETAILS. ANY LOW
TORNADO RISK APPEARS TOO SPECULATIVE DURING THE DAY 2 TIME FRAME
WITH CURRENT THINKING BEING THAT ANY MINI-SUPERCELLS WILL BE WELL
OFFSHORE.

..GUYER.. 05/06/2015




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