DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 101951
SWODY1
SPC AC 101949

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0249 PM CDT SUN JUN 10 2012

VALID 102000Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MS
VALLEY...MID-MO VALLEY...CNTRL PLAINS AND SRN PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE ERN GULF
COAST STATES...

SEVERAL CHANGES HAVE BEEN MADE TO THE OUTLOOK AT 20Z. THE FIRST
CHANGE IS TO EXPAND THE SIGNIFICANT HAIL HATCHED AREA SSWWD ACROSS
MUCH OF ERN KS WHERE MESOANALYSIS SHOWS STRONG INSTABILITY IN PLACE
WITH MLCAPE IN THE 3000 TO 4000 J/KG RANGE. SHORT-TERM MODELS
DEVELOP CONVECTION ALONG THE I-35 CORRIDOR FROM WICHITA TO TOPEKA
INCREASING CONFIDENCE IN THAT A THREAT FOR HAIL GREATER THAN 2
INCHES WILL EXIST THERE. THE SECOND CHANGE IS TO TRIM THE ERN EDGE
OF THE 15 PERCENT HAIL PROBABILITY IN THE UPPER MS VALLEY WHERE
CONVECTION IS NOT EXPECTED UNTIL LATER TONIGHT FROM NCNTRL WI SSWWD
INTO ERN IA. THE THIRD CHANGE TO THE OUTLOOK IS TO TRIM THE WRN EDGE
OF THE SLIGHT RISK AREA ACROSS AL AND THE FAR WRN FL PANHANDLE
BEHIND THE LINEAR MCS CURRENTLY MOVING EWD INTO SW GA.
OTHERWISE...THE ONLY CHANGES ARE MINOR ADJUSTMENTS TO THE LINES.

..BROYLES.. 06/10/2012

.PREV DISCUSSION... /ISSUED 1117 AM CDT SUN JUN 10 2012/

...SYNOPSIS...

ELONGATED VORTICITY MAXIMUM AND ASSOCIATED MID AND UPPER-LEVEL JET
STREAKS OVER THE NRN HIGH PLAINS WILL PROGRESS ENEWD WITH A CORRIDOR
OF 500-MB HEIGHT FALLS IN EXCESS OF 50-100 M/12-HR OVERSPREADING THE
RED RIVER AND UPPER MS VALLEYS. STRENGTHENING MIDLEVEL FLOW FIELD
ON THE SRN PERIPHERY OF THE N-CNTRL CONUS TROUGH WILL CONTRIBUTE TO
THE ENEWD MOVEMENT OF UPPER TROUGH OVER THE LOWER MS VALLEY AND
CNTRL GULF STATES.

AT THE SURFACE...COLD FRONT ATTENDANT TO THE FORMER SYSTEM MENTIONED
ABOVE WILL ADVANCE FROM THE ERN DAKOTAS EWD INTO THE UPPER
MIDWEST/UPPER GREAT LAKES. THE SRN EXTENSION OF THIS BOUNDARY WILL
PUSH SWD/SEWD INTO THE SRN PLAINS. ELSEWHERE...SEGMENTED WARM FRONT
ACROSS THE GULF STATES INTO SRN APPALACHIANS WILL TEND TO WEAKEN
THROUGH THE D1 PERIOD.

...UPPER MS VALLEY/UPPER MIDWEST INTO KS/OK...

12Z REGIONAL SOUNDINGS INDICATE THAT A WELL-DEFINED EML AND
ASSOCIATED STRONG CAP HAS BEEN ADVECTED ACROSS THE CNTRL PLAINS INTO
MID MO VALLEY ON THE SRN/SERN PERIPHERY OF N-CNTRL CONUS UPPER
TROUGH. AS SUCH...INITIAL SURFACE-BASED STORM DEVELOPMENT IS
ANTICIPATED BY MID AFTERNOON ALONG NRN EXTENSION OF COLD FRONT /AND
PERHAPS PRE-EXISTING CONVECTIVE OUTFLOW BOUNDARY/ OVER THE UPPER MS
VALLEY WHERE MORE SIGNIFICANT HEIGHT FALLS AND LOW-LEVEL UPLIFT WILL
ERODE WEAKER CAP. SUBSEQUENT SWWD DEVELOPMENT OF STORMS ALONG FRONT
THROUGH THE MID MO VALLEY INTO PORTIONS OF KS/OK WILL LIKELY OCCUR
LATE THIS AFTERNOON INTO EVENING OWING TO STRONG BOUNDARY LAYER
HEATING AND SUSTAINED LOW-LEVEL CONVERGENCE.

THE PRESENCE OF THE STEEP MIDLEVEL LAPSE RATES...BOUNDARY LAYER
DEWPOINTS IN THE 60S...AND INCREASED DIABATIC WARMING WILL YIELD A
MODERATE-STRONGLY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE VALUES
RANGING FROM 1000-2000 J/KG OVER THE UPPER MS VALLEY TO 2500-3500
J/KG ACROSS PARTS OF KS/OK. LATEST MODEL GUIDANCE SUGGESTS THAT THE
STRONGEST MID AND HIGH-LEVEL WIND FIELD /AND RESULTANT VERTICAL
SHEAR/ WILL LAG WARM SECTOR TO THE W. HOWEVER...FORECAST HODOGRAPHS
DO SUGGEST THAT THE ERN FRINGE OF STRONGER DEEP-LAYER SHEAR /I.E.
30-40 KT/ WILL COINCIDE WITH SURFACE FRONT...THOUGH ORIENTATION OF
SHEAR VECTORS WILL BE ALIGNED LARGELY PARALLEL WITH FRONT...
ESPECIALLY ACROSS THE UPPER MS VALLEY. THIS WOULD SUGGEST THAT
STORMS MAY TRANSITION TO A LINEAR CONVECTIVE MODE WITHIN THE FIRST
HOUR OR TWO AFTER INITIATION WITH DAMAGING WINDS AND HAIL BEING THE
PRIMARY HAZARDS. THE GREATEST RISK FOR A TORNADO OR TWO WILL EXIST
ACROSS PORTIONS OF MN/WI LATE THIS AFTERNOON INTO EVENING WHERE
LOW-LEVEL SHEAR WILL BE ENHANCED ALONG LLJ AXIS.

...CNTRL/ERN GULF COAST STATES...

LATEST MODEL GUIDANCE SUGGESTS THAT A BELT OF 30-35 KT SWLY WINDS IN
THE 700-500-MB LAYER WILL DEVELOP NNEWD THROUGH THE FL PNHDL INTO
AL/WRN GA ALONG ERN PERIPHERY OF UPPER TROUGH. THIS STRENGTHENING
WIND FIELD WILL ALIGN WITH A SLY LLJ OF SIMILAR MAGNITUDE...YIELDING
A VERTICALLY VEERING WIND PROFILE WITH DEEP-LAYER SHEAR INCREASING
TO 30-35 KT. GIVEN THE MOIST/MODERATELY UNSTABLE AIR MASS PRESENT
ACROSS THE REGION...ENVIRONMENT IS EXPECTED TO BECOME INCREASINGLY
SUPPORTIVE OF ORGANIZED STORM MODES...INCLUDING SUPERCELLS...WITH AN
ASSOCIATED RISK FOR A COUPLE TORNADOES AND DAMAGING WINDS. IN
FACT...VARIOUS CONVECTION-ALLOWING MODEL SOLUTIONS DEPICT THE
DEVELOPMENT OF AN ARCING CONVECTIVE LINE DEVELOPING OVER SRN AL AND
THE FL PNHDL WHICH SUBSEQUENTLY MOVES INTO W-CNTRL/SWRN GA BY THIS
AFTERNOON INTO EVENING.

FOR ADDITIONAL NEAR-TERM GUIDANCE ON THIS AREA...SEE MCD 1111.

...SWRN OK INTO THE EDWARDS PLATEAU OF TX...

A VERY HOT BOUNDARY LAYER /I.E. TEMPERATURES OF 100-105+ F/ IS
EXPECTED TO DEVELOP INVOF DRYLINE AND NWRN TX THERMAL LOW THIS
AFTERNOON. AND WHILE LARGE-SCALE FORCING FOR ASCENT WILL REMAIN
NEGLIGIBLE THROUGH THE PEAK OF THE DIURNAL HEATING CYCLE...THE
STRONG INSOLATION AND SUSTAINED LOW-LEVEL CONVERGENCE MAY BE
SUFFICIENT TO INITIATE ISOLATED STORMS. GIVEN THE STEEP LAPSE RATE
ENVIRONMENT WITH MLCAPE APPROACHING 3000-4000+ J/KG...SETUP WILL
FOSTER INTENSE UP/DOWNDRAFTS WITH AN ASSOCIATED RISK FOR LARGE HAIL
AND STRONG DOWNBURST WINDS THROUGH THIS EVENING.

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