DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 301946
SWODY1
SPC AC 301943

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0243 PM CDT SUN JUN 30 2013

VALID 302000Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL AND
SRN HIGH PLAINS...

...SRN ROCKIES AND ADJACENT CNTRL/SRN HIGH PLAINS...
TEMPERATURES ARE WARMING INTO THE 70S/80S EARLY THIS AFTERNOON OVER
THE SRN ROCKIES AND ADJACENT HIGH PLAINS...WHICH IS AIDING IN
STEEPENING LOW-LEVEL LAPSE RATES. THIS DESTABILIZATION IN THE
BOUNDARY LAYER WILL SUPPORT A THREAT FOR DAMAGING WIND GUSTS AND
ISOLATED LARGE HAIL AS MULTICELL CLUSTERS AND SMALL LINES STRENGTHEN
AND MOVE SWD ACROSS THE AREA THIS AFTERNOON AND EVENING. REFER TO
MCD 1314 FOR ADDITIONAL SHORT-TERM DETAILS.

...NERN GULF COAST INTO THE CAROLINAS THIS AFTERNOON AND TONIGHT...
PREVIOUS FORECAST REASONING IS ON TRACK.

...MID-ATLANTIC STATES INTO THE NORTHEAST THIS AFTERNOON AND
EVENING...
TWO CHANGES HAVE BEEN MADE TO THE PREVIOUS OUTLOOK. THE FIRST IS A
WWD EXTENSION OF THE 5 PERCENT HAIL PROBABILITY INTO CNTRL
OH...WHERE THUNDERSTORMS CLUSTERS FORMING INVOF A SURFACE BAROCLINIC
ZONE ARE INTERACTING WITH AN ENVIRONMENT CHARACTERIZED BY COOL
MIDLEVEL TEMPERATURES /NEAR -10C AT 500 MB/...MODERATE MLCAPE
/AROUND 1000 J PER KG/...AND 30-40 KT OF EFFECTIVE BULK SHEAR. OVER
NEW ENGLAND...LOW SEVERE WEATHER PROBABILITIES HAVE BEEN EXPANDED
NEWD INTO SRN ME...MAINLY CENTERED ON A SURFACE THETA-E AXIS THAT
EXTENDS FROM NRN VA INTO SRN VT/NH/ME. REFER TO MCD 1313 FOR
ADDITIONAL SHORT-TERM DETAILS.

...CNTRL MT/NWRN WY THIS AFTERNOON AND EVENING...
PREVIOUS FORECAST REASONING IS ON TRACK...ONLY MINOR CHANGES HAVE
BEEN MADE TO THE 5 PERCENT HAIL/WIND DELINEATIONS.

..GARNER.. 06/30/2013

.PREV DISCUSSION... /ISSUED 1113 AM CDT SUN JUN 30 2013/

...SYNOPSIS...

AN INTENSE VORTICITY MAXIMUM OVER THE OZARKS AND ASSOCIATED MID AND
UPPER-LEVEL JET STREAKS FROM THE CNTRL PLAINS INTO OZARK PLATEAU
WILL PROGRESS SSEWD INTO THE LOWER MS VALLEY...CONTRIBUTING TO
FURTHER AMPLIFICATION OF THE LONG-WAVE TROUGH PRESENT OVER ERN NORTH
AMERICA. THESE DEVELOPMENTS COUPLED WITH THE CONTINUED ESEWD
MOVEMENT OF A SHORT-WAVE TROUGH THROUGH AB/SK AND THE NRN HIGH
PLAINS WILL RESULT IN A SLIGHT RETROGRESSION OF THE HIGH-AMPLITUDE
RIDGE PRESENT FROM THE INTERIOR WEST INTO CANADIAN ROCKIES.

IN THE LOW LEVELS...AN EXPANSIVE ANTICYCLONE WILL BUILD SWD FROM THE
CANADIAN PRAIRIE PROVINCES THROUGH THE GREAT PLAINS...EFFECTIVELY
CONTRIBUTING TO THE SWD MOVEMENT OF THE FRONTAL SEGMENT OVER THE
LOWER MS VALLEY TO THE SHELF WATERS OF THE N-CNTRL G.O.M. FARTHER
E/NE...THE SURFACE FRONT WILL REMAIN QUASI-STATIONARY ALONG THE
APPALACHIANS...WHILE TO THE W THIS BOUNDARY WILL REMAIN BANKED ALONG
THE ROCKIES.

...CNTRL/SRN HIGH PLAINS THIS AFTERNOON INTO TONIGHT...

12Z UPPER-AIR ANALYSIS AND MORNING WATER VAPOR IMAGERY SUGGEST A
WEAK MIDLEVEL IMPULSE OVER THE CNTRL HIGH PLAINS WHICH WILL CONTINUE
SSEWD. THIS FEATURE APPEARS WELL CORRELATED WITH AN ACCAS FIELD AND
WIDELY SCATTERED ELEVATED TSTMS OVER NERN AND E-CNTRL CO AS OF 16Z.
THE DOWNSTREAM ENVIRONMENT ACROSS ERN NM/WRN TX SHOULD EXPERIENCE
RATHER STRONG HEATING...WHICH WHEN COUPLED WITH BOUNDARY LAYER
DEWPOINTS IN THE 50S WILL YIELD AFTERNOON MLCAPE VALUES APPROACHING
1000-1500 J/KG.

THE INFLUENCE OF THIS IMPULSE IN CONCERT WITH LOW-LEVEL UPSLOPE FLOW
WILL GIVE RISE TO AN INCREASE IN TSTMS THIS AFTERNOON FROM THE CO
FRONT RANGE TO THE RATON MESA AMIDST A KINEMATIC ENVIRONMENT
FEATURING 25-30 KT NNWLY FLOW IN THE MIDLEVELS. GIVEN FAIRLY
SIZABLE BOUNDARY LAYER T-TD SPREADS...STORMS SHOULD QUICKLY GROW
UPSCALE INTO ONE OR MORE CONVECTIVE SYSTEMS WHICH WILL PROGRESS SWD
THROUGH THE SRN HIGH PLAINS THIS EVENING INTO TONIGHT WITH A RISK
FOR HAIL AND DAMAGING WINDS.

...NERN GULF COAST INTO THE CAROLINAS THIS AFTERNOON AND TONIGHT...

12Z REGIONAL SOUNDINGS SHOW THE PRESENCE OF A VERY MOIST AIR MASS
ACROSS PRE-FRONTAL WARM SECTOR WITH BOUNDARY LAYER DEWPOINTS IN THE
LOWER TO MID 70S AND PW VALUES OF 2.0-2.1 INCHES. THIS MOISTURE
WILL COMBINE WITH DAYTIME HEATING TO PROMOTE A MODERATE TO STRONGLY
UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE VALUES OF 1500-3000 J/KG.
LOW-LEVEL CONVERGENCE ASSOCIATED WITH A WEAK SURFACE LOW DEVELOPING
NEWD FROM THE FL PNHDL WILL BE AUGMENTED BY DEEP ASCENT IN THE
ENTRANCE REGION OF AN UPPER-LEVEL JET STREAK TO FOSTER WIDESPREAD
TSTMS THIS AFTERNOON INTO EVENING.

A STEADILY STRENGTHENING SSWLY TROPOSPHERIC WIND FIELD LATER TODAY
INTO TONIGHT MAY ALLOW FOR SOME STORM ORGANIZATION WITH THE
POTENTIAL FOR MARGINAL SUPERCELL STRUCTURES CAPABLE OF LOCALLY
DAMAGING WINDS AND PERHAPS A TORNADO. SUB-SLIGHT-RISK WIND AND
TORNADO PROBABILITIES WILL BE MAINTAINED OWING TO THE POTENTIAL FOR
CONSIDERABLE CONVECTIVE OVERTURNING PRIOR TO FORECAST INCREASE IN
VERTICAL SHEAR.

...MID-ATLANTIC STATES INTO THE NORTHEAST THIS AFTERNOON AND
EVENING...

TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY TODAY FROM
THE VICINITY OF THE SFC FRONT ALONG THE CNTRL/NRN APPALACHIANS EWD
ACROSS THE WARM SECTOR WHERE DAYTIME HEATING AND A VERY MOIST AIR
MASS CONTRIBUTE TO MLCAPE VALUES OF 1000-2000 J/KG. THIS
INSTABILITY WILL COINCIDE WITH A BELT OF MODESTLY STRONG MIDLEVEL
FLOW /I.E. 500-MB WIND SPEEDS OF 30-40 KT/ WHICH WILL BOOST VERTICAL
SHEAR AND INCREASE THE RISK FOR A FEW SEVERE STORMS CAPABLE OF
MAINLY HAIL AND LOCALLY STRONG WIND GUSTS. FOR ADDITIONAL NEAR-TERM
GUIDANCE ON THIS AREA...SEE MCD 1311.

...CNTRL MT/NWRN WY THIS AFTERNOON AND EVENING...

DESPITE RISING MIDLEVEL HEIGHTS...STRENGTHENING TERRAIN-INDUCED
CIRCULATIONS AND/OR CONVERGENCE ALONG NRN EXTENSION OF SYNOPTIC
FRONT WILL CONTRIBUTE TO ISOLATED TO WIDELY SCATTERED TSTM
DEVELOPMENT WITHIN A STEEP LAPSE RATE ENVIRONMENT WHERE MLCAPE MAY
APPROACH 500-1000 J/KG. GIVEN 30-35 KT OF DEEP NWLY SHEAR...SOME
POTENTIAL WILL EXIST FOR STORM ORGANIZATION/ROTATION WITH AN
ISOLATED WIND/HAIL THREAT.

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