DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 082002
SWODY1
SPC AC 082000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT FRI JUN 08 2012

VALID 082000Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE WRN GREAT
LAKES AND UPPER MS VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NERN
STATES...

SEVERAL CHANGES HAVE BEEN MADE TO THE OUTLOOK AT 20Z. THE FIRST
CHANGE IS TO MAKE THE 30 PERCENT HAIL AND WIND DAMAGE PROBABILITIES
ACROSS ERN MT SMALLER AND FOCUSED SLIGHTLY TO THE NORTHWEST WHERE
THE MODELS ARE IN AGREEMENT CONVECTIVE COVERAGE WILL BE THE
GREATEST. HAVE LEFT THE SIGNIFICANT HAIL HATCHED AREA THE SAME
EXTENDING FROM SW ND SWD INTO THE RAPID CITY AREA WHERE THE
THERMODYNAMIC ENVIRONMENT IS PRISTINE FOR SUPERCELLS WITH LARGE
HAIL. CONVECTIVE COVERAGE MAY BE ISOLATED ALONG THIS CORRIDOR BY
HAIL LARGER THAN 2 INCHES IN DIAMETER WILL BE POSSIBLE WITH ANY
SUPERCELL THAT CAN INITIATE AND DEVELOP. A SECOND CHANGE TO THE
OUTLOOK HAS BEEN TO FOCUS THE SLIGHT RISK AREA IN THE UPPER MS
VALLEY AND WRN GREAT LAKES FURTHER TO THE NORTH WHERE OBJECTIVE
ANALYSIS SHOWS AN AXIS OF MODERATE INSTABILITY EXTENDING ESEWD FROM
THE ARROWHEAD OF MN INTO NRN WI. ALTHOUGH CONVECTIVE INITIATION IN
THIS AREA IS UNCERTAIN...MODERATE INSTABILITY AND STRONG DEEP LAYER
SHEAR WILL BE SUFFICIENT FOR SUPERCELLS WITH LARGE HAIL. THE FINAL
CHANGE TO THE OUTLOOK IS TO MAKE THE SLIGHT RISK AREA IN THE NERN
STATES SMALLER AND CONFINED TO THE AREA WITH ANALYZED MODERATE
INSTABILITY. THE SEVERE THREAT IN THE NERN STATES IS EXPECTED TO BE
GREATEST THIS AFTERNOON WITH A DIMINISHED THREAT BY EARLY EVENING.

..BROYLES/BUNTING.. 06/08/2012

.PREV DISCUSSION... /ISSUED 1121 AM CDT FRI JUN 08 2012/

...SYNOPSIS...

UPPER LOW OFF THE BRITISH COLUMBIA AND WA COASTS WILL MOVE INLAND
INTO THE INTERIOR PACIFIC NW WITH AN ASSOCIATED MIDLEVEL JET STREAK
AND 500-MB HEIGHT FALLS OF 60-90 M/12-HR DEVELOPING EWD ACROSS THE
NRN HIGH PLAINS. DOWNSTREAM FROM THIS FEATURE...A SHORTWAVE TROUGH
CURRENTLY CRESTING MIDLEVEL RIDGE AXIS OVER THE RED RIVER VALLEY
INTO SRN MANITOBA/WRN ONTARIO WILL WEAKEN WHILE PROGRESSING INTO AN
INCREASINGLY CONFLUENT FLOW REGIME OVER THE UPPER GREAT LAKES.
FARTHER E...MID TO UPPER-LEVEL JET STREAKS OVER ERN ONTARIO WILL
DEVELOP SEWD THROUGH THE HUDSON VALLEY/WRN NEW ENGLAND...
CONTRIBUTING TO THE AMPLIFICATION OF UPPER TROUGH ACROSS NEW
ENGLAND/NEW BRUNSWICK/NOVA SCOTIA.

AT THE SURFACE...LOW PRESSURE OVER ERN MT WILL DEEPEN IN RESPONSE TO
INCREASING HEIGHT FALLS MENTIONED ABOVE WITH CYCLONE DEVELOPING INTO
WRN ND BY 09/12Z. THIS SYSTEM WILL BE ATTENDED BY A COLD FRONT
WHICH WILL MOVE THROUGH THE NRN HIGH PLAINS. ELSEWHERE...A COLD
FRONT WILL ADVANCE SEWD THROUGH THE ST. LAWRENCE VALLEY INTO NEW
ENGLAND IN CONJUNCTION WITH AMPLIFYING UPPER TROUGH.

...NRN HIGH PLAINS...

SELY LOW-LEVEL FLOW WILL GRADUALLY STRENGTHEN TODAY OWING TO
DEEPENING LEE CYCLONE WITH BOUNDARY LAYER DEWPOINTS INCREASING
THROUGH THE 50S BENEATH AN EML/STEEP LAPSE RATE PLUME PRECEDING
PACIFIC NW SYSTEM. LATEST MODEL GUIDANCE REMAINS CONSISTENT IN
SUGGESTING AN INCREASED LIKELIHOOD FOR STORM DEVELOPMENT BETWEEN
08/21-09/00Z N/NW OF SURFACE LOW WHERE CONVERGENCE/UPSLOPE FLOW IS
ENHANCED. MORE ISOLATED STORMS WILL BE POSSIBLE AT THIS TIME SWD
ALONG LEE TROUGH INTO FAR ERN WY/WRN SD. LOCAL ENVIRONMENT BY LATE
AFTERNOON/EARLY EVENING WILL BE CHARACTERIZED BY MLCAPE OF 1000-2500
J/KG AND VERTICALLY VEERING WIND PROFILES WITH 35-50 KT DEEP-LAYER
SHEAR. AS SUCH...SETUP WILL FAVOR SUPERCELLS AS THE INITIAL STORM
MODE WITH A RESULTANT RISK FOR LARGE HAIL AND DAMAGING WINDS. WHILE
A TORNADO IS POSSIBLE...A MORE ROBUST THREAT WILL BE LIMITED BY
RELATIVELY HIGH LCL HEIGHTS OWING TO SIZABLE T-TD SPREADS.

UPSCALE GROWTH OF STORMS INTO AN MCS IS POSSIBLE BY MID-LATE EVENING
OVER ERN MT WITH A RISK FOR DAMAGING WINDS AND HAIL CONTINUING
TONIGHT INTO WRN ND.

...NERN U.S...

DESPITE MODEST BOUNDARY LAYER MOISTURE /I.E. DEWPOINTS IN THE
50S/...COOLING MIDLEVEL TEMPERATURES AND DAYTIME HEATING WILL
CONTRIBUTE TO AIR MASS DESTABILIZATION WITH MLCAPE VALUES
APPROACHING 500-1000 J/KG. FORCING/HEIGHT FALLS ASSOCIATED WITH THE
AMPLIFYING UPPER SYSTEM WILL GIVE RISE TO WIDELY SCATTERED TSTMS
THIS AFTERNOON WITHIN AN ENVIRONMENT OF GRADUALLY STRENGTHENING DEEP
LAYER SHEAR. GIVEN THE POTENTIAL FOR MODERATE INSTABILITY AND
RELATIVELY COOL THERMODYNAMIC PROFILES...A FEW SEVERE STORMS WILL BE
POSSIBLE WITH A RISK FOR LOCALLY DAMAGING WINDS AND SEVERE HAIL INTO
THIS EVENING.

...UPPER GREAT LAKES...

GLANCING INFLUENCE OF MIDLEVEL PERTURBATION AND SUSTAINED LOW-LEVEL
WAA ARE EXPECTED TO CONTRIBUTE TO A SLOW INCREASE IN STORM COVERAGE
THROUGH THE PEAK OF THE DIURNAL HEATING CYCLE. INITIALLY ELEVATED
STORMS MAY BECOME PROGRESSIVELY MORE ROOTED IN A WARMING/MOISTENING
BOUNDARY LAYER THIS AFTERNOON WHERE MLCAPE WILL INCREASE TO
1000-2000 J/KG. KINEMATIC ENVIRONMENT WILL FEATURE A VERTICALLY
VEERING WIND PROFILE WITH 35-45 KT OF DEEP NWLY SHEAR WHICH WILL
SUPPORT ROTATING/SUSTAINED UPDRAFTS. DAMAGING WINDS AND LARGE HAIL
WILL BE THE PRIMARY HAZARDS THOUGH A TORNADO IS POSSIBLE OWING TO
THE PRESENCE OF A 30 KT SWLY LLJ AND RESULTANT ENHANCEMENT OF
LOW-LEVEL SHEAR.

...CNTRL/SRN FL PENINSULA...

12Z TAMPA/MIAMI/KEY WEST SOUNDINGS INDICATE THE PRESENCE OF A VERY
MOIST BOUNDARY LAYER /I.E. DEWPOINTS IN THE LOW-MID 70S AND LOWEST
100-MB MEAN-MIXING RATIOS OF 16-17+ G PER KG/ WHICH IS ALREADY
CONTRIBUTING TO A MODERATELY UNSTABLE ENVIRONMENT WITH MLCAPE OF
1500-2500 J/KG. ONGOING STORMS SHOULD FURTHER INCREASE IN AREAL
COVERAGE TODAY...FOCUSED ALONG DEVELOPING SEA BREEZE CIRCULATIONS
AND SYNOPTIC FRONT STALLED ACROSS THE AREA. GIVEN THE VERY MOIST
ENVIRONMENT...SOME POTENTIAL WILL EXIST FOR LOCALLY DAMAGING WIND
GUSTS OWING TO WATER LOADING EFFECTS.

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