DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 131956
SWODY1
SPC AC 131954

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT SAT JUL 13 2013

VALID 132000Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE
CENTRAL/NRN PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE OH AND TN
VALLEY REGION...

FORECAST REASONING FROM PREVIOUS OUTLOOK REMAINS ON TRACK. HAVE
ADDED 2 PERCENT TORNADO PROBABILITIES ACROSS FAR ERN MT/WRN ND WHERE
TSTM DEVELOPMENT IS EXPECTED LATER THIS AFTN/EVENING. STRONG
HEATING/DESTABILIZATION HAS RESULTED IN 2000 J/KG OF MLCAPE ACROSS
THIS AREA WITH GUSTY SELY LO-LEVEL FLOW BENEATH 35 KT MID LEVEL
WINDS. RELATIVELY LONG HODOGRAPHS WOULD FAVOR SPLITTING STORMS WITH
PRIMARILY A SVR WIND AND HAIL THREAT...BUT A TORNADO CANNOT BE RULED
OUT WITH ANY DISCRETE TSTM NEAR THE MT/ND BORDER INTO FAR WRN ND.

NO OTHER SIGNIFICANT CHANGES WERE MADE TO THE PREVIOUS OUTLOOK.

..BUNTING.. 07/13/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT SAT JUL 13 2013/

...SYNOPSIS...
IN RESPONSE TO STRENGTHENING WRN ATLANTIC/NEW ENGLAND
ANTICYCLONE...KY UPR LOW EXPECTED TO CONTINUE WWD THIS
PERIOD...REACHING SRN IL THIS EVE AND SRN MO EARLY SUN...AS
STRONG/ELONGATED RIDGE PERSISTS FROM THE FOUR CORNERS ACROSS THE NRN
PLNS TO THE UPR GRT LKS. THE SRN STREAM OF THE WLYS WILL CONTINUE
ALONG THE NRN FRINGE OF THE RIDGE...EXTENDING FROM THE PACIFIC
NORTHWEST THROUGH THE CANADIAN PRAIRIES TO THE LABRADOR CST.

SHORTWAVE IMPULSE THAT CROSSED WA YESTERDAY SHOULD DEAMPLIFY AS IT
CONTINUES ENE ACROSS SRN SK/MB LATER TODAY. FARTHER S...A WEAKER
DISTURBANCE NOW NEAR SLC SHOULD TRACK NE TO THE NRN HIGH PLNS. COLD
FRONT ASSOCIATED WITH THE CANADIAN IMPULSE WILL ADVANCE SLOWLY SE
ACROSS ERN MT/ND...ACCOMPANIED BY WEAK LEE CYCLOGENESIS.
MEANWHILE...FRONT ASSOCIATED WITH YESTERDAY'S STORMS IN ND/MN SHOULD
DISSIPATE OVER SD...WHILE LEE TROUGH PERSISTS FROM WRN NEB INTO FAR
WRN KS.

...NRN PLNS THIS AFTN/EVE...
SATELLITE SHOWS THAT STRONG HEATING WILL OCCUR OVER ERN MT AND WRN
ND TODAY...ALONG/AHEAD OF FRONT ASSOCIATED WITH CANADIAN SHORTWAVE
IMPULSE. CURRENT OBSERVATIONS AND DEVELOPMENT OF WEAK LEE LOW IN SE
MT ALSO SUGGEST THAT SFC WINDS LIKELY WILL REMAIN SELY ACROSS
REGION. COUPLED WITH TERRAIN-INDUCED CIRCULATIONS AND ASCENT
ASSOCIATED WITH UT UPR IMPULSE...CONFIDENCE FAIRLY HIGH FOR THE
DEVELOPMENT OF STRONG AFTN/EVE STORMS...ESPECIALLY OVER FAR ERN MT
AND WRN ND.

35-40 KT WSWLY 500 MB FLOW IN CONJUNCTION WITH 15-20 KT SLY 850 MB
WINDS WILL YIELD FAIRLY LONG...SLIGHTLY ELONGATED
HODOGRAPHS THAT COULD FOSTER SUSTAINED STORMS/SUPERCELLS AND
SUPERCELL SPLITS WITH LARGE HAIL AND LOCALLY DMGG WIND. A TORNADO OR
TWO ALSO COULD OCCUR...ESPECIALLY IN THE WRN DAKOTAS WHERE TEMP/DEW
POINT SPREADS SHOULD BE LEAST. THE STORMS MAY EVOLVE SMALL LINES OR
CLUSTERS THIS EVE...BUT SHOULD NOT PERSIST TOO LATE INTO THE NIGHT
GIVEN MODEST LLJ.

THE SVR WEATHER RISK APPEARS MORE CONDITIONAL FARTHER S AND
SE...WHERE WEAKER DEEP SHEAR WILL EXIST INVOF DISSIPATING SFC FRONT
AND LEE TROUGH. NEVERTHELESS...RATHER RICH MOISTURE WILL LINGER
INVOF THESE FEATURES /WITH PW AOA 1.50 INCHES AND SFC DEWPOINTS IN
THE UPR 60S TO LOW 70S F/. COUPLED WITH STRONG HEATING...EXPECT
MLCAPE TO BE AOA 3000 J/KG BY LATE AFTN. WEAK ASCENT MAY OCCUR ON
SRN FRINGE OF PASSING UPR IMPULSE...BUT OVERALL LARGE SCALE SUPPORT
WILL BE MINIMAL. NEVERTHELESS...GIVEN DEGREE OF SFC-BASED BUOYANCY
AND LIKELIHOOD FOR AT LEAST MODEST LOW-LVL CONVERGENCE...SETUP
APPEARS TO WARRANT A SLIGHT RISK FOR MULTICELLS AND PERHAPS A
TRANSIENT SUPERCELL OR TWO CAPABLE OF SVR WIND/HAIL.

...LWR OH VLY TO SOUTHEAST THIS AFTN/EVE...
KY UPR LOW IS RETROGRESSING RATHER QUICKLY WWD ATTM...AND SHOULD
MAINTAIN THIS SPEED THROUGH THE PERIOD. THIS WILL RESULT IN FAIRLY
RAPID AND SUBSTANTIAL SPATIAL-TEMPORAL CHANGES IN THE ASSOCIATED
WIND AND THERMODYNAMIC FIELDS ACROSS THE REGION FROM ERN KY TO SRN
IL/MO.

IN THE SHORT TERM...MODERATE DESTABILIZATION APPEARS TO BE IN
PROGRESS OVER PARTS OF KY AND IND AS SFC HEATING OCCUR BENEATH
MID-LVL COLD POCKET /WITH 500 MB TEMP AROUND MINUS 13 C/. WHILE
LOW-LVL MOISTURE IS MODEST BY JULY STANDARDS...IT IS SUFFICIENT FOR
STRONG STORMS GIVEN COOL AIR ALOFT AND PRESENCE OF AT LEAST WEAK
CONVERGENCE ALONG ASSOCIATED SFC TROUGH.

WITH AREA VWP DATA ALREADY SHOWING AN INCREASE IN LOW TO MID-LVL
FLOW...AND SOME DEGREE OF LOW TO MID-LVL VEERING...WITH 700 MB WINDS
AROUND 25 KTS AT LOUISVILLE...THERE IS SOME CONCERN THAT A FEW
STORMS COULD BECOME SUSTAINED ENOUGH TO POSE A RISK FOR SVR
HAIL...LOCALLY DMGG WIND...AND PERHAPS A TORNADO OR TWO. ANY SUCH
THREAT SHOULD BE GREATEST DURING THE EARLY STAGES OF STORM
DEVELOPMENT...WITH THE ACTIVITY TENDING TO MERGE INTO SMALL CLUSTERS
LATER TODAY INTO TNGT.

FARTHER SE...BELT OF DEEP...CONFLUENT SSELY FLOW EXTENDING S AND SE
OF UPR LOW MAY YIELD SUFFICIENT DEEP SHEAR TO PRODUCE A FEW
MULTICELL CLUSTERS WITH A CONDITIONAL DMGG WIND THREAT...ESPECIALLY
ALONG THE S ATLANTIC CST...WHERE PW IS GREATEST AND SFC HEATING WILL
BE MAXIMIZED.

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