DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 142001
SWODY1
SPC AC 141959

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN JUL 14 2013

VALID 142000Z - 151200Z

...NO SVR TSTM AREAS FORECAST...

TWO CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THIS ISSUANCE. THE
FIRST CHANGE IS TO EXTEND THE 5 PERCENT WIND DAMAGE AND HAIL
PROBABILITIES SWD TO AREAS NEAR AND TO THE WEST OF CORPUS CHRISTI.
THUNDERSTORMS CURRENTLY IN CNTRL TX WILL MOST LIKELY MOVE SWD ACROSS
THE TX COASTAL PLAINS TO NEAR THE MIDDLE TX COAST WHERE OBJECTIVE
ANALYSIS SHOWS MODERATE INSTABILITY IN PLACE. THE SECOND CHANGE TO
THE OUTLOOK IS TO ADD PARTS OF NE MT AND NW ND INTO THUNDER WHERE
SOME CONVECTION IS ONGOING ASSOCIATED WITH A SHORTWAVE TROUGH
EVIDENT ON WATER VAPOR IMAGERY.

..BROYLES.. 07/14/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT SUN JUL 14 2013/

...SYNOPSIS...
SRN MO CLOSED LOW SHOULD CONTINUE WSW INTO ERN OK TODAY AND INTO WRN
OK EARLY MON AS NORTHEAST U.S. ANTICYCLONE EXPANDS W INTO THE OH VLY
AND RIDGE REMAINS STNRY OVER THE SRN GRT BASIN. FARTHER
NW...SHORTWAVE IMPULSE NOW OVER ID IS EXPECTED TO WEAKEN AS IT
TRACKS ENE ACROSS MT TODAY AND ACROSS SRN SK/MB TNGT/EARLY MON.

FEATURES WILL REMAIN WEAK AT THE SFC. SYNOPTIC-SCALE COOL BUBBLE
ASSOCIATED WITH THE MO-OK UPR LOW SHOULD DRIFT WSW WITH THE LOW
TODAY...WITH ITS WRN/SRN EDGE ACTING MORE OR LESS AS A BACK-DOOR
COLD FRONT OVER TX. THE ERN FRINGE OF THE COOL AIR DOME WILL BE
MARKED BY A CORRIDOR OF DIFFUSE LOW-LVL WAA/MOISTURE RETURN OVER THE
LWR TN VLY AND PARTS OF MS/AL. MEANWHILE...COLD FRONT/OUTFLOW
BOUNDARY ASSOCIATED WITH YESTERDAY STORMS IN THE NRN PLNS SHOULD
WEAKEN AND BECOME QSTNRY FROM WRN NEB TO NRN MN.

THE POTENTIAL FOR SIZABLE AREAS OF ORGANIZED/SUSTAINED SVR TSTMS
APPEARS RELATIVELY LOW THIS PERIOD DUE TO LACK OF JUXTAPOSITION OF
DEEPLY-SHEARED WIND FIELD WITH APPRECIABLE LOW TO MID-LVL
INSTABILITY. NEVERTHELESS...A CONDITIONAL RISK FOR SVR TSTMS MAY
EVOLVE OVER PARTS OF THE S CNTRL AND SERN STATES IN ASSOCIATION WITH
MO-OK UPR LOW.

...SRN PLNS THIS AFTN/EVE...
DIFFERENTIAL SFC HEATING ON SRN FRINGE OF LOW-LVL COOL DOME WITH
MO-OK UPR LOW SHOULD YIELD A CORRIDOR OF STRONG TO PERHAPS LOCALLY
SVR TSTMS LATER TODAY OVER CNTRL/SE TX...WHERE 20-25 KT WNWLY 500 MB
SHOULD EXIST ATOP FAIRLY STEEP LOW-LVL LAPSE RATES. SFC HEATING AND
GRADUAL EROSION OF EXISTING MID-LVL WARM LAYER SHOULD SUPPORT
DEVELOPMENT OF STORMS AS SBCAPE INCREASES TO AROUND 1500 J/KG.
MODEST COMBINATION OF SHEAR/BUOYANCY MAY YIELD A FEW SVR WIND/HAIL
EVENTS. FARTHER N...BENEATH THE POCKET OF COLDER MID-LVL TEMPS WITH
UPR LOW...THE LIKELIHOOD FOR SUFFICIENT SFC HEATING TO INITIATE
SFC-BASED STORMS APPEARS MORE UNCERTAIN. WHILE A CONDITIONAL RISK
FOR SUCH DEVELOPMENT WILL EXIST...THE POTENTIAL APPEARS TOO LOW ATTM
TO WARRANT UPGRADE TO SLIGHT RISK.

...AR/TN/MS/AL TO S ATLANTIC CST THIS AFTN...
A BELT OF DEEPLY CONFLUENT SELY FLOW WILL LINGER OVER THE CNTRL GULF
CST STATES AND TN VLY TODAY IN WAKE OF WWD-MOVING UPR LOW...WITH 500
MB SPEEDS AOA 30 KTS EXPECTED OVER MUCH OF TN...ERN AR...AND NRN
PARTS OF MS/AL. ESELY WINDS ARE LIKELY TO PERSIST AT LWR LVLS...ON
SRN FRINGE OF EXPANDING MID-ATLANTIC SFC RIDGE.

WHILE LOW-LVL LAPSE RATES ARE WEAK ATTM...THEY SHOULD SOMEWHAT
STEEPEN THIS AFTN OVER ERN AR/WRN TN AND MS...WHERE AT LEAST
MODERATE SFC HEATING WILL OCCUR. LOW-LVL DESTABILIZATION
WILL...HOWEVER...PROBABLY REMAIN MORE LIMITED FARTHER E AND SE.

WITH RICH MOISTURE IN PLACE /PW AROUND 2 INCHES/...SETUP COULD
SUPPORT SCTD AREAS OF STORMS WITH A POTENTIAL FOR ISOLD DMGG WIND
GUSTS OR EVEN SHORT-LIVED TORNADOES GIVEN A FOCUSED AREA OF LOW-LVL
CONVERGENCE. ATTM...HOWEVER...IT APPEARS THAT LOW-LVL FORCING FOR
ASCENT WILL REMAIN WEAK. IF LOW-LVL FOCUSING MECHANISMS BECOME
BETTER DEFINED A BIT LATER TODAY /SUCH AS BY DIFFERENTIAL HEATING
OVER PARTS OF MS OR TN/...IT IS POSSIBLE THAT SUFFICIENT
JUXTAPOSITIONING OF LOW TO MID-LVL SHEAR WITH WARM/VERY MOIST
BOUNDARY LAYER MAY EXIST TO YIELD AN AREA WORTHY OF UPGRADE TO
SLIGHT RISK.

...CNTRL HIGH PLNS TO NRN PLNS/UPR MS VLY TODAY...
SVR THREAT SHOULD BE LIMITED OVER THIS REGION RELATIVE TO PREVIOUS
DAYS AS AREA WILL DISPLACED FROM THE WLYS AND FORCING FOR ASCENT
ASSOCIATED WITH ID-MT IMPULSE. MID-LVL LAPSE RATES ALSO WILL BE
RELATIVELY WEAK. NEVERTHELESS...POCKETS OF SFC HEATING/LOW-LVL
DESTABILIZATION MAY YIELD SMALL CLUSTERS OF LATE AFTN/EVE STORMS
ISOLD STRONG WIND GUSTS GIVEN HIGH PW /1 TO 2 INCHES/ OVER REGION.

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