DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 141957
SWODY1
SPC AC 141955

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT FRI JUN 14 2013

VALID 142000Z - 151200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL
PLAINS...NRN PLAINS AND LOWER TO MID MO VALLEY...

SEVERAL CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THIS ISSUANCE. THE
FIRST CHANGE IS TO EXTEND THE SLIGHT RISK AREA SEWD A FEW COUNTIES
ACROSS NW MO. SEVERAL SHORT-TERM HIGH RES MODELS SUGGEST A LINE
SEGMENT WILL MOVE SEWD INTO NW MO THIS EVENING. HAIL AND DAMAGING
WIND GUSTS WILL BE POSSIBLE WITH THIS LINE IF A CONVECTIVE SYSTEM
CAN ORGANIZE. THE SECOND CHANGE TO THE OUTLOOK IS TO REMOVE THE
SLIGHT RISK AREA FROM NRN FL. CELLS DEVELOPING IN NRN FL SHOULD HAVE
A WIND DAMAGE POTENTIAL DUE TO MODERATE INSTABILITY AND STEEP
LOW-LEVEL LAPSE RATES. HOWEVER...THE THREAT IS NOT EXPECTED TO
INCREASE MARKEDLY THIS AFTERNOON. THE THIRD CHANGE TO THE OUTLOOK IS
TO EXTEND THE 5 PERCENT WIND DAMAGE PROBABILITY WWD TO THE FRONT
RANGE OF ECNTRL CO WHERE THE STRONGER CELLS COULD HAVE A MARGINAL
SEVERE THREAT THIS AFTERNOON.

..BROYLES.. 06/14/2013

.PREV DISCUSSION... /ISSUED 1107 AM CDT FRI JUN 14 2013/

...SYNOPSIS...
A MIDLEVEL SHORTWAVE TROUGH WILL CONTINUE TO PROGRESS EWD OFF THE
MID ATLANTIC COAST...AS A TRAILING COLD FRONT SAGS SWD INTO N FL AND
THE N CENTRAL/NE GULF COAST. THE WRN PORTION OF THE BAROCLINIC ZONE
WILL DRIFT SWWD INTO EXTREME E TX AND ERN OK...AND THEN TRANSITION
INTO A WARM FRONT ALIGNED PRIMARILY NW-SE BY LATER THIS AFTERNOON
FROM ERN NEB TO NEAR THE KS/MO BORDER. FARTHER N...A COLD/OCCLUDED
FRONT WILL MOVE EWD ACROSS THE DAKOTAS TO WRN MN BY TONIGHT...IN
ASSOCIATION WITH A MIDLEVEL TROUGH EJECTING FROM WY/MT. THE SURFACE
BAROCLINIC ZONE WILL BE THE PRIMARY FOCUS FOR STRONG/SEVERE
THUNDERSTORM DEVELOPMENT THIS AFTERNOON/EVENING.

...MID MO VALLEY THIS AFTERNOON/EVENING...
AN MCV PERSISTS THIS MORNING OVER ERN NEB...WITHIN THE REMNANTS OF
OVERNIGHT CONVECTION. DOWNSTREAM FROM THE MCV...A NEW CLUSTER OF
ELEVATED STORMS HAS FORMED IN SW IA/NRN MO. THESE STORMS WILL POSE
A MARGINAL RISK OF HAIL/DAMAGING WINDS AS THE LOW LEVELS DESTABILIZE
THROUGH THIS AFTERNOON ACROSS SW IA/NW MO. FARTHER
W/NW...ADDITIONAL THUNDERSTORM DEVELOPMENT IS EXPECTED ALONG THE
SYNOPTIC COLD FRONT FROM NW KS INTO S CENTRAL NEB...WHERE STRONG
SURFACE HEATING S OF THE FRONT ERODES CONVECTIVE INHIBITION. THE
INITIAL HIGH-BASED CONVECTION WILL POSE A RISK FOR DAMAGING OUTFLOW
GUSTS AS IT SPREADS NEWD INTO NEB. FARTHER E INTO ERN NEB...RICHER
MOISTURE /BOUNDARY LAYER DEWPOINTS OF 68-70 F/ WILL SUPPORT LARGER
CAPE...IN AN ENVIRONMENT WITH STRONGER LOW-LEVEL SHEAR NEAR THE
SYNOPTIC WARM FRONT. STORMS THAT SPREAD INTO OR DEVELOP WITHIN THE
ERN NEB ENVIRONMENT WILL HAVE THE POTENTIAL TO BECOME SUPERCELLS
CAPABLE OF PRODUCING LARGE HAIL...AND POSSIBLY A TORNADO OR TWO WITH
THE MORE DISCRETE/PERSISTENT STORMS.

...ERN ND THIS AFTERNOON/EVENING...
LOW-LEVEL MOISTURE WILL BE MORE LIMITED ACROSS ERN ND...AND CLOUDS
WILL LIMIT SURFACE HEATING...COMPARED TO AREAS FARTHER S IN SD/NEB.
STILL...DEEP-LAYER VERTICAL SHEAR WILL BE SUFFICIENT FOR SUPERCELLS
WITH THE EJECTING MIDLEVEL TROUGH/SPEED MAX. GIVEN QUESTIONS ABOUT
THE MAGNITUDE OF THE INSTABILITY THIS AFTERNOON...WILL MAINTAIN LOW
SEVERE PROBABILITIES IN THIS UPDATE.

...N FL TODAY...
DEEP CONVECTION HAS ALREADY DEVELOPED NEAR CTY AS OF 15Z...AND
ADDITIONAL STORMS ARE LIKELY THIS AFTERNOON ACROSS N FL ALONG A
DIFFUSE PRE-FRONTAL TROUGH...AND PERHAPS FARTHER N ALONG THE
SYNOPTIC COLD FRONT. THE COMBINATION OF MODEST DEEP-LAYER SHEAR
WITH THE SWRN FRINGE OF THE MID ATLANTIC SHORTWAVE TROUGH AND STRONG
INSTABILITY /MLCAPE AOA 300O J PER KG/ WILL SUPPORT ORGANIZED
MULTICELL CLUSTERS CAPABLE OF PRODUCING A FEW DAMAGING OUTFLOW GUSTS
AND MARGINALLY SEVERE HAIL THROUGH THE AFTERNOON.

...SRN LA/EXTREME SE TX THIS AFTERNOON/EVENING...
STRONG SURFACE HEATING /TEMPERATURES WELL INTO THE 90S/ AND RICH
BOUNDARY LAYER MOISTURE /DEWPOINTS IN THE MID-UPPER 70S/ WILL
CONTRIBUTE TO MLCAPE NEAR 4000 J/KG AND SUPPORT THUNDERSTORM
DEVELOPMENT THIS AFTERNOON ALONG THE WNW-ESE ORIENTED SYNOPTIC
FRONT. THOUGH VERTICAL SHEAR WILL BE RELATIVELY WEAK...THE STRONG
INSTABILITY WILL SUPPORT A FEW MULTICELL CLUSTERS WITH STRONG
UPDRAFTS/PRECIPITATION LOADING...WHILE DCAPE OF 1250-1500 J/KG WILL
BE FAVORABLE FOR ISOLATED DAMAGING DOWNBURSTS. THE INITIAL STORMS
SHOULD FORM BY 21-22Z IN SRN LA...AND THEN SPREAD WWD-WSWWD TOWARD
THE SABINE RIVER THIS EVENING.

...RIO GRANDE VALLEY IN TX TODAY...
A PLUME OF RICH TROPICAL MOISTURE /PW VALUES AOA 2 INCHES/ HAS
SPREAD NWD OVER THE RIO GRANDE VALLEY...TO THE E OF A WEAK MIDLEVEL
LOW OVER THE BIG BEND. THOUGH WIDESPREAD CLOUDS WILL LIMIT SURFACE
HEATING...THE DRT VWP SHOWS SUFFICIENT LOW-LEVEL SHEAR FOR WEAKLY
ROTATING STORMS. THUS...WILL ADD LOW TORNADO PROBABILITIES FOR A
BRIEF/WEAK TORNADO TODAY /SEE MD 1078 FOR ADDITIONAL INFORMATION/.

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