SPC AC 071959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN JUN 07 2009
VALID 072000Z - 081200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS NORTHEAST KS/SOUTHEAST
NEB/SOUTHWEST IA/NORTHWEST MO...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL PLAINS AND
MIDWEST...
...CENTRAL PLAINS AND MIDDLE/LOWER MO VALLEY...
WITH A SURFACE LOW ACROSS SOUTHWEST/EAST CENTRAL KS...LATEST SURFACE
ANALYSIS FEATURES THE COLD FRONT CONTINUING TO SLIP SOUTHWARD ACROSS
CENTRAL KS...WITH THE SYNOPTIC FRONT OTHERWISE EXTENDING
NORTHEASTWARD ACROSS SOUTHEAST NEB INTO CENTRAL IA. SEVERAL RESIDUAL
OUTFLOW BOUNDARIES INTERCEPT THE SURFACE FRONT FROM THE
EAST...INCLUDING AN APPARENT WEST-EAST BOUNDARY ACROSS SOUTHERN
IA...AND ANOTHER NW-SE ARCING BOUNDARY FROM FAR NORTHEAST KS INTO
NORTHERN MO.
ATOP A DEEPENING/MIXED BOUNDARY LAYER...A 19Z SPECIAL OBSERVED RAOB
FROM TOPEKA REFLECTS A SLIGHT WARMING OF THE ELEVATED MIXED LAYER
SINCE THIS MORNING. THE DEGREE OF WARM SECTOR CAPPING COMPLICATES
THE TIMING OF INITIAL DEEP CONVECTIVE INITIATION THAT IS ANTICIPATED
ACROSS EASTERN KS/SOUTHEAST NEB INTO ADJACENT PORTIONS OF
IA/NORTHWEST MO. ON SATELLITE IMAGERY...OF NOTE IS NORTH-SOUTH BAND
OF MID-HIGH CLOUD COVER CROSSING CENTRAL KS AND WEST-CENTRAL OK AT
MID AFTERNOON. IT APPEARS THIS FEATURE IS PROBABLY TIED TO THE
LEADING EDGE OF HEIGHT FALLS/COOLING ALOFT AHEAD OF THE PARENT UPPER
TROUGH OVER THE NORTHERN ROCKIES...WHICH SHOULD ULTIMATELY PROVE
FAVORABLE WITH RESPECT TO THE INITIATION OF DEEP CONVECTION LATE
THIS AFTERNOON/EARLY EVENING. ALONG THESE LINES...A SPECIAL 19Z RAOB
FROM DODGE CITY REFLECTED AROUND 2 DEG C OF COOLING AROUND 700 MB
SINCE 12Z.
REGIONAL PROFILERS/WSR-88D DERIVED VWPS REFLECT VERTICAL SHEAR MORE
THAN ADEQUATE FOR SUPERCELLS. WITH FEW CHANGES TO PRIOR
OUTLOOK...LARGE HAIL/DAMAGING WINDS AND A FEW TORNADOES ARE STILL
EXPECTED...ESPECIALLY WITHIN THE MODERATE RISK AREA AND WHERE
AFOREMENTIONED RESIDUAL OUTFLOW/BACKED SOUTHEASTERLY FLOW EXISTS
ADJACENT TO THE SYNOPTIC FRONT. FOR ADDITIONAL INFORMATION...SEE
MESOSCALE DISCUSSION 974.
...CENTRAL HIGH PLAINS...
UPSLOPE REGIME WILL CONTINUE TO SUPPORT AN ISOLATED TORNADO /MAINLY
NORTHEAST CO AND FAR WESTERN NEB PANHANDLE/ AND LARGE HAIL THREAT
THROUGH THE AFTERNOON. 18Z DENVER OBSERVED RAOB REFLECTED AROUND
2000 J/KG OF SBCAPE WITH VERY STEEP LAPSE RATES /8.5C PER KM H7-H5/.
FOR ADDITIONAL INFORMATION...SEE MESOSCALE DISCUSSION 973.
..GUYER.. 06/07/2009
.PREV DISCUSSION... /ISSUED 1129 AM CDT SUN JUN 07 2009/
...CENTRAL PLAINS AREA THROUGH TONIGHT...
A SRN STREAM MID LEVEL TROUGH IS EJECTING NEWD FROM CENTRAL NM/CO
TOWARD KS/NEB...AROUND THE SERN PERIPHERY OF A LARGE MID LEVEL LOW
FORMING OVER SRN SK. FARTHER S...A MORE SUBTLE WAVE ALSO MOVES NEWD
FROM W TX TOWARD OK. AT THE SURFACE...A BAROCLINIC ZONE EXTENDS
FROM NE CO ACROSS WRN KS TO A REMNANT LEE CYCLONE IN CENTRAL
KS...THEN NEWD ACROSS SE NEB AND SRN IA. A SEPARATE OUTFLOW
BOUNDARY FROM OVERNIGHT CONVECTION IS LOCATED FARTHER S FROM NE KS
ACROSS CENTRAL MO /S OF I-70/. S OF THE SURFACE LOW...A DRYLINE
WILL MIX EWD THIS AFTERNOON INTO S CENTRAL KS...WRN OK...AND NW TX.
THE SURFACE BAROCLINIC ZONE...AS WELL AS THE DRYLINE NEAR THE TRIPLE
POINT AND PERHAPS THE REMNANT OUTFLOW BOUNDARY...WILL ACT TO FOCUS
THUNDERSTORM DEVELOPMENT THIS AFTERNOON INTO TONIGHT.
THE PRIMARY CONCERN ACROSS THE OUTLOOK AREA WILL BE THE STRENGTH OF
THE CAP AND THUNDERSTORM COVERAGE THIS AFTERNOON/EVENING. REGIONAL
12Z SOUNDINGS SHOW THAT A VERY WARM EML HAS OVERSPREAD THE KS/OK
WARM SECTOR...AND LOW-LEVEL MOISTURE IS STILL MARGINAL ACROSS TX/OK.
WITH SURFACE TEMPERATURES OF 95-100 F NEEDED TO MINIMIZE CONVECTIVE
INHIBITION ACROSS KS/OK...IT APPEARS THAT FOCUSED LOW-LEVEL ASCENT
FROM THE TRIPLE POINT NEWD WILL BE NEEDED TO INITIATE THUNDERSTORMS
THIS AFTERNOON...AS THE MID LEVEL WAVE APPROACHES FROM THE W.
FARTHER S...STORM COVERAGE ALONG THE DRYLINE SHOULD BE MORE ISOLATED
THAN PREVIOUS DAYS GIVEN THE DRYLINE LOCATION AT A LOWER ELEVATION
AND THE WARMER EML. THE 12Z NAM DEVELOP CONVECTIVE PRECIPITATION
ACROSS NRN OK THIS AFTERNOON...THOUGH THIS MAY BE AN ARTIFACT OF MID
LEVEL MOISTENING /WITH THE N-S CLOUD BAND CROSSING NW TX AND WRN OK/
TRIGGERING THE BMJ SCHEME IN AN OTHERWISE CAPPED PROFILE.
THE MORE PROBABLE AREA FOR SURFACE-BASED STORM DEVELOPMENT THIS
AFTERNOON WILL BE TO THE NE OF THE STRONGER CAPPED AREAS IN
KS/OK...WHERE LOW-LEVEL MOISTURE WILL BE MAXIMIZED INVOF THE REMNANT
OUTFLOW BOUNDARY AND THE BAROCLINIC ZONE. THE COMBINATION OF
MODERATE-STRONG INSTABILITY /MLCAPE OF 2000-3000 J/KG/ AND BACKED
LOW-LEVEL FLOW WITH CLOCKWISE TURNING HODOGRAPHS WILL BE SUPPORTIVE
OF SUPERCELLS WITH A FEW TORNADOES...VERY LARGE HAIL...AND DAMAGING
WINDS. FARTHER SW INTO SRN KS/NRN OK...ANY STORM DEVELOPMENT WILL
REMAIN QUITE ISOLATED...WITH PRIMARILY A THREAT FOR LARGE HAIL.
OVERNIGHT...EXPECT CONVECTION TO INCREASE IN COVERAGE AS THE MID
LEVEL WAVE EJECTS NEWD OVER KS/NEB AND THE SURFACE LOW DEVELOPS NEWD
TOWARD IA...WITH A CONTINUING THREAT FOR LARGE HAIL AND DAMAGING
WINDS.
...NE CO THIS AFTERNOON...
CLOUD BREAKS N OF THE SURFACE COLD FRONT AND A MOIST UPSLOPE FLOW OF
LOW-MID 50S BOUNDARY LAYER DEW POINTS WILL CONTRIBUTE TO WEAKENING
CONVECTIVE INHIBITION AND THE POTENTIAL FOR THUNDERSTORM DEVELOPMENT
BY 17-19Z. VERTICAL SHEAR WILL BE FAVORABLE FOR SUPERCELLS TO
PROPAGATE EWD ALONG THE COOL SIDE OF THE FRONT...WITH AN
ACCOMPANYING THREAT FOR LARGE HAIL AND PERHAPS AN ISOLATED TORNADO
WHERE SHEAR IS MAXIMIZED ALONG THE COOL SIDE OF THE BOUNDARY BUT THE
CONVECTION REMAINS ROOTED AT THE SURFACE. THIS CONVECTION WILL
LIKELY PERSIST AND SPREAD NEWD ABOVE THE SHALLOW COOL AIR MASS INTO
NEB...WITH LARGE HAIL THE MAIN THREAT INTO THIS EVENING.
...CENTRAL/S FL THIS AFTERNOON...
THE LINGERING COLD CORE MID LEVEL LOW OVER FLOW AND SEA BREEZE
BOUNDARIES WILL PROMOTE SCATTERED-NUMEROUS THUNDERSTORMS THROUGH THE
AFTERNOON ACROSS CENTRAL/S FL. MODERATE INSTABILITY AND SEASONALLY
COOL MID LEVEL TEMPERATURES WILL AGAIN PROMOTE A THREAT FOR AT LEAST
ISOLATED LARGE HAIL AND STRONG DOWNBURST WINDS.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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