DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 042003
SWODY1
SPC AC 042000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT FRI OCT 04 2013

VALID 042000Z - 051200Z

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
PARTS OF EXTREME EASTERN NEB AND WESTERN/CENTRAL IA...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE MID MO VALLEY
AND CENTRAL/SOUTHERN PLAINS...

...NEB/IA/MN...
RELATIVELY FEW CHANGES TO THE EXISTING OUTLOOK AND ASSOCIATED
REASONING...SEE PRIOR DISCUSSION BELOW...TORNADO WATCH 539 AND
RELATED MESOSCALE DISCUSSIONS. WITH SURFACE BASED TSTMS LIKELY TO
STEADILY INCREASE THROUGH LATE AFTERNOON ESPECIALLY NEAR/SOUTHEAST
OF A SURFACE TRIPLE POINT...THE GREATEST OVERALL SEVERE THREAT AND
TORNADO POTENTIAL /POSSIBLY STRONG/ IS STILL EXPECTED ACROSS FAR
EASTERN NEB INTO WESTERN IA INCLUDING AREAS ALONG THE I-80 CORRIDOR.
THIS IS IN VICINITY OF A WARM FRONT/RESIDUAL OUTFLOW BOUNDARY WHERE
LOW-LEVEL SHEAR/SRH WILL BE MAXIMIZED.

...KS/MO/OK...
DEEPENING CU FIELD IS BECOMING READILY APPARENT IN VISIBLE SATELLITE
IMAGERY AT 20Z ACROSS EAST-CENTRAL/SOUTH-CENTRAL KS INTO
NORTHWEST/FAR WESTERN OK. TSTMS ARE EXPECTED TO DEVELOP/INCREASE
THROUGH LATE AFTERNOON ALONG THE EAST-SOUTHEASTWARD ADVANCING COLD
FRONT...WITH SOME ADDITIONAL DEVELOPMENT ALONG THE DRYLINE ACROSS
NORTHWEST/WEST-CENTRAL OK. ESPECIALLY NEAR THE
DRYLINE...SEMI-DISCRETE/POTENTIALLY SUPERCELLULAR DEVELOPMENT WILL
BE POSSIBLE /INCLUDING HAIL AND PERHAPS SOME TORNADO RISK/ PRIOR TO
THE DRYLINE GRADUALLY BEING OVERTAKEN /FROM NORTHWEST TO SOUTHEAST/
INTO THIS EVENING.

..GUYER.. 10/04/2013

.PREV DISCUSSION... /ISSUED 1126 AM CDT FRI OCT 04 2013/

...NEB/IA/MN...
MORNING WATER VAPOR LOOPS SHOW A STRONG UPPER LOW OVER NORTHWEST
CO...WITH MULTIPLE SHORTWAVE TROUGHS ROTATING THROUGH THE BASE OF
THE LOW AND INTO THE CENTRAL PLAINS. ONE SUCH TROUGH IS NOW OVER
SOUTHEAST CO/SOUTHWEST KS AND IS EXPECTED TO TRACK INTO EASTERN
NEB/KS BY EVENING. AT THE SURFACE...THE PRIMARY LOW IS ANALYZED
OVER SOUTHERN NEB WITH A COLD FRONT EXTENDING SOUTHWESTWARD INTO THE
OK PANHANDLE. THIS FRONT WILL MIX EASTWARD THROUGH THE DAY...LIKELY
EXTENDING FROM SOUTHEAST NEB INTO EASTERN KS BY LATE AFTERNOON.
THIS CORRIDOR WILL LIKELY SEE THE INITIATION OF STRONG/SEVERE
THUNDERSTORMS. THE INITIAL STORMS SHOULD FORM NEAR THE TRIPLE POINT
OVER EASTERN NEB AND TRACK INTO WESTERN IA DURING THE EARLY EVENING.
DEEP LAYER SHEAR VECTORS PERPENDICULAR TO THE SURFACE BOUNDARY WILL
PROMOTE DISCRETE CONVECTIVE MODE...WITH SUFFICIENT VERTICAL SHEAR
FOR SUPERCELL STORMS. VERY LARGE HAIL AND A FEW TORNADOES /POSSIBLY
STRONG/ MAY OCCUR ACROSS THE MODERATE RISK AREA. STORMS MAY
ORGANIZE INTO A BOWING LINE DURING THE EVENING WITH A CONTINUED
SEVERE THREAT INTO SOUTHERN MN AND NORTHEAST IA.

...SOUTHERN IA THIS AFTERNOON...
ANOTHER IMPORTANT SURFACE FEATURE IS A RESIDUAL OUTFLOW BOUNDARY
FROM MORNING CONVECTION THAT ARCS FROM SOUTHEAST NEB ACROSS
NORTHWEST MO INTO SOUTHEAST IA. THIS BOUNDARY WILL LIKELY LIFT
SLOWLY NORTHWARD AND WEAKEN TODAY...WITH SLOW EROSION OF CLOUD COVER
AND DESTABILIZATION OCCURRING OVER SOUTHERN IA. DEPENDING ON THE
EXTENT OF DESTABILIZATION...THIS REGION MAY BECOME QUITE FAVORABLE
FOR SUPERCELL STORMS. BACKED LOW LEVEL WINDS... RESIDUAL LOW LEVEL
MOISTURE /DEWPOINTS IN THE MID-UPPER 60S/...AND A WEAKENED CAPPING
INVERSION MAY ENHANCE THE SEVERE RISK. THEREFORE HAVE SHIFTED THE
MODERATE RISK AREA FARTHER SOUTH TO INCLUDE THIS REGION. IF
DISCRETE STORMS FORM...VERY LARGE HAIL AND A FEW TORNADOES WOULD BE
POSSIBLE.

...KS/MO/OK...
THUNDERSTORMS ARE EXPECTED TO FORM ALONG THE COLD FRONT FROM CENTRAL
KS INTO NORTHERN OK BY MID-LATE AFTERNOON. FORECAST SOUNDINGS
SUGGEST SUFFICIENT CAP TO LIMIT THE POTENTIAL FOR DISCRETE STORMS
AHEAD OF THE FRONT. THE MAIN RISK APPEARS TO BE A SQUALL LINE
COINCIDENT WITH THE COLD FRONT...CAPABLE OF DAMAGING WINDS AND HAIL
FOR A FEW HOURS DURING THE EVENING. THIS ACTIVITY WILL LIKELY BEGIN
TO WEAKEN BEFORE MIDNIGHT AS DIURNAL COOLING TAKES PLACE.

...SOUTHERN LA...
TS KAREN IS MOVING SLOWLY NORTHWARD ACROSS THE CENTRAL GULF OF
MEXICO. IT APPEARS THAT SUBSTANTIAL STRENGTHENING OF LOW LEVEL
WINDS FIELDS IN THE NORTHERN SEMICIRCLE OF THE CIRCULATION WILL NOT
REACH SOUTHERN LA UNTIL VERY LATE TONIGHT. HAVE MAINTAINED THE LOW
TORNADO PROBABILITIES IN THE CURRENT OUTLOOK...BUT THE RISK IS MORE
LIKELY TO BE DELAYED UNTIL THE DAY2 PERIOD.

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