SWODY1
SPC AC 041955
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT SAT APR 04 2009
VALID 042000Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN PORTIONS OF THE
CENTRAL PLAINS AND PARTS OF THE LOWER MO VALLEY REGION...
...N CENTRAL AND ERN KS/SERN NEB AND INTO WRN MO AND VICINITY...
FORECAST REMAINS ON TRACK ACROSS THE RISK AREA THIS AFTERNOON...WITH
INITIAL/VIGOROUS STORM DEVELOPMENT CONTINUING NEAR THE N CENTRAL
KS/S CENTRAL NEB BORDER -- JUST TO THE NE OF THE SURFACE LOW
OBSERVED NEAR HLC. STORMS SHOULD CONTINUE TO DEVELOP IN THIS AREA
-- WHERE LOW-LEVEL UVV IS MAXIMIZED...AND SHIFT NNEWD WITH TIME
BECOMING INCREASINGLY-ELEVATED.
MEANWHILE...THE SURFACE DRYLINE HAS SURGED EWD THROUGH CENTRAL
KS...AND NOW EXTENDS FROM ROUGHLY SLN TO ICT. ONGOING STORMS OVER N
CENTRAL KS SHOULD TEND TO DEVELOP SLOWLY SWD ALONG THE ADVANCING
DRYLINE...THOUGH MARGINAL INSTABILITY -- RESTRAINED BY SURFACE
DEWPOINTS ONLY IN THE LOW TO MID 40S -- WILL CONTINUE TO ACT AS A
LIMITING FACTOR WITH RESPECT TO STORM COVERAGE/INTENSITY ALONG THE
DRYLINE.
THE STRENGTH OF THIS STORM SYSTEM AND POTENCY OF THE WIND FIELD WILL
CONTINUE TO SUPPORT A LIMITED SEVERE THREAT INTO THIS EVENING...AS
CONVECTION SPREADS EWD INTO NWRN MO. WILL MAINTAIN SLIGHT RISK AS
FAR S AS FAR NERN OK/SWRN MO...THOUGH THE COVERAGE OF ANY STORM
DEVELOPMENT -- AND THUS OVERALL SEVERE THREAT -- IS EXPECTED TO
DECREASE WITH SWD EXTENT.
THOUGH CONVECTION SHOULD CONTINUE ACROSS IA/MO AND INTO IL
OVERNIGHT...INSTABILITY DIMINISHING BOTH WITH EWD EXTENT INTO MO AND
WITH TIME INTO THE EVENING/OVERNIGHT HOURS SHOULD LIMIT THE EWD
EXTENT OF SEVERE THREAT TO WRN MO/SWRN IA.
..GOSS.. 04/04/2009
.PREV DISCUSSION... /ISSUED 1114 AM CDT SAT APR 04 2009/
...CENTRAL PLAINS...
VIGOROUS UPPER TROUGH/LOW AND ASSOCIATED POWERFUL MID LEVEL JET MAX
EMERGING FROM CENTRAL ROCKIES THIS MORNING INTO CENTRAL HIGH PLAINS.
W/V AND IR IMAGERY DEPICTS A STRONG VORT CURRENTLY MOVING INTO SWRN
KS WHICH WILL CONTINUE TO MOVE RAPIDLY ENEWD ACROSS KS THIS
AFTERNOON TO THE SERN NEB/KS BORDER AREA THIS EVENING. THE SURFACE
LOW NOW WRN KS MOVES NEWD IN CONCERT WITH THE UPPER SYSTEM PRECEEDED
BY STRONG LLJ OF 50-60KT.
THE DYNAMICS/KINEMATICS WITH THIS SYSTEM HAVE ALL THE PARAMETERS TO
SUPPORT SEVERE THUNDERSTORMS WITH THE IMPORTANT EXCEPTION OF LOW
LEVEL MOISTURE. DEWPOINTS IN THE 40S ABOUT THE BEST THAN CAN BE
EXPECTED TO MAKE IT INTO SCENTRAL NEB BY MID AFTERNOON...WITH
SOMEWHAT HIGHER VALUES INTO LOW 50S INTO ERN KS/WRN MO BY THIS
EVENING.
THE VERY STRONG ASCENT/MID LEVEL COOLING THAT IS ACCOMPANYING THE
UPPER VORT INTO WRN KS COUPLED WITH STEEPENING LOW LEVEL LAPSE RATES
TO E OF THE DRY LINE WILL BE SUFFICIENT FOR MLCAPES RISING TO 300 TO
500 J/KG BY 21Z JUST E OF DRY LINE/COLD FRONT. THE BACKED STRONG
SELY BOUNDARY LAYER FLOW INTO SCENTRAL/SERN NEB PROVIDES FOR A VERY
FAVORABLE ENVIRONMENT FOR CONVECTIVE INITIATION IN THE NERN QUAD OF
THE TRACK OF THE SURFACE LOW AND AREA OF INTENSE PVA/COLD ADVECTION
WITH THE UPPER VORT/WIND MAX. THUS HAVE SHIFTED THE AREA OF
POTENTIAL SEVERE THUNDERSTORM WWD INTO MORE OF SERN/SCENTRAL NEB.
CANNOT RULE OUT THE DEVELOPMENT OF LOW TOPPED SUPERCELLS AND
ISOLATED TORNADOES ACROSS SERN NEB INTO NERN KS...EVEN WITH THE
LIMITED MOISTURE/INSTABILITY AS OTHERWISE SHEAR AND LARGE SCALE
SUPPORT IS VERY FAVORABLE.
HAIL/SOME LARGE WILL BE LIKELY WITH ANY VIGOROUS UPDRAFT THAT IS
ABLE TO DEVELOP...PARTICULARLY WITH SUPERCELLS. STORMS WILL FORM
FIRST AS MENTIONED IN THE NERN QUAD OF THE SURFACE LOW AND THEN
ZIPPER SWD THRU ERN KS ALONG THE DRY LINE/PACIFIC FRONT. HAVE ALSO
INCREASED THE WIND DAMAGE POTENTIAL GIVEN 80-100KT MID LEVEL JET
THAT WILL BE TRACKING ACROSS KS THIS AFTERNOON.
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