MESOSCALE DISCUSSION 2046
   NWS STORM PREDICTION CENTER NORMAN OK
   0545 PM CDT SUN SEP 30 2007
   
   AREAS AFFECTED...NWRN THROUGH SERN IA
   
   CONCERNING...TORNADO WATCH 698...
   
   VALID 302245Z - 302345Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 698 CONTINUES.
   
   THREAT FOR ISOLATED TORNADOES IS EXPECTED TO PERSIST THROUGH 01Z 
   FROM NWRN THROUGH SERN IA AND E CNTRL IA...FOLLOWED BY A GRADUAL
   WEAKENING TREND. THREAT MAY SHIFT A ROW OF COUNTIES OR TWO EAST OF
   WW 698 AND IF NECESSARY WATCH CAN BE LOCALLY EXTENDED INTO PARTS OF
   E CNTRL IA.
   
   A FEW SUPERCELLS CONTINUE DEVELOPING OVER NWRN IA ALONG PRE-FRONTAL
   BOUNDARY THAT ARCS FROM NWRN THROUGH SWRN IA. NWRN PART OF THIS
   BOUNDARY IS LIFTING NWD WHERE THE ATMOSPHERE REMAINS MARGINALLY
   UNSTABLE WITHIN ABOUT A 40-50 MILE SWATH ACROSS NWRN IA. OBJECTIVE
   ANALYSIS SHOWS SUFFICIENT VERTICAL VORTICITY AND 0-3 KM CAPE IN
   VICINITY OF THE BOUNDARY FOR A THREAT OF ISOLATED TORNADOES NEXT 1-2
   HOURS. OTHERWISE...DEEP SHEAR OF 40 TO 50 KT WILL SUPPORT SUPERCELLS
   WITH A THREAT OF LARGE HAIL. OTHER STORMS ARE DEVELOPING IN CLOSER
   PROXIMITY TO LOW LEVEL JET AXIS ACROSS SERN IA WHERE 0-1 KM STORM
   RELATIVE HELICITY FROM 200 TO 250 M2/S2 AND STRONG DEEP SHEAR ARE
   SUPPORTING POTENTIAL FOR LOW LEVEL MESOCYCLONES. THREAT MAY SHIFT A
   ROW OF COUNTIES OR TWO EAST OF CURRENT WW. HOWEVER...WITH TIME THE
   STORMS WILL BEGIN SHIFTING EAST OF INSTABILITY AXIS...AND AS THE
   BOUNDARY LAYER BEGINS TO COOL A GRADUAL WEAKENING TREND IS EXPECTED.
   
   ..DIAL.. 09/30/2007
   
   
   ATTN...WFO...DVN...DMX...FSD...
   
   40649444 41749484 42069529 42459619 43069606 43159494
   42559356 41189235 40649302