Issued by NWS Springfield, MO
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000 FXUS63 KSGF 051930 AFDSGF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPRINGFIELD MO 130 PM CST WED NOV 5 2008 ...MESOSCALE CONVECTIVE DISCUSSION... .UPDATE... CONDITIONS COMING TOGETHER TO SUPPORT RAPID THUNDERSTORM DEVELOPMENT DURING THE MID/LATE AFTERNOON HOURS. AT 100 PM...SFC ANALYSIS INDICATES A STRONG AREA OF LOW PRESSURE OVER SOUTHEASTERN SOUTH DAKOTA. A COLD FRONT EXTENDS SOUTHWARD FROM THIS LOW THROUGH EASTERN NEB...CENTRAL KS AND INTO THE PANHANDLES OF OK AND TX. A DRYLINE IS LOCATED ROUGHLY FROM CENTRAL KS SOUTHWARD INTO WESTERN OK. A BROAD AREA OF PRESSURE FALLS IS LOCATED AHEAD OF THE SFC FRONTS. THE TIGHTENING PRESSURE GRADIENT HAS KEPT WINDS QUITE GUSTY...WITH SUSTAINED WINDS AROUND 25 MPH OR SO AND GUSTS NEAR 40 MPH. STRONG LOW LEVEL WINDS...AROUND 40KT AT 925MB AND 40KT TO 50KT AT 850MB...HAVE AIDED IN CONTINUED MOISTURE ADVECTION AHEAD OF THE DRYLINE AND COLD FRONT. SFC DEWPOINTS ARE IN THE UPPER 50S TO AROUND 60F...AND LITTLE CHANGE IN VALUES ARE EXPECTED AHEAD OF THE FRONT. OVER THE OZARKS...THERE HAS BEEN A DECENT MOISTURE GRADIENT FROM WEST TO EAST. UPPER 50S DEWPOINTS ARE MAKING THEIR WAY INTO AREAS NEAR THE MO/KS STATE LINE...BUT VALUES ARE STILL ONLY AROUND 50F OVER THE EASTERN OZARKS. STRONG FLOW JUST OFF THE SFC AND A MORE SOUTHERLY OR JUST SOUTH OF WEST COMPONENT TO THE SFC WILL WILL RESULT IN A SLOW...BUT STEADY INCREASE IN DEWPOINT ACROSS THE REST OF THE AREA THIS AFTERNOON. ALOFT...THERE ARE A FEW FEATURES OF INTEREST TO NOTE. FIRST...A 100KT JET STREAK LOCATED ON THE EASTERN PERIPHERY OF THE DEEP TROUGH OVER THE ROCKIES HAS RESULTED IN BROAD SCALE LIFT. THIS IS HIGHLIGHTED IN WAT VAP IMAGERY BY A PLUME OF MOISTURE FROM THE TX PANHANDLE THROUGH WESTERN AND CENTRAL PORTIONS OF OK/KS. ANOTHER 120KT JET STREAK IS GEARING UP ON THE WESTERN PERIPHERY OF THE TROUGH AND THERE ARE INCREASING INDICATIONS OF LIFT OVER NEW MEXICO IN THE WAT VAP IMAGERY. LOOKING AT 18Z RAOBS AT KTOP AND KOUN...IT IS CLEAR THAT THE BROAD SCALE LIFT AHEAD OF THE TROUGH HAS BEEN ENOUGH TO SUBSTANTIALLY WEAKEN A RATHER STAUNCH CAP THAT WAS OBSERVED WITH THE 12Z RAOBS. OVER THE NEXT FEW HOURS...THROUGH APPROXIMATELY 430 PM... CONDITIONS WILL REMAIN QUIET OVER EXTREME SE KS AND THE MO OZARKS...SANS A FEW WAA SHRA OVER WESTERN ZONES. ALL EYES WILL BE FOCUSED ON A DEVELOPING PREFRONTAL TROUGH OVER SE KS AND NE OK AS BROAD SCALE LIFT FINALLY ZAPS THE REMAINING CAP AND DISCRETE SUPERCELLS ERUPT. AFTER 430 PM...STORMS THAT HAVE DEVELOPED OVER SE KS AND NE OK WILL QUICKLY SPREAD TO THE NORTHEAST AND IMPINGE ON OUR EXTREME SE KS AND FAR WESTERN MO COUNTIES. TO SAY THE LEAST...THERE IS SUBSTANTIAL DEEP LAYER AND LOW LEVEL SHEAR. WITH DEWPOINTS SETTLING FIRMLY IN THE UPPER 50S TO AROUND 60F...MLCAPE AROUND 1000 J/KG IS EXPECTED. LARGE HAIL...DAMAGING WIND GUSTS AND A FEW TORNADOES ARE EXPECTED. GIVEN SUCH SUBSTANTIAL LOW LEVEL SHEAR...ANY STORMS NEAR THE HIGHEST AXIS OF INSTABILITY WILL RUN AN INCREASED RISK FOR A FEW STRONG...LONG LIVED TORNADOES. DURING THE EVENING HOURS...SUPERCELLS WILL CONGEAL INTO A SQUALL LINE AS THE COLD FRONT ACCELERATES TO THE EAST. THIS WILL TRANSITION THE SEVERE WEATHER RISK TO DAMAGING STRAIGHT LINE WINDS AND A FEW EMBEDDED TORNADOES FOR AREAS ALONG AND WEST OF THE HIGHWAY 65 CORRIDOR. AS THIS LINE HEADS FURTHER INTO THE OZARKS OVERNIGHT...A GENERAL WEAKENING TREND IS EXPECTED...THOUGH THE RISK FOR DAMAGING WIND GUSTS WILL REMAIN. GAGAN && .DISCUSSION... MAIN FOCUS WITH THIS PACKAGE WILL BE CENTERED ON STRONG SYNOPTIC SCALE STORM SYSTEM TAKING AIM AT THE PLAINS AND MISSISSIPPI VALLEY REGION OVER THE NEXT COUPLE OF DAYS. WATER VAPOR IMAGERY SHOWS A STRONG UPPER LEVEL WAVE IN THE NORTHERN ROCKIES WITH STRONG 120-130KT UPPER LEVEL JET STREAK DIGGING SOUTH ON THE WESTERN SIDE OF THE TROUGH. STORM SYSTEM IS EXPECTED TO CLOSE OFF OVER THE HIGH PLAINS LATER TODAY. FURTHER EAST AHEAD OF THE LOW...SOUTHERLY WINDS OF 10 TO 20 KTS WAS KEEPING TEMPERATURES IN THE MID 50S TO LOW 60S WEST OF THE PLATEAU SO FAR TONIGHT. DEW POINTS CONTINUE TO CREEP UP...AIDED BY THE STRONG LOW LEVEL JET OF 45 TO 60 KTS IN THE PLAINS. THIS WAS ALSO AIDING IN SOME WARM SECTOR CONVECTION BREAKING OUT TO OUR NORTH AT THE MOMENT. MODELS ARE IN DECENT AGREEMENT WITH MAIN FEATURES THROUGH THE FIRST FEW PERIODS OF THE FORECAST. AS MENTIONED ABOVE...UPPER LOW IS EXPECTED TO CLOSE OFF IN THE HIGH PLAINS TODAY. LOW LEVEL MOISTURE TRANSPORT WILL CONTINUE IN EARNEST TODAY WEST OF THE PLATEAU WITH DEWPOINTS TRYING TO CREEP INTO THE UPPER 50S TO LOW 60S OVER SOUTHEAST KANSAS AND FAR SOUTHWEST MISSOURI BY 00Z. STRONG SOUTH WINDS WILL BE THE MAIN STORY FOR TODAYS WEATHER WITH SOME GUSTS OF 35 TO 40 KTS POSSIBLE WEST OF THE PLATEAU. SHOULD REMAIN BELOW ADVISORY CRITERIA BUT WILL MAKE MENTION IN THE MORNING HWO. MAY SEE SOME SCATTERED CONVECTION IN THE WARM SECTOR OVER THE NORTHWEST 1/4 OF THE CWA DURING THE DAY AND HAVE BUMPED UP POPS THERE SLIGHTLY. THE MAIN ACTION IS SLATED FOR TONIGHT HOWEVER FOR CONVECTION. STRONG UPPER JET STREAK 110-120KT WILL BE ROUNDING THE BASE OF THE UPPER LEVEL LOW THIS EVENING WHILE LOW STARTS TO BECOME NEGATIVELY TILTED. STRONG 850 WINDS WILL CONTINUE OUT OF THE SOUTH TO SOUTHWEST AT 40 TO 50KTS AND WILL HAVE PLENTY OF LOW LEVEL SHEAR. MODELS IN AGREEMENT THAT SOME DISCRETE SUPERCELLS WILL BE POSSIBLE OVER EASTERN KANSAS SOUTHWARD INTO EASTERN OKLAHOMA LATE THIS AFTERNOON INTO THE EVENING AND MAY CREEP INTO THE SOUTHWEST CORNER OF THE CWA LATE THIS EVENING BEFORE FORMING INTO A SQUALL LINE OVERNIGHT. WILL BE MENTIONING THE THREAT OF ISOLATED TORNADOES OVER THE SOUTHWEST PORTION OF THE CWA FOR TONIGHT. MAIN HAZARD ACROSS THE REMAINDER OF THE CWA WILL BE WITH STRAIGHT LINE WINDS AS SQUALL LINE SHIFTS EAST OVERNIGHT INTO THURSDAY MORNING. SHEAR STILL PRETTY STRONG OVERNIGHT WITH THE SQUALL LINE AND WOULDNT BE SURPRISED TO SEE SOME ROTATING STORMS ALONG THE LINE. STORM EVENT SHOULD BE FAIRLY SHORT LIVED HOWEVER WITH PRECIPITATION ENDING BY MIDDAY OVER THE EASTERN CWA. ATTENTION THEN TURNS TO TEMPERATURES HEADING INTO THE LATER PART OF THE WORK WEEK. PRETTY GOOD PUNCH OF COOLER AIR WILL MOVE INTO THE AREA WITH SEVERAL WAVES OF UPPER LEVEL ENERGY ROTATING THROUGH THE AREA. PRECIPITATION CHANCES WITH THESE SHORTWAVES WILL BE FAIRLY LOW...ESPECIALLY FURTHER SOUTHWEST. SHOULD BE LOOKING AT HIGHS STRUGGLING TO REACH THE LOW 50S IN CENTRAL MO BY FRIDAY...ESPECIALLY IF CLOUD COVER PERSISTS IN THAT REGION. LINDENBERG && .AVIATION... FOR THE 18Z KSGF/KJLN TAFS...THERE WILL BE SEVERAL AVIATION HAZARDS THAT ARE EXPECTED TO AFFECT THE TAF SITES THROUGH THE NEXT 24 HOURS. GUSTY SOUTHERLY WINDS WILL CONTINUE TO AFFECT THE TAF SITES THIS AFTERNOON INTO THE OVERNIGHT HOURS...AHEAD OF AN APPROACHING COLD FRONT. AS THE FRONT MOVES INTO WESTERN KANSAS...SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP AHEAD OF THE FRONT. THE BEST CHANCES FOR THESE STORMS WILL OCCUR ACROSS SOUTHEASTERN KANSAS AND NORTHWESTERN MISSOURI...HOWEVER A FEW OF THESE STORMS MAY MOVE INTO EXTREME SOUTHWESTERN MISSOURI THIS EVENING. HAVE INCLUDED CB IN THE KJLN TAF TO ACCOUNT FOR THIS...AS CONFIDENCE IS TOO LOW TO INCLUDE A TEMPO OR PREVAIL GROUP AT THIS TIME. THESE STORMS WILL HAVE THE POTENTIAL OF BECOMING STRONG TO SEVERE. AS THE FRONT PUSHES EAST A SQUALL LINE IS LIKELY TO DEVELOP NEAR THE FRONT AND WILL PUSH THROUGH THE TAF SITES OVERNIGHT...FIRST AT THE KJLN SITE THEN THE KSGF SITE. HEAVY RAINFALL AND GUSTY WINDS WILL BE POSSIBLE WITH THESE STORMS. HAVE INCLUDED A TEMPO GROUP FOR THIS ACTIVITY AS CONFIDENCE IS HIGHER IN THIS OCCURRING. A STRONG LOW LEVEL JET WILL REMAIN ACROSS THE AREA INTO THE OVERNIGHT HOURS...AND HAVE KEPT THE LOW LEVEL WIND SHEAR IN THE TAFS TO ACCOUNT FOR THE WIND SHEAR. WISE && .SGF WATCHES/WARNINGS/ADVISORIES... MO...WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR MOZ066-067-077- 078-088-089-093-094-101-102. KS...WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR KSZ073-097-101. && $$