Issued by NWS Topeka, KS
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000 FXUS63 KTOP 222326 AFDTOP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 526 PM CST SUN NOV 22 2009 .UPDATE... UPDATED FOR 0Z AVIATION. && .DISCUSSION... SEE PREVIOUS DISCUSSION. && .AVIATION... POOLING OF MOISTURE ALONG A WEAK FRONTAL BOUNDARY IN CTRL KS ATTM MOVING SLOWLY TOWARD MHK. UPPER SHORTWAVE PROGGED TO MOVE THIS AREA ACROSS THE CWA IN THE EARLY OVERNIGHT HOURS. COULD STILL GET SOME REDUCED VISBYS RIGHT AROUND SUNRISE AS WE DECOUPLE WITH MOISTURE IN PLACE AND STRATUS/BR DEVELOP. BEYOND THE MORNING HOURS MODELS SUGGEST MVFR CLOUDS TO REMAIN THROUGH THE DAY BUT THINK THAT THIS MAY SCATTER OUT TOWARDS AFTERNOON. WILL ADJUST AS NECESSARY. 67 && .PREV DISCUSSION... /ISSUED 320 PM CST SUN NOV 22 2009/ DISCUSSION... SHORT TERM (THROUGH MONDAY)... A MINOR UPPER LEVEL TROUGH WAS LIFTING EAST ACROSS THE PLAINS THIS AFTERNOON. THERE MAY BE ENOUGH LIFT FOR ISOLATED TO SCT SPRINKLES THROUGH 600 PM. A STRONGER UPPER LEVEL TROUGH WAS DIGGING SOUTHEAST ACROSS THE GREAT BASIN. THE 200 PM SURFACE MAP SHOWED A WEAK SFC LOW EAST OF DDC WITH A STATIONARY FRONT EXTENDING NORTHWARD ACROSS CENTRAL KS...JUST EAST OF HLC. THE FRONT EXTENDS NORTHWARD ACROSS CENTRAL NE INTO WESTERN MN. TONIGHT AND MONDAY...THE UPPER LEVEL TROUGH ACROSS THE GREAT BASIN WILL DIG SOUTHEAST INTO THE CENTRAL HIGH PLAINS BY LATE MONDAY AFTERNOON. LOW-LEVEL WINDS WILL VEER TO THE SOUTHWEST TONIGHT BEHIND THE DEPARTING WEAK UPPER LEVEL TROUGH AND THE SFC FRONT MAY SLOWLY MOVE EAST INTO THE EXTREME WESTERN COUNTIES OF THE CWA. WEST OF THE SLOW MOVING FRONT TEMPERATURES MAY DROP ENOUGH FOR AREAS OF DENSE FOG TO DEVELOP...BUT MOST OF THE WIDESPREAD DENSE FOG SHOULD REMAIN WEST OF THE CWA. AS THE 5H TROUGH DIGS AND AMPLIFIES INTO THE CENTRAL HIGH PLAINS THE LOW-LEVEL WINDS ACROSS EASTERN KS WILL BACK TO THE SOUTH AND TRANSPORT DEEPER MOISTURE NORTH. THE RESULTING ISENTROPIC LIFT WILL CAUSE AN INCREASE IN STRATO CU AND ISOLATED SHOWERS DEVELOPING ACROSS MOST OF THE AREA DURING THE LATE AFTERNOON HOURS. THE SFC FRONT SHOULD REMAIN STATIONARY ACROSS THE EXTREME WESTERN COUNTIES OF THE CWA...AND MAY PROVIDE ENOUGH SFC CONVERGENCE ALONG THE FRONT FOR HIGHER POP CHANCES ACROSS NORTH CENTRAL KS MONDAY AFTERNOON. LOWS TONIGHT WILL BE MILD WITH LOWER TO MID 40S...THOUGH IF THE FRONT MOVES EAST ACROSS THE WESTERN COUNTIES...THEN LOWS ACROSS THE EXTREME WESTERN COUNTIES MAY DIP INTO THE MID TO UPPER 30S. MOST OF THE CWA WILL BE IN THE WARM SECTOR ON MONDAY AND HIGHS SHOULD REACH THE UPPER 50S TO LOWER 60S. IF SOME AREAS ACROSS EAST CENTRAL KS RECEIVE MORE INSOLATION DURING THE AFTERNOON HOURS...THEN HIGHS MAY BE IN THE MID 60S. GARGAN LONG TERM (TUESDAY THROUGH MONDAY)... LONG WAVE TROUGH WILL BE CUT OFF OVER SW NEBRASKA BY 00 UTC TUESDAY WITH SOME WARM SECTOR PRECIP LIKELY OUT AHEAD OF THE SYSTEM MONDAY NIGHT UNDER FAVORABLE DYNAMICS AND MODERATE ISENTROPIC LIFT. WILL EVEN BE SOME ELEVATED INSTABILITY PRESENT WHICH MAY ALLOW AN ISOLATED THUNDERSTORM OR TWO TO DEVELOP. AT LEAST SHOULD LEAD TO A MORE CONVECTIVE SCATTERING OF RAIN SHOWERS. MODEL SOLUTIONS BEGIN TO DIVERGE JUST A BIT BY TUESDAY MORNING WITH THE OPERATIONAL GFS AND ECMWF BEING A BIT FASTER WITH THE CLOSED LOW AND TRAILING COLD FRONT THAN THE MOST RECENT NAM RUNS. AT THIS TIME...A SLIGHTLY SLOWER RENDITION OF THE GFS WAS PREFERRED FOR THE FORECAST PACKAGE. PRECIPITATION IS EXPECTED TO BE PRIMARILY IN THE FORM OF RAIN...BUT TEMP PROFILES MAY BECOME CONDUCIVE TO A RAIN SNOW MIX OVER THE WEST AT TIMES. DYNAMIC LIFT WILL BE RELATIVELY IMPRESSIVE WITH THE SYSTEM BUT THE QUALITY OF DEEP MOISTURE FIELDS IS STILL A BIT OF AN UNKNOWN. REGARDLESS...DO FEEL THAT THERE WILL BE WIDESPREAD PRECIPITATION WITH BEST CHANCES IN THE NORTHERN HALF OF THE CWA. IT SHOULD ALSO BE NOTED THAT THE MOST RECENT NAM RUN HAS TRENDED FURTHER SOUTH. IF THIS NAM FORECAST WERE TO VERIFY...WOULD SEE SLIGHTLY INCREASED PRECIP CHANCES AND SLIGHTLY BETTER CHANCES FOR SOME SNOW MIXING IN. THE SYSTEM QUICKLY MOVES OFF TO THE NORTHEAST AND SKIES SHOULD BE CLEARING BY LATE TUESDAY NIGHT. A SECONDARY TROUGH WILL QUICKLY DROP IN ON THE BACK SIDE OF THE FIRST DURING THE DAY ON WEDNESDAY. THIS WILL BRING A COLD FRONT THROUGH THE PLAINS WITH A SLIGHTLY COLDER AIRMASS IN ITS WAKE. THIS SHOULD BE A DRY FRONT AS ANY MOISTURE LOOKS TO GET SCOURED OUT PRETTY WELL BY THE FIRST SYSTEM. THE COOL AIRMASS WILL REMAIN IN PLACE THROUGH LATE IN THE WEEK WITH HIGHS IN THE 40S THROUGH THURSDAY. WILL THEN SEE LONG WAVE RIDGING BUILD BACK IN WITH A WARMING TREND AND WHAT LOOKS TO BE A PLEASANT START TO NEXT WEEKEND. MODEL SOLUTIONS SIGNIFICANTLY DIVERGE AT THAT TIME...BUT CAN AGREE THAT ANOTHER CHUNK OF ENERGY MAY BE BRINGING PRECIP TO THE PLAINS BY THE FIRST PART OF NEXT WEEK. BARJENBRUCH .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$
