000 FXUS63 KTOP 291958 AFDTOP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 258 PM CDT FRI AUG 29 2008 .DISCUSSION... 12Z UPPER AIR ANALYSIS INDICATED BROAD UPPER RIDGE OVER MUCH OF THE SOUTHERN HALF OF THE CONUS. A STRONG SHORTWAVE TROUGH HAD PUSHED WELL EAST OF THE PLAINS LEAVING BROAD UPPER LVL SUBSIDENCE IN PLACE THROUGH MUCH OF THE NORTHERN AND CENTRAL PLAINS. A WEAK UPSTREAM SHORTWAVE TROUGH WAS ANALYZED OVER CENTRAL WY. AT H850 A NEARLY STATIONARY BOUNDARY WAS ANALYZED OVER SOUTHERN KS...REPRESENTING MORE THAN ANYTHING ELSE A STRONG LOW LVL MOISTURE DISCONTINUITY WITH -4 DEG C DEW POINT VALUES AT KTOP AND 18 DEG C DEW POINT VALUES AT BOTH KDDC AND KSGF. AT THE SFC AT 18Z HIGH PRESSURE WAS ROUGHLY DRAPED ALONG THE KS/NE BORDER. A WEAK PACIFIC TYPE FRONT WAS MOVING SOUTHEAST THROUGH THE NORTHERN PLAINS. TONIGHT...THE PACIFIC FRONT OVER THE NORTHERN PLAINS WILL NOT HAVE MUCH OF AN EFFECT ON LOCAL WX...HOWEVER IT MAY HELP USHER THE SFC RIDGE OFF TO THE EAST OVERNIGHT POSSIBLY BRINGING A SLIGHT SOUTHERLY COMPONENT TO THE PREVAILING EASTERLY WINDS OVER MUCH OF THE CWA A BIT QUICKER THAN GUIDANCE INDICATES. WATER VAPOR IMAGERY INDICATES A STRONG UPPER LVL TROUGH DIGGING INTO THE PACIFIC NORTHWEST WHICH MODELS INDICATE WILL AMPLIFY BROAD UPPER LVL RIDGING OVER THE CENTRAL PLAINS TONIGHT. WITH LARGE SCALE FLOW FAVORING AN AMPLIFICATION OF RIDGING OVER THE CENTRAL CONUS FEEL THAT THE UPSTREAM SHORTWAVE TROUGH PUSHING INTO THE NE PANHANDLE AT FORECAST TIME WILL HAVE LITTLE EFFECT ON THE CWA TONIGHT. WITH UPPER RIDGE AXIS BUILDING OVER EASTERN KS TONIGHT EXPECT CLEAR SKIES AND LIGHT EASTERLY WINDS TO PREVAIL. LOWS WILL LIKELY DIP INTO THE MID TO LOWER 50S FOR MUCH OF EASTERN KS...WITH PORTIONS OF NORTH CENTRAL KS REMAINING CLOSER TO 60 IF SFC RIDGE MOVES EAST FAST ENOUGH TO ALLOW FOR SOME WEAK SOUTHEASTERLY FLOW TONIGHT. SATURDAY...SOUTHERLY FLOW WILL EVENTUALLY RETURN TO THE CWA AS SFC AND UPPER RIDGING MOVES INTO THE EASTERN CONUS. FEEL LOW LVL MOISTURE WILL BE SLOW TO RETURN AS LOW LVL TRAJECTORIES WILL CONTINUE DRY AIR ADVECTION FROM THE EAST THROUGH MUCH OF THE DAY. MOSTLY SUNNY SKIES SHOULD PREVAIL WITH LITTLE CHANCE OF PRECIPITATION ASSOCIATED WITH RETURN FLOW/WAA REGIME WITH LITTLE LOW LVL MOISTURE TO WORK WITH. HIGHS ARE EXPECTED TO CLIMB A FEW DEGREES HIGHER THAN TODAY WITH WAA RETURNING. CAVANAUGH SUN/MON...UPPER PATTERN STRENGTHENS AS UPPER TROF MOVES INTO THE GREAT BASIN AND HIGH PRESSURE AMPLIFIES OVER THE NORTHEAST. FRONT WHICH MOVED SOUTH LATE IN THE WEEK IS LIFTED NORTHWARD AND WASHED OUT IN DEVELOPING SOUTHERLY FLOW ON THE LEE SIDE OF THE ROCKIES. WHILE SOME INSTABILITY DEVELOPS IN THE AFTERNOON...THINK WITHOUT A SOURCE OF LIFT THAT ATMOSPHERE WILL REMAIN CAPPED WITH CHANCES FOR POPS FARTHER WEST. EXPECT HIGHS AROUND THE 90 MARK AS AREA MIXES OUT TO 850MB EACH AFTERNOON. TUES-FRI...A COMPLICATED PATTERN SETTING UP AS WESTERN TROF MOVES SLOWLY EASTWARD...AND IS LIFTED INTO THE NORTHERN PLAINS TUESDAY. CURRENT EC BRINGS GUSTAV REMNANTS INTO OKLAHOMA BY EARLY WEDNESDAY. MEANWHILE WESTERN TROF GETS ANOTHER PUSH AS ENERGY DROPS INTO THE BASE AND THE LONGWAVE TROF PUSHES EASTWARD ONCE AGAIN AND LIFTS GUSTAV OVER EASTERN KANSAS THURSDAY. GFS KEEPS SYSTEM SOUTH OF THE EASTERN RIDGE AND DOES NOT LIFT GUSTAV INTO THE PLAINS BUT RATHER STALLS THE SYSTEM OUT OVER LOUISIANA BEFORE BEING USHERED EASTWARD BY SECOND PUSH OF THE WESTERN TROF. CENTERS LEAN TOWARD AN EC SOLUTION. CONSIDERING AT LEAST A FRONTAL PASSAGE ON WEDNESDAY HAVE INCREASED POPS SLIGHTLY FOR THAT TIME PERIOD. SINCE GFS KEEPS THE SECONDARY WESTERN TROF MUCH FARTHER NORTH...WILL ONLY GO WITH ISOLD POPS FRIDAY AS AN UNCERTAINTY AND FOR BETTER COLLABORATION IN THE GRIDS. KEPT TEMPS IN THE 90S TUESDAY AHEAD OF THE FROPA THEN COOLED GRIDS INTO THE EXTENDED WITH EXPECTED ROUND OR TWO OF PRECIP AND CLOUDS. 67 && .AVIATION... FOR THE 18Z TAFS...SFC HIGH PRESSURE WILL MOVE EAST THROUGH NORTHEASTERN KS AND SOUTHEASTERN NE INTO NORTHERN MO OVERNIGHT. HIGH PRESSURE EXPECTED TO KEEP P6SM SKC CONDITIONS OVER TAF SITES FOR THE NEXT 24 HRS. DRY LOW LVL AIRMASS HAS MOVED OVER TAF SITES...SO DESPITE CLEAR SKIES DO NOT SEE MUCH MORE THAN A MIFG POTENTIAL...SO VFR CONDITIONS EXPECTED OVER THE NEXT 24 HRS. CAVANAUGH && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$