905 FXUS63 KTOP 270449 AFDTOP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 1149 PM CDT THU APR 26 2012 ...UPDATE TO AVIATION... .DISCUSSION... SHORT TERM (TODAY THROUGH FRIDAY)... 19Z WATER VAPOR SHOWS A SHORTWAVE LIFTING EAST THROUGH AZ WITH A LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST. MID LEVEL RIDGING REMAINS OVER THE CENTRAL PLAINS. AT THE SFC 19Z OBS SHOWED RIDGING THROUGH MUCH OF KS WITH A FRONTAL BOUNDARY NEAR THE RED RIVER VALLEY. A BAND OF LIGHT SHOWER ACTIVITY HAS SET UP WITHIN A NARROW AXIS OF ISENTROPIC UPGLIDE ACROSS CENTRAL KS. FOR THIS AFTERNOON AND THIS EVENING...THE RUC AND NAM SHOW THE NARROW AXIS OF ISENTROPIC LIFT ON THE 310K SFC GRADUALLY LIFTING NORTH AND EAST. BECAUSE OF THIS HAVE INCLUDED SOME SCATTERED SHOWERS ACROSS NORTH CENTRAL KS WERE MID LEVEL MOISTURE IS A LITTLE BETTER. THE NEXT SHIFT WILL NEED TO WATCH THE EASTWARD PROGRESSION. BUT FOR NOT THINK SHOWERS WILL HAVE A HARD TIME MOVING EAST DUE TO A LITTLE MORE DRY AIR IN THE MID LEVELS. OVERNIGHT...THE SHORTWAVE OVER AZ WILL LIFT OUT OF THE SOUTHERN ROCKIES AND MOVE INTO SOUTHERN NEB THROUGH THE DAY FRIDAY. THIS WAVE IS EXPECTED TO PROVIDE THE FORCING TO SPARK CONVECTION LATE TONIGHT AND THROUGH THE DAY FRIDAY. AT THIS POINT IT LOOKS LIKE THERE COULD BE ELEVATED CONVECTION FORM DURING THE MORNING HOURS AND LIFT ACROSS NORTHEAST KS. BOTH THE NAM AND GFS SHOW A NARROW WARM SECTOR DESTABILIZING BY THE LATE MORNING OR EARLY AFTERNOON WITH SURFACE BASED CAPES ON THE ORDER OF 1000 TO 1500 J/KG. WHILE A LITTLE ON THE MARGINAL SIDE...DEEP LAYER SHEER OF 50 KTS WOULD BE SUFFICIENT FOR STORMS IN THE WARM SECTOR TO BECOME SUPERCELLS. AT THIS POINT THE MODELS PROG THE WARM FRONT TO SET UP JUST TO THE SOUTHWEST OF THE FORECAST AREA WITH IT LIFTING NORTHEAST TOWARDS A CNK TO EMP LINE BY FRIDAY EVENING. STORMS SOUTHWEST OF THIS LINE WILL HAVE THE GREATER LIKELY HOOD OF BECOMING SEVERE. ALTHOUGH ELEVATED STORMS ACROSS NORTHEAST KS COULD ALSO HAVE HAIL WITH THEM. THERE COULD BE AN ISOLATED TORNADO THREAT ALONG THE WARM FRONT AS WELL IF A STORM WERE TO DEVIATE TO THE SOUTHEAST AND RIDE ALONG THE BOUNDARY TAPPING INTO THE GREATER HELICITY JUST NORTH OF THE BOUNDARY. WITH A CONVERGENCE IN SOLUTIONS AMONG THE MODELS...HAVE INCREASED POPS INTO THE CATEGORICAL RANGE ACROSS NORTHERN KS WHERE THE BEST FORCING IS ANTICIPATED. HAVE LIKELY POPS ACROSS EAST CENTRAL KS THINKING THAT COVERAGE OF STORMS MAY BE A LITTLE MORE BROKEN IN NATURE. FRIDAY IS ALSO EXPECTED TO BECOME WINDY AS THE SFC LOW DEEPENS TO THE WEST. THE INCREASING PRESSURE GRADIENT WILL LIKELY CAUSE EAST AND SOUTHEAST WINDS TO GUST OVER 30 MPH. LOWS TONIGHT SHOULD NOT DROP OFF AS MUCH GIVEN INCREASING CLOUD COVER AND A BETTER MIXED BOUNDARY LAYER. THINK LOWS WILL BE IN THE MID 50S TO AROUND 60 FOR MOST LOCATIONS. EXPECT A GOOD GRADIENT IN MAX TEMPS FOR TOMORROW WITH CLOUDS AND EASTERLY WINDS KEEPING HIGHS IN THE LOW 60S OVER FAR NORTHEAST KS. NEAR AND SOUTHWEST OF THE WARM FRONT...HIGHS SHOULD WARM INTO THE MID 70S. WOLTERS MID TERM (FRIDAY EVENING THROUGH SUNDAY)... BY FRIDAY EVENING MODELS AGREE ON A SIMILAR POSITION OF THE UPPER TROUGH AND SURFACE LOW ACROSS CENTRAL INTO NORTHEAST KANSAS. SHOWERS AND THUNDERSTORMS WILL REMAIN POSSIBLE EARLY FRIDAY EVENING BEFORE THE SYSTEM QUICKLY EXITS NORTHEAST AND A DRIER AIR MASS FILLS IN ITS PLACE WITH THE PASSAGE OF A COLD FRONT. BY SATURDAY MORNING THE FRONTAL BOUNDARY WILL STALL NORTHEAST TO SOUTHWEST OVER SOUTHERN KANSAS INTO CENTRAL OKLAHOMA. SURFACE RIDGE SETTLING OVER THE CWA SHOULD KEEP MUCH OF THE AREA STABLE AND CAPPED THROUGHOUT THE SATURDAY AFTERNOON PERIOD BEFORE ADDITIONAL SHOWERS AND A POSSIBLE THUNDERSTORM OR TWO DEVELOPS ALONG AND NORTH OF THE BOUNDARY. WHILE MUCH OF THE INSTABILITY REMAINS JUST SOUTH OF THE CWA...WOULD NOT BE SURPRISED FOR AN ISOLATED THUNDERSTORM OR TWO. BEST CHANCE FOR PRECIP ATTM APPEARS TO BE SUNDAY AFTERNOON INTO THE EVENING HOURS AS ISENTROPIC LIFT INCREASES AND THE WARM FRONT LIFTS NORTHWARD. THE COVERAGE AND SEVERITY OF ANY THUNDERSTORM STILL REMAINS UNCERTAIN AS THE MODELS DEPICT VARYING SOLUTIONS ON THE PLACEMENT OF THE WARM FRONT WITH RESPECT TO OUR AREA. HOWEVER...AMPLE MOISTURE ASSOCIATED WITH THE BOUNDARY AND THE PRESENCE OF A SHORTWAVE TROUGH PASSING THROUGH SUNDAY EVENING LEADS TO A DECENT CHANCE FOR ADDITIONAL PRECIPITATION. TEMPERATURES STILL APPEAR TO BE ON TRACK FOR SATURDAY AS CLEARER SKIES AND WEAK COLD AIR ADVECTION BEHIND THE SYSTEM SHOULD HELP RAISE HIGHS INTO THE MIDDLE AND UPPER 60S TOWARDS EAST CENTRAL KANSAS. CLOUD COVER ON SUNDAY WILL INHIBIT TEMPS TO ONLY THE LOWER 60S. EXTENDED TERM (SUNDAY EVENING THROUGH THURSDAY)... VERY UNSETTLED PATTERN FOR THE EXTENDED TERM WITH CHANCES FOR SHOWERS AND THUNDERSTORMS EACH DAY. A STALLED SURFACE FRONT SUNDAY EVENING INTO EARLY NEXT WEEK WILL PROVIDE THE SURFACE CONVERGENCE ALONG WITH A SERIES OF SHORTWAVES EJECTING FROM THE MAIN TROUGH OVER THE PACIFIC NORTHWEST INTO THE CENTRAL AND NORTHERN PLAINS. MODELS ARE STILL HAVING DIFFICULTY WITH RESPECT TO THE TIMING OF EACH SHORTWAVE TROUGH TO AFFECT THE CWA COMBINED LACK OF STRONG FORCING FROM ANY FRONTAL BOUNDARIES. REGARDLESS...CONTINUOUS WARM AIR ADVECTION AND DEWPOINTS RANGING FROM THE UPPER 50S TO MIDDLE 60S SUGGEST CONTINUING CHANCES FOR SHOWERS AND THUNDERSTORMS THROUGH THURSDAY. SOUNDING PROFILES SHOW 0-6KM BULK SHEAR VALUES MARGINAL AROUND 35 KTS WITH MIXED LAYER MUCAPE BETWEEN 1100 AND 1500 J/KG SUGGEST ANY STORMS ABLE TO DEVELOP WILL BE ELEVATED AND COULD BE STRONG. HEAVY RAIN MAY ALSO BE LIKELY AS BOTH THE GFS AND ECMWF SHOW PWAT VALUES WELL OVER AN INCH FOR EACH PERIOD IN THE FORECAST. MAIN CONCERN WILL BE IF THE MAIN FORCING ALOFT WILL COINCIDE WITH ANY SURFACE FEATURES TO ALLOW THE STRONGER STORMS TO FORM. BESIDES THE PRECIP POSSIBILITIES...NEAR NORMAL TEMPERATURES ON MONDAY ARE EXPECTED TO GRADUALLY WARM INTO THE UPPER 70S BY THURSDAY AS THE THERMAL RIDGE AXIS STRETCHES NORTHWARD OVER THE CENTRAL PLAINS. BOWEN && .AVIATION... GIVEN LATEST TRENDS...HAVE SLOWED ONSET OF MVFR CIGS AND PRECIP AS WELL AS THE IMPROVING TIMING AROUND 20Z. STILL NOT CONFIDENT ENOUGH TO INCLUDE ANY TS AROUND 0Z. NOT CERTAING ON TIMING OF WINDS INCREASING AROUND 12Z...WITH POSSIBLE VCSH HINDERING BETTER MIXING. 65 && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$