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.
&&

$$