FXUS63 KTOP 112328
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
528 PM CST FRI DEC 11 2009

.UPDATE...
UPDATED THE AVIATION DISCUSSION FOR THE 00Z TAFS. 

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.DISCUSSION...
SEE PREV DISCUSSION.

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.AVIATION...
CIGS WILL DETERIORATE THROUGH THE FORECAST PERIOD. ONLY QUESTION IS 
WHEN AND HOW LOW. MODEL PROGS NOT DOING A GOOD JOB WITH CLOUDS 
MOVING NORTH NOW. WITH OBS OVER SOUTHERN KS GENERALLY VFR NOW...WILL 
MAINTAIN A VFR FCST UNTIL 15-16Z WHEN ISENTROPIC SFCS BRING BETTER 
SATURATION IN WITH MORE PERSISTENT ISENTROPIC LIFT. HAVE HELD OFF ON 
INSERTING IFR FOR LATE AFTERNOON...BUT IF 00Z MODEL DATA CONTINUES 
THIS TREND...MAY HAVE TO WITH THE 06Z FCST AND INCLUDE SOME -DZ AND 
MVFR VSBY.

WOLTERS

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.PREV DISCUSSION.../313 PM CST FRI DEC 11 2009/
PRIMARY FORECAST CONCERN IN THE SHORT TERM WILL BE THE ARRIVAL OF 
STRATUS...AND POTENTIALLY FOG AND DRIZZLE/FREEZING DRIZZLE SATURDAY.

TODAY...UPPER LEVEL PATTERN CONTINUES TO TRANSITION TO A MORE ZONAL 
REGIME...WITH SOME SOUTHWESTERLY COMPONENT TO THE FLOW HELPING TO 
BREAK THE ARCTIC INFLUENCE OBSERVED THE PAST FEW DAYS. TEMPS HAVE 
WARMED TO NEAR 40 SOUTH OF THE SNOWPACK...AND INTO THE MID 20S ALONG 
THE NE BORDER WHERE NEARLY A FOOT OF SNOW REMAINS ON THE GROUND. 
OTHERWISE AT THE SFC...BROAD REGION OF HIGH PRESSURE CONTINUES TO 
SHIFT EASTWARD...WHILE WEAK TROUGHING DEVELOPS IN THE LEE OF THE 
ROCKIES. 

OVERNIGHT...SOUTHERLY FLOW GRADUALLY TAPS INTO MOISTURE OFF THE GOM. 
HIGH RH AREA IN THE FORM OF LOW STRATUS...AND POTENTIALLY SOME FOG  
BEGINS TO SHIFT NORTHWARD. HIGH CLOUDS ASSOCIATED WITH A SHORTWAVE 
TROUGH NOW LIFTING THROUGH THE OKLAHOMA PANHANDLE ARRIVE FIRST LATE 
TONIGHT. DRY COLUMN BEGINS TO SATURATE IN THE 925:850MB 
LAYER...GENERALLY AFTER 12Z. CURRENT OBS INDICATE TDS AOA 20F ARE 
RELEGATED NEAR THE OK/TX BORDER...BUT SHOULD SHOVE NORTHWARD WITH 
THE SOUTHERLY FLOW THROUGH THE NIGHT. THE MOIST...HIGH TD AIRMASS 
RUNS OVER THE SNOWPACK...MAY SEE SOME ADVECTION FOG DEVELOP 
OVERNIGHT ACROSS PORTIONS OF NORTH CENTRAL KANSAS. WARMED LOWS A FEW 
DEGREES...ESPECIALLY EAST CENTRAL.

SATURDAY...SATURATED 925:850MB LAYER WILL PERSIST THROUGH THE DAY. 
OMEGA VIA WEAK MIDLEVEL WARM ADVECTION THROUGH THE MOIST LAYER LOOKS 
TO BRING DRIZZLE THROUGH MUCH OF THE AFTERNOON TO THE AREA. DRY 
COLUMN ABOVE 850MB...NOTABLY THROUGH THE PRIME DENDRITIC GROWTH ZONE 
FROM -12C TO -16C...SUGGESTS DRIZZLE...AND POTENTIALLY LIGHT RAIN 
SHOWERS AS THE PRIMARY PRECIPITATION TYPE. SOME CONCERN ACROSS THE 
ENTIRE AREA BEFORE 18Z...AND OVER PORTIONS OF NORTH CENTRAL AND 
NORTHEAST KANSAS IN THE AFTERNOON WHERE HOURLY SFC TEMPS REMAIN 
BELOW FREEZING. CONFIDENCE IS LOW THAT MINIMAL ACCUMULATIONS WILL 
SIGNIFICANTLY IMPACT INDIVIDUALS...SO WILL REFRAIN FROM ISSUING ANY 
HEADLINES...NAMELY AN ADVISORY...AT THIS TIME. 

LUNDE 

EXTENDED FORECAST /SATURDAY NIGHT TO FRIDAY/

SEMI ZONAL FLOW TAKES OVER ON SATURDAY NIGHT WITH A WEAK SHWV MOVING 
INTO THE CWA ON SATURDAY NIGHT.  BUFKIT SOUNDINGS SHOW A VERY MOIST 
LAYER FROM THE SFC TO APPROX H8 AS A SOUTH WIND ACROSS THE SNOW PACK 
WILL PROVIDE AMPLE MOISTURE.  A DECENT INVERSION HANGS AROUND SO 
CLOUDY SKIES...FOG AND DRIZZLE IS EXPECTED.

WARM ADVECTION TAKES OVER ON SUNDAY INTO MONDAY AS A SFC LOW MOVE 
SOUTHEAST TOWARD THE CWA.  A COLD FRONT WILL PASS THROUGH ON MONDAY 
BRINGING A REINFORCING SHOT OF COLD AIR ON MONDAY NIGHT. THE NAM/GFS 
ARE WARMER THIS RUN /AND WARMER THAN THE ECMWF/ KEEPING THE BULK OF 
THE COLD AIR IN NEBRASKA.  OVERNIGHT LOWS ON MONDAY NIGHT AND TUES 
NIGHT WILL STILL BE IN THE TEENS AND POSSIBLY SINGLE DIGITS BUT MAY 
START TRENDING WARMER DEPENDING ON LATER RUNS.  

TUES TO FRI SFC HIGH MOVES EAST ACROSS THE NORTHERN PLAINS.  BY 
WEDNESDAY WE ARE ON THE BACK SIDE OF THE HIGH AND A WARM UP CAN BE 
EXPECTED TOWARD THE END OF THE WORK WEEK NEXT WEEK.

SALLY

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.TOP WATCHES/WARNINGS/ADVISORIES...NONE.

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$$