FXUS63 KTOP 010538
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1138 PM CST MON NOV 30 2009

.UPDATE...

UPDATED FOR 06 UTC AVIATION.

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.DISCUSSION...

SEE PREVIOUS DISCUSSION.

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.AVIATION...

MAIN CONCERN THROUGH EARLY MORNING WILL BE POTENTIAL FOR LOW LEVEL
WIND SHEAR. VAD AND PROFILER WINDS INCREASING TO NEAR 30 KTS AND
ARE FORECAST TO INCREASE TO AROUND 40 KTS NEAR 1 KFT AFTER 08Z
THIS MORNING. WINDS BELOW THE INVERSION WILL BE LESS THAN 10 KTS
THROUGH 14Z TUESDAY SO WILL KEEP MENTION OF LLWS IN FORECAST. NEXT
COLD FRONT TO MOVE SOUTHEAST INTO NORTHEAST KANSAS TUESDAY EVENING
AND WILL SHIFT THE WINDS TO THE NORTH IN THE 03Z-06Z PERIOD. VFR
CIGS AND VSBYS FORECAST.

53

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.PREV DISCUSSION... /ISSUED 221 PM CST MON NOV 30 2009/

DISCUSSION...

19Z WATER VAPOR SHOWS THE UPPER LOW CUT OFF FROM THE MEAN WESTERLIES 
OVER MEXICO WITH A SHORTWAVE TROUGH MOVING ACROSS THE OHIO RIVER 
VALLEY. SFC OBS INDICATED A DRY AIRMASS HAD MOVED IN WITH A SFC 
RIDGE THAT WAS CENTERED TO THE SOUTHWEST OF THE FORECAST AREA. 

FOR TONIGHT AND TUESDAY...MOISTURE IS SLOW TO RETURN WITH THE CUT 
OFF REMAINING TO THE SOUTH...AND NO REAL FORCING IS PROGGED UNTIL 
LATE IN THE DAY TUESDAY AS THE CUT OFF LOW BEGINS TO LIFT INTO 
CENTRAL TX. THEREFORE THE PERIOD SHOULD BE QUIET WITH ONLY SOME HIGH 
CLOUDS INCREASING TUESDAY AFTERNOON IN ADVANCE OF THE UPPER LOW. 
LOWS TONIGHT SHOULD BE SEVERAL DEGREES WARMER IN THE LOWER 30S DUE 
TO A SOUTHWESTERLY WIND PERSISTING AROUND 5 MPH. THERE APPEARS TO BE 
NO REAL CHANGE IN AIRMASS FOR TUESDAY SO PERSISTENCE WITH HIGHS IN 
THE MID TO UPPER 50S LOOKS REASONABLE.

WOLTERS

MINOR CHANGES TO FORECAST PACKAGE TUESDAY NIGHT AND BEYOND. NEAR 
TERM FOCUS CENTERS ON SOUTHERN TRACK UPPER DISTURBANCE OVER THE 
SOUTHERN PLAINS AND DIGGING UPPER TROUGH OVER THE NORTHERN PLAINS 
TUE NIGHT INTO WEDNESDAY MORNING. OPERATIONAL RUNS OF NAM/GFS ALONG 
WITH SREF OUTPUT CONTINUE TO HINT AT A NARROW WINDOW FOR 
PRECIPITATION TO DEVELOP OVER EAST CENTRAL KANSAS DURING THIS TIME. 
BEST LARGE SCALE ASCENT WILL ARRIVE ACROSS EC KS BETWEEN 06-12Z WED. 
LOW LEVELS INITIALLY QUITE DRY BUT CONTINUED MOISTENING FROM 
TOP-DOWN DURING THIS PERIOD SHOULD ALLOW FOR COLUMN TO BECOME 
SATURATED IN THIS REGION. BEST REGION OF FRONTOGENESIS WILL BE 
LOCATED JUST SOUTHEAST OF THE CWA. SATURATION THROUGH SNOW GROWTH 
ZONE WILL EXIST SO NEXT VARIABLE IS VERTICAL TEMP PROFILE NEAR/JUST 
ABOVE THE SFC. INITIAL PRECIPITATION IS EXPECTED TO BE IN THE FORM OF 
LIQUID OVER MOST OF EC KS. HOWEVER AS COLDER AIR ADVECTS INTO THE 
REGION AND LOCALIZED EVAPORATIONAL COOLING IS UNDERWAY...PROFILE 
BECOMES FAVORABLE FOR A RA/SN MIX...POSSIBLY SOME AREAS ALL SNOW BY 
WED MORNING. ATTM...EXPECTING LITTLE TO NO ACCUMULATION IN OUR CWA 
AND CERTAINLY NOTHING THAT SHOULD IMPACT THE ROADWAYS. MOST LIKELY 
AREAS TO EXPERIENCE DESCRIBED SCENARIO WILL BE ALONG AND SOUTHEAST OF 
A LINE FROM EMPORIA TO CARBONDALE KANSAS. AS THE CASE WITH WINTER 
WEATHER...FORECAST CAN BE SENSITIVE TO SLIGHT CHANGES AND WILL 
CONTINUE TO REFINE FORECAST.

BEYOND WED MORNING...FORECAST REMAINS DRY. AN OUTSIDE CHANCE OF 
FLURRIES ACROSS THE FAR NORTH ON THU AS SNOW GROWTH ZONE HOVERS JUST 
OFF THE SFC WITH A SATURATED LAYER BETWEEN H75-H9. HOWEVER MOST OF 
THE REGION EXPECTED TO SEE DOWNGLIDE THROUGH THE LAYER SO WILL LEAVE 
OUT OF FORECAST ATTM. WITH COLDER AIR ON THE WAY BEHIND A COUPLE 
FRONTAL PASSAGES...TEMPERATURES WILL BE BELOW NORMAL WED THROUGH 
FRI. COLDEST DAY OF THE PERIOD LOOKS TO BE FRIDAY WITH MORNING LOWS 
IN THE TEENS AND HIGHS IN THE 30S. SPREAD BETWEEN GUIDANCE GREATLY 
INCREASES BY THE WEEKEND SO LEFT THINGS DRY WITH NEAR NORMAL 
READINGS.

BLAIR

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

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$$