FXUS63 KTOP 060537
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1137 PM CST SAT DEC 5 2009

.UPDATE...

UPDATED FOR 06Z AVIATION.

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.DISCUSSION...

SEE PREVIOUS DISCUSSION.

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.AVIATION...

VFR CONDITIONS EXPECTED OVERNIGHT THROUGH THE MORNING HOURS.
HIGH/MID LEVEL CLOUDS WILL CONTINUE TO INCREASE OVERNIGHT WITH
AREAS OF 4-6KFT CLOUDINESS DEVELOPING BETWEEN 13-17Z AT TAF SITES.
VISIBILITIES WILL DECREASE AND CEILINGS WILL RAPIDLY FALL TO MVFR
DURING THE LATE AFTERNOON TO EARLY EVENING AS LIGHT PRECIPITATION
DEVELOPS. COULD SEE A MIX BETWEEN LIGHT SNOW OR LIGHT FREEZING
DRIZZLE AT TAF SITES.

BLAIR

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PREV DISCUSSION... /ISSUED 344 PM CST SAT DEC 5 2009/ 

DISCUSSION...

WATER VAPOR SHOWING VORT MAX OVER ID BEGINNING TO MAKE A TURN TO THE 
EAST WILL ENCOUNTER SHEAR AND WEAKEN AS IT MOVES EASTWARD INTO THE 
CENTRAL PLAINS ON SUNDAY. THIS WILL PUSH A COLD FRONT INTO THE 
WESTERN CWA OVERNIGHT WHICH WILL BECOME NEARLY STATIONARY ACROSS THE 
CENTRAL PORTIONS OF THE CWA THRU MIDDAY SUNDAY BEFORE BEGINNING TO 
ADVANCE ONCE AGAIN BY LATE AFTERNOON. EXPECT MAINLY HIGH CLOUDS 
INCREASING THROUGH THE NIGHT WHICH WILL HELP TO SLOW COOLING WITHIN 
THE DRY AIRMASS...EXCEPT THE NORTH CENTRAL WHERE THE FRONT MOVES 
THROUGH LATER TONIGHT WITH CAA. WILL GO WITH LOWS FROM THE UPPER 
TEENS BEHIND THE FRONT NORTHWEST CWA TO MID 20S SOUTHEAST. 

DRY AIR IN THE MID LEVELS WILL STILL BE IN PLACE ACROSS THE CWA 
EARLY SUNDAY IN THE WAKE OF YESTERDAYS SHORTWAVE. ALTHOUGH THE LLVLS 
WILL MOISTEN ALONG AND BEHIND THE FRONT...THE MID LEVELS WILL BE 
MUCH SLOWER TO MOISTEN. THE STRONGER LIFT AND DEEPER MOISTURE WILL 
BE IN THE COLDER AIR OVER NORTH CENTRAL KANSAS AND ALONG THE 
NEBRASKA BORDER...AND MAINLY IN THE AFTERNOON HOURS WHERE SATURATION 
OF THE SNOW GROWTH REGION IS MOST LIKELY THROUGH THE DAY WITH THE 
POTENTIAL FOR LIGHT ACCUMULATIONS OF THE SNOW GENERALLY IN THE HALF 
TO 1 INCH RANGE. WARMER LOW LEVELS AND WEAKER LIFT WILL OCCUR IN THE 
AFTERNOON OVER THE SOUTHEAST HALF OF THE CWA AS HIGHS TOP OUT IN THE 
MIDDLE TO UPPER 30S. THE DRY MID LEVELS WILL BE SLOWER TO MOISTEN 
THERE...SO ALTHOUGH LIGHT SNOW IS POSSIBLE...SO IS DRIZZLE...BUT 
EXPECT SFC TEMPS TO BE ABOVE FREEZING. IN BETWEEN THESE TWO 
AREAS...SOME CONCERN FOR MORNING FREEZING DRIZZLE ESPECIALLY 
SOUTHWEST AREAS...BUT CONFIDENCE ON THE TIMING AND AMOUNTS 
SIGNIFICANT ENOUGH TO WARRANT AN ADVISORY THIS FAR ARE LOW. THERE 
HAVE DECIDED TO HOLD OFF ON ANY HEADLINE ISSUANCE. NEXT COUPLE OF 
SHIFTS WILL NEED TO REEVALUATE THIS POTENTIAL HOWEVER. DO NOT EXPECT 
ANY SNOW ACCUMULATIONS OF SNOW ALONG AND SOUTHEAST OF THE TURNPIKE.

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SUNDAY NIGHT MID LEVEL WAVE WILL QUICKLY MOVE THROUGH THE AREA. BEST 
LIFT WILL REMAIN ACROSS THE NORTHERN CWA AND HAVE INCREASED SNOW 
CHANCES THERE. FURTHER SOUTH FORECAST SOUNDINGS INDICATE A PERIOD OF 
LIGHT SNOW INTO CENTRAL KANSAS WITH DRIZZLE OR SOME FREEZING DRIZZLE 
DEVELOPING ACROSS EAST CENTRAL KANSAS. DO NOT EXPECT MUCH IN THE WAY 
OF GLAZE AS THE SYSTEM PULLS OUT RATHER QUICKLY BY 06Z AND HAVE 
CONTINUED A DRY FORECAST AFTER 06Z. 

FOCUS THEN TURNS TO THE MORE SIGNIFICANT SYSTEM FORECAST TO AFFECT 
THE PLAINS MONDAY NIGHT THROUGH TUESDAY NIGHT. INITIALLY AHEAD OF 
THE UPPER WAVE MOVING ACROSS THE ROCKIES A PROLONGED PERIOD OF 
ISENTROPIC LIFT MONDAY NIGHT. FAVORED THE 00Z ECMWF AND GEM MODELS 
AND THE 12Z GFS BLEND. PREFER THE MORE SOUTHERLY SOLUTION OF THE 
SURFACE LOW FROM THE TEXAS PANHANDLE THEN MOVING ACROSS OKLAHOMA 
INTO MISSOURI TUESDAY NIGHT. WARM SECTOR SETS UP ACROSS SOUTHERN AND 
EAST CENTRAL KANSAS ON TUESDAY...THIS WILL LIKELY LEAD TO A RAIN AND 
SNOW MIX POSSIBLY TURING OVER TO ALL RAIN SOUTHEAST OF THE TURN 
PIKE. LAYER FRONTOGENESIS ACROSS NORTHERN CWA AND DYNAMIC LIFT WITH 
THE APPROACHING UPPER WAVE WILL LEAD TO A PROLONGED PERIOD OF 
MODERATE TO HEAVY SNOWFALL. EXPECTING MOST SIGNIFICANT ACCUMULATIONS 
ACROSS NORTH CENTRAL KANSAS NORTHEAST AND ALONG THE NEBRASKA BORDER. 
FURTHER SOUTH OF INTERSTATE 70 AMOUNTS NOT AS CLEAR AND WILL BE 
DEPENDENT ON THE AMOUNT OF WARM AIR THAT MOVES INTO THE AREA ON 
TUESDAY AFTERNOON AND EARLY EVENING. WITH THE LOW PASSING EAST 
TUESDAY EVENING WILL SEE A TRANSITION BACK TO ALL SNOW. SNOWFALL 
AMOUNTS WILL NOT BE SIGNIFICANT. WILL CONTINUE TO HIT IN THE HWO 
HARD FOR NOW. WINDS INCREASE TUESDAY NIGHT BEHIND THE SURFACE LOW 
AND THE 00Z ECMWF WOULD SUGGEST THAT WINDS WOULD GUST TO NEAR 35 TO 
40 MPH SO HAVE ADDED AREAS OF BLOWING SNOW TUESDAY NIGHT. 

53

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

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$$