FXUS63 KTOP 042245
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
445 PM CST FRI DEC 4 2009

.UPDATE...UPDATED FOR 00Z AVIATION.

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.AVIATION...VFR THROUGH THE PD. CLEAR SKIES OVERNIGHT AND SOME
INCREASING HIGH CLOUDS ON SATURDAY. WIND WILL SHIFT AROUND TO THE
SOUTH AND BECOME GUSTY LATE SATURDAY MORNING INTO THE EVENING.

SALLY
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.PREV DISCUSSION... /ISSUED 349 PM CST FRI DEC 4 2009/ 

DISCUSSION...

WATER VAPOR SHOWING VORT LOBE EXTENDING SOUTH FROM THE GREAT LAKES 
TROUGH INTO EASTERN KS. SOME STRATOCU WHICH DEVELOPED ACROSS THE 
NORTHERN AND FAR EASTERN CWA AROUND NOON IS ALREADY SHIFTING MAINLY 
NORTH AND EAST OF THE AREA...SO EXPECT MOSTLY CLEAR SKIES TO BE THE 
RULE TONIGHT IN SATURDAY MORNING BEFORE SOME HIGH CLOUDS WILL BEGIN 
TO OVERSPREAD THE AREA FROM WEST TO EAST IN THE AFTERNOON AHEAD OF 
THE NEXT UPPER TROUGH. DIMINISHING LLVL WINDS AROUND SUNSET WITH 
VERY DRY AIR WILL ALLOW TEMPS TO FALL OFF QUICKLY THIS EVENING. 
HOWEVER...THE COMBINATION OF A SLIGHT INCREASE IN WINDS WEST TO EAST 
LATER TONIGHT WITHIN WAA MAY ALLOW TEMPS TO LEVEL OFF AFTER 
MIDNIGHT. THIS WOULD STILL SUPPORT LOWS IN THE MID/UPPER TEENS. 

AS PRESSURE GRADIENT/WAA STRENGTHENS AHEAD OF THE ADVANCING COLD 
FRONT AND SUNNY SKIES IN THE MORNING...SHOULD SEE TEMPERATURES 
RECOVER NICELY BEFORE SLOWING IN THE AFTERNOON AS SOME HIGH CLOUDS 
GRADUALLY INCREASE. STILL...SHOULD SEE HIGHS IN THE LOW/MID 40S.

SW

INITIAL CONCERN WILL BE SUNDAY AND SUNDAY NIGHT PERIOD WITH THE MID 
LEVEL WAVE MOVING OUT OF THE ROCKIES. INITIAL DRY AIRMASS WILL BE IN 
PLACE. INITIAL VERTICAL MOTION WILL LEAD TO CLOUD FORMATION ACROSS 
THE AREA COME SUNDAY MORNING. FORECAST SOUNDINGS ARE SUPPORTIVE OF 
THIS AND MOISTURE IS RATER SHALLOW TO START OFF THE DAY. BY 
AFTERNOON THE COMBINATION OF LAYER FRONTOGENETICAL FORCING AND 
DYNAMIC LIFT AHEAD OF THE MID LEVEL WAVE WILL LEAD TO AN AREA OF 
LIGHT SNOW WITH ACCUMULATING SNOWS ACROSS PARTS OF NORTHEAST INTO 
CENTRAL AND NORTH CENTRAL KANSAS. FURTHER TO THE SOUTHEAST FORECAST 
SOUNDINGS FROM NAM/GFS/EURO ALL DO NOT SATURATE THE SNOW CRYSTAL 
GROWTH REGION THROUGH THE DAY ON SUNDAY. DURING THE AFTERNOON THE 
850 MB MOISTURE TRANSPORT SHIFTS EASTWARD INTO MISSOURI BY 00Z 
MONDAY. PRIOR TO THAT MAINLY WILL SEE DRIZZLE AS THE MAIN 
PRECIPITATION TYPE ACROSS PARTS OF NORTHEAST AND EAST CENTRAL 
KANSAS. BY EARLY EVENING AS THE COOLER AIR BECOMES DEEPER COULD SEE 
SOME LIGHT SNOW THROUGH EARLY EVENING. AFTER 03Z MONDAY LIFT SHIFTS 
EAST AND WILL END PRECIPITATION BY MIDNIGHT. 

HIGH PRESSURE WILL BUILD INTO THE PLAINS BEHIND THIS SYSTEM ON 
MONDAY. ISENTROPIC LIFT INCREASES MONDAY NIGHT ALONG WITH 
FRONTOGENETIC FORCING SETTING UP ACROSS THE NORTHERN CWA. AN INITIAL 
WAVE ALSO EJECTS OUT OF THE WESTERN TROUGH AND INTO THE PLAINS 
MONDAY NIGHT. ON TUESDAY UPPER TROUGH MOVES OUT INTO THE PLAINS WITH 
MOISTURE TRANSPORT WRAPPING BACK INTO THE NORTHERN AND WESTERN CWA. 
WARM SECTOR LOOKS TO SET UP ACROSS SOUTHEAST AND EAST CENTRAL KANSAS 
ON TUESDAY. THIS AREA MOST LIKELY TO SEE A RAIN SNOW MIX BASED ON 
LAYER THICKNESS AND SOUNDINGS...THEN TRANSITION TO ALL SNOW BY THE 
EVENING HOURS. DIFFERENCES STILL EXIST BETWEEN THE GFS AND THE ECMWF 
WITH THE PLACEMENT AND STRENGTH OF THE SURFACE LOW AND MID LEVEL 
FEATURES SO HEAVY SNOW BAND COULD BE ANYWHERE FROM THE CENTRAL AND 
NORTHERN PORTIONS OF THE CWA OR MAINLY ACROSS THE WEST AND NORTH. 
STILL EXPECT THAT SEVERAL INCHES OF SNOW WILL BE POSSIBLE FROM 
MONDAY NIGHT THROUGH TUESDAY NIGHT. LEFT WEDNESDAY DRY AS SYSTEM 
MOVES OFF TO THE EAST. SNOW COVER AND PRESENCE OF HIGH PRESSURE 
ALONG WITH FEW CLOUDS WILL LEAD TO TEMPERATURES DROPPING INTO THE 
SINGLE DIGITS AND TEENS WITH TEMPERATURES ONLY RECOVERING INTO THE 
20S WEDNESDAY AND AGAIN ON THURSDAY.

53

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

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$$