FXUS63 KTOP 222327
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
527 PM CST TUE DEC 22 2009

.UPDATE...
UPDATED FOR 0Z AVIATION.

&&

.DISCUSSION...
SEE PREVIOUS DISCUSSION.

&&

.AVIATION...
CONCERNS FOR FORECAST PERIOD ARE CIG HEIGHTS AND ONSET OF
PRECIPITATION. GUIDANCE IS LITTLE HELP AT TOP/FOE AS SOUNDINGS
INDICATE CIGS SHOULD ALREADY BE IFR. UPSTREAM TRENDS AND WARMER
TEMPS IN THE AREA SHOULD HOLD ONTO MVFR CIGS FOR ANOTHER HOUR OR
SO AND THINK THEY WILL DECLINE THEREAFTER. OTHER CONCERN IS FOR
TEMPERATURES AT MHK. AGAIN MODELS INDICATE A RISE BACK ABOVE
FREEZING AND WITH TEMPS AT TOP AT 39 THINK THIS IS STILL ON TRACK.
WILL HAVE TO MONITOR CLOSELY AS PRECIP DEVELOPS LATER TONIGHT...AS
COULD BE FZDZ OUT WEST IF FREEZING LINE DOESNT RETREAT AS PROGGED. 67 

&&

.PREV DISCUSSION... /ISSUED 348 PM CST TUE DEC 22 2009/ 

DISCUSSION...

SHORT TERM...FOCUS IS ON PRECIP TYPE/TEMPS TONIGHT INTO WEDS.

WEAK CAA IS ONGOING NORTH OF A STATIONARY BOUNDARY THAT STRETCHES 
FROM NEAR KANSAS CITY TO NEAR THE KS/OK LINE. SFC WETBULB TEMPS OF 
32 OR LOWER ARE IN PLACE ACROSS THE NORTHERN TIER OF COUNTIES. 3HR 
PRESSURE CHANGES INDICATE FALLS ALREADY IN PLACE ACROSS THE REGION 
SO I DO NOT ANTICIPATE THE COLDER/DRIER AIR MAKING IT TOO MUCH 
FURTHER SOUTH. LIFT TONIGHT WILL COME FROM WAA/ISENTROPIC LIFT AS 
THE FIRST OF SEVERAL WAVES WILL EJECT OUT OF THE ROCKIES INTO THE 
PLAINS. PRECIP IN THE FORM OF RAIN OR FREEZING RAIN WILL DEVELOP. A 
ANALYSIS OF FCST SOUNDINGS FROM THE NAM/GFS SUGGEST THAT FREEZING 
RAIN WILL BE A THREAT TO OCCUR MAINLY NORTHWEST OF AN ABILENE TO 
MANHATTAN TO HIAWATHA LINE AND WE HAVE OPTED TO HOIST A WINTER 
WEATHER ADVISORY WHERE AMOUNTS OF AROUND ONE TENTH COULD ACCUMULATE 
TONIGHT. WE HAVE DECIDED AGAINST ISSUING A WINTER STORM WARNING FOR 
THIS AREA BASED ON THE EXPECTED SCENARIO OF WARMER AIR PUSHING 
DAYTIME AIR TEMPS BACK TO OR ABOVE FREEZING SO ANY ICE ACCUMS WOULD 
BE MITIGATED AND PRECIP WOULD CHANGE BACK TO RAIN. 

WE HAVE ALSO INCLUDED ISOLATED THUNDERSTORM WORDING ACROSS THE SE 
COUNTIES WHERE MUCAPES AND LLJ WILL COEXIST ON WEDS.

CO

AS THE INITIAL SHORTWAVE ROTATES NORTHEAST ACROSS THE AREA
WEDNESDAY EVENING A SFC LOW WILL MOVE NORTHWARD ACROSS THE FAR 
EASTERN CWA AND SWITCH WINDS AROUND TO THE NORTHWEST OVERNIGHT. 
COLDER AIR ALOFT WILL MOVE INTO THE NORTH CENTRAL AND BEGIN TO 
SWITCH PRECIPITATION TO ALL SNOW IN THE NORTHCENTRAL AND A MIXTURE
BY MIDNIGHT NORTH AND WEST OF A COUNCIL GROVE TO HIAWATHA LINE.
ELEVATED INSTABILITY WILL LINGER INTO THE EVENING OVER THE FAR
SOUTHEAST CWA SO HAVE KEPT ISOLATED THUNDER THERE. AS THE COLD AIR
PLUNGES SOUTHEAST OVERNIGHT...SNOW WILL CONTINUE IN THE NORTH
CENTRAL WITH RAIN IN THE FAR SOUTHEAST CORNER AND A MIXTURE OF
FREEZING RAIN...SLEET AND SNOW IN BETWEEN. THE NORTHWEST HALF OF THE
CWA SHOULD GENERALLY RECEIVE 1 TO 3 INCHES OVERNIGHT BEFORE A DRY
SLOT TEMPORARILY DECREASES PRECIP AS THE INITIAL WAVE MOVE BY.
PRECIP SHOULD REDEVELOP CHRISTMAS EVE AS A SECOND WAVE MOVES INTO
THE AREA FROM THE SOUTHWEST AND DEEPENS THE UPPER TROUGH AND AN
ASSOCIATED SFC LOW IN MO. WITH COLD AIR IN PLACE...PRECIP WITH
THIS WAVE WILL BE IN THE FORM OF SNOW...BUT SHOULD FAVOR THE NORTH
AND EASTERN CWA WITH SNOW AMOUNTS.

AS THE UPPER LOW LIFTS TOWARDS THE UPPER MS VALLEY...TROWAL WILL 
KEEP SNOW WRAPPING BACK INTO THE CENTRAL PLAINS. WILL KEEP LIGHT 
SNOW AND BLOWING SNOW IN THE GRIDS INTO CHRISTMAS 
MORNING...EXPECIALLY NEAR THE NEBRASKA AND MO BORDERS...WITH CHANCES 
THEN TAPERING OFF DURING THE DAY ON CHRISTMAS. AT THIS TIME EXPECT 
STORM TOTALS TO RANGE FROM AROUND 3 INCHES IN THE FAR SOUTHEAST TO 7 
TO 8 INCHES NEAR THE NEBRASKA BORDER. THE COMBINATION OF COLDER 
AIR POURING INTO THE AREA WITH SNOWCOVER AND STRONG WINDS WILL 
PRODUCE WINDCHILLS COMMONLY IN THE ZERO TO 10 BELOW RANGE CHRISTMAS 
MORNING.

AS THE UPPER TROUGH SHIFTS EASTWARD THROUGH THE WEEKEND AND WEAK 
UPPER RIDGING DEVELOPS ACROSS THE CENTRAL PLAINS IN ITS WAKE...WILL 
KEEP EXTENDED DRY THROUGH THE WEEKEND. ANOTHER SYSTEM DIGS INTO THE 
SOUTHERN ROCKIES/SOUTHERN PLAINS EARLY NEXT WEEK...BUT AT THIS 
TIME...IT APPEARS WILL REMAIN SOUTH OF THE CWA. WITH THE EXPECTED 
SNOWCOVER WILL KEEP TEMPS BELOW NORMAL.

63

&&

.TOP WATCHES/WARNINGS/ADVISORIES...WINTER WEATHER ADVISORY FROM 11
PM TUESDAY TO 9 AM WEDNESDAY FOR
KSZ008-KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ034.

WINTER STORM WATCH FROM 6 PM WEDNESDAY TO NOON FRIDAY FOR KSZ008-
KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-KSZ024-
KSZ034-KSZ035-KSZ036-KSZ037.

&&

$$