FXUS63 KTOP 230600
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1200 AM CST WED DEC 23 2009
.UPDATE...
UPDATED FOR AVIATION.
&&
.DISCUSSION...
SEE PREVIOUS DISCUSSION.
&&
.AVIATION...
LITTLE CHANGE TO PREVIOUS THINKING WITH IFR CIGS EITHER AT OR ON
THE DOORSTEP OF ALL TAF SITES. PROLONGED LIFT OVERNIGHT EXPECTED
TO KEEP VISBY DOWN AND SAW LITTLE NEED TO ADD MORE THAN A WIND
SHIFT TO THE FORECAST PERIOD LATE TOMORROW AFTERNOON AS SFC TROF
DEVELOPS. 67
&&
.PREV DISCUSSION... /ISSUED 926 PM CST TUE DEC 22 2009/
UPDATE...
DRIZZLE AND LIGHT FREEZING DRIZZLE DEVELOPING OVER THE CWA ATTM.
TEMPS LINGER AT OR ABOVE FREEZING ACROSS THE EAST CENTRAL AND
NORTHEAST WITH THE NOSE OF WARM AIR SLOWLY WORKING NORTHWEST. MHK
HAS COME IN RIGHT AT FREEZING AND EXPECT LOCALES TO THE NORTH AND
WEST TO BE NEAR OR BELOW FREEZING AND WILL LET ADVISORY CONTINUE
THERE. TEMPERATURES CONTINUE TO RISE IN THE FAR NE COUNTIES AND
WILL WATCH THESE AREAS TO POSSIBLY ADJUST ADVISORY.
NAM COMING IN ATTM AND PATTERN REMAINS TRICKY. ENERGY CONTINUES TO
EJECT INTO THE PLAINS IN PIECES RATHER THAN ONE LARGE SYSTEM. OR
RATHER AS ONE BIGGER SYSTEM WITH SMALLER ONES TO MAKE FORECAST
MORE COMPLICATED. WARM AIR ALOFT CONTINUES TO SURGE
NORTHWARD...AND TONIGHTS RUN TAKES 850MB FREEZING LINE FAR ENOUGH
WEST TO MAKE FREEZING RAIN ACCUMULATIONS AN INCREASING CONCERN
WEDNESDAY NIGHT FOR NORTH CENTRAL KANSAS AND AS FAR SOUTHEAST AS
MANHATTAN...BUT IS ALSO FASTER AT SURGING THE COLDER AIR
SOUTHWARD WHICH WOULD MAKE FOR QUICK CHANGEOVER TO SNOW THURSDAY
MORNING. /ALSO OF NOTE IS THE 1-2 INCHES OF RAIN OVER EASTERN KS
WEDNESDAY NIGHT./ LEAD WAVE DEVELOPS SFC LOW OVER EASTERN MO LATE
THURSDAY AFTERNOON...WITH STRONG WINDS AND COLD AIR OVER EASTERN
KS BEHIND. SECONDARY UPPER SYSTEM THEN MOVES INTO THE STATE OFF
THE HIGH PLAINS THURSDAY NIGHT AND KEEPS LIFT IN PLACE OVER THE
MUCH COLDER AIR...WHICH WOULD LIKELY INCREASE SNOW RATIOS.
CERTAINLY COULD BE IN A POSITION TO SEE ACCUMULATING SNOW IN
EASTERN KS...AND WOULDNT BE SURPRISED IF HEADLINES WERE NEEDED
LATE IN THE GAME. WILL CONTINUE TO MONITOR INCOMING DATA WITH NO
CHANGES AT THIS TIME FOR THE WINTER STORM WATCH. 67
&&
.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 UNTIL 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.
&&
$$
