FXUS63 KTOP 070544
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1144 PM CST SUN DEC 6 2009
.UPDATE...
UPDATED FOR 06Z AVIATION.
&&
.DISCUSSION...
SEE PREVIOUS DISCUSSION.
&&
.AVIATION...
MVFR CEILINGS EXPECTED TO PREVAIL THROUGH THE TAF FORECAST
PERIOD. NEXT CONCERN WILL BE MONDAY NIGHT AS NEXT STORM SYSTEM
ENTERS THE PICTURE. COULD SEE CONDITIONS DETERIORATE FIRST AT MHK
THEN TOP/FOE BETWEEN 03-05Z. OPTED TO INCLUDE MENTION OF THIS AT
THE END OF TAF FORECAST...WHICH WILL BEGIN A SNOWY PERIOD WITH
MVFR/IFR CONDITIONS LIKELY.
&&
PREV DISCUSSION... /ISSUED 321 PM CST SUN DEC 6 2009/
DISCUSSION...
WATER VAPOR LOOP AND PROFILERS SHOWING SHEARING UPPER LEVEL WAVE
LIFTING NORTHEAST OUT OF WESTERN KS/SW NE. THIS HAS ALLOWED THE
STRONGEST ISENTROPIC LIFT AND FRONTOGENETIC FORCING TO OCCUR TO THE
NORTH OF THE CWA...BUT SHOULD STILL CONTINUE TO DEVELOP LIGHT SNOW
OVER THE NORTHERN CWA INTO THIS EVENING AS WAVE LIFTS OUT. MUCH
LIGHTER SNOW AND SOME DRIZZLE (WITH SOME DRY AIR STILL IN THE MID
LEVELS)...WILL DEVELOP FURTHER SOUTH AS WELL...WITH SOME LIGHT
FREEZING DRIZZLE POSSIBLE AT TIMES ALONG AND SOUTH OF I-70 AS
TEMPERATURES COOL BACK DOWN THIS EVENING. EXPECT LITTLE IF ANY SNOW
ACCUMULATION TO THE SOUTH OF I 70. SO FAR SNOW TOTALS ACROSS THE FAR
NORTHWEST CORNER OF THE CWA HAVE BEEN AROUND A HALF INCH OR
LESS...BUT ANOTHER INCH OF SNOW MAY STILL FALL ACROSS THE NORTHERN
CWA...HIGHWAY 36 CORRIDOR...BEFORE RAPIDLY TAPERING OFF LATER THIS
EVENING AS THE WAVE LIFTS TO THE NORTHEAST. WILL CARRY
CATEGORICAL POPS THERE...THEN TAPER OFF TO CHC POPS ALONG AND SOUTH
OF HIGHWAY 24....THEN DRY ALL AREAS AFTER MIDNIGHT. AS THE COLD
FRONT BISECTING THE CWA ADVANCES SOUTHEASTWARD THIS AFTERNOON AND
EVENING TEMPERATURES WILL FALL OFF QUICKLY. HAVE KEPT LOWS FROM THE
MID 20S FAR SOUTHEAST CWA TO MID TEENS NORTH CENTRAL.
THE CWA WILL BE IN BETWEEN SYSTEMS ON MONDAY WITH DRY...BUT COLD
CONDITIONS. THE CLOUDS WILL LINGER INTO MONDAY AND WITH THE COLD AIR
IN PLACE...HIGHS WILL BE BELOW FREEZING IN ALL BUT THE FAR SOUTHEAST
CORNER IN THE GARNETT AREA. WILL ONLY RAISE TEMPS INTO THE LOW TO
MID 20S WITH SNOWCOVER IN THE FAR NORTHWEST CWA.
63
SYSTEM TUESDAY THROUGH TUESDAY NIGHT CONTINUES TO BE THE MAIN
FOCUS FOR THIS FORECAST.
PROLONGED PERIOD OF ISENTROPIC LIFT IS FORECAST AHEAD OF THE
APPROACHING UPPER TROUGH OVER THE ROCKIES. ISENTROPIC LIFT OVER THE
COLD AIR WILL SATURATES THE COLUMN RATHER QUICKLY MONDAY NIGHT. AREA
OF HIGHEST SNOWFALL AMOUNTS MONDAY NIGHT WILL BE ACROSS THE NORTHERN
AND WESTERN COUNTIES COINCIDENT WITH THE STRONGEST ISENTROPIC OMEGA.
GARCIA METHOD SUGGEST AROUND 3 INCHES OF SNOW IS POSSIBLE BY TUESDAY
MORNING NEAR THE NEBRASKA BORDER. WITH INCREASING LIFT ASSOCIATED
WITH THE ADVANCE OF THE UPPER TROUGH AND STRONG ISENTROPIC UPGLIDE
AMOUNTS ON TUESDAY WILL INCREASE ESPECIALLY ALONG THE NEBRASKA
BORDER. FURTHER SOUTH SNOW AMOUNTS ARE NOT AS CLEAR CUT WITH THE
WARM SECTOR MOVING INTO THE SOUTHEAST CWA DURING THE DAY ON TUESDAY.
AT THIS TIME IT LOOKS LIKE THE WARM AIR WILL MAKE IT UP TO THE
TURNPIKE DURING THE AFTERNOON HOURS LEADING TO A MIX OF RAIN AND
SNOW. LEFT A TRANSITION AREA JUST TO THE NORTH FOR SLEET...SNOW AND
RAIN MIX. LATEST RUNS OF THE GFS AND ECMWF WOULD PLACE THE COLDER
AIR JUST SLIGHTLY SOUTH OF CURRENT FORECAST AND AFTER COORDINATION
WITH SURROUNDING OFFICES HAVE DECIDED TO ADD AN ADDITIONAL ROW OF
COUNTIES TO THE WINTER STORM WATCH. STRONG WINDS DEVELOP ON THE BACK
SIDE OF THE SURFACE LOW TUESDAY EVENING AND THIS WILL LEAD TO
BLOWING SNOW. WILL NEED TO MONITOR THE WINDS FOR POSSIBLE BLIZZARD
CONDITIONS FORMING IN PARTS OF THE CWA. WARMED TEMPERATURES UP SOME
IN THE SOUTHEAST AND SLIGHTLY FURTHER NORTH ACROSS NORTHEAST AND
NORTH CENTRAL KANSAS. THE PROGRESSIVE NATURE OF THE SYSTEM AS
DEPICTED BY THE GFS AND ECMWF WILL QUICKLY BRING TO AN END
PRECIPITATION AFTER 06Z WEDNESDAY.
IN THE WAKE OF THE UPPER TROUGH AND SURFACE LOW THE WINDS MAY CAUSE
SOME ADDITIONAL BLOWING SNOW IN THE EARLY MORNING HOURS ON
WEDNESDAY. AS PRESSURE GRADIENT DECREASES WITH THE HIGH BUILDING IN
THE AFTERNOON WINDS WILL DROP TO AROUND 10 KTS OR LESS. A COLD NIGHT
IS ON TAP FOR WEDNESDAY NIGHT AS COLD HIGH SITS OVER THE AREA WITH
LIGHT WINDS AND SNOW COVER WILL SEE TEMPERATURES BOTTOM OUT IN THE
SINGLE DIGITS. THE UPPER FLOW BECOME MORE ZONAL FLOW WITH A SPLIT IN
THE NORTHERN AND SOUTHERN STREAMS. TEMPERATURES WILL MODERATE SOME
ON THURSDAY WITH SOUTHERN AREAS RISING TO ABOVE FREEZING AND AREAS
OVER THE DEEPER SNOW PACK ONLY IN THE MID AND UPPER 20S.
ECMWF AND THE 06Z AND 12Z RUNS OF THE GFS DIFFER WITH THE EJECTION
ON A WAVE THROUGH THE SOUTHERN STREAM ON FRIDAY WITH THE GFS A
LITTLE FASTER. THERE IS SOME ISENTROPIC LIFT AHEAD OF THE WAVE
ACROSS NORTHERN OKLAHOMA AND SOUTHEAST KANSAS FRIDAY NIGHT. 850 MB
WINDS VEER THROUGH THE NIGHT AND SHUNT MOISTURE INTO MISSOURI. LOOKS
LIKE A PART OF THE AREA WILL BE ON THE NORTH EDGE OF THE LIFT AND
MOISTURE TRANSPORT SO INSERTED A SLIGHT CHANCE OF SNOW FRIDAY NIGHT.
BUILDING RIDGE TO THE WEST IN THE ROCKIES NEXT WEEKEND WILL FAVOR A
SHIFT TO A MORE NORTHWEST UPPER FLOW BY SUNDAY. ANOTHER WAVE WILL
MOVE ACROSS THE NORTHERN PLAINS AND INTO THE GREAT LAKES REGION.
53
&&
.TOP WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH FROM MIDNIGHT TUESDAY TO 6 AM WEDNESDAY FOR
KSZ008-KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-
KSZ024-KSZ026-KSZ034-KSZ035-KSZ036-KSZ038-KSZ039.
&&
$$
