FXUS63 KTOP 231119
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
519 AM CST WED DEC 23 2009
.UPDATE...
UPDATED FOR 12Z AVIATION.
&&
.DISCUSSION...
SEE PREVIOUS DISCUSSION.
&&
.AVIATION...
LITTLE CHANGE TO PREVIOUS AVIATION PACKAGE. IFR CONDITIONS ARE
EXPECTED TO PERSIST THROUGH THE TAF PERIOD. PERIODS OF RAIN WILL
CONTINUE THROUGH THE DAY. PRECIPITATION WILL TRANSITION TO SNOW AT
MHK TOWARDS THE END OF THE FORECAST PERIOD. MIGHT SEE A SMALL
WINDOW OF FREEZING RAIN BEFORE THE CHANGEOVER BUT DID NOT INCLUDE
IN TAF DUE TO LARGE UNCERTAINTY IN TIMING AND DURATION. BLAIR
&&
.PREV DISCUSSION... /ISSUED 408 AM CST WED DEC 23 2009/
..SIGNIFICANT WINTER STORM TO AFFECT THE AREA TONIGHT THROUGH CHRISTMAS...
DISCUSSION...H5 LOW WAS NEAR THE 4 CORNERS REGION WITH A SECOND LOW OVER SW
CANADA. THIS WILL BE THE MAIN FOCUS FOR THE UPCOMING WINTER STORM
LATER TONIGHT THROUGH CHRISTMAS DAY.
00Z RUNS MADE QUITE A SHIFT TO THE EAST WITH THIS SYSTEM COMPARED TO
YESTERDAYS 00Z RUNS. THE 06Z NAM/GFS SO FAR HAVE NOT DIGRESSED MUCH
FROM THE 00Z RUNS SO THERE IS SLIGHTLY MORE CONFIDENCE WITH THE SNOW
FORECAST THAN PREVIOUSLY THOUGHT.
TODAY/TONIGHT...AREA OF PRECIP WAS MOVING NORTH ACROSS THE STATE
AHEAD OF A SHWV AND ASSOCIATED WMFNT. TEMPS WERE RISING BY A FEW
DEGREES AS THE PRECIP GOES THROUGH AND THERE IS SOME CONCERN THAT
THE FZRA MAY NOT MATERIALIZE OVER THE ENTIRE ADVISORY AREA. WILL
CONTINUE TO MONITOR AND KEEP THE ADVISORY HEADLINE FOR NOW AND WILL
REASSESS OVER THE NEXT FEW HOURS. THE NEXT BEST CHANCE FOR ANY FZRA
WILL BE LATER TONIGHT. H5 LOW CONTINUES TO DEEPEN AS IT DIVES SOUTH
INTO SOUTHWEST TEXAS LATER TONIGHT. A SURGE OF WARMER AIR OVER THE
CWA AT H85 WITH LITTLE CHANGE IN TEMPS AT THE SURFACE, WHICH ARE
HOVERING AROUND FREEZING IN THE ADVISORY AREA, WILL RESULT IN
PERIODS OF FZRA/IP THIS EVENING FOR NORTH CENTRAL KANSAS. MOST OF
THE AREA HOWEVER WILL SEE RAIN AND POSSIBLY THUNDERSTORMS THIS
AFTERNOON AND EVENING.
THURSDAY/THURS NIGHT...THIS IS THE START OF THE WORST PART OF THE
STORM. SNOW BEGINS TO BECOME THE PREDOMINANT WEATHER TYPE ON
THURSDAY AS THE SOUTHERN STREAM LOW BEGINS TO JOIN UP WITH THE
NORTHERN STREAM AND BECOME NEGATIVELY TILTED. THE RESULTANT SURFACE
LOW DEEPENS VERY RAPIDLY AND THE 00Z RUNS TRACK THIS LOW FARTHER TO
THE EAST THEREFORE MOVING THE HEAVY SNOW AXIS TO THE EAST AS WELL.
ITS LOOKING LIKE THE TOPEKA/LAWRENCE AREA WILL BEAR THE BRUNT OF
THIS STORM. WITH THE RAPIDLY DEEPENING SURFACE LOW COMES VERY
STRONG WIND AS WELL AS BLOWING SNOW. NEAR BLIZZARD CONDITIONS WILL
BE POSSIBLE ON THURSDAY AFTERNOON AND EVENING MAKING ANY TRAVEL VERY
TREACHEROUS. THE SURFACE LOW WILL SWING NORTH INTO IOWA BY LATE
THURSDAY NIGHT KEEPING THE EASTERN THIRD OF THE TOP CWA IN THE HEAVY
SNOW AXIS FOR MOST OF THE NIGHT.
CHRISTMAS DAY/NIGHT...THE H5 SYSTEM BECOMES VERY WOUND UP AND BEGINS
TO PUSH THE SURFACE LOW BACK WEST SLIGHTLY INTO NEBRASKA. MY BIG
CONCERN ARE THE FEW NORTHEAST COUNTIES THAT BORDER NEBRASKA AND
MISSOURI AS THIS LOW PIVOTS AROUND AND A VERY STRONG TROWAL SETS UP
THAT AREA COULD SEE CONTINUOUS SNOW FROM THURSDAY NIGHT INTO FRIDAY
EVENING. THIS OF COURSE IS ASSUMING THE H5 AND SFC LOW TAKE THE
TRACK THAT IS CURRENTLY FORECAST BY THE MODELS BUT IT BEARS
WATCHING. EITHER WAY THE H5 SYSTEM DOESNT MOVE MUCH AT ALL AND A
BLOCKING PATTERN EMERGES MAKING CONTINUED SNOW ON CHRISTMAS DAY EVER
MORE LIKELY.
SATURDAY AND SUNDAY...LITTLE CHANGES MADE TO THE GOING FORECAST AS
SNOW TAPERS OFF ON SATURDAY. COLD TEMPS CAN BE EXPECTED THROUGH
THE WEEKEND.
SALLY
&&
.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 6 PM FRIDAY FOR KSZ008-
KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-KSZ024-
KSZ026-KSZ034-KSZ035-KSZ036-KSZ037-KSZ038-KSZ039-KSZ040-KSZ054-
KSZ055-KSZ056-KSZ058-KSZ059.
&&
$$
