FXUS63 KEAX 251745
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1145 AM CST FRI DEC 25 2009

...UPDATED FOR AVIATION...

.DISCUSSION...
/308 AM CST FRI DEC 25 2009/
MAJOR CHRISTMAS DAY WINTER STORM CONTINUES TO BE THE PRIMARY FOCUS 
FOR THIS FORECAST PACKAGE.

SYNOPSIS:
VERY INTENSE PV ANOMALY WAS MOVING THROUGH ARKANSAS/SOUTHERN 
MISSOURI. AT THE SURFACE...AHEAD OF THE ANOMALY...A DEEP LOW  
PRESSURE ~986MB WAS LOCATED IN CENTRAL MISSOURI. AN INVERTED TROUGH 
WAS PRESENT NORTHWARD FROM THE LOW WHICH WAS KEEPING THE NORTHEAST 
PORTIONS OF THE FORECAST AREA VERY WARM STILL. WATER VAPOR SHOWED 
SEVERAL DRY POCKETS MOVING NORTHWESTWARD FROM THE MAIN DRY SLOT 
THROUGH THE NIGHT. THIS LED TO PERIODS OF HEAVY SLEET IN SOUTHERN 
SECTIONS OF THE FORECAST AREA. RADAR SHOWED AN IMPRESSIVE 
DEFORMATION BAND THAT TRACKED EASTWARD FROM ROUGHLY THE METRO AREA 
INTO CENTRAL PORTIONS OF THE FORECAST AREA.

TODAY THROUGH TONIGHT:
FOR THE VERY NEAR TERM IT APPEARED THE NAM AND THE RUC WERE 
DEPICTING THE MESOSCALE FEATURES OF THIS SYSTEM NICELY. THE NAM EVEN 
CAPTURED THE VARIOUS DRY POCKETS THAT WORKED INTO THE AREA AT 
VARIOUS TIMES DURING THE OVERNIGHT. THE DEFORMATION BAND ALIGNED 
REASONABLY WELL WITH LOW LEVEL FN CONVERGENCE FROM THE 00Z/25 NAM AS 
WELL AS VARIOUS RUNS OF THE RUC. THIS BAND WILL LIKELY PERSIST 
THROUGH THE EARLY MORNING WHILE MIGRATING EASTWARD AND WEAKENING AS 
THE SURFACE LOW LIFTS NORTHWARD. THE MAIN SYSTEM IS EXPECTED TO 
WEAKEN SOME THROUGH THE DAY AS IT GETS MORE VERTICALLY STACKED. A 
SECONDARY PV ANOMALY WILL THEN ROTATE AROUND THE MAIN UPPER VORTEX 
BEFORE IT TOO BECOMES BAROTROPIC THIS WEEKEND. AS THIS ANOMALY MOVES 
THROUGH THE AREA IT SHOULD CONTINUE TO BRING US A CHANCE OF 
SNOW..HOWEVER LITTLE ADDITIONAL SNOW IS EXPECTED FROM THIS SECONDARY
FEATURE. ACROSS THE NORTH AN ADDITIONAL SEVERAL INCHES ARE POSSIBLE
AS THE LOW RETROGRADES BACK TO THE MISSOURI RIVER. THIS ADDITIONAL
SNOWFALL MAY PUSH NORTHWEST MISSOURI TO OVER A FOOT OF TOTAL
ACCUMULATION. WITH IMPROVING CONDITIONS THROUGH THE MORNING IT IS
POSSIBLE THAT CURRENT WARNINGS MAY BE DOWNGRADED TO ADVISORIES BUT
FOR NOW WILL LET THE CURRENT HAZARDS RUN AS THEY ARE.

TEMPERATURES FOR TONIGHT ARE A LITTLE TRICKY. WITH WINDS NOT 
DIMINISHING AND THE AREA STILL UNDER THE INFLUENCE OF THE UPPER LOW 
NOT SURE JUST HOW COLD WE'LL GET. THE DIURNAL SWING WILL BE LARGELY 
MUTED FOR THE NEXT 24 HOURS AS A RESULT BUT WITH FRESH NOW COVER 
FELT GOING ON THE COOL SIDE WAS WARRANTED.

SATURDAY THROUGH SUNDAY:
THE UPPER LOW WILL CONTINUE TO SPIN OVER THE REGION RESULTING IN 
CONTINUED CHANCES OF SNOW. WITH THE SYSTEM VERTICALLY STACKED WOULD 
ONLY ANTICIPATE MINOR SNOWFALL. BY SUNDAY AS THE SYSTEM LOOKS TO 
FINALLY MOVE EAST IT ROTATES ONE LAST ANOMALY ACROSS THE FORECAST 
AREA. THIS SHOULD BE ABLE TO GENERATE FLURRIES OR LIGHT SNOW ACROSS 
MAINLY NORTHEAST SECTIONS OF THE FORECAST AREA. TEMPERATURES SHOULD 
REMAIN ON THE COLD SIDE DUE TO SNOW COVER AND PRESENCE OF THE UPPER 
LOW.

CDB

&&

.AVIATION...

FOR ALL INTENSIVE PURPOSES...EXPECTING LIGHT SNOW AND BLOWING SNOW TO
CONTINUE THROUGH AT LEAST THE OVERNIGHT HOURS. WRAP AROUND
DEFORMATION BAND WILL CONTINUE TO PRODUCE LIGHT SNOW THROUGH THE
OVERNIGHT HOURS...DESPITE EXTENSIVE DRY AIR WRAPPING IN THROUGHOUT THE
MATURE UPR LOW. MVFR/IFR CIGS ACROSS NORTHERN KS AND SOUTHERN NE/IA
WILL SINK SOUTHWARD BY THIS EVENING.  

OTHERWISE SFC WINDS WILL REMAIN VERY STRONG THROUGH THE OVERNIGHT
HOURS...AS DEEP SFC LOW RETROGRADES WESTWARD THROUGH THE AFTERNOON
AND EVENING. SUSTAINED WEST TO NORTHWEST WINDS AT 15-20 KT WITH GUSTS
UP TO 25-30 KNOTS WILL LEAD TO WIDESPREAD AND EXTENSIVE DRIFTING OF
VERY LIGHT AND POWDERY SNOW OVER N-S RUNWAYS. SOME IMPROVEMENT CAN BE
EXPECTED AFTER 12Z SAT AS SECONDARY VORTEX ROTATES THROUGH THE
REGION...PUSHING THE SFC LOW NE AND EASING THE SFC PRESSURE GRADIENT.

DUX

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR 
     MOZ001>008-011>017-020>025-028>033-037>040-043>046-053-054.

KS...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR KSZ025-
     057-060-102>105.

&&

$$