FXUS63 KEAX 251122
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
521 AM CST FRI DEC 25 2009
...UPDATED AVIATION DISCUSSION...
.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 THE 12Z TAFS...SNOW HAS DECREASED IN INTENSITY AND WILL CONTINUE
THIS TREND THIS MORNING. HOWEVER...VSBYS WILL CONTINUE TO BE REDUCED
DUE TO THE COMBINATION OF THE LIGHT SNOW FALLING AND THE BLOWING
SNOW RESULTING FROM THE STRONG NORTHWEST WINDS. SNOW SHOULD BE
DECREASING IN THE KANSAS CITY AREA BY AFTERNOON...WHICH SHOULD HELP
VSBYS SOME...BUT STILL BLOWING SNOW SHOULD KEEP VSBYS NEAR GROUND
LEVEL IN THE IFR RANGE. SOME IMPROVEMENT TO MVFR VSBYS SHOULD TAKE
PLACE BY EVENING AS WINDS DROP OFF JUST A BIT. FOR KSTJ...THE
IMPROVEMENT IN THE WINDS AND SNOW WILL BE MUCH MORE GRADUAL AS THE
SURFACE LOW SLOWLY MOVES TO THE NORTHWEST OVER IOWA.
PC
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WARNING UNTIL 6 PM CST THIS EVENING FOR MOZ003>008-
014>017-022>025-030>033-038>040-044>046-054.
BLIZZARD WARNING UNTIL 6 PM CST THIS EVENING FOR MOZ001-002-
011>013-020-021-028-029-037-043-053.
KS...BLIZZARD WARNING UNTIL 6 PM CST THIS EVENING FOR KSZ025-057-060-
102>105.
&&
$$
