FXUS63 KEAX 081043
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
443 AM CST TUE DEC 8 2009

.DISCUSSION...

COMPLEX SCENARIO UNFOLDING THIS MORNING WITH POTENT WINTER STORM
EXPECTED TO DEVELOP ACROSS THE CENTRAL PLAINS TODAY. CURRENT SFC
ANALYSIS INDICATING SFC LOW BECOMING BETTER ESTABLISHED ACROSS
WESTERN COLORADO THIS MORNING AS HEIGHT FALLS CONTINUE TO ACROSS THAT
REGION. ACROSS OUR NECK OF THE WOODS...MODEST ISENTROPIC ASCENT HAS
RESULTED IN WIDESPREAD SNOWFALL FROM AREAS ALONG AND NORTH OF A
LEAVENWORTH KANSAS TO MACON MISSOURI LINE. REPORTS THUS FAR HAVE INDICATED
ACCUMULATIONS OF 1-2 INCHES ACROSS THESE AREAS WITH REPORTS OF UPWARD
OF 3-4 INCHES ALONG A NARROW STRIP FROM ATCHISON KANSAS TO KIRKSVILLE
MISSOURI. SOUTH OF THE SNOW LINE...A LLVL POCKET OF DRY AIR AS
ANALYZED VIA 00Z RAOBS HAS LIMITED PRECIPITATION PRODUCTION SO FAR.
THIS HAS RESULTED IN BASICALLY TWO SEPARATE AREAS OF PRECIPITATION
OVERNIGHT...ONE A BAND OF SNOW STRETCHING FROM CENTRAL KANSAS
NORTHEASTWARD ACROSS NORTHERN MISSOURI AND TWO A BAND OF DRIZZLE AND
FREEZING DRIZZLE FROM NORTHEAST OKLAHOMA INTO SOUTHWEST MISSOURI. 00Z
DETERMINISTIC MODEL GUIDANCE INDICATES THIS DRY POCKET TO GRADUALLY
LIFT OFF THE NORTHEAST THROUGH THE MORNING. THIS IS ALSO SUPPORTED
BY POINT BUFR SOUNDINGS ACROSS PORTIONS OF SOUTHEAST KANSAS INTO
CENTRAL MISSOURI SHOWING THE ATMOSPHERIC COLUMN TO GRADUALLY SATURATE
BETWEEN 15-18Z.

FOR THIS MORNING...EXPECT THE CURRENT AREA OF SNOW TO PERSIST AS
ISENTROPIC ASCENT CONTINUES WITH PERHAPS A GRADUAL WEAKENING OF
ECHOES THROUGH MID MORNING. SOUTH OF THIS LINE...MAY SEE SOME AREAS
OF DRIZZLE/FREEZING DRIZZLE OR LIGHT SNOW THROUGH THIS TIME FRAME
BEFORE MORE AMPLE SATURATION IS ALLOWED TO OCCUR. BY MID TO LATE
MORNING AND INTO THE MID AFTERNOON HOURS...MODELS INDICATE THE DRY POCKET
TO PUSH NORTHEASTWARD ALLOWING DEEPER ISENTROPIC LIFT TO OVERSPREAD
THE ENTIRE CWA AND THE POSSIBILITY OF MORE WIDESPREAD PRECIP. HOWEVER
DURING THIS TIME...WARMER LLVL TEMPS WILL ADVECT NORTHWARD LEADING TO
A MIXED BAG OF PRECIP TO TRANSITION ALONG AND SOUTH OF A KANSAS CITY
TO MACON LINE. 

THEN BY THE MID AFTERNOON HOURS...STRONG HEIGHT FALLS OVERSPREAD THE
CENTRAL PLAINS AND MIDWEST AS THE UPPER TOUGH AXIS SWINGS OUT AND
BECOMES SLIGHTLY NEGATIVELY TILTED. THIS WILL ALLOW ADDITIONAL
DYNAMICALLY FORCED PRECIPITATION TO DEVELOP ACROSS THE AREA WITH SFC
LOW SLIDING ACROSS CENTRAL MISSOURI. AS THIS OCCURS...EXPECT DRY
SLOT TO ROTATE IN ACROSS SOUTHWEST MISSOURI AND MAY PUSH INTO THE
SOUTHERN COUNTIES AS WELL. THIS MAY LEAD TO A BREAK IN PRECIP BY THE
MID TO LATE AFTERNOON HOURS ACROSS THIS AREA. THEN AS THE SYSTEM
TRANSITIONS EASTWARD BY TONIGHT INTO WEDNESDAY MORNING...A TRANSITION
TO MOSTLY ALL SNOW ON THE BACK SIDE SHOULD OCCUR...WITH THE EXCEPTION
PERHAPS BEING THE FAR SOUTHERN COUNTIES.

GIVEN WHERE THE CURRENT SNOW LINE IS LOCATED AND THE ACCUMULATIONS
RECEIVED THUS FAR...CURRENT WARNINGS LOOK TO BE IN GOOD SHAPE AND
WILL MAINTAIN CURRENT HEADLINES FOR NOW. AFOREMENTIONED REASONING MAY
LIMIT OVERALL ACCUMULATIONS ACROSS CENTRAL MISSOURI TO PERHAPS A
DUSTING TO UPWARD OF A COUPLE OF INCHES...MAINLY AS THE SYSTEM
DEPARTS EASTWARD. IN CONTRAST...AREAS OF NORTHERN MISSOURI AND
NORTHEAST KANSAS STILL STAND A CHANCE TO SEE UPWARD OF 6 TO GREATER
THAN 10 INCHES IN SOME LOCATIONS. HOWEVER...UNCERTAINTY STILL LIES AS
TO WHETHER THERE WILL BE A CONTINUOUS SNOW BAND ACROSS THIS AREA
THROUGH THE DAY OR IF THERE WILL BE A TRANSITION PERIOD DURING THE
MIDDLE OF THE DAY WHEN PRECIP SHUTS OFF FOR A WHILE OR A LEAST
WEAKENS CONSIDERABLY. 

BY WEDNESDAY...STRONG CAA COUPLED WITH THE EXPECTED SNOW PACK WILL
LEAD TO BITTERLY COLD TEMPERATURES ACROSS MOST
LOCATIONS...ESPECIALLY BY WEDNESDAY NIGHT IF CLOUDS BEGIN TO CLEAR
AS EXPECTED. MOST AREAS WILL SEE WIND CHILL READINGS NEAR OR WELL
BELOW ZERO...ESPECIALLY ACROSS PORTIONS OF NORTHERN MISSOURI WHERE
READINGS COULD DIP FROM -10 TO -15 BELOW BY THURSDAY MORNING. 

OTHERWISE...ONLY MINOR CHANGES MADE BEYOND DAY 3.

DEROCHE

&&

.AVIATION...

FOR THE 06Z TAFS...CURRENT RADAR TRENDS CONFIRMING THE EARLIER 
ANTICIPATION THAT A BAND OF SNOW WOULD DEVELOP FROM NE KS INTO NW 
MO. EFFECTS OF DRY AIR RESULTING IN A LARGE REFLECTIVITY GRADIENT 
RIGHT OVER MCI...AND DO NOT EXPECT THIS TO SHIFT MUCH OVERNIGHT.

FOR THE REST OF TONIGHT... 
KSTJ SHOULD REMAIN IN A STEADY LIGHT TO OCCASIONALLY MODERATE SNOW 
WITH SEVERAL INCHES OF ACCUMULATION.
KMCI WILL CONTINUE TO WAFFLE IN AND OUT OF THE SNOW BAND...BUT THINK 
ENOUGH NORTHWARD DRY ADVECTION WILL OCCUR THAT PREDOMINANTLY THE 
SNOW HERE FORWARD SHOULD BE MAINLY LIGHT (4-6SM VISIBILITIES).
KMKC WILL LARGELY REMAIN OUT OF THE PRECIPITATION WITH GENERALLY VFR 
VISIBILITIES AND IFR CEILINGS.

FOR TUESDAY...LIGHT SNOW TO CONTINUE AT ST. JOSEPH...BUT AS ALLUDED 
TO EARLIER...QUITE A BIT OF DRY AIR ALOFT AND WEAK FORCING TO 
CONTEND WITH. WILL LIKELY BE A LONG DURATION LULL OF JUST LIGHT SNOW 
AND POSSIBLE SOME INTERMITTENT FREEZING DRIZZLE. ICING ALOFT COULD 
BECOME AN INCREASING CONCERN GIVEN THE SUPERCOOLED WATER DROPLETS 
AND WEAK VERTICAL MOTIONS.

AS THE MAIN STORM SYSTEM APPROACHES...SNOW WILL QUICKLY OVERSPREAD 
THE TERMINALS (IF NOT ALREADY ONGOING AT KSTJ) AFTER 20Z AND 
BECOMING HEAVY AT TIMES IN THE EVENING. MODERATE ACCUMULATIONS 
EXPECTED (POSSIBLY HEAVY STJ). WINDS WILL SHIFT ABRUPTLY FROM EAST 
TO WEST-NORTHWEST WITH A MID EVENING FRONTAL PASSAGE...WITH SPEEDS 
INCREASING TO 15-25 KNOTS AFTER THE END OF THE TAF CYCLE.

BOOKBINDER

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR MOZ032-033-
     037>039-043-044.

     WINTER STORM WARNING UNTIL 6 AM CST WEDNESDAY FOR MOZ001>008-
     011>017-020>025-028>031.

KS...WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR KSZ057-105.

     WINTER STORM WARNING UNTIL 6 AM CST WEDNESDAY FOR KSZ025-102>104.

&&

$$