FXUS63 KEAX 262054
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
254 PM CST SAT DEC 26 2009

.DISCUSSION...

IN ONE OF THE MOST UNIQUE WINTER WEATHER CASES AS OF RECENT AND 
EXTENDED HISTORY ACROSS THE LOWER MISSOURI RIVER VALLEY...A FULL
SCALE FUJIWARA EFFECT HAS TAKEN PLACE AS TODAYS BANDED SNOW WAS THE
RESULT OF THE SAME SOUTHWEST LOW WHICH BROUGHT HEAVY SNOW AND
BLIZZARD CONDITIONS TO THE AREA ON THU. MUCH LIKE THU...THE REMNANTS
OF THE ONCE POWERFUL STORM SYSTEM WAS STILL ABLE TO PRODUCE A BAND OF
1 TO 3 INCHES OF SNOW ACROSS THE HEART OF THE CWA DURING THE DAYTIME
HOURS. HOWEVER...BEFORE WE CAN COMPLETELY SIGN OFF ON THIS EVENT AS
BEING FINISHED...ONE LAST PIECE OF THE PUZZLE (THE 4TH ACTUALLY) HAS
TO SWING THROUGH THE AREA LATER TONIGHT. THIS BEING SAID...PRIMARY
CONCERNS IN THE SHORT TERM WILL BE YET ANOTHER DECENT SHOT AT
ACCUMULATING SNOWFALL AS WELL AS CONTINUING STRUGGLE WITH TEMPS
THROUGH MONDAY NIGHT.

FOR THE LATE AFTN HOURS AND OVERNIGHT HOURS...NOW ON THE BACKSIDE OF THE
OLD SOUTHWEST LOW AS IT CONTINUES TO DEGRADE...WEAK LOW-LVL
FRONTOGENESIS WILL PERSIST INTO THE EARLY EVENING HOURS.
FORTUNATELY...SNOW RATIOS IN THE 15-17:1 RANGE HAVE YIELDED VERY
LIGHT AND FLUFFY SNOW. THIS SNOW IS EXPECTED TO GRADUALLY DIMINISH AS
FRONTOGENESIS AND UPR LIFT BECOMES UNORGANIZED. THIS MAY TAKE AWHILE
AND THESE BANDS MAY NOT COMPLETELY GO AWAY GIVEN INDICATIONS OF
CONTINUED FRONTOGENESIS ALOFT. TO FINISH THE FULL ROTATION OF THE 2
PARENT CYCLONES...THE OLD POLAR LOW CURRENTLY ACROSS EASTERN MN AND
WESTERN WI WILL PIVOT SSE LATER THIS EVENING. AS IT DOES
SO...FAVORABLE CONDITIONS COME TOGETHER FOR A VERY DECENT SHOT OF
ACCUMULATING SNOW OVER THE NORTHEASTERN THIRD OF THE CWA AFTER
MIDNIGHT TONIGHT. IMPRESSIVE DYNAMICAL LIFT AHEAD OF THE PIVOTING
ANOMALY ALONG WITH RE-INTENSIFYING FRONTOGENESIS AXIS AND UPR
DIVERGENCE FROM THE LEFT EXIT REGION OF A NEAR 100 KNOT UPR JET
POSITION THEMSELVES ACROSS WEST CENTRAL IA AND INTO NORTHEASTERN MO
AFTER 06Z. MODEL QPF SUGGESTS UPWARDS OF A TENTH OF AN INCH OF
LIQUID...WITH A 16-18:-1 FROM COBB OUTPUT INDICATING THE POTENTIAL
FOR 1 TO 3 INCH SNOWFALL. ONE CONCERN HOWEVER IS A POOR CORRELATION
BETWEEN THE DGZ AND UVV. NEVERTHELESS...WILL NEED TO KEEP AN EYE ON
THE FORMATION OF THIS BAND AS MODELS HAVE STRUGGLED IN RESOLVING THIS
UPR TROUGH...WITH MANY OF THESE BAND SHIFTING FURTHER SW THAN
INDICATED BY MODEL GUIDANCE.

THE OTHER CONCERN OVERNIGHT WILL BE TEMPS.  AS OF RIGHT NOW...HAVE 
BUMPED UP OVERNIGHT LOWS OVER MUCH OF THE AREA.  INCREASING CLOUD 
COVER WILL CONTINUE TO SURGE INTO THE AREA...HOWEVER MOST NOTABLE IN 
SFC OBS IS THE LACK OF ANY SIGNIFICANT DRY AIR INTRUSION INTO THE 
LOWER MO RIVER VALLEY EXCEPT IN NE MO. THIS IS DUE IN PART TO THE
SIGNIFICANT MODIFICATION OF THE BOUNDARY LAYER AIRMASS STREAMING INTO
THE REGION WITH ITS ORIGIN POINT IN SOUTHERN ONTARIO AND THE WESTERN
GREAT LAKES. THUS...MUCH LIKE LAST NIGHT...LOCAL DEWPOINTS REMAIN IN
THE UPR TEENS TO LOWER 20S...WHICH SHOULD EFFECTIVELY KEEP OVERNIGHT
LOWS IN THE LOWER 20S.

FOR SUNDAY...UPR TROUGH WILL FINALLY EJECT FAR ENOUGH TO THE EAST TO 
REMOVE MUCH OF ITS IMPACT FROM THE REGION.  HOWEVER...LINGERING LOW 
STRATUS WILL STILL PROVIDE A CHANCE FOR LIGHT SNOW OR FLURRIES OVER 
MUCH OF THE AREA.  REASONABLY SPEAKING WITH A WESTERLY WIND 
CONTINUING...HIGH TEMPS SHOULD BE IDENTICAL TO TODAY WITH THE COLDEST
READINGS IN THE NE AND WARMER READINGS APPROACHING 30 DEGREES NEAR
THE KS/MO BORDER.

THE MAIN FCST ISSUES FROM SUN NIGHT THROUGH MON NIGHT REMAIN ON LOW
TEMPS. FOR SUN NIGHT...DESPITE THE UPR TROUGH MOVING WELL TO THE
EAST...AIRMASS MODIFICATION WILL BE SLOW TO COMMENCE AS THE DRIER
AIRMASS TUCKED INTO THE WESTERN CANADIAN PROVINCES CAN FINALLY BE
TAPPED MONDAY. SFC WINDS WILL REMAIN RATHER MIXY SUNDAY NIGHT AND
UNCERTAINTIES REMAIN IN REGARDS TO CLOUD COVER. HOWEVER...DO NOT SEE
THE ARRIVAL OF DRIER SFC AIR UNTIL THE DAYTIME HOURS OF MONDAY WHICH
MAY IN FACT LEAVE OVERNIGHT LOWS SUNDAY IN THE SINGLE DIGITS TO LOWER
TEENS (OR WARMER) DESPITE SIGNIFICANT CLOUD COVER. HAVE INCREASED
OVERNIGHT LOWS.

IT APPEARS THE BEST CHANCE FOR GOOD RADIATIONAL COOLING WILL BE 
MON NIGHT INTO TUE MORNING. MODELS ARE IN CONSENSUS OF BRINGING THE
SFC RIDGE AXIS OVERHEAD AND KEEPING THE 850 RIDGE AXIS JUST TO OUR
WEST. THIS COULD SETUP A POTENTIAL PLUNGE IN OVERNIGHT LOWS OVER THE
SNOWPACK TO BELOW ZERO LEVELS. HOWEVER...GIVEN THE PROGRESSIVE NATURE
OF THE SYSTEM EXPECTED FOR TUE THE IMPACTS OF HIGH CIRRUS WILL NEED
TO BE CONSIDERED. FOR NOW HAVE DROPPED TEMPS EVEN FURTHER...WITH
LOCALIZED DROPS FURTHER TO INDIVIDUAL AREAS WHICH WILL HAVE AN EASIER
TIME DECOUPLING.

DUX     

MEDIUM RANGE (TUESDAY THROUGH SATURDAY)...

MID RANGE DETERMINISTIC AND ENSEMBLE MODELS CONTINUE TO ALL POINT TO 
A BREAK DOWN IN THE WESTERN CONUS BLOCKING RIDGE BY EARLY NEXT WEEK AS
SHORTWAVES FROM THE EASTERN PACIFIC UNDERCUT THE RIDGE. ALSO OF NOTE
FOR THE MID RANGE IS THE DEVELOPMENT OF AN EXTENSIVE /ALL BE IT
TRANSIENT/ POLAR VORTEX ACROSS HUDSON BAY EARLY IN THE WORK
WEEK...AND THE DEVELOPMENT OF A BROAD TROUGH ACROSS THE CONUS AS THE
EAST PACIFIC SHORTWAVES MOVE ACROSS THE CONUS AND THE RIDGE
DISSIPATES.

AS TUESDAY DAWNS ACROSS THE PLAINS STATES WE WILL HAVE A SHORTWAVE 
RIDGE ALOFT MOVING EAST THROUGH THE REGION AHEAD OF AN EAST PACIFIC 
SHORTWAVE MOVING THROUGH THE DESERT SOUTHWEST. DESPITE THE MODEST 
WARM AIR ADVECTION ALOFT WITH THE RIDGE...AND SOUTH TO SOUTHWEST 
WINDS FROM THE SURFACE THROUGH H8...A COLD SURFACE HIGH WILL STILL 
BE OOZING SLOWLY EAST ACROSS OUR REGION. THOUGHTS ARE THAT THIS 
SHOULD KEEP TEMPERATURES FROM REBOUNDING TOO MUCH...THOUGH WE MIGHT 
JUST BARLEY BE ABLE TO REACH AFTERNOON HIGHS AROUND FREEZING TUESDAY 
AFTERNOON. 

TUESDAY NIGHT THROUGH THURSDAY...THE BROAD CONUS TROUGH AXIS WILL BE 
TO OUR WEST LEAVING THE REGION UNDER A SOUTHWEST FLOW...WHICH WILL 
BE TRYING TO ADVECT MOISTURE BACK INTO THE CENTRAL PLAINS. 
SHORTWAVES MOVING THOUGH THE BROAD TROUGH ARE EXPECTED TO TRY AND 
PUSH A COLD FRONT THROUGH EASTERN KANSAS AND MISSOURI BY THURSDAY 
MORNING. WITH SOME CONSISTENCY IN THE MID-RANGE ABOUT THE MOISTURE 
RETURN...AND COLD SURFACE TEMPERATURES STILL PREVAILING...HAVE OPTED 
TO ADD A CHANCE OF SNOW INTO THE FORECAST FOR TUESDAY NIGHT THROUGH 
WEDNESDAY. EXPECT TYPICAL MODEL TIMING ADJUSTMENTS OVER THE NEXT FEW 
DAYS MIGHT ALLOW THIS POTENTIAL PRECIPITATION TO SLIDE INTO A 
WEDNESDAY THROUGH EARLY THURSDAY MORNING TIME FRAME...BUT WILL STICK 
CLOSE TO GUIDANCE TIMING FOR NOW TILL CONFIDENCE GROWS IN THE AMOUNT 
OF MOISTURE RETURN.

FOR THE NEW YEAR...FRIDAY AND SATURDAY...THE TROUGH AXIS SHOULD HAVE 
WORKED ITS WAY TO THE EAST OF MISSOURI. WITH THE POLAR VORTEX ACROSS 
THE HUDSON BAY...HEMISPHERIC CHARTS INDICATE THAT THERE MIGHT BE A 
CROSS POLAR FLOW GOING ON DURING THE WORK WEEK...WHICH COULD LEAD TO 
SOME TRULY ARCTIC AIR SINKING SOUTH INTO THE PLAINS. HAVE PUSHED 
GOING FORECAST NUMBERS DOWN FOR THE LATE PORTION OF THE WORK WEEK 
AND NEXT WEEKEND AS A RESULT...GOING EVEN BELOW THE COLD ENSEMBLE 
LOW GUIDANCE VALUES. STILL...MIGHT NOT HAVE PUSHED TEMPERATURES DOWN
ENOUGH...BUT BELIEVE THAT THEY ARE IN THE BALL PARK FOR NOW.

CUTTER

&&

.AVIATION...

WEAK SNOW SHOWERS WILL CONTINUE TO IMPACT THE TERMINALS THROUGH THE 
LATE AFTN HOURS IN THE WAKE OF YET ANOTHER S/W TROUGH.  IN THE WAKE 
OF THIS S/W WINDS SHOULD GRADUALLY DIMINISH THIS EVENING WHICH 
SHOULD END THE PERSISTENT BLSN THREAT.  UPSTREAM OBS CONTINUE TO 
INDICATE A WIDESPREAD MVFR STRATUS DECK WHICH WILL ADVECT SE BEHIND 
THIS SYSTEM AND MAINTAIN THROUGH THE NIGHT.

A STRONGER PV ANOMALY OVER WESTERN WISCONSIN AND EASTERN MN WILL 
ROTATE SE AFTER MIDNIGHT.  IT APPEARS THE HIGHEST IMPACT OF THIS 
WAVE WILL BE TO THE NE OF THE TERMINALS...HOWEVER MODELS HAVE 
STRUGGLED IN TRACKING THESE ANOMALIES AND THE POTENTIAL DOES EXIST 
THAT LIGHT SNOW COULD ONCE AGAIN TRACK INTO ALL 3 TERMINALS AFTER 
09Z.  GIVEN THE UNCERTAINTIES...WILL HOLD OFF ON ANY INDICATION OF 
THIS IN THE CURRENT TAF.

DUX  

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

$$