FXUS63 KEAX 090554
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1154 PM CST TUE DEC 8 2009

...UPDATED AVIATION DISCUSSION...

.DISCUSSION...
/740 PM CST TUE DEC 8 2009/
MONITORING A NARROW NW-SE ORIENTED BAND OF MODERATE INTENSITY SNOW 
LIFTING QUICKLY NORTHEAST THROUGH EAST CENTRAL KS/WEST CENTRAL MO. 
THIS MAY BE THE ONLY ACCUMULATING SNOW FOR AREAS SOUTH OF THE MO 
RIVER. APPEARS THIS BAND OF SNOW WILL END UP LINING UP WEST-EAST 
NEAR THE NE/KS BORDER EASTWARD ACROSS FAR NORTHERN MO. UPSTREAM 
SATELLITE DATA SHOWS CLOUD TEMPERATURES BEHIND THIS BAND OF SNOW 
WILL NOT SUPPORT ICE CRYSTALS SO NO SNOW. UPSTREAM OBSERVATIONS ALSO 
NOT SHOWING MUCH IN THE WAY OF BLOWING SNOW SO AM TAKING THAT INTO 
CONSIDERATION AS WELL. WOULD LIKE TO GET A QUICK LOOK AT THE FIRST 
6-9 HOURS OF THE 00Z NAM BEFORE MAKING ANY SIGNIFICANT CHANGES TO 
THE FORECAST BUT WE ARE CONSIDERING LOWERING SNOW AMOUNTS AND 
ADJUSTING THE COUNTIES UNDER THE ADVISORIES AND WARNINGS.

MJ

&& 

.PREV DISCUSSION...
/349 PM CST TUE DEC 8 2009/
MAIN CHALLENGES FOR THE SHORT TERM FOCUS ON THE WINTER STORM AND ALL
OF ITS IMPACTS.

TONIGHT THROUGH WEDNESDAY:
AN INTENSE PV ANOMALY WAS BEGINNING TO EJECT OUT OF THE SOUTHERN
ROCKIES. THE INITIAL ANOMALY THAT LED TO A DRY SLOT MOVING ACROSS THE
FORECAST AREA IS STARTING TO MOVE EAST OF THE AREA. WITH A
REINTRODUCTION OF ICE CRYSTALS ALOFT A TRANSITION BACK TO SNOW CAN BE
EXPECTED. THE INTENSITY OF THIS ANOMALY CAN BE SEEN BY THE EXTREME
WIND OCCURRING IN THE TEXAS PANHANDLE AND EASTERN NEW MEXICO.
WIDESPREAD WIND GUSTS GREATER THAN 50 KTS AND EVEN A FEW GREATER THAN
70 KTS HAVE BEEN OBSERVED. SURFACE PRESSURE FALLS ARE IMPRESSIVE 
WITH 8 TO 12 MB IN 3 TO 6 HOURS. THIS IS PRODUCING AN INTENSE 
SURFACE LOW IN THE NORTHEAST TEXAS PANHANDLE. INTENSE PRESSURE FALLS 
ARE ALSO NOTED ACROSS SOUTHERN MISSOURI SO THE SURFACE LOW WILL 
EITHER TRACK OR EXPAND/INTENSIFY EASTWARD POSSIBLY REFORMING IN 
SOUTHERN MISSOURI. REGARDLESS... AN INTENSE PRESSURE GRADIENT WILL 
ALLOW FOR VERY STRONG WINDS TO OVERSPREAD THE AREA. WITH HEAVY SNOW 
ALREADY FORECAST AND A HIGH PROBABILITY OF THIS SNOW BEING 
COINCIDENT WITH THE HIGH WINDS THERE IS GOOD CHANCE OF SEEING 
BLIZZARD CONDITIONS FROM ALONG AND NORTH OF LINE FROM GENERALLY A 
KSTJ TO KIRK LINE. AS A RESULT WE HAVE ISSUED A BLIZZARD WARNING FOR 
OUR NORTHERN FEW TIERS OF COUNTIES IN MISSOURI AND EXTREME NORTHEAST 
KANSAS. CLIMATOLOGY SUGGEST THAT VERIFICATION OF BLIZZARD WARNINGS 
IN MISSOURI IS LOW OR NONEXISTENT. HOWEVER FEEL THE FORECAST RISKS 
WARRANT THE PRODUCT ISSUANCE. THE BLIZZARD WARNING WILL EXTEND PAST 
THE END OF THE HEAVIEST SNOWFALL. FEEL THAT THE COMBINATION OF HIGH 
WINDS AND THICK SNOW COVER WILL CONTINUE TO LEAD TO SIGNIFICANT 
REDUCTIONS IN VISIBILITY DUE TO HEAVY BLOWING SNOW. THE PRESSURE 
GRADIENT SHOULD RELENT BY WEDNESDAY AFTERNOON AS THE LOW MOVES INTO 
THE GREAT LAKES REGION.

CDB

MEDIUM RANGE (WEDNESDAY NIGHT THROUGH TUESDAY)...

HIGH PRESSURE RIDGE WILL BE BUILDING INTO THE CENTRAL PLAINS 
WEDNESDAY NIGHT...WITH THE RIDGE AXIS SOUTH OF THE CWFA BY 12Z 
THURSDAY. THIS WILL KEEP A WEST WIND OVERNIGHT...WHICH SHOULD 
PREVENT STRONG RADIATIONAL EFFECTS. HOWEVER...WITH HEAVY SNOWPACK 
ACROSS THE NORTHERN THIRD OF THE FORECAST AREA...SUB ZERO READINGS
STILL LOOK GOOD WITH THE INCOMING AIRMASS TAPPING THE COLD AIR 
CURRENTLY SITTING OVER MONTANA. 

PAST THURSDAY...CONFIDENCE IS LOW ON THE FORECAST AS MODELS CONTINUE 
TO STRUGGLE WITH HANDLING OF SOUTHERN STREAM SHORT WAVES EMANATING 
FROM THE PACIFIC. MODELS ARE ALSO NOT IN GOOD AGREEMENT WITH THE 
HANDLING OF THE CANADIAN VORTEX...WHICH HAS IMPACTS ON SHORT WAVES 
WHICH MAY AFFECT THE FORECAST AREA. FOR NOW WILL KEEP SLIGHT CHANCE  
POPS GOING FOR FRIDAY NIGHT THAT FITS WITH A WEAK WAVE THAT BOTH THE 
ECMWF AND GFS SHOWING MOVING INTO EASTERN KANSAS BY 12Z SATURDAY. 

FOR LATE IN THE WEEKEND...BOTH THE GFS AND THE ECMWF PRODUCE 
PRECIPITATION ACROSS THE FORECAST AREA...BUT DUE TO DIFFERING 
SOLUTIONS. WILL HAVE SLIGHT CHANCE POPS IN FOR SUNDAY NIGHT AND INTO 
MONDAY WITH THE ACTIVE WAVE PATTERN...BUT CONFIDENCE IS JUST NOT 
HIGH ENOUGH TO PLACE ANY HIGHER POPS IN THIS EXTENDED PERIOD. 

PC

&&

.AVIATION...

FOR THE 06Z TAFS...WRAP AROUND AREA OF LIGHT SNOW WILL AFFECT THE 
TERMINALS INTO THE PRE-DAWN HOURS WITH IFR VISIBILITIES/MVFR 
CEILINGS. THE STORM SYSTEM IS CONTINUING TO WIND UP AND THE 
TIGHTENING PRESSURE GRADIENT WILL YIELD VERY STRONG/GUSTY WNW 
SURFACE WINDS THROUGH THE MORNING HOURS. STRONG SUBSIDENCE ON THE 
BACK SIDE OF THE SYSTEM WILL SCOUR OUT THE LOW LEVEL MOISTURE/CLOUD 
COVER ON THE BACKSIDE OF THE SYSTEM TOMORROW MORNING. MAY SEE CLOUDS 
SCATTER OUT FOR A COUPLE OF HOURS IN THE MORNING BUT A MVFR  
STRATOCU DECK SHOULD QUICKLY FILL BACK IN UNTIL LATE IN THE DAY. 
WINDS WILL DROP OFF QUICKLY AS SUNSET APPROACHES AND SKIES CLEAR.

MJ

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR MOZ023>025-
     029>033-037>039.

     WINTER STORM WARNING UNTIL 6 AM CST WEDNESDAY FOR MOZ021-022-028.

     BLIZZARD WARNING UNTIL NOON CST WEDNESDAY FOR MOZ001>008-011>017-
     020.

KS...WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR KSZ104-105.

     WINTER STORM WARNING UNTIL 6 AM CST WEDNESDAY FOR KSZ025-103.

     BLIZZARD WARNING UNTIL NOON CST WEDNESDAY FOR KSZ102.

&&

$$