FXUS63 KEAX 292309
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
508 PM CST SUN NOV 29 2009

...UPDATED FOR AVIATION...

.DISCUSSION...
/231 PM CST SUN NOV 29 2009/
SHORT TERM (TONIGHT-TUESDAY NIGHT)...

COLD ADVECTION STRATO-CU CONTINUES TO BREAK UP ACROSS ALL BUT THE 
NORTHEAST CWA THIS AFTERNOON...WHERE THE LOSS OF DAYTIME HEATING AND 
THE INFLUENCE OF LOW LEVEL CYCLONIC FLOW WILL ACT TO ERODE THE CLOUD 
COVER LATER THIS EVENING. TEMPERATURES TONIGHT SHOULD FALL INTO THE 
20S WITH EASE OVER THE NRN CWA TONIGHT AS WINDS DIMINISH AND DRY 
BOUNDARY LAYER AIRMASS BECOMES WELL ESTABLISHED UNDER CLEARING 
SKIES. FURTHER SOUTH...TEMPS A BIT MORE OF A QUESTION AS LAGGING 
UPPER TROUGH HAS ALLOWED ABUNDANT MID-HIGH LEVEL CLOUDS TO STREAM UP 
FROM THE SOUTH. THIS MAY BLANKET THE SRN CWA LONG ENOUGH OVERNIGHT 
TO KEEP AREAS ALONG AND SOUTH OF THE MISSOURI RIVER FROM FALLING 
BELOW FREEZING. ONCE AGAIN...KC METRO RIGHT ON THE CUSP AND WITH THE 
LATEST HARD FREEZE RECORD NOW AWARDED TO 2009...ITS SIMPLY SEMANTICS 
AS TO WHETHER THIS IS WRITTEN INTO THE BOOKS TONIGHT OR THURSDAY 
MORNING WITH A MORE SOLID COLD INTRUSION.

OTHERWISE...A SPLIT FLOW REGIME WILL CONTINUE FOR THE NEXT FEW DAYS 
WITH THE AREA SITUATED WITHIN THE LIMITING STREAM LINES ALOFT 
BETWEEN A DEVELOPING STORM OVER SOUTHERN TEXAS AND A LOW AMPLITUDE 
SHORTWAVE RIDGE TO OUR NORTH. A MODIFIED WEST-SOUTHWEST LOW LEVEL 
COMPONENT SHOULD ALLOW FOR A NICE AIRMASS RECOVERY WITH READINGS 
MODERATING BACK IN THE 50S TO NEAR 60 BY TUESDAY ALONG WITH ABUNDANT 
SUNSHINE.

BOOKBINDER

MEDIUM RANGE (WEDNESDAY THROUGH SUNDAY)...

MEDIUM RANGE PERIOD WILL FEATURE BELOW AVERAGE TEMPERATURES FOR THE 
FIRST HALF OF THE PERIOD...WITH A NICE MODERATING TREND TOWARDS 
CLIMATOLOGY FOR THE END OF THE PERIOD. THE OVERALL EXPECTED FLOW 
REGIME WILL ALSO FAVOR BELOW AVERAGE PRECIPITATION FOR THE ENTIRE 
TIME FRAME. OPERATIONAL ECMWF WAS FAVORED EARLY IN THE PERIOD WITH 
ITS SLOWER EJECTION AND LESS PHASED APPEARANCE TO THE CLOSED LOWER 
HEIGHTS PROPAGATING ACROSS THE NRN GULF COAST AND UP THE ERN 
SEABOARD...AS WELL AS SLIGHTLY HIGHER POSITIVELY TILTED HEIGHTS OVER 
THE GREAT LAKES. THEREAFTER...A FORECAST CLOSELY RESEMBLING AN 
ENSEMBLE MEAN WAS PREFERRED TO ACCOUNT FOR SOME OF THE 
BIASES/DEFICIENCIES OF THE OPERATIONAL MEMBERS. 

BY THE END OF THE WEEK...THE OPERATIONAL GFS STILL REMAINS SOMEWHAT 
OF AN OUTLIER IN RAPIDLY PRESSING ENERGY THROUGH THE WRN CONUS RIDGE 
AXIS...THOUGH NOT AS QUICKLY AS PREVIOUS RUNS...AND NOW HAS BETTER 
AGREEMENT WITH THE MAJORITY OF ENSEMBLE MEMBERS. THE OPERATIONAL 
ECMWF LIES ON THE SLOWEST ENVELOPE OF SOLUTIONS IN BOTH BRINGING 
ENERGY OVER THE RIDGE AXIS...AND PULLING ERN CONUS LOWER HEIGHTS 
INTO FAR ERN CANADA (MOST LIKELY A RESULT OF STRONGER DOWNSTREAM 
BLOCKING INFLUENCE). PROBLEM IS VALID ARGUMENTS COULD BE PRESENTED 
TO SUPPORT EITHER OPERATIONAL MODEL. BLOCKED DOWNSTREAM FLOW WOULD 
GENERALLY FAVOR THE SLOWEST OF ALL POSSIBLE OUTCOMES...ALTHOUGH 
ENHANCED ENERGY ACROSS THE PACIFIC BASIN WOULD ARGUE FOR MORE 
ONSHORE ENERGY TRANSLATION...AND A REALIGNMENT/RETROGRESSION OF 
RIDGING ALONG THE WEST COAST. GIVEN THE INTENSE SET OF WAVES 
CROSSING INTO THE CNTRL EXTRATROPICAL PACIFIC BASIN (HIGHLIGHTED BY 
A DISTINCT TROPICAL LINKAGE TO TYPHOON NIDA FEEDING EXTREMELY 
ANOMALOUS PWATS MEASURED BY SATELLITE IN EXCESS OF 1.5 INCHES...OR 
GREATER THAN 200 PERCENT OF NORMAL...INTO THE ALEUTIAN 
VORTEX)...FEEL A SOLUTION SOMEWHAT CLOSER TO THE GFS HOLDS SLIGHTLY 
MORE VOLITION. 

SOUTHERN STREAM SYSTEM WILL BE PROGRESSING THROUGH THE LOWER 
MISSISSIPPI RIVER VALLEY ON WEDNESDAY...HELPING RAPIDLY PULL A COLD 
FRONT THROUGH THE CWA...WITH STRONG ADVECTION OF COLDER AND DRIER 
AIR FROM THE NRN PLAINS. SEVERAL RECENT MODEL RUNS DEPICT THE 
PRIMARY DEFORMATION/FRONTOGENETICAL FORCING BANDS TO ALIGN IN AN 
I-40 TO OHIO RIVER VALLEY TRACK...WHICH CONCEPTUALLY FITS THIS 
TRADITIONAL SPLIT FLOW PATTERN. GOOD AGREEMENT AMONG MODELS THAT THE 
POST FRONTAL AIRMASS WILL BE CHARACTERIZED BY 1000-850MB THICKNESSES 
AOB 127DM (CORRESPONDING TO 1-2 NORMALIZED STANDARD DEVIATIONS BELOW 
AVERAGE). HAVE REDUCED TEMPERATURE FORECASTS TO JUST BELOW ENSEMBLE 
AVERAGES (AROUND 1 STANDARD DEVIATION BELOW CLIMATOLOGY)...THOUGH AS 
MENTIONED THE PAST SEVERAL DAYS...WITH AN ALMOST TOTAL LACK OF SNOW 
COVER TO THE NORTH OF THE AREA...FEEL MUCH COLDER READINGS WOULD BE 
DIFFICULT TO ACHIEVE. MAY NEED TO INTRODUCE FLURRIES THURSDAY 
AFTERNOON FOR PARTS OF THE FORECAST AREA...THOUGH CHANCES ARE 
CERTAINLY BETTER ACROSS IOWA/NRN ILLINOIS CLOSER TO THE COLD CORE 
ALOFT. UNCERTAINTY HERE LIES WITH THE MAGNITUDE OF DRY AIR IN THE 
BOUNDARY LAYER...AND THE ABILITY TO SATURATE A LOWER SC DECK IN 
ORDER TO SUPPORT FLURRIES/SNOW REACHING THE SFC. 

OTHERWISE...TRENDED TEMPERATURES TOWARDS CLIMATOLOGY FOR THE 
UPCOMING WEEKEND...AS SFC HIGH PRESSURE SLIDES INTO THE ERN 
CONUS...ALLOWING FOR MODIFIED RETURN FLOW. KEPT TEMPERATURES WELL 
BELOW MEX GUIDANCE AND GFS SOUNDING DATA...AS TYPICALLY WARMING 
AROUND SUCH COOLER HIGH PRESSURE SYSTEMS TAKES LONGER THAN MODELS 
ANTICIPATE. MAY ALSO NEED TO INTRODUCE SOME PRECIP CHANCES TOWARDS 
THE END OF THE WEEKEND...AS ENSEMBLE MEANS SHOW A FRONTAL BOUNDARY 
SINKING INTO THE FORECAST AREA...THOUGH CURRENT UNCERTAINTY 
PRECLUDES A MENTION YET. MOST INTERESTING SETUP MAY OCCUR JUST AFTER 
THIS MEDIUM RANGE PERIOD...AS PROBABLE RIDGE RETROGRESSION TOWARDS A 
140W LONGITUDE IS FAR MORE FAVORABLE FOR STRONGER CONTINENTAL SFC 
PRESSURE RISES AND TRAJECTORIES OF A TRUE ARCTIC NATURE. BIGGEST 
QUESTIONS CONCERN THE AMOUNT OF DOWNSTREAM AMPLIFICATION AND ABILITY 
FOR HIGH PRESSURE TO BUILD SOUTH INTO THE CNTRL CONUS...HOWEVER 
PROBABILITIES POINT SLIGHTLY TOWARDS BETTER CHANCES FOR TRULY COLD 
WEATHER BY DECEMBER STANDARDS BEYOND NEXT WEEKEND.

21

&&

.AVIATION...

FOR 00Z TAFS...LARGE SWATH OF CIRRUS ASSOCIATED WITH SUB-TROPICAL 
JET WILL CONTINUE TO ADVECT ACROSS REGION FOR THE NEXT COUPLE 
HOURS...BUT CLEARING TREND EXPECTED AT ALL THREE TERMINAL SITES AS 
H8 TROUGH AXIS CONTINUES TO PUSH EAST AND H5 RIDGE BEGIN TO BUILD 
OVER CENTRAL PLAINS. NAM TRIES TO DEVELOP LIGHT HAZE/FOG AT KSTJ IN 
THE 09-12Z TIMEFRAME...BUT TEMPERATURE/DEWPOINT PROFILE DO NOT 
SUPPORT AND WIND IS NOT IN A FAVORABLE DIRECTION FOR ADVECTION 
FOG/HAZE...THUS WILL LEAVE OUT FOR NOW.  WINDS WILL GRADUALLY BACK 
DURING THE OVERNIGHT HOURS...BECOMING WESTERLY DURING THE MORNING 
HOURS OF MONDAY AT SPEEDS LESS THAN 10 KNOTS.

24

&&

.CLIMATE...

THERE WILL BE POTENTIAL FOR THE TEMPERATURE AT THE KANSAS CITY 
INTERNATIONAL OFFICIAL REPORTING SITE TO REACH 28 DEGREES TONIGHT. 
THAT WILL BECOME THE LATEST DATE THAT 28 DEGREES HAS OCCURRED. IF IT 
DOES NOT OCCUR TONIGHT...THEN BY THURSDAY MORNING WE WILL SEE A HARD 
FREEZE. HERE ARE THE TOP 5 LATEST OCCURRENCES OF 28 DEGREE LOW 
TEMPERATURES IN KANSAS CITY:

RANK        DATE              YEAR
-----      ------            ------
1          ??????             2009
2          NOV 29             1905
3          NOV 27             1944
4          NOV 26             1902
5          NOV 26             1958

FOR ADDITIONAL INFORMATION...PLEASE VISIT OUR WEBSITE AT 
WWW.WEATHER.GOV/KC.

&&

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

$$