FXUS63 KEAX 280539
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1139 PM CST FRI NOV 27 2009
...UPDATED AVIATION DISCUSSION...
.DISCUSSION...
SHORT TERM (TONIGHT-SUNDAY NIGHT)...
AFTER A COLD START...THOSE BRAVING THE BLACK FRIDAY CROWDS WERE
REWARDED A RAPID WARMUP THAT HAS SENT TEMPERATURES SOARING WELL INTO
THE 60S THIS AFTERNOON. A 35 TO 40 DEGREE DIURNAL RANGE IS QUITE
REMARKABLE CONSIDERING THE LOW SUN ANGLE AND RATHER WEAK SURFACE
WINDS. MKC/MCI ALSO BOTH CAME CLOSE BUT FAILED TO REACH 28 DEGREES
LAST NIGHT...KEEPING THE HARD FREEZE STREAK AT BAY FOR AT LEAST THE
NEXT TWO DAYS...ENSURING THAT WE WILL AT LEAST TIE THE RECORD FOR
LATEST HARD FREEZE IN THE KC METRO.
WEAK SOUTH-SOUTHWEST WINDS WILL CONTINUE THROUGH THE DAY TOMORROW
BEFORE A WEAK SURFACE BOUNDARY SETTLES INTO THE REGION SATURDAY
NIGHT. CIRRUS LOOKING TO BE LESS OF A FACTOR FOR TOMORROW...AND THUS
READINGS SHOULD BE INTO THE 60S FOR ALL BUT FAR NRN MO...AND MAY BE
WELL INTO THE MID 60S AGAIN SOUTH OF THE MISSOURI RIVER.
PRECIPITATION CHANCES LOOKING INCREASINGLY MEAGER ALONG THE DECAYING
FRONT...WITH GULF MOISTURE NOT LIKELY INTERCEPTED UNTIL THE BOUNDARY
PASSES WELL SOUTH OF THE REGION. THUS POPS CONTINUE TO DIMINISH OVER
THE SRN ZONES. EVEN SUCH...DIURNAL RESPONSE WILL BE WEAK WITH
ABUNDANT CLOUD COVER AND BREEZE NORTH WINDS.
BOOKBINDER
MEDIUM RANGE (MONDAY THROUGH FRIDAY)...
CHALLENGES THROUGH THE MEDIUM RANGE PERIOD WILL LARGELY HINGE ON
LARGE MODEL DISCREPANCIES IN THE LATTER HALF OF THE PERIOD...AND
EFFECTS ON TEMPERATURES ACROSS THE CNTRL CONUS. BOTH THE
DETERMINISTIC 12Z GFS AND 00Z ECMWF ARE DISTINCT OUTLIERS IN THEIR
OWN RESPECT CONSIDERING 1) THE DEPTH AND POSITION OF TROUGHING
ACROSS THE GREAT LAKES AND ERN CONUS AS A RESULT OF ENERGY SPILLING
OVER A WRN NORTH AMERICA RIDGE...AND 2) THE AMPLITUDE AND EVENTUAL
DEGRADATION OF THE AFOREMENTIONED WRN RIDGING AT THE END OF THE
PERIOD. THE 00Z ECMWF WAS A CLEAR OUTLIER VERSUS A MULTI-MODEL
ENSEMBLE IN THE FIRST NOTED RESPECT...KEEPING MUCH LOWER HEIGHTS
BOTTLED THROUGH THE WRN GREAT LAKES...WHILE MAINTAINING MUCH HIGHER
AMPLITUDE RIDGING OVER WRN CANADA (OF NOTE...THE 12Z ECMWF H5
HEIGHTS ARE SLIGHTLY HIGHER AND POSITIONED MORE INTO SERN CANADA
CLOSER TO THE ENSEMBLE CLUSTER...YET MAINTAINING A FORMIDABLE WRN
CANADIAN RIDGE). THE 12Z GFS (AND PREVIOUS RUNS FOR THAT MATTER)
CARRIED MUCH BETTER AGREEMENT WITH ENSEMBLES IN THIS FIRST RESPECT
OF NERN CONUS TROUGHING...HOWEVER RAPIDLY ELIMINATED WRN RIDGING
THROUGH AN INTENSE WAVE PUSHING THROUGH THE GULF OF ALASKA AND INTO
THE PACIFIC NW COAST (TYPICAL KNOWN BIAS FOR THIS MODEL TO KNOCK
DOWN THIS TYPE OF RIDGE POSITION TOO QUICKLY...BUT SOME WEAKER OR
DAMPENED EVENTUALITY IS NOT COMPLETELY OUT OF THE REALM OF
POSSIBILITY FOR REASONS STATED BELOW).
LARGE SPREAD BETWEEN DETERMINISTIC MODELS AND AMONG ENSEMBLE MEMBERS
CAN BE TRACED TO TWO SEPARATE AREAS OF INTEREST...BUT TYPICALLY
OCCURRING PROCESSES DURING THE COLD SEASON. FIRST...AS PROGRESSIVE
ENERGY CURRENTLY ALONG THE NORTHEAST COAST ENCOUNTERS HIGH LATITUDE
BLOCKING OVER THE NORTH ATLANTIC...AND UNDERCUTS THIS BLOCK INTO A
HEIGHT WEAKNESS OVER WRN EUROPE...ENSEMBLE SPREAD GROWS RAPIDLY IN
RESPONSE TO FURTHER DOWNSTREAM BLOCKING OVER WRN ASIA. H5 SPREAD
STARTS RATHER SMALL AT THE BEGINNING OF THE PERIOD...BUT GROWS IN
EXCESS OF 180DM AMONG ENSEMBLES BY LATE IN THE PERIOD OVER THE ERN
NORTH ATLANTIC BASIN AND WRN EUROPE AS A RESULT OF THE DOWNSTREAM
BLOCKING INFLUENCES. THIS INFLUENCE IS READILY FELT UPSTREAM INTO
ERN NORTH AMERICA WITH RESPECT TO NOT ONLY THE LATITUDINAL
ORIENTATION OF THE TROUGHING...BUT LONGITUDINALLY AS WELL. IN THIS
RESPECT...FELT AN ENSEMBLE MEAN WHICH CAPTURED A GOOD BLEND OF THE
OPERATIONAL GFS AND ECMWF WAS THE BEST BET. SECOND...OVER THE
PACIFIC BASIN SEVERAL SUB-SEASONAL PROCESSES ARE CURRENTLY EVOLVING
THAT MAY HAVE TREMENDOUS EFFECTS ON DOWNSTREAM FLOW TOWARDS THE END
OF THIS MEDIUM RANGE PERIOD. HEMISPHERIC IR SATELLITE IMAGERY
CLEARLY SHOWS A PRONOUNCED TROPICAL/EXTRA-TROPICAL LINKAGE BETWEEN
SUPER TYPHOON NIDA AND AN ANOMALOUS EXTENSION OF THE EAST ASIAN JET
INTO THE CNTRL MIDLATITUDE PACIFIC. THIS MOISTURE AND ENERGY STREAM
ALONG WITH ANTICIPATED FUTURE TROPICAL PLUMES EMANATING FROM
CONVECTION SUPERIMPOSED OVER A BASE EL NINO STATE COINCIDENT WITH
INCREASING H2 NEGATIVE VELOCITY POTENTIALS WILL LIKELY DISPERSE
ROBUST ENERGY POLEWARD INTO THE OVERALL FLOW PATTERN. GLOBAL MODELS
LIKELY DO NOT CAPTURE OR SIMULATE THESE LINKAGES ACCURATELY...AND
ONLY ADD ANOTHER DEGREE OF UNCERTAINTY TO THE FORECAST. THUS...IT IS
NOT OUT OF THE QUESTION THAT ENHANCED ENERGY PROPAGATING INTO THE
ERN PACIFIC BASIN COULD ERODE HIGHER HEIGHTS ALONG THE COASTLINE
QUICKER THAN NORMALLY ANTICIPATED.
REGARDING SENSIBLE WEATHER...DRY CONDITIONS ARE EXPECTED THROUGH THE
ENTIRE PERIOD...WITH CENTERS OF ACTION WELL REMOVED TO THE SOUTH AND
EAST (AN INTENSE EAST COAST CYCLOGENIC EVENT REMAINS QUITE
PLAUSIBLE). HAVE PUSHED TEMPERATURES MONDAY AND TUESDAY AT OR ABOVE
THE HIGHEST AVAILABLE GUIDANCE...AS THE INITIAL POST FRONTAL SFC
HIGH WILL CARRY LITTLE IN THE WAY OF UNSEASONABLY COLD AIR...AND
SINKING SOUTH OF THE LOCAL REGION WILL FORCE AGGRESSIVE DOWNSLOPING
AND COMPRESSIONAL WARMING IN ADVANCE OF THE NEXT COLD FRONT MOVING
SOUTH FROM THE NRN PLAINS. KEPT FORECAST TEMPERATURES FOR THE END OF
THE WEEK AT AND JUST BELOW ENSEMBLE MEAN GUIDANCE GIVEN THE OVERALL
LARGER THAN USUAL UNCERTAINTY (PUSHING TOWARDS 1 STANDARD DEVIATION
BELOW AVERAGE). SHOULD THE DEEPER AND SLOWER ECMWF COME TO
FRUITION...H9 TEMPERATURES AND 1000-850MB THICKNESSES SUGGEST
SEVERAL CATEGORIES WILL NEED TO BE SHAVED (DECREASING CLOSER TO A 2
STANDARD DEVIATION ANOMALY). HOWEVER...LARGE CAVEATS EXIST WHEN
CONSIDERING THE TOTAL LACK OF SNOW COVER BETWEEN THE FORECAST AREA
AND NRN ALBERTA/SASKATCHEWAN...WHICH WOULD LIKELY ALLOW FOR
SUBSTANTIAL AIRMASS MODIFICATION...EVEN IN THE FACE OF HIGHER SFC
PRESSURES AND LOWER THICKNESSES. ALL IN ALL...IT STILL MAY TAKE
SEVERAL MORE DAYS BEFORE MODEL CONSISTENCIES AMONG MASS FIELDS
DICTATE SIGNIFICANT TEMPERATURE TRENDS IN ONE DIRECTION OR THE OTHER.
21
&&
.AVIATION...
FOR THE 06Z TAFS...WITH A DRY AIRMASS IN PLACE ACROSS THE PLAINS VFR
CONDITIONS ARE EXPECTED OVER THE NEXT 24 HOURS. MODEST SOUTHERLY
WINDS WILL PREVAIL ACROSS THE REGION AHEAD OF A FRONT THAT WILL MOVE
THROUGH THE TERMINALS SATURDAY EVENING...SWITCHING WINDS TO THE
NORTH.
CUTTER
&&
.CLIMATE...
THE CURRENT FORECAST LOW TEMPERATURE AT KANSAS CITY THROUGH SUNDAY
MAKES IT UNLIKELY THAT A HARD FREEZE (TEMPERATURES AT OR BELOW 28
DEGREES) WILL OCCUR THROUGH AT LEAST NOVEMBER 29TH. THAT DATE STANDS
AS THE LATEST OCCURRENCE OF 28 DEGREES. HERE ARE THE TOP 5 LATEST
OCCURRENCES OF 28 DEGREE LOW TEMPERATURES IN KANSAS CITY:
RANK DATE YEAR
----- ------ ------
? ?????? 2009
1 NOV 29 1905
2 NOV 27 1944
3 NOV 26 1902
4 NOV 26 1958
5 NOV 25 1928
FOR ADDITIONAL INFORMATION...PLEASE VISIT OUR WEBSITE AT
WWW.WEATHER.GOV/KC.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
