FXUS63 KEAX 252013
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
213 PM CST WED NOV 25 2009
.DISCUSSION...
ONLY MINOR CONCERNS IN THE SHORT TERM PORTIONS OF THE FCST...WITH
DETAILS HINGING MAINLY ON TEMPS THROUGH THE END OF THE WEEK. THIS
AFTN...UPR LVL PV ANOMALY CONTINUE TO RAPIDLY RACE SE THROUGH IOWA.
THIS UPR WAVE HAS PUSHED A VERY WEAK COLD FRONT THROUGH THE AREA BY
MID-DAY. LITTLE OR NO TEMP CHANGE BEHIND THIS FRONT...BUT A
PRONOUNCED WIND INTENSIFICATION HAS BEEN REALIZED DUE IN PART TO THE
STRONG SUBSIDENCE INDUCED POST FRONTAL CLEARING.
FOR TONIGHT...THIS UPR WAVE WILL BEGIN TO PIVOT ACROSS EASTERN
IA/CENTRAL IL THIS EVENING...BRINGING A RATHER EXTENSIVE LOW-MID LVL
CLOUD DECK THROUGH THE NORTHEASTERN CWA. GIVEN THE RATHER COLD 500
MB TEMPS WOULD EXPECT SOME SORT OF ISO-SCT RA/SN SHOWER ACTIVITY
WITH IT. WILL MAINTAIN LOW CHC POPS...WITH SOUNDINGS AND SFC TEMPS
SUPPORTING A RA/SN MIX. AS FAR AS TEMPS ARE CONCERNED...12Z SFC OBS
FROM THIS MORNING ACROSS NORTH AND SOUTH DAKOTA ARE A DECENT PROXY
AS TO WHAT OVERNIGHT LOWS MAY BE BY THANKSGIVING MORNING. GIVEN
SOME AIRMASS MODIFICATION ALONG WITH THE LIKELIHOOD THAT WINDS WILL
REMAIN RATHER MIXY OVERNIGHT AND NOT ALLOW DECOUPLING TO
OCCUR...FEEL MUCH OF EASTERN KS AND WESTERN MO WILL RUN RIGHT AROUND
30 DEGREES. FURTHER EAST...UNCERTAINTIES OF CLOUD COVER AND
LINGERING SFC MOISTURE MAY KEEP READINGS NEAR OR ABOVE FREEZING.
A NEAR AVERAGE BUT PLEASANT DAY CAN BE EXPECTED ON THANKSGIVING AS
SUNNY SKIES AND LIGHT WINDS PREVAIL. SFC RIDGING AND LOW-LVL THERMAL
GRADIENT WILL APPROACH FROM THE WEST IN THE LATE AFTN AND SHOULD
ALLOW READINGS TO CLIMB NEAR NORMAL. TEMPS MAY BE SLIGHTLY COOLER IN
NE MO GIVEN A MORE PRONOUNCED NWLY FETCH.
THU NIGHT AND FRIDAY...LOWER TROPOSPHERIC WAA WILL COMMENCE IN
EARNEST. OVERNIGHT LOWS MAY OCCUR VERY EARLY IN THE EVE ON THU DUE
TO QUICK RADIATIONAL COOLING. HOWEVER AS SFC WINDS QUICKLY TURN TO
THE SW BY MIDNIGHT READINGS MAY HOLD STEADY OR RISE THROUGH
DAYBREAK. FRIDAY ITSELF WILL BE SPECTACULAR WITH STRONG WAA ALOFT
AND SUNNY SKIES. 925-850 TEMPS WILL SOAR WELL INTO THE 12-16C
RANGE...HOWEVER THE ONE THING PREVENTING A MUCH STRONGER WARMUP WILL
BE THE LIMITED AMOUNT OF MIXING WITH SOUNDINGS ONLY SUGGESTING WE
MIX UP TO AROUND 950-925 MB. THE END RESULT WILL BE TEMPS EITHER
SIDE OF 60 IN THE WEST WITH LOW TO MID 50S EAST.
DUX
MOST NOTABLE HEIGHT ANOMALIES THROUGH THE MAJORITY OF THE MEDIUM
RANGE PERIOD WILL LIE ACROSS THE SUBTROPICS FROM THE CNTRL AND ERN
PACIFIC BASIN THROUGH THE GULF OF MEXICO...WITH STANDARDIZED
ANOMALIES SOME 2 TO 3 STANDARD DEVIATIONS BELOW AVERAGE.
CONCURRENTLY...WEAKER NORTHERN STREAM POSITIVE HEIGHT ANOMALIES
ACROSS THE GULF OF ALASKA TELECONNECTS FAIRLY WELL WITH DOWNSTREAM
POSITIVE TILT SPLIT FLOW ACROSS THE CONUS. OPERATIONAL GFS
CONTINUITY HAS LEFT MUCH TO BE DESIRED...THOUGH MOST RECENT 12Z RUN
MORE STRONGLY RESEMBLES THE PREFERRED ECMWF/ENS ECMWF/GFS ENSEMBLE
MEAN THAN PREVIOUS SOLUTIONS. REGARDLESS...THE BULK OF THIS MEDIUM
RANGE PACKAGE WAS DERIVED PRIMARILY FROM A BLEND OF THE 00Z ECMWF
AND ENSEMBLE MEANS (OF NOTE...THE 12Z ECMWF HAS BROUGHT QPF BACK
FURTHER NORTH INTO THE BULK OF THE FORECAST AREA...HOWEVER
INVESTIGATION OF ENSEMBLE MEMBERS SHOWS THIS IDEA IS ON THE VERY NRN
EDGE OF MODEL SPREAD AND A GENERAL OUTLIER...THOUGH NOT TOTALLY OUT
OF THE REALM OF POSSIBILITY).
AFTER AN UNSEASONABLY WARM SATURDAY AFTERNOON (PUSHED HIGH TEMPS
TOWARDS THE UPPER END OF ENSEMBLE GUIDANCE)...INITIAL FRONTAL PUSH
WILL BEGIN SATURDAY EVENING...AND BE COMPLETED BY SUNDAY AFTERNOON.
QUITE SIMILAR TO TODAY...BOUNDARY LAYER MOISTURE WILL BE LACKING
WITH MIDLEVEL FRONTOGENETICAL FORCING FOCUSING A FEW LIGHT SHOWERS
OR SPRINKLES. POST FRONTAL AIRMASS WILL BE OF ALMOST ENTIRELY
PACIFIC ORIGIN...SO ONLY SLIGHT DEVIATIONS AWAY FROM CLIMATOLOGY
APPEAR NECESSARY FOR THE REMAINDER OF THIS FORECAST PERIOD.
LARGEST FORECAST UNCERTAINTY LIES WITH THE SOUTHWARD EXTENT OF THE
BAROCLINICITY PUSH EARLY NEXT WEEK (IN RESPONSE TO UPSTREAM
SHORTWAVE RIDGING FORCING SFC PRESSURE RISES IN THE NRN
STREAM)...AND THE SRN SHORTWAVE EJECTION ACROSS THE SRN PLAINS/GULF
COAST (QUESTIONS IN TIMING OF SUCH EJECTION UNDERSTOOD).
REGARDLESS...ONCE THE SRN STREAM DISTURBANCE AND HEIGHT FALLS ALOFT
BEGIN TO CROSS INTO THE PLAINS...HIGHER THETA-E AIRMASS ADVECTION TO
THE NORTHEAST ALONG THE ENHANCED BAROCLINICITY WILL COMMENCE. MODEL
TRENDS HAVE GENERALLY BEEN FOR A SLIGHTLY MORE AGGRESSIVE SRN PUSH
TO THE FRONTAL BOUNDARY...AND GIVEN THE PREFERENCE TOWARDS POSITIVE
TILT SPLIT FLOW WITH ENHANCED SUBTROPICAL JET FLOW...FEEL THIS TREND
IS FAIRLY ACCURATE. ALSO GIVEN THE SEASONAL EL NINO INFLUENCE AND
STRONG TENDENCY FOR SUCH A PATTERN...THINKING THE I-44 CORRIDOR
WOULD BE MOST LIKELY TO BE AFFECTED BY THIS THETA-E ADVECTION
PATTERN. THUS...HAVE KEPT PRECIPITATION MENTION LIMITED TO THE SRN
PORTIONS OF THE CWA...WITH POPS MODEST AT BEST. ALSO KEPT MENTION OF
RAIN OR SNOW IN THESE GRIDS SUNDAY NIGHT...AS PARTIAL THICKNESS
METHODS ALIGN VERY NEAR THE TRADITIONAL CUTOFF VALUES FOR RAIN
VERSUS SNOW. HAD THE POST FRONTAL AIRMASS BEEN OF MORE NRN
CONTINENTAL ORIGIN (AND SHALLOW IN NATURE)...WOULD BE MORE CONCERNED
ABOUT AN ICING EVENT GIVEN THE OVERALL PATTERN RECOGNITION.
NEVERTHELESS...THE LATEST 12 ECMWF (ALONG WITH PRIOR SOLUTIONS FROM
THIS MODEL AS WELL AS THE GFS) LEADS TO CONTINUED UNCERTAINTY WITH
RESPECT TO PRECIPITATION PROBABILITIES AND TYPE. WITHOUT THE STRONG
CONTINENTAL INFLUENCE OF THE POST FRONTAL HIGH PRESSURE SYSTEM...IT
IS NOT OUT OF THE QUESTION TO ARGUE FOR LESS OF A SRN PUSH TO THE
BAROCLINIC BOUNDARY...AND ANY FURTHER TRENDS TOWARDS THE 12Z ECMWF
WILL NEED TO BE WATCHED FOR.
21
&&
.AVIATION...
FOR THE 18Z TAFS...SECONDARY COLD FRONT HAS NOW MOVED THROUGH THE
TERMINALS...WITH PRECIP MOVING SE. MOST CONTENTIOUS ISSUES THROUGH
THU MORNING WILL BE SFC WINDS. PARTLY SUNNY SKIES WILL BREAK OUT
THIS AFTN...ALLOWING FOR QUALITY MIXING OF THE 20 TO 30 KNOT LOW-LVL
WINDS VISIBLE ON REGIONAL PROFILER DATA. THESE WINDS WILL BEGIN TO
SUBSIDE AS WE MOVE INTO THE EVENING HOURS AND THE UPR LOW IN THE
GREAT LAKES BEGINS TO SLIDE FURTHER EAST. HOWEVER PREVAILING WINDS
SHOULD REMAIN BREEZY IN NATURE AOA 10 KNOTS.
HIGH PRESSURE WILL RACE INTO THE REGION FOR THURSDAY...WITH VFR
CONDITIONS EXPECTED.
DUX
&&
.CLIMATE...
WITH LOW TEMPERATURES FCST IN THE UPR 20S TO NEAR 30...WED NIGHT WILL
LIKELY BE THE PIVOTAL TIMEFRAME TO TIE OR BREAK THE RECORD FOR THE
LATEST HARD FREEZE (TEMPERATURE OF 28 DEGREES) IN KANSAS CITY.
ATTM...FORECAST LOW TEMPERATURES THROUGH THE END OF THE NOVEMBER REMAIN
AT OR ABOVE 30 DEGREES. HERE ARE THE TOP 5 LATEST OCCURRENCES OF 28
DEGREE LOW TEMPERATURES IN KANSAS CITY:
RANK DATE YEAR
----- ------ ------
1 NOV 29 1905
2 NOV 27 1944
3 NOV 26 1902
4 NOV 26 1958
5 NOV 25 1928, 2009
FOR ADDITIONAL INFORMATION...PLEASE VISIT OUR WEBSITE AT
WWW.WEATHER.GOV/KC.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
