FXUS63 KEAX 042235
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
435 PM CST FRI DEC 4 2009
.DISCUSSION...
NEXT 36 HOURS ARE RATHER BENIGN AS THE UPPER FLOW QUICKLY
TRANSITIONS TO A MORE ZONAL FLOW FROM THE ROCKIES EASTWARD IN
RESPONSE TO THE ENERGY DIGGING INTO THE CENTRAL PLATEAU AREA.
DEPARTING SURFACE HIGH WILL SOON YIELD A SOUTHERLY RETURN TO THE
BOUNDARY LAYER. BUT EVEN WITH THE SURFACE WINDS SHIFTING TO THE
SOUTH OVERNIGHT THE AIRMASS IS QUITE DRY AND A SHARP NOCTURNAL
INVERSION WILL SET UP SO GOOD RADIATIONAL COOLING EXPECTED. FAVORED
COLDER MAV MOS MINIMUMS.
MADE FEW IF ANY CHANGES TO TOMORROW WITH INCREASING SOUTHERLY LOW
LEVEL WINDS ALLOWING FOR A RELATIVELY GOOD WARMUP.
PRIMARY ATTENTION TURNS TOWARDS SUNDAY/SUNDAY NIGHT SYSTEM.
AFOREMENTIONED ENERGY DIGGING INTO THE CENTRAL PLATEAU WILL EJECT
QUICKLY EAST SATURDAY NIGHT AND FLY THROUGH THE CENTRAL PLAINS ON
SUNDAY. WHILE THERE ARE DISCERNIBLE DIFFERENCES BETWEEN THE MODELS
THEY ARE ALL PRETTY CLEAR THAT THIS WILL BE A FAST MOVING SYSTEM.
PRECIPITATION AMOUNTS OVER THE CWA WILL BE LIMITED BY THIS FAST
MOVEMENT AND A DRY BOUNDARY LAYER THAT MUST BE OVERCOME FIRST BEFORE
ANYTHING CAN REACH THE GROUND. LAST COUPLE OF GFS/NAM MODEL RUNS
HAVE BEEN PROGRESSIVELY FASTER. GFS APPEARS TO BE THE OUTLIER WITH
PLACEMENT OF SURFACE/H8 FRONTS TOO FAR SOUTH. WENT WITH A
NAM/ECMWF/UKMET BLEND WHICH ALIGNS THE H8 FRONT SW-NE FROM EAST
CENTRAL KS THROUGH NORTH CENTRAL MO. THUS NORTHWEST/NORTH CENTRAL
MO/FAR NORTHEAST KS WILL HAVE THE BEST CHANCE OF SEEING MEASURABLE
SNOWFALL. AROUND AN INCH OF SNOW IS POSSIBLE OVER THIS REGION BY
MIDNIGHT SUNDAY. WITH ALL MODELS SHOWING THE MID LEVEL MOISTURE
BEING STRIPPED AWAY AFTER MIDNIGHT HAVE LOWERED POPS IN THE 06Z-12Z
MONDAY PERIOD. LATER SHIFTS MAY BE ABLE TO GO WITH HIGHER POPS
SHOULD THE NEXT MODEL RUN OR TWO SHOW GOOD RUN-TO-RUN CONSISTENCY.
SOUTH OF THE FRONT GFS/NAM BUFR SOUNDINGS SUGGEST MOST OF THE
INITIAL ENERGY ON SUNDAY WILL GO TOWARDS CLOUD PRODUCTION. WITH
TEMPERATURES LIKELY ABOVE FREEZING AM SKEPTICAL OF ANY MEASURABLE
PRECIPITATION. UNLESS THE FRONT DROPS FURTHER SOUTH ANY
PRECIPITATION SOUTH OF THE BOUNDARY WILL BE LIQUID SO HAVE DROPPED
MENTION OF FREEZING DRIZZLE. POST FRONTAL MEASURABLE PRECIPITATION
SOUTH OF A KANSAS CITY TO MACON LINE IS QUESTIONABLE AS ALL THE
MODELS ARE QUICK TO STRIP AWAY THE HIGHER ICE PRODUCING CLOUD LAYER
LEAVING BEHIND A LAYER THAT SHOULD ONLY BE DEEP ENOUGH TO PRODUCE
FLURRIES OR VERY LIGHT SNOW.
MJ
MEDIUM RANGE (MON-THU)...
THE BIG WEATHER MAKER FOR NEXT WEEK REMAINS ON TRACK FOR AN ARRIVAL
IN THE TUE TO WED TIMEFRAME. WHILE THERE IS HIGH CONFIDENCE THAT
PRECIP WILL BE RECEIVED IN THE CWA...MUCH LIKE TYPICAL WINTER STORMS
IN MISSOURI AND KANSAS...STORM TRACK...STORM INTENSITY...AND PRECIP
TYPE REMAIN HIGHLY IN QUESTION. NEVERTHELESS...PRECIP CHANCES HAVE
BEEN SIGNIFICANTLY INCREASED.
THIS BEING SAID...MED RANGE GUIDANCE CONTINUES TO WAFFLE A BIT IN
REGARDS TO THE MOST IMPORTANT DETAILS OF THE FCST. MUCH OF THIS IS
DUE TO THE POOR SAMPLING OF UPR LVL DYNAMICS ASSOCIATED WITH THIS
WAVE JUST NOW ROTATING ACROSS THE WESTERN CANADIAN COASTLINE. OF
MORE CONCERN ON MODEL EVOLUTION OF THIS SYSTEM IS THE INTENSITY OF
THE HIGHLY AMPLIFIED RIDGE OFF THE PAC NW ALONG WITH THE JET
DYNAMICS ASSOCIATED BETWEEN THESE SYSTEMS.
WHILE THE 12Z GFS WAS A BIT OF AN OUTLIER...WE'RE ALSO BEGINNING TO
SEE SOME DISTINCT SIGNALS FROM THE 06Z/12Z ENSEMBLE MEMBERS AS WELL
AS THE NAEFS SUPER ENSEMBLE SUPPORTING THE DEVELOPMENT OF A MUCH
STRONGER SFC AND LOW LVL CIRCULATION BY TUESDAY AFTN AS SUGGESTED BY
BOTH THE GEM/ECWMF/GFS IN PREVIOUS RUNS. BOTH THE U AND V
COMPONENTS (ESPECIALLY THE U COMPONENT) OF THE 850MB WINDS ARE MUCH
MORE ANOMALOUS THIS MORNING...SUGGESTING A MUCH STRONGER COLD
CONVEYOR BELT AND DEEPER INFLUX OF WARM AND RICH THETA E AIR FROM
THE SOUTHWEST. THIS MAY ONLY FURTHER INCREASE THE BAROCLINICITY OF
THIS SYSTEM AND COULD RESULT IN EVEN SLOWER...FURTHER SOUTH...AND
POTENTIALLY MORE INTENSE SOLNS IN THE SHORT TERM DESPITE THE
PROGRESSIVE NATURE OF THE EVENT. THE 06Z/12Z GEFS CONFIDENCE MAPS
CONTINUE TO SHOW AND ABOVE NORMAL CONFIDENCE LEVEL IN BRINGING
FREEZING TO ABOVE FREEZING TEMPERATURES WELL INTO NORTHERN MISSOURI
TUE AFTN...GIVEN CONSISTENT CLUSTERING AND STRONGER LOW-LVL
FEATURES. NAEFS MEANS ALSO SUGGEST 850MB TEMPS CLIMBING ABOVE 0 BY
18Z TUE FROM A KMCI TO KIRK LINE SIMILAR TO THE OPERATIONAL 12Z
GFS/00Z ECMWF. ALL IN ALL...THIS IDEA WOULD SUPPORT A MUCH HIGHER
PROBABILITY THAT EITHER MIXED PRECIP OR RA/SN WOULD CREEP MUCH
FURTHER NORTH TUE AFTN THAN WHAT PREVIOUS OPERATIONAL MODELS HAVE
SUGGESTED AND THE OVERALL BAROCLINICITY OF THE LOWER-LVLS WILL BE
HIGHER THAN SUGGESTED. FOR NOW...WILL BUMP UP MAX TEMPS IN THE
SOUTHERN CWA AND INTRODUCE RA/SN UP TO I-70 TUE AFTN.
THIS BEING SAID...WE'RE STILL OVER 4 DAYS OUT ON THIS STORM...WITH
MANY VARIABLES TO BE IRONED OUT. HOWEVER...ALL INDICATIONS POINT TO
THIS SYSTEM HAVING A HIGH PROBABILITY OF PRODUCING WHAT COULD BE
SIGNIFICANT IMPACTS TO A PORTION OF THE MID-LOWER MISSOURI RIVER
VALLEY. FROM A PROBABILITY STANDPOINT FROM CURRENT
DATA...INDICATIONS POINT TO THE HIGHEST PROBABILITY OF HEAVY SNOW TO
FALL IN NORTHERN KANSAS AND NORTHERN MO. WITH PROBABILITIES
DECREASING FURTHER SOUTH INTO CENTRAL/SOUTHERN MO DUE TO THE PENDING
UNCERTAINTY IN THE INFLUX OF WARM AIR ALOFT. THERE WILL LIKELY BE A
SHARP CUTOFF TO SNOWFALL FOR THIS SYSTEM.
BEHIND THIS SYSTEM...GROWING CONFIDENCE IN A TEMPORARY INTRUSION OF
VERY COLD TO PERHAPS ARCTIC AIR (GIVEN POTENTIAL CROSS POLAR FLOW
SETUP AND SHIFTING OF POLAR LOW FURTHER SW). WITH A GOOD LIKELIHOOD
OF SNOW COVER IN NORTHERN MO BY WED NIGHT INTO THUR MORNING HAVE
DROPPED LOWS TO SINGLE DIGIT READINGS. WINDS WILL ALSO BE A MAJOR
CONCERN ON WEDNESDAY GIVEN THE EXPECTED DEEPER CYCLOGENESIS AT THE
SFC.
DUX
&&
.AVIATION...
FOR THE 18Z TAF...VFR CONDITIONS FOR THIS FORECAST PERIOD. SLIGHT
WARMING WILL OCCUR AS WINDS BACK TO THE SOUTH TONIGHT. WILL SEE SOME
SCT AFTERNOON STRATOCUMULUS.
MJ
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
