FXUS63 KEAX 231757
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1155 AM CST WED DEC 23 2009
...UPDATED AVIATION DISCUSSION...
.UPDATE...
/1050 AM CST WED DEC 23 2009/
CLUSTER OF THUNDERSTORMS CURRENTLY LIFTING ACROSS PORTIONS OF
SOUTHEAST KANSAS WILL CONTINUE NORTHWARD THROUGH THE REMAINDER OF THE
MORNING HOURS. THIS ACTIVITY SEEMS TO BE LOCATED WITHIN FAVORABLE
EXIT REGION OF APPROACHING UPPER JET COUPLED WITH BROAD ISENTROPIC
ASCENT AS MODEST LLVL H85 FLOW OF 20-30 KTS...VIA LATEST REGIONAL
VWP...NOSES INTO THE REGION. THIS HIGHER THETA E AIR MASS WAS
TRANSPORTING WEAK ELEVATED INSTABILITY INTO THE REGION ON THE ORDER
OF MUCAPE VALUES OF 100-200 J/KG. COUPLED WITH MODEST LLVL SHEAR HAS
RESULTED IN PERIODIC INTENSIFICATION OF ISOLATED UPDRAFTS WITHIN THE
CLUSTER. GIVEN VERY LOW FREEZING LEVELS...IE 7500 FT AGL VIA 12Z TOP
RAOB...AND MODEST MID LEVEL LAPSE RATES...SMALL HAIL APPEARS TO BE
THE MAIN THREAT WITH THIS ACTIVITY ALTHOUGH A BRIEF HIGHER WIND GUST
MAY ALSO BE CAPABLE OF MIXING DOWN. THE ACTIVITY SHOULD WEAKEN
GRADUALLY WITH NORTHERN EXTENT AS IT BECOME FURTHER REMOVED FROM THE
WEAK INSTABILITY/STRONGER LLVL SHEAR AXIS.
DEROCHE
&&
.DISCUSSION...
/440 AM CST WED DEC 23 2009/
...SIGNIFICANT WINTER STORM TO AFFECT THE AREA DURING PEAK TRAVEL
TIME THURSDAY AND FRIDAY...
DOUBLE BARRELED PV ANOMALY STRETCHES FROM SRN CALIFORNIA THROUGH
WRN NEW MEXICO EARLY THIS MORNING...ON THE NRN EDGE OF A 150 KT
UPPER JET AXIS THROUGH NRN MEXICO (SLIGHTLY STRONGER THAN FORECAST
THE PAST SEVERAL DAY...AND HAVING SERIOUS RAMIFICATIONS ON THE
FORECAST THROUGH THE REST OF THE WEEK). MEANWHILE...A SECONDARY NRN
STREAM PV ANOMALY WAS DIVING SOUTH THROUGH SRN ALBERTA...AND THE
EVENTUAL INTERACTION BETWEEN THESE TWO ANOMALIES WILL BE A KEY
FEATURE IN THE EVOLUTION OF THE DEEP CYCLONGENIC EVENT OVER THE
LOWER MISSOURI RIVER VALLEY THROUGH THE END OF THE WEEK.
IN THE NEAR TERM...A WARM/QUASI-STATIONARY FRONT ALIGNED JUST SOUTH
OF THE CWA BORDER TO THE SOUTH...THEN ARCING BACK THROUGH SOUTH
CENTRAL KANSAS AND INTO SWRN OKLAHOMA TO THE PRIMARY SFC LOW. A VERY
EVIDENT LEAD SHORTWAVE IN SERN KANSAS ON THE NOSE OF THE IMPINGING
JET AXIS (AND COLLOCATED VERY WELL WITH THE FAVORABLE LEFT FRONT
DIFFLUENT REGION) HAS INDUCED DEEP LAYER ISENTROPIC LIFT WITH AN
UNSEASONABLY HIGH THETA-E AIRMASS ADVECTING NORTH WITH A 35KT LLJ
AXIS. TSTM AND LIGHTNING ACTIVITY HAS BECOME FAR MORE PREVALENT
SINCE LAST EVENING...AND MODEL FORECAST SOUNDINGS SUPPORT AMPLE
MUCAPES ASSOCIATED WITH THE WARM SATURATED H8 +4C TO +6C
TEMPERATURES BENEATH SUFFICIENT ELEVATED LAPSE RATES THROUGH AT
LEAST THIS MORNING (WITH SOME MEASURE OF SUBSIDENCE AND DRYING
DURING THE AFTERNOON HOURS). FOR SIMPLICITY SAKE...JUST KEPT
STRAIGHT CATEGORICAL POPS GOING THROUGHOUT THE DAYLIGHT
HOURS...THOUGH CERTAINLY A GOOD BREAK IN PRECIPITATION SHOULD BE
EXPECTED FOR PARTS OF THE AFTERNOON AND EVENING HOURS. WITH THE
POSSIBLE EXCEPTION OF A FEW LOCATIONS IMMEDIATELY ALONG THE IOWA
BORDER...THE ENTIRE AREA REMAINS ABOVE FREEZING (AND EVEN DEWPOINTS
AND WET BULB TEMPERATURES AOA FREEZING)...AND FEEL ICING POTENTIAL
IS NEARLY NEGLIGIBLE THROUGH THIS EVENING. TEMPERATURES ACROSS THE
AREA WILL BE HIGHLY VARIABLE...WITH LOWER 50S LURKING NOT FAR TO THE
SOUTH...YET THE AFOREMENTIONED BOUNDARY BECOMING REINFORCED BY
PRECIPITATION. THERE IS A VERY GOOD CHANCE THAT ONCE THE BACK EDGE
OF THE CONVECTION LIFTS INTO NRN MISSOURI LATER THIS AFTERNOON...A
DISCRETE JUMP IN THE BOUNDARY LOCATION (AND HENCE TEMPERATURES)
WOULD OCCUR. HAVE DEPICTED A 20+ DEGREE RANGE ACROSS THE CWA FOR
THIS POSSIBILITY.
WILL CONTINUE WILL A HYDROLOGIC OUTLOOK (ESF) IN LIEU OF A FLOOD
WATCH FOR THE ENTIRE AREA THROUGH THURSDAY. INITIAL ROUNDS OF
CONVECTION THIS MORNING WILL ONLY PRIME PARTIALLY FROZEN SOILS FOR
INCREASED RUNOFF IN NEAR FUTURE RAIN EVENTS TONIGHT. GENERAL MODEL
TREND (AND A GOOD CONCEPTUAL FIT) IS TO FOCUS TO MOST ROBUST
CONVECTION FROM THE I-44 CORRIDOR THROUGH CNTRL MISSOURI TONIGHT.
WITH INCREASING MERIDIONAL FLOW...FEEL MAIN CORRIDOR MAY ACTUALLY
ALIGN SLIGHTLY FURTHER WEST...AND MANY BASINS ACROSS THE CWA MAY BE
SUSCEPTIBLE (ESPECIALLY THOSE WITH MORE FROZEN GROUND).
MINOR TREND CHANGES IN MODEL OUTPUT OVER THE PAST 12 HOURS HAS
CREATED HAVOC ON THE ENTIRE FORECAST PROCESS FOR THE REMAINDER OF
THE WEEK. FROM THE BEST THAT CAN BE PULLED FROM 00Z OBSERVATIONS AND
MODEL INITIALIZATIONS...IT APPEARS A STRONGER AND MORE EASTWARD
EXTENDED SUBTROPICAL JET MAY BE RESPONSIBLE FOR PULLING THE
AFOREMENTIONED SRN PV ANOMALIES FURTHER EAST INTO SRN MISSOURI...AND
KEEPING THIS ANOMALY CENTER MORE DISCONNECTED FROM THE NRN ANOMALY
MUCH LONGER (THERE MAY ALSO BE SOME CONVECTIVELY INDUCED INFLUENCE
ON PULLING THE ANOMALY FURTHER EAST AS WELL). ASSUMING THIS SCENARIO
PLAYS OUT...THE MOST INTENSE SFC CYCLOGENESIS WOULD OCCUR FROM THE
OZARKS THROUGH NERN MISSOURI THURSDAY AFTERNOON THROUGH FRIDAY
MORNING. THIS WOULD PULL THE CRITICAL INVERTED TROUGH MUCH FURTHER
EAST THAN PREVIOUSLY ANTICIPATED...PLACING A LARGE PORTION OF THE
FORECAST AREA IN OR CLOSE TO THE MORE PREFERRED DEFORMATION
BAND...CHARACTERIZED BY STRONGER H7-H5 UVV AND LAYERED
FRONTOGENETICAL FORCING NORTHWEST OF THE PRIMARY PV ANOMALY AND
TROPOPAUSE UNDULATION (TRACKING FROM CNTRL OKLAHOMA THROUGH ERN
KANSAS/WRN MISSOURI...AND INTO WRN IOWA AND SRN MINNESOTA).
PARTICULARLY DISCONCERTING IS CROSS SECTION ANALYSIS INDICATING SOME
BRIEF PERIODS OF LAYERED FRONTOGENETICAL FORCING AND NEGATIVE EPV
COINCIDENT IN A STATICALLY UNSTABLE ATMOSPHERE...SUGGESTING
MESOSCALE BANDING ENHANCEMENT. FEEL THE WORST CONDITIONS WOULD ALIGN
ON THE NORTHERN PERIPHERY OF A CLASSIC OCCLUDING TROWAL SIGNATURE
INTERSECTING THE INVERTED TROUGH (BASICALLY SETTING UP OVER THE
KANSAS CITY METRO LATE THURSDAY AFTERNOON...AND LIFTING INTO SWRN
IOWA THURSDAY NIGHT). THIS COULD NOT COME AT A WORSE TIME GIVEN THE
PEAK TRAVEL DURING THE HOLIDAY...AND HAVE ISSUED A WINTER STORM
WATCH AS THE FIRST HEADS UP.
SECONDARY NRN STREAM PV ANOMALY PROPAGATES SOUTHEAST INTO THE PLAINS
BY FRIDAY MORNING...AND ALMOST IN A FUJIWARA EFFECT CONSOLIDATES
INTO A SINGLE BAROTROPICALLY STACKED ENTITY THROUGH FRIDAY
AFTERNOON. AS THIS PROCESS UNFOLDS...SEVERAL ENERGY PACKETS ROTATING
ABOUT THE MAIN VORTEX CENTER SHOULD PROVIDE SUFFICIENT LIFT WITHIN A
DEEPER COLDER SATURATED ENVIRONMENT TO FORCE NUMEROUS SNOW SHOWERS
THROUGHOUT THE DAY FRIDAY (AND LIKELY INTO SATURDAY AS WELL). MOST
LIKELY NOT NEARLY AS INTENSE AS BRIEF MODERATE TO HEAVY SNOWS
THURSDAY EVENING...AN ADDITIONAL SEVERAL INCHES OF ACCUMULATION WILL
LOCALLY BE LIKELY INTO THE WEEKEND. WITH EXPECTED EXTENSIVE SNOW
PACK...HAVE CUT BELOW MOST GUIDANCE FOR THE UPCOMING WEEKEND.
21
&&
.AVIATION...
FOR THE 18Z TAF CYCLE...A NARROW LINE OR CLUSTER OF THUNDERSTORMS
MOVING NORTHEAST IN BETWEEN KMCI AND KMKC TERMINALS. BASED ON
UPSTREAM OBSERVATIONS...CURRENT TREND OF IFR CIGS WILL
CONTINUE...BUT VISIBILITIES WILL INCREASE FROM LIFR TO IFR CATEGORY.
THREAT OF CONVECTION IS SHORT-LIVED...AND EXPECT THREAT OF TSRA TO
END IN THE 19-20Z TIMEFRAME. A PERIOD OF LIGHT TO MODERATE RAIN
WITH IFR CIGS/VSBYS WILL CONTINUE FOR THE THROUGH
MID-AFTERNOON...THEN ALL TERMINALS SHOULD EXPERIENCE A BRIEF LULL IN
PRECIPITATION AS SHORTWAVE PASSAGE WILL BRING SUBSIDENCE...THUS
PRECIPITATION WILL TREND TOWARD DRIZZLE. A PERSISTENT PERIOD OF
MODERATE RAIN AND IFR CIGS/VSBYS WILL REDEVELOP BY 02-04Z AS ANOTHER
SHORTWAVE FEATURE ENHANCES BROADSCALE ISENTROPIC LIFT. PRECIPITATION
WILL CONTINUE INTO THE MORNING HOURS OF THE 24TH...WITH FORECAST
SOUNDINGS INDICATING SLEET MIXING WITH RAIN BY 16-17Z AT KMKC AND
KMCI...AND SNOW AT KSTJ. CIGS/VSESULT IN ABAND OF HEAVIER RAIN
MOVING NORTHEAST ACROSS T
SF
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY
AFTERNOON FOR MOZ005>007-014>016-022>024-029>032-037>039-
043>045-053-054.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON
FOR MOZ001-002-011-012.
WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY
AFTERNOON FOR MOZ003-004-013-020-021-028.
KS...WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON
FOR KSZ025-102.
WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY
AFTERNOON FOR KSZ057-060-103>105.
&&
$$
