FXUS63 KEAX 230839
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
238 AM CST WED DEC 23 2009
...UPDATED AVIATION DISCUSSION...
.DISCUSSION...
/335 PM CST TUE DEC 22 2009/
SHORT TERM (TONIGHT-THURSDAY NIGHT)...
IMPRESSIVE 20 DEGREE TEMPERATURE GRADIENT ACROSS THE CWA THIS AFTN
WITH SHARP STATIONARY FRONT BISECTING THE AREA. EVEN NORTH OF THIS
BOUNDARY UNDER NE WINDS AND LOW OVERCAST...SUFFICIENT WARM/MOISTURE
ADVECTION HAS PLACED IA/NE BORDER LOCATIONS ABOVE FREEZING.
EXTENSIVE LOW CLOUD COVER AND CONTINUED WARM AIR/MOISTURE ADVECTION
ALOFT SHOULD MITIGATE ANY SIGNIFICANT ICING POTENTIAL ACROSS FAR NW
MO...BUT WILL LEAVE A MIXED MENTION OF LIGHT FZDZ/FZRA IN THAT
VICINITY IN CASE ANY ELEVATED BRIDGES/ROADS BECOME SLICK AS PRECIP
DEVELOPS OVERNIGHT.
FOR THE OVERNIGHT HOURS...GULF STRATUS SHOULD ENVELOP THE REMAINDER
OF THE CWA...EVENTUALLY MERGING WITH THE LOWER DECK NORTH OF THE
STATIONARY FRONT. WITH DWPTS OVER SRN MO EXCEEDING THE AIR
TEMPERATURES OVER NRN MO...SHOULD BEGIN TO SEE DRIZZLE DEVELOP INTO
THE EVENING. MEANWHILE...WATER VAPOR IMAGERY DEPICTS A RATHER POTENT
LEAD SHORTWAVE OVER NEW MEXICO WHICH WILL QUICKLY PIVOT TOWARD THE
NORTHEAST THIS EVENING. THIS WILL HELP TO ACCENTUATE THE LOW LEVEL
MOISTURE TRANSPORT...AS WELL AS BRING MODESTLY STEEP MID-LEVEL LAPSE
RATES IN FROM THE SOUTHERN PLAINS LATER TONIGHT. WITH THE DEEPER
MOISTURE PRESENT...SHOWERS AND EMBEDDED THUNDERSTORMS ARE EXPECTED
TO DEVELOP AND SHIFT NORTHWARD THROUGH THE REGION AFTER MIDNIGHT
INTO WEDNESDAY MORNING.
DEEPENING SOUTHERLY FLOW ALOFT IN THE WAKE OF THIS WAVE WILL ACT TO
SHARPEN A SECONDARY INVERTED TROUGH WEST OF THE CWA WHICH WILL BE
THE DEMARCATION OF FROZEN PRECIPITATION. THE INVERTED TROUGH WILL
LIKELY SERVE AS A BETTER FOCUS FOR PRECIPITATION DURING THE
AFTERNOON/EARLY EVENING HOURS...WITH A POTENTIAL LULL IN
PRECIPITATION FOR THE BALANCE OF THE AFTERNOON HOURS ELSEWHERE.
SHOULD BE SEASONABLY MILD DAY AS WELL FOR AREAS SOUTH OF HIGHWAY 36
WITH AFTERNOON READINGS RISING INTO THE LOWER 50S AND EVEN MID 50
CENTRAL MO. NORTH OF THE EXISTING FRONT...NORTHEAST FLOW
TRAJECTORIES WILL KEEP READINGS IN THE 30S TO AROUND 40 ALONG AND
NORTH OF THE HIGHWAY 36 CORRIDOR.
LARGE SCALE ASCENT AHEAD OF THE PRIMARY MID LEVEL CORE WILL BRING
THE SECOND WAVE OF PRECIPITATION WEDNESDAY NIGHT INTO THURSDAY.
DESPITE THE LARGE NEGATIVE HEIGHT ANOMALY...THE OVERALL STORM TRACK
IS NOT ATYPICAL FOR THIS REGION AND HAS MANY CLOSE ANALOGS. THE
PROSPECTS FOR HIGH-EFFICIENCY DEEP MOIST CONVECTION FROM THE OZARKS
INTO EASTERN MISSOURI ARE NEARLY CERTAIN...WITH SOME SPILLOVER INTO
OUR EASTERN CWA. A LARGE QPF GRADIENT IS EXPECTED GIVEN THE VEERED
LOW LEVEL JET AND DIRECT GULF AXIS IN THIS REGION...WITH THE EASTERN
CWA ON THE FRINGES OF THE HEAVIER RAIN. ALTHOUGH SOME THAW IS
EXPECTED OVER THE NEXT 48 HOURS WITH MILDER TEMPERATURES...AT LEAST
PARTIALLY FROZEN SUBSTRATE WILL YIELD MORE RUNOFF THAN USUAL...SO
EVEN AN INCH OR MORE OF RAIN WOULD RESULT IN SOME CONCERN FOR RIVER
FLOODING INTO THE WEEKEND.
FURTHER WEST...RAIN WILL BE CONTINUE TO BE MORE SHOWERY IN NATURE
UNTIL THURSDAY EVENING WHEN THE WESTWARD EXTENSION OF A FULLY
GULF-TAPPED WARM CONVEYOR FINALLY INTERSECTS THE ELEVATED
FRONTOGENETIC REGION OF THE SRN EXTENSION OF THE OCCLUDING CYCLONE.
SECONDARY TROWAL DEVELOPMENT WILL OCCUR COINCIDENT WITH STRONG LOW
LEVEL COLD ADVECTION AS THE SURFACE BOUNDARY FINALLY SHIFTS TO THE
NORTHEAST. THE RESULT WILL BE SHORT BURST OF MDT/HVY SNOW THAT WILL
LIFT NORTHWARD ALONG THE KS/MO BORDER CHRISTMAS EVE BENEATH THE LOW
CORE. THE LOW WILL THEN DECREASE IN FORWARD SPEED AS A SECONDARY
PIECE OF ARCTIC ENERGY DUMBBELLS WITH THE INITIAL
CYCLONE...MAINTAINING WRAPAROUND LIGHT SNOWS OVER NW MO EVEN AS THE
PRIMARY FORCING SHIFTS NORTH AND EAST.
AT THIS TIME...SNOWFALL ACCUMULATIONS ARE HIGHLY CONTINGENT ON THE
EXACT TRACK OF THIS STORM WHICH ITSELF IS CONTINGENT ON THE ARRIVAL
OF UPSTREAM ENERGY. RIGHT NOW THE PROSPECTS OF A WHITE CHRISTMAS
OVER WRN MO/ERN KS ARE HIGH...WITH SOME 2-4 INCHES POSSIBLE OVER WRN
MO...AND POSSIBLY UPWARDS OF 6 INCHES OF WIND BLOWN SNOW OVER FAR NW
MO/NE KS. STILL A LOT OF SPECIFIC DETAILS TO PINPOINT AT THIS
JUNCTURE BUT ADVISORY SNOWS LOOK REASONABLY OVER THE WRN THIRD OF
THE CWA. SEE BELOW FOR MORE DETAILS.
BOOKBINDER
MEDIUM RANGE (FRIDAY THROUGH TUESDAY)...
ATTENTION FOR THE MEDIUM RANGE FOCUSES EARLY ON IN THE PERIOD AS
POTENT WINTER STORM CONTINUES TO INFLUENCE SENSIBLE WEATHER ACROSS
THE REGION. BY FRIDAY...NORTHERN STREAM PV ANOMALY DIVING SOUTH
WITHIN OVERALL LARGER SCALE TROUGH ACROSS THE CONUS WILL BEGIN TO
WRAP INTO THE DEEPENING UPPER LOW CENTERED ACROSS EASTERN
KANSAS/WESTERN MISSOURI. THIS LOOKS TO OCCUR AS THE SYSTEM CONTINUES
ITS MATURATION PROCESS AND BEGINS OCCLUDING ACROSS THE
MIDWEST...BECOMING MORE BAROTROPIC IN NATURE WITH TIME. AS THIS
OCCURS THROUGH FRIDAY MORNING...PRIMARY FORCING FROM ATTENDANT JET
DYNAMICS AS WELL AS ASCENT FROM ISENTROPIC PROCESSES SEEMS TO SHIFT
WELL EAST INTO THE OHIO VALLEY AND GREAT LAKES REGION.
THEREFORE...IT APPEARS PRECIPITATION PRODUCTION WILL BE HEAVILY
DEPENDENT ON FORCING WITHIN THE CORE OF THE UPPER LOW AS IT DEEPENS
OVERHEAD AND PV ANOMALY SLIDES ACROSS THE AREA. BY THIS
TIME...ATMOSPHERIC COLUMN SHOULD SATURATE SUFFICIENTLY AND BE
ADEQUATELY COLD TO ALLOW SNOW ACROSS ALL AREAS. GIVEN THE BULK OF
DYNAMICS WILL BE DISPLACED WELL EAST OF THE FORECAST BY THIS
TIME...NOT EXPECTING PERIODS OF HEAVY SNOW. HOWEVER...FAIRLY LONG
DURATION OF LIGHT TO OCCASIONALLY MODERATE SNOW MAY LEAD TO
ADDITIONAL ACCUMULATIONS ON THE ORDER OF 1-2 INCHES ACROSS AREAS
ALONG AND NORTH OF THE MISSOURI RIVER ON FRIDAY...WITH ISOLATED
HIGHER AMOUNTS. THIS COMBINED WITH ACCUMULATION FROM THURSDAY NIGHT
LOOKS TO LEND SUPPORT FOR A WHITE CHRISTMAS ACROSS MANY LOCATIONS.
AGAIN HIGHEST SNOW AMOUNTS LOOK TO FALL ACROSS NORTHERN PORTIONS OF
THE CWA...WITH FAR NORTHWEST MO/NORTHEAST KS LOOKING TO SEE THE
HIGHEST AMOUNTS AT THIS TIME.
WITH UPPER LOW STILL IN THE VICINITY BY SATURDAY...LIGHT SNOW OR
FLURRIES WILL REMAIN POSSIBLE UNTIL THE SYSTEM LIFTS SUFFICIENTLY
NORTHWARD BY SATURDAY NIGHT INTO SUNDAY MORNING. COLD AIR WILL
FILTER SOUTHWARD THROUGH THE END OF THE WEEK AND THE WEEKEND AND
HAVE BASICALLY KEPT TEMPERATURES BELOW THE FREEZING MARK THROUGH
THIS TIME FRAME. TEMPERATURES SHOULD EVEN FALL AS FAR AS THE SINGLE
DIGITS WHERE INFLUENCE OF SNOWPACK WILL BE MORE SUBSTANTIAL.
ENSEMBLE GUIDANCE SPREAD INCREASES MARKEDLY BY THE BEGINNING OF THE
WEEK AS MODELS TRY TO HANDLE THE NEXT SHORT WAVE TROUGH WITHIN
SOUTHERN STREAM. REMAINED CLOSE TO HPC GUIDANCE ALONG WITH THE GFS
ENSEMBLE MEAN THROUGH THE BEGINNING OF THE UPCOMING WORK WEEK TO
ACCOUNT WHICH KEEPS DRY AND COLD CONDITIONS IN PLACE.
DEROCHE
&&
.AVIATION...
FOR THE 06Z TAF CYCLE...A BAND OF SHOWERS WITH EMBEDDED THUNDER WILL
BE WORKING ITS WAY NORTHWARD OVERNIGHT. THUNDER MAY NOT REACH AS FAR
NORTH AS KSTJ AS INSTABILITY WILL BECOME SOMEWHAT LIMITED...BUT NOT
OUT OF THE QUESTION. FURTHER SOUTH...WILL HAVE A PERIOD OF THUNDER
EARLY THIS MORNING ASSOCIATED WITH THIS BAND OF RAIN OCCURRING AS AN
INITIAL SHORT WAVE LIFTS NORTH ACROSS THE REGION. IFR TO POSSIBLY
LIFR CIGS AND LIGHTER RAIN SHOULD REMAIN AFTER THAT HEAVIER RAIN
MOVES PAST AS MOISTURE CONTINUES TO BE PUMPED NORTHWARD ALONG AN
INVERTED SURFACE TROUGH SITTING ACROSS THE REGION.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
