FXUS63 KEAX 260539
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1139 PM CST FRI DEC 25 2009
...UPDATED AVIATION DISCUSSION...
.UPDATE...
/930 PM CST FRI DEC 25 2009/
A QUICK CALL TO A FEW COUNTIES ACROSS THE FORECAST AREA HAS YIELDED
REPORTS OF VISIBILITIES AROUND ONE HALF MILE OR LESS IN MANY
AREAS...MAINLY OUTSIDE OF TOWNS AND CITIES WHERE FEW OBSTRUCTIONS TO
THE WIND EXIST. HAVE EXPANDED THE WINTER WEATHER ADVISORY FOR THE
OVERNIGHT HOURS SOUTHWARD TO INCLUDE ALL AREAS WHICH RECEIVED THE
HEAVIEST SNOWFALL. HAVE ALSO INCLUDED ANOTHER TIER OF COUNTIES
EASTWARD WHERE THE SNOW BANDS ARE MORE LIKELY TO IMPACT THROUGH THE
NIGHT. NEW SNOWFALL SO FAR THIS EVENING HAS BEEN LESS THAN ONE INCH.
INTENSITIES OVERNIGHT ARE NOT EXPECTED TO BE MUCH GREATER PER THE
WEAKENING TREND SEEN ON VARIOUS SATELLITE IMAGES. DECREASED EXPECTED
SNOW AMOUNTS TO AROUND 1 INCH FROM ABOUT KIRKSVILLE MISSOURI TO
PAOLA KANSAS...1 TO 2 INCHES WITH LOCALLY 3 POSSIBLE NORTHWEST OF
I-35.
NRR
&&
.DISCUSSION...
/300 PM CST FRI DEC 25 2009/
THE CHRISTMAS STORM OF 2009 CONTINUES TO CONSOLIDATE ITSELF THIS
AFTN...AS POLAR VORTEX TO THE NORTHWEST AND DEEP SOUTHWEST LOW IN A
FUJIWARA EFFECT BEGIN TO ROTATE AROUND EACH OTHER. THESE NEARLY TWO
WHOLLY DISTINCT IDENTITIES ARE EXPECTED TO REMAIN IN THEIR INDIVIDUAL
SHELLS UNTIL SATURDAY NIGHT WHEN THE UPR LOW BECOMES NEARLY
BAROTROPIC OVER THE WESTERN GREAT LAKES. THIS BEING SAID...THIS UPPER
LVL PEST WILL CONTINUE TO PRODUCE ADDITIONAL IMPACTS OVER MUCH OF
THE CWA WHICH WAS BLANKETED WITH 4-8 INCHES OF SNOWFALL CHRISTMAS
EVE.
FOR THIS AFTN AND TONIGHT...WV IMAGERY CONTINUES TO INDICATE
SEPARATE MOISTURE STREAMS ADVECTING INTO THIS UPR STORM. IN AN
IMPRESSIVE SHOW OF STRENGTH...PACIFIC MOISTURE STREAM CONTINUES TO
SURGE ALL THE WAY AROUND THE NORTHEAST STATES AND BACK SOUTHWEST
INTO THE MID-MISSOURI RIVER VALLEY. DESPITE CONTINUE ENTRAINMENT OF
DRY AIR INTO THIS SYSTEM...A NARROW CORRIDOR OF WARM MOIST AIR ALOFT
BETWEEN 850:700 CONTINUES TO PIVOT AROUND THIS SYSTEM...WITH
INCREASED LIFT ALONG THE NORTHERN EDGE OF THIS MOIST AXIS PROPAGATING
A WIDE CORRIDOR OF LIGHT SNOW FROM CENTRAL TO SOUTHEAST
NEBRASKA...ALONG WITH NE KANSAS AND NW MO. AS THE REMNANTS OF THE
SOUTHWEST LOW OVER NORTHERN IA SPIN SW THIS EVENING...THIS BAND IS
EXPECTED TO PIVOT OVER THE NORTHERN THIRD OF THE CWA. QPF AMOUNTS
SHOULD REMAIN LIGHT...BUT SEE THE POTENTIAL FOR AN ADDITIONAL 1-3
INCHES OF FLUFFY SNOW IN THE NORTHERN THIRD OF THE CWA. AT THE
SFC...RETROGRADING SFC LOW WILL BEGIN TO PIVOT ACROSS SW IOWA THIS
EVE AHEAD OF THE UPR RETROGRADING S/W. THIS FEATURE WILL MAKE
OVERNIGHT LOWS TRICKY AS INCREASED CLOUD COVER AND WARMER AIR WILL BE
PULLED AROUND THIS SYSTEM INTO NORTHERN MO AFTER MIDNIGHT. TO THE
SOUTH...SFC WINDS WILL REMAIN FAIRLY STRONG THROUGH AT LEAST 06Z AND
WILL LEAD TO ADDITIONAL BLOWING SNOW BEFORE SFC LOW BEGINS TO
DIMINISH.
THUS...AM PLANNING ON EXTENDING THE CURRENT WINTER WX ADVISORY
THROUGH 06Z FOR AREAS FROM KC SOUTHWARD WHERE PRESSURE GRADIENT WILL
BE STRONGEST THIS EVENING. FURTHER NORTH...WILL EXTEND THE WINTER
WX ADVISORY UNTIL 12Z TO ACCOUNT FOR LIGHT SNOWFALL ACCUMULATIONS
ALONG WITH BLOWING SNOW. ACROSS THE FAR SE...WILL ALLOW ADVISORY TO
EXPIRE AT 00Z AS LITTLE TO NO SNOW ACCUMULATED THU NIGHT AND BLOWING
SNOW SHOULD BE MINIMAL.
CONDITIONS ON SATURDAY WILL BE IMPROVED...ONLY SLIGHTLY. WITH
PRIMARY SOUTHWEST S/W NOW ABSORBED INTO THE OLD POLAR LOW...OUR
PRECIP WILL BECOME LESS ORGANIZED AND MORE CHAOTIC IN NATURE.
HOWEVER...STILL EXPECTING TO SEE A BAND OF RICH THETA-E AIR ROTATE
AROUND THIS SYSTEM AND THIS SHOULD BE ENOUGH TO PRODUCE ADDITIONAL
LIGHT SNOWFALL IN THE NORTHEASTERN 2/3 OF THE AREA. WITH THE SYSTEM
TO OUR NE BECOMING MORE BAROTROPIC IN NATURE...WE WILL BEGIN TO LOSE
SOME OF THE INTENSE SFC WAA ASSOCIATED WITH THE SFC LOW CURRENTLY.
WITH A LIGHTER WESTERLY WIND OVERHEAD...AND FACTORING IN SNOW
COVER...TEMPS MAY RISE INTO THE LOWER 20S.
FOR SAT NIGHT AND SUNDAY...NEARLY IDENTICAL CONDITIONS CAN BE
EXPECTED. A CONTINUED SLIGHT CHC TO CHC OF SNOW IN THE NE WITH
FLURRIES ELSEWHERE. TEMPERATURES WILL BE THE MOST TRICKY ASPECT OF
THE FCST. GIVEN THE MODIFIED AIRMASS OVER THE WESTERN CANADIAN
PROVINCES WHICH ACCOMPANIED THIS UPR SYSTEM...AND THE FACT THAT THE
PARENT LOW WILL CONTINUE TO SLIGHTLY MODIFY THIS AIRMASS EVEN
FURTHER TO OUR NORTH...SUNDAYS TEMPS MAY HOLD VERY SIMILAR TO
SATURDAY IF NOT A DEGREE OR TWO WARMER. REGARDING OVERNIGHT
LOWS...WHILE IN MOST CIRCUMSTANCES 6-8 INCHES OF SNOW COVER IN NW
FLOW WOULD SUGGEST NEAR ZERO TO BELOW ZERO TEMPS...THE VAST QUANTITY
OF CLOUD COVER...UNIFORM AIRMASS WITH NO REALLY DRY INTRUSION...AND
CONSISTENT LIGHT MIXY WIND MAY KEEP READINGS EVEN OVER THE SNOWPACK
IN THE UPR SINGLE DIGITS TO LOWER TEENS.
DUX
MEDIUM RANGE (MONDAY THROUGH FRIDAY)...
BY THE BEGINNING OF NEXT WORK WEEK...OUR HOLIDAY STORM SYSTEM WILL
HAVE SHIFTED WELL TO THE EAST AND WILL BE IN THE PROCESS OF
ABSORBING INTO THE POLAR VORTEX THAT WILL HAVE DEVELOPED ACROSS THE
HUDSON BAY. WITH THE WINTER SYSTEM EXITING THE PLAINS STATES...THIS
WILL LEAVE PLENTY OF ROOM FOR THE WEST CONUS RIDGE TO EXPAND EAST AS
IT BEGINS TO BREAK DOWN. UNFORTUNATELY...SURFACE TEMPERATURES WILL
NOT RESPOND MUCH TO THE SYNOPTIC LEVEL GAIN IN HEIGHTS AS A SPLIT
FLOW WILL BE PREVAILING ACROSS THE CENTRAL PLAINS MONDAY AND
TUESDAY... THUS LEAVING A COLD SURFACE HIGH TO SLOWLY OOZE SOUTH AND
EAST MONDAY AND TUESDAY. HAVE KEPT THE GOING TREND OF ONLY SLOWLY
ALLOWING TEMPERATURES TO RISE MONDAY THROUGH WEDNESDAY AS A RESULT.
GENERAL CONSENSUS AMONG THE MID-RANGE MODELS IS THAT AS THE RIDGE
BREAKS DOWN NEXT WEEK...ENOUGH ENERGY WILL MAKE IT ACROSS THE DESERT
SOUTHWEST TO HELP DEFINE A BROAD TROUGH ACROSS THE CENTRAL SECTIONS
OF THE CONUS. THIS WILL ALLOW A SHORTWAVE TO ZIP EAST ACROSS THE
NORTHERN PLAINS...DRAGGING A COLD FRONT ACROSS THE LOWER MISSOURI
RIVER VALLEY SOMETIME WEDNESDAY. CONFIDENCE IN AVAILABLE MOISTURE IS
STILL A LITTLE LOW...BUT THE PATTERN WOULD SUGGEST THAT SOME
PRECIPITATION MIGHT OCCUR NEXT TUESDAY NIGHT AND WEDNESDAY. HAVE
CONTINUED TO HEDGE IN THAT DIRECTION WITH SOME SILENT SLIGHT CHANCE
SNOW POPS...BUT WITH THE SPLIT FLOW PREVAILING THROUGH
MONDAY...THOUGHTS ARE THAT WE HAVE A MUCH BETTER CHANCE OF STAYING
DRY AS MOISTURE COULD BE SCARCE.
OTHERWISE...FOR THURSDAY...HAVE HEDGED TEMPERATURES BACK DOWN
TOWARDS THE COLD END OF THE VALUES OFFERED BY THE ENSEMBLE GUIDANCE.
POST FRONTAL COLD AIR ADVECTION SHOULD HAVE READINGS RANGING WELL
BELOW NORMAL.
CUTTER
&&
.AVIATION...
PERIODS OF LIGHT SNOW WILL CONTINUE THROUGH MUCH OF THE TAF CYCLE.
GUSTY SOUTHWESTERLY WINDS AT 15 TO 20 KTS OVERNIGHT WILL GRADUALLY
TURN BACK TO DUE WEST BY LATE MORNING. OCCASIONAL GUSTS WILL LIKELY
CONTINUE THROUGH THE DAY. WINDS WILL DECREASE FURTHER BY LATE
AFTERNOON. VSBY WILL LIKELY BE 2 TO 4 MILES IN SNOW AND BLOWING SNOW
OVERNIGHT. THAT MAY CONTINUE THROUGH THE DAY SATURDAY. EXPECT
IMPROVEMENT AS WINDS DECREASE. WILL HOLD ON TO MVFR CIGS THROUGH THE
TAF PERIOD.
NRR
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY UNTIL 6 AM CST SATURDAY FOR MOZ001>008-
011>017-020>024-028>031-037-038-043-044-053-054.
KS...WINTER WEATHER ADVISORY UNTIL 6 AM CST SATURDAY FOR KSZ025-057-
060-102>105.
&&
$$
