FXUS63 KSGF 241802
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1202 PM CST THU DEC 24 2009

...UPDATE TO PUBLIC AND AVIATION...

.UPDATE...

HAVE STARTED THE WINTER STORM WARNING ALONG AND WEST OF THE
HIGHWAY 71 CORRIDOR AT 18Z. THE 17Z MESOSCALE ANALYSIS INDICATES
THE FREEZING LINE LOCATED FROM IOLA TO INDEPENDENCE KANSAS. THE
PRESSURE FALLS WE SAW EARLIER THIS MORNING ACROSS EASTERN KANSAS
DUE TO DEEPENING LOW PRESSURE OVER THE ARKLATEX HAVE BEEN REPLACED
BY WEAK PRESSURE RISES. MEANWHILE...STRONG COLD AIR ADVECTION
CONTINUES ACROSS EASTERN KANSAS AND WESTERN MISSOURI AS NORTH TO
NORTHWEST WINDS CONTINUE TO INCREASE WITH THE DEEPENING SURFACE
LOW. THE FREEZING LINE WILL THEREFORE CONTINUE TO PROGRESS
EASTWARD EARLY THIS AFTERNOON INTO THE HIGHWAY 71 CORRIDOR.

ABOVE THIS SHALLOW COLD LAYER...WEAK WARM ADVECTION CONTINUES WITH
AN EASTERLY FETCH NOTED AROUND 850 MB. THIS TREND WILL CONTINUE
THROUGH THE EARLY AFTERNOON. BY LATE THIS AFTERNOON...RAPIDLY
INCREASING AND DEEPENING FRONTOGENESIS WILL BEGIN TO ELIMINATE THE
WARM NOSE AS THAT SURFACE LOW AND ATTENDANT UPPER LEVEL LOW BEGIN
TO PULL NORTH TOWARDS THE OZARKS.

MEANWHILE...SYNOPTIC SCALE LIFT WILL QUICKLY INCREASE ACROSS
SOUTHEAST KANSAS AND WESTERN MISSOURI EARLY THIS AFTERNOON. THE
STRONG FRONTOGENETIC ZONE COMBINED WITH A SLUG OF MID AND UPPER
LEVEL UPWARD OMEGA WILL SET THE STAGE FOR INCREASING PRECIPITATION
COVERAGE AND INTENSITY.

WITH ALL THAT SAID...EXPECT A PERIOD OF FREEZING RAIN WITH PERHAPS
SOME SLEET THIS AFTERNOON ALONG AND WEST OF HIGHWAY 71. MAY SEE A
TENTH OF AN INCH OF GLAZING...WITH LOCALLY HIGHER AMOUNTS
POSSIBLE. PRECIPITATION OVER THIS REGION SHOULD THEN RAPIDLY
CHANGE TO SNOW BY EARLY THIS EVENING.

THE FORECAST APPEARS TO BE MAINLY ON TRACK ACROSS THE REST OF THE
OZARKS. WE WILL BE CLOSELY MONITORING THE PROGRESS OF A MATURING
TROWAL ACROSS THE CENTRAL AND SOUTHERN PLAINS. WE MAY NEED TO BUMP
UP SNOW AMOUNTS ACROSS PORTIONS OF WESTERN MISSOURI OR EXTREME
SOUTHEAST KANSAS ONCE WE GET A BETTER HANDLE ON THIS FEATURE.

ONE OTHER CAVEAT TO THROW OUT THERE IS THAT WIND ADVISORY CRITERIA
(SUSTAINED WINDS OF 30 MPH OR GREATER AND/OR GUSTS OF 45 MPH OR
GREATER) IS EXPECTED OVER MUCH OF SOUTHEAST KANSAS AND WESTERN
MISSOURI. THIS FACET OF THE STORM SYSTEM WILL BE COVERED IN THE
WINTER STORM WARNING.

SCHAUMANN

&&

.DISCUSSION...

FORECAST CHALLENGES CONTINUE TO DEAL WITH HEAVY RAINS/FLASH FLOOD
POTENTIAL TODAY...FOLLOWED BY WINTER WEATHER CONDITIONS THIS
EVENING AND TEMPERATURES THROUGH THE WEEKEND.

CURRENTLY...SURFACE COLD FRONT KNOCKING ON THE DOOR...CURRENTLY
EXTENDING FROM A SURFACE LOW OVER NORTHWEST MISSOURI...EXTENDING
SOUTHWEST TO A SECOND SURFACE LOW LOCATED IN EASTERN OKLAHOMA
THIS MORNING. UPPER SHORTWAVE CURRENTLY OVER SOUTHWEST
TEXAS...MOVING SLOWLY TO THE NORTHEAST. TO OUR SOUTH AND
EAST...SIGNIFICANT GULF MOISTURE CONTINUES TO PUMP NORTH WITH
WIDESPREAD MODERATE RAINS OVER MUCH OF ARKANSAS...MOVING INTO
SOUTHEASTERN MISSOURI THIS MORNING. WILL CONTINUE THE FLASH FLOOD
WATCH FOR OUR SOUTHEASTERN COUNTIES TO ACCOUNT FOR THIS
SIGNIFICANT RAINFALL HEADING THAT WAY.

FOR TODAY...SOME MODELS DIFFERENCES IN REFERENCE TO THE MOVEMENT
OF THE SYSTEM OVER TEXAS. WRF MOVES THE SYSTEM FURTHER EAST WITH
HEAVIER SNOWS MOVING INTO OUR EASTERN COUNTIES...AS WELL AS NORTHEASTERN
MISSOURI AND SOUTHERN ILLINOIS. GFS...WHICH HAS BEEN MORE
CONSISTENT OVER THE PAST FEW DAYS...KEEPS SYSTEM FURTHER WEST. THE
NEW ECMWF ALSO SUPPORTS THIS SOLUTION FURTHER WEST...SO HAVE
TRENDED FORECAST MORE IN LINE WITH THE GFS TODAY. GFS BRINGS THE
SOUTHERN LOW INTO SOUTH CENTRAL MISSOURI THIS AFTERNOON...WITH
COLDER AIR WRAPPING INTO THE LOW FROM THE NORTHWEST BY MID
AFTERNOON. 850MB TEMPERATURES FALL QUITE RAPIDLY THIS
AFTERNOON...FALLING FROM +6C THIS MORNING TO -8C BY EARLY
EVENING ACROSS SOUTHWEST MISSOURI AND SOUTHEAST KANSAS...A 25
DEGREE F DROP IN LOW LEVEL TEMPERATURES FOR OUR WESTERN COUNTIES.
SIGNIFICANT UPGLIDE SEEN ON ISENTROPIC SURFACES ACROSS WESTERN
MISSOURI IN THE TROWAL FEATURE THAT SETS UP BEHIND THE LOW. THERE
IS GOING TO BE A BRIEF WINDOW...SAY FROM 00Z THIS AFTERNOON TO
MAYBE 12Z CHRISTMAS DAY...WHERE WE BELIEVE THERE IS GOING TO BE
SUBSTANTIAL SNOWFALL ACROSS OUR WESTERN HALF OF THE CWA. WITH
850MB TEMPERATURES RAPIDLY FALLING THROUGH THE EVENING AS 850MB
TEMPERATURES FALL TO -13C BY 12Z FRIDAY. SURFACE WINDS WILL BE
QUITE GUSTY AS WELL FROM THE NORTHWEST AS WE SEE A 25MB PRESSURE
GRADIENT SETTING UP FROM THE SURFACE LOW CENTER OUT TO WICHITA
KANSAS. THESE STRONG WINDS...COMBINED WITH SNOW ACCUMULATIONS OF 4
TO 8 INCHES POSSIBLE...LED US TO ISSUE A WINTER STORM WARNING FOR
COUNTIES WEST OF A LINE FROM CASSVILLE TO SPRINGFIELD TO
VERSAILLES FOR THIS EVENING THROUGH FRIDAY AFTERNOON. SNOW SHOULD
RAPIDLY DECREASE DURING THE MORNING HOURS CHRISTMAS DAY...BUT WITH
THE GUSTY NORTHWEST WINDS CONTINUING...DECIDED TO ERR ON THE SIDE
OF SAFETY AND KEEP THE WARNING GOING THROUGH THE AFTERNOON HOURS
AS BLOWING AND DRIFTING SNOW WILL BE COMMON. FURTHER
EAST...DECIDED TO GO WITH A WINTER WEATHER ADVISORY AS THESE AREAS
WILL SEE A LESSER AMOUNT OF SNOW FALL AS THE SYSTEM PULLS TO THE
NORTHEAST AND COLDER AIR WILL BE DELAYED SOME THIS EVENING. DAY
SHIFT MAY NEED TO ADD A FEW MORE COUNTIES TO THE WARNING SHOULD
THE TROWAL SHIFT FURTHER EAST AS THE WRF SUGGESTS.

BY FRIDAY AFTERNOON...MAJORITY OF PRECIPITATION SHOULD SHIFT TO
THE NORTH AS THE LOW CONTINUES TO MOVE INTO IOWA. COLD AIR WILL
STILL BE IN PLACE ALONG WITH GUSTY NORTHWEST WINDS OVERNIGHT INTO
SATURDAY. TEMPERATURES ARE GOING TO BE VERY COLD AND HAVE UNDERCUT
GUIDANCE ON TEMPERATURES FOR BOTH SATURDAY MORNING AND AFTERNOON.

COLD AIR TO STAY IN PLACE THROUGH THE WEEKEND WITH 850MB
TEMPERATURES STAYING IN THE NEGATIVE DOUBLE DIGITS. A STRATUS DECK
SHOULD REMAIN IN PLACE AS WELL IN THE CYCLONIC NORTHWESTERLY FLOW
TO LIMIT ANY SUNSHINE...SO CONTINUED UNDERCUTTING GUIDANCE ON
TEMPERATURES THROUGH THE WEEKEND. THE WAY IT LOOKS...WE SHOULD
CONTINUE TO SEE BELOW NORMAL TEMPERATURES IN THE NORTHWEST FLOW
UNTIL AT LEAST TUESDAY...WHEN WINDS SHIFT TO A MORE WESTERLY DIRECTION.

CLAYCOMB

&&

.AVIATION...

RAIN AND DRIZZLE WILL PERSIST ACROSS SOUTHWEST MISSOURI EARLY THIS
AFTERNOON WITH MAINLY IFR CONDITIONS EXPECTED. A TRANSITION TO
FREEZING RAIN IS THEN EXPECTED AT KJLN AROUND MID AFTERNOON. THERE
MAY THEN BE A BRIEF PERIOD OF SLEET BEFORE A CHANGE OVER TO ALL
SNOW EARLY THIS EVENING. A TRANSITION TO SNOW IS EXPECTED THIS
EVENING AT KSGF AND KBBG. THERE COULD BE A BRIEF PERIOD OF
FREEZING RAIN OR SLEET AT THESE TERMINALS. MODERATE TO
OCCASIONALLY HEAVY SNOW IS THEN EXPECTED AT ALL TERMINALS BY LATE
THIS EVENING INTO THE OVERNIGHT. WITH STRONG AND GUSTY NORTHWEST
WINDS...LIFR CONDITIONS WILL PREVAIL. THE SNOW WILL SLOWLY LIGHTEN
UP LATE TONIGHT AND FRIDAY MORNING...WITH FLIGHT CONDITIONS SLOWLY
IMPROVING. HOWEVER...STRONG AND GUSTY WEST TO NORTHWEST WINDS WILL
CONTINUE...SO MVFR CONDITIONS WILL PERSIST THROUGH AT LEAST THE
LATE MORNING.

SCHAUMANN

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 6 PM CST 
     FRIDAY FOR MOZ057-058-070-071-081>083-091-092-096>098-
     104>106.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST FRIDAY 
     FOR MOZ055-056-067>069-078>080-089-090-094-095-102-103.

     WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR MOZ066-077-088-
     093-101.

KS...WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR KSZ073-097-101.

&&

$$