FXUS63 KARX 250938
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
314 AM CST FRI DEC 25 2009
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
COMPLICATED WINTER STORM WITH VARYING PRECIPITATION TYPES AFFECTING
THE AREA TODAY WILL BE THE MAIN TOPIC OF CONCERN.
CURRENT SURFACE MAP HAS 986MB LOW NEAR KIRK MO. MEANWHILE...WATER
VAPOR REVEALED TWO MID-LEVEL LOWS...ONE MOVING SOUTHEAST ACROSS THE
PANHANDLE OF NEBRASKA...AND THE OTHER OVER NORTHERN ARKANSAS. ALSO
NOTED ON WATER VAPOR WAS THE MASSIVE MOISTURE PLUME WRAPPING NORTH
AND NORTHWESTWARD INTO THE UPPER MIDWEST IN ADVANCE OF THE LOW/S.
REGIONAL RADAR MOSAIC/SURFACE OBS SHOWING MOSTLY RAIN NOW ACROSS THE
AREA NOW AS STRONG WARM AIR ADVECTION IS CURRENTLY NOSING IN.
TEMPERATURES ACROSS THE AREA CURRENTLY RANGING FROM 34 TO 38 DEGREES.
LATEST GFS/NAM/SREF ALL IN PRETTY GOOD AGREEMENT THROUGH THE SHORT
TERM.
FOR TODAY...WILL BE WATCHING THE LOW OVER NORTHERN MO THIS MORNING
BECOME VERTICALLY STACKED WITH MID-LEVEL LOW AS IT MOVES INTO
CENTRAL IA BY LATE THIS AFTERNOON. AXIS A BEST 850MB MOISTURE
TRANSPORT/WARM AIR ADVECTION INTO THE AREA WILL BE THIS MORNING IN
ADVANCE OF THE LOW. BY NOON AND THEREAFTER...DYNAMIC COOLING THROUGH
THE COLUMN WILL TAKE PLACE FROM SOUTH TO NORTH ACROSS THE AREA AS
THE VERTICALLY STACKED LOW APPROACHES. THIS IS EXPECTED TO
TRANSITION THE RAIN OR RAIN/SLEET MIXTURE ACROSS MOST OF THE AREA
TODAY...SLOWLY TO SNOW THROUGH THE AFTERNOON FROM SOUTH TO NORTH.
FURTHER WEST...WEST OF A KRST MN-KCCY IA LINE...THERE MAY BE ENOUGH
COLD AIR THROUGHOUT THE DAY TODAY FOR PERHAPS A SLUSHY 1-1.5 INCHES
OF SNOW. ANY ICE ACCUMULATION TODAY IS ALSO EXPECTED TO BE LIGHT AND
MAINLY FROM SLEET AS TEMPERATURES TODAY HOVER IN THE MID/UPPER 30S.
BASED ON ALL THIS...WILL BE DOWNGRADING ALL WINTER STORM WARNINGS TO
WINTER WEATHER ADVISORIES TODAY.
THE VERTICALLY STACKED LOW WILL MOVE OVER THE AREA TONIGHT AND THEN
REMAINED ANCHORED AND SLOWLY FILL THROUGH SUNDAY. POCKETS OF LIGHT
SNOW EXPECTED TO ROTATE AROUND THIS LOW...AFFECTING THE AREA WITH AN
OCCASIONAL DUSTING TO PERHAPS AN INCH OR SO THROUGH THE PERIOD.
OTHERWISE...DAYTIME TEMPERATURES WILL COOL FROM THE MID/UPPER 30S
TODAY INTO THE 20S THROUGH THE WEEKEND. OVERNIGHT LOWS WILL COOL
FROM THE UPPER TEENS LOWER 20S TONIGHT INTO THE LOWER AND MIDDLE
TEENS.
.LONG TERM...MONDAY THROUGH THURSDAY
24.12Z ECMWF/25.00Z GFS MODELS BOTH IN FAIRLY GOOD AGREEMENT THROUGH
THE PERIOD. BOTH SHOW A WEAK MID-LEVEL SHORTWAVE TROUGH DROPPING
SOUTHEAST THROUGH EASTERN MN/GREAT LAKES REGION ON MONDAY FOR A
CHANCE OF -SN. BY TUESDAY...BRIEF RIDGING OVERTAKES THE REGION FOR
A PERIOD OF RELATIVELY QUIET WEATHER. THIS WILL BE SHORT-LIVED
THOUGH AS BOTH GFS/ECMWF SHOWING A FAIRLY VIGOROUS MID-LEVEL/SURFACE
LOW SCOOTING ALONG THE U.S./CANADIAN BORDER WEDNESDAY. THIS WILL
BRING A COLD FRONT THROUGH THE AREA. MEANWHILE...THE ECMWF HAS A
SLIGHTLY STRONGER THAN THE GFS TROUGH MOVING THROUGH THE PLAINS.
THIS BRINGS A GOOD SURGE OF MOISTURE BACK INTO THE AREA FOR A CHANCE
OF -SN. BOTH THE GFS/ECMWF THEN WANT TO CARVE OUT A MID-LEVEL
TROUGH/CLOSED LOW RESPECTIVELY AND MOVE IT THROUGH THE UPPER MIDWEST
BY THURSDAY. FORCING/COLD CYCLONIC FLOW ALOFT ASSOCIATED WITH THIS
FEATURE MAY LEAD TO AREAS OF LIGHT SNOW/SCATTERED SNOW SHOWERS.
CURRENT EXTENDED FORECAST GRIDDED DATABASE LOOKS TO BE IN PRETTY
GOOD SHAPE WITH THESE GIVEN SCENARIOS AND THEREFORE NO CHANGES WERE
MADE AT THIS TIME.
&&
.AVIATION...
PRECIPITATION IS EXPECTED TO CONTINUE ACROSS THE REGION THROUGH
SATURDAY AS A LOW PRESSURE SYSTEM CURRENTLY OVER NORTHEAST MISSOURI
TRACKS TO THE NORTHWEST INTO IOWA ON FRIDAY. RAIN IS EXPECTED TO BE
THE PREDOMINANT PRECIPITATION TYPE AT BOTH RST/LSE THROUGH THE REST
OF THIS MORNING AS WARM LOW LEVEL AIR SHOULD KEEP TEMPERATURES WARM
ENOUGH TO KEEP THE PRECIPITATION IN LIQUID FORM. AS COLDER AIR
WRAPS INTO THE SYSTEM LATE THIS MORNING INTO THE
AFTERNOON...PRECIPITATION SHOULD CHANGE OVER TO SNOW BUT COVERAGE
MAY BE MORE SCATTERED THAN IT HAS BEEN OVER THE PAST FEW DAYS WITH
THIS STORM SYSTEM.
CEILINGS ARE EXPECTED TO REMAIN LOW INTO SATURDAY AS HIGH AMOUNTS
OF MOISTURE REMAIN IN THE LOW LEVELS OF THE ATMOSPHERE. SHOULD SEE
A DRY SLOT MOVING INTO THE REGION ON SATURDAY WHICH SHOULD HELP
IMPROVE CONDITIONS. WINDS WILL START TO VEER FROM THE EAST TO THE
SOUTHEAST AS THE LOW REACHES IOWA THIS AFTERNOON.
EXPECT MVFR TO IFR CONDITIONS TO PREVAIL THROUGH SATURDAY
MORNING...MAINLY DUE TO LOW CEILINGS BUT SOME LOW VISIBILITIES WILL
LIKELY OCCUR WITH ANY SNOW THAT FALLS THIS AFTERNOON AND OVERNIGHT.
&&
.HYDROLOGY...THROUGH TODAY
CLIMATE REPORTS OVERNIGHT REVEALED ONE HALF TO ONE INCH OF RAIN OR
LIQUID EQUIVALENT ACROSS PORTIONS OF THE AREA YESTERDAY. WITH
ANOTHER SLUG OF A QUARTER TO ONE HALF INCH EXPECTED TO FALL
TODAY...THERE REMAINS THE CONCERN FOR SOME RUNOFF AND RIVER RISES.
ANY INCREASE IN RUNOFF INTO THE STREAMS AND RIVERS MAY CAUSE SOME
ICE TO BREAK UP AND POSSIBLY CAUSE ICE JAMS AND LOCALIZED FLOODING.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR WIZ017-
WIZ029-WIZ032-WIZ033-WIZ034-WIZ041-WIZ042-WIZ043-WIZ044-
WIZ053-WIZ054-WIZ055-WIZ061.
MN...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR MNZ079-
MNZ086-MNZ087-MNZ088-MNZ094-MNZ095-MNZ096.
IA...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR
IAZ008-IAZ009-IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030.
&&
$$
SHORT/LONG TERM...DAS
AVIATION..........HALBACH
