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000
FXUS63 KARX 300923
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
323 AM CST SAT NOV 30 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 323 AM CST SAT NOV 30 2013

A WARMER DAY IS ON TAP FOR THE REGION AS A WEAK TROUGH/COLD FRONT
MOVES THROUGH LATER IN THE DAY.

CURRENTLY...A TIGHT PRESSURE GRADIENT AT THE SURFACE HAS LED TO
WINDS STAYING UP FOR MUCH OF THE NIGHT. THE MIXING PROVIDED BY
THESE WINDS AND MID TO UPPER LEVEL CLOUD COVER HAS ALLOWED FOR
TEMPERATURES TO TAKE LONGER TO DROP. WARMER 850MB AIR WILL GET
ADVECTED INTO THE REGION FROM THE WEST ALONG A WEAK COLD FRONT
THAT IS CURRENTLY IN THE EASTERN DAKOTAS. WITH THIS FRONT NOT
COMING THROUGH UNTIL LATER IN THE DAY AND SKIES BEING SUNNY FOR A
PORTION OF THE DAY...EXPECT THAT TEMPERATURES WILL CLIMB TOWARD
40F. COOLER AIR WILL MOVE IN FOR TONIGHT WITH TEMPERATURES AGAIN
DROPPING DOWN INTO THE LOW 20S.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 323 AM CST SAT NOV 30 2013

MUCH OF THE FOCUS WITH THIS FORECAST PACKAGE IS WITH THE
PRECIPITATION CHANCES AND DIFFERENCES IN THE MODELS THROUGH THE
UPCOMING WEEK.

THE FIRST WEAK MID LEVEL TROUGH/WARM AIR ADVECTION COMES IN FROM
THE WEST ON SUNDAY NIGHT. DUE TO THE WEAK FORCING AND LACK OF
MOISTURE...MOST OF THE 30.00Z GUIDANCE DOES NOT PRODUCE MUCH/IF
ANY PRECIPITATION. THE 30.00Z NAM IS THE DEEPEST WITH THE
MOISTURE/LIFT AND IS THE ONLY MODEL THAT WOULD PRODUCE SOME LIGHT
SNOW. HAVE KEPT SOME SMALL CHANCES FOR LIGHT SNOW TO ACCOUNT FOR
THIS NAM SOLUTION.

THE MAIN CHANCES FOR ANY PRECIPITATION FOR THE REST OF MONDAY INTO
TUESDAY WILL COME THROUGH THE WARM AIR ADVECTION BAND WHICH LOOKS
LIKE IT WILL MAINLY BE IN CENTRAL MINNESOTA TO NORTHERN WISCONSIN.
WITH MID LEVEL RIDGING OVERHEAD...THE LIFT JUST IS NOT THAT DEEP
SO CONFIDENCE IS NOT VERY HIGH WITH THE PRECIPITATION CHANCES THAT
ARE OUT THERE. THE THERMAL PROFILE IS ALSO WARMING OVER THIS TIME
FRAME AS WELL...SO THERE ARE QUESTIONS ABOUT WHETHER THE
PRECIPITATION WILL MAINLY FALL AS SNOW OR RAIN. IT MAINLY LOOKS
LIKE IT WOULD BE SNOW VIA 30.00Z NAM GUIDANCE...BUT THE 30.00Z GFS
THERMAL PROFILES SHOW A SUBSTANTIAL WARM LAYER THAT WOULD MAKE IT
FALL ALL AS RAIN. HOWEVER...FROM TUESDAY ON OUT...WPC HAS MARKED
THE 30.00Z RUN AS AN OUTLIER AND IS FAVORING THE 30.00Z
ECMWF/UKMET SOLUTION.

IF THE 30.00Z ECMWF AND UKMET ARE THE FAVORED SOLUTIONS...THEN THE
HIGHEST PRECIPITATION CHANCES WILL COME ON WEDNESDAY AS THE MAIN
TROUGH AND SURFACE LOW/FRONT APPROACH FROM THE WEST. THE 30.00Z
ECMWF IS MUCH DEEPER WITH THIS SURFACE LOW THAT TRACKS THROUGH
NORTHERN MINNESOTA AND ALSO SHOWS SOME STRONGER COLD AIR ADVECTION
IN BEHIND IT FOR THE LATER PORTION OF THE WEEK. TEMPERATURES MAY
BE WARMER THAN CURRENTLY ADVERTISED ON WEDNESDAY IF THE ECMWF IS
CORRECT. MOST OF THIS PRECIPITATION ON WEDNESDAY IS GOING TO FALL
AS RAIN WITH THE COLD FRONT MARKING THE END OF THE RAIN EARLY ON
THURSDAY.

THE SIGNAL THAT IS CONSISTENT IN THE LONG RANGE IS WITH THE MAJOR
TEMPERATURE PLUNGE THAT WE WILL SEE GOING INTO NEXT WEEKEND.
30.00Z ECMWF 850MB TEMPERATURE ANOMALIES ARE IN THE -2 TO -3 RANGE
WHICH IS INDICATIVE OF A RECORD COLD AIR MASS. THE MAIN LIMITING
FACTOR IN HOW FAR TEMPERATURES DROP IS WITH SNOW COVER...WHICH IS
LACKING AT THE MOMENT. WHILE SOME SNOW COULD FALL OVER THE EARLY
PORTION OF NEXT WEEK...THE WARM SECTOR ON WEDNESDAY WILL LIKELY
WIPE OUT ANYTHING THAT FALLS EARLIER IN THE WEEK. REGARDLESS...WE
ARE LOOKING AT ANOTHER PERIOD OF COLD AIR MOVING IN BY LATE THIS
WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY EVENING)
ISSUED AT 1145 PM CST FRI NOV 29 2013

MAIN AVIATION CONCERN IS FOR INCREASING LOW LEVEL WINDS AND THE
LIKELIHOOD OF LLWS AT BOTH KRST/KLSE. WINDS AT 2 KFT ARE EXPECTED TO
INCREASE INTO THE 40-50 KT RANGE THIS EVENING...WITH KARX VWP
ALREADY INDICATING 30 KTS AT 2 KFT AND 40 KTS AT 3 KFT AT 03Z. THE
LOW LEVEL JET SHOULD PERSIST TIL 09-12Z TIME FRAME. SFC PRESSURE
GRADIENT STAYS UP...AND WITHOUT MUCH DECOUPLING...CLOSE TO 10 KTS
ARE EXPECTED THROUGH THE OVERNIGHT. WILL CONTINUE MENTION IN THE
TAFS.

4-5KFT CLOUD DECK HAS SHIFTED OVER PARTS OF EASTERN MN INTO
NORTHWEST WI...WITH SOME EXTENSION SOUTHWARD. HOWEVER...THERE HAS
BEEN LITTLE/IF ANY LOWERING TO THE CLOUD DECK...STAYING VFR. THE
CLOUDS APPEAR TO BE ASSOCIATED WITH THE NOSE OF 850 MB MOISTURE
TRANSPORT AND SOME LOW LEVEL ISENTROPIC UPGLIDE. RAP/NAM FAVOR
SOME INCREASE IN THE LOW LEVEL MOISTURE...BUT ALSO SOME LOW LEVEL
WARMING. THIS COULD EFFECTIVELY PREVENT SATURATION FROM
DEEPENING/WORKING FARTHER SOUTH. WILL SIDE WITH KEEPING THE BULK
OF ANY LOWER CLOUDS TO THE NORTH FOR NOW.

FRONT SLATED TO SLIP ACROSS THE TAF SITES TOWARD 00Z SUN...SHIFTING
THE WINDS TO NORTH/NORTHWEST. NAM HINTS AT SOME LOWER MVFR CIGS
MOVING IN POST FRONT...THE GFS IS NOT AS AGGRESSIVE. GOING TO
STAY WITH VFR FOR NOW...BUT TRENDS BEAR WATCHING.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

$$

SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION.....RIECK