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000
FXUS63 KARX 292342
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
540 PM CST FRI NOV 29 2013

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 328 PM CST FRI NOV 29 2013

AT 3 PM...A STRONG SHORT WAVE WAS LOCATED OVER LAKE WINNIPEG. THE
29.12Z MODELS CONTINUE TO SHOW THAT THIS SYSTEM WILL MOVE
SOUTHEAST ACROSS SOUTHERN ONTARIO TONIGHT AND SATURDAY. THERE IS
WEAK TO MODERATE 285 TO 295K ISENTROPIC LIFT AHEAD OF THIS WAVE.
HOWEVER MUCH OF THIS LIFT IS GOING INTO GENERATING CLOUDS THAN
PRECIPITATION. THE NAM/WRF BUFKIT SOUNDINGS ARE CURRENTLY OVERDOING
THE MOISTURE BELOW 800 MB...SO LOOKED MORE AT THE GFS SOUNDINGS.
THESE SOUNDINGS SHOW A VERY SHALLOW MOISTURE LAYER BETWEEN 800 AND
850 MB. AS A RESULT...IT IS GOING TO BE VERY HARD TO GENERATE ANY
PRECIPITATION IN NORTHERN CLARK AND TAYLOR COUNTIES TONIGHT. AS A
RESULT...TOOK OUT THE MENTION OF PRECIPITATION TONIGHT.

THE WEAK TO MODERATE WARM AIR ADVECTION GRADUALLY INCREASES THIS
EVENING. AS A RESULT...EXPECT THAT THE TEMPERATURES WILL LIKELY
SLOWLY FALL EARLY THIS EVENING...THEN STABILIZE AND MAYBE RISE A
FEW DEGREES LATE THIS EVENING AND OVERNIGHT.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 328 PM CST FRI NOV 29 2013

FROM SUNDAY NIGHT INTO MONDAY...THERE CONTINUE TO BE SOME
QUESTIONS ON WHETHER LIGHT SNOW WILL DEVELOP ACROSS THE AREA.
THE GFS HAS A WEAK 925-700 MB LOW LOCATED OVER THE DAKOTAS AS A
RESULT ITS FRONTOGENESIS AND WARM AIR ADVECTION REMAINS WELL WEST
AND NORTH OF THE FORECAST AREA...THEREFORE...IT CONTINUES IN
IMPLY THAT MUCH OF THE FORECAST AREA WILL REMAIN DRY. ONLY 3 OF 12
GFS 29.12Z GFS ENSEMBLE MEMBERS HAVE PRECIPITATION IN OUR AREA.
MEANWHILE THE NAM/WRF...GEM...AND ECMWF HAVE THE WEAK SURFACE LOW
LOCATED OVER SOUTHWEST MINNESOTA WHICH ALLOWS FOR MORE WARM AIR
ADVECTION ACROSS THE AREA AND LIGHT SNOW ACROSS THE AREA. SINCE
THE MODELS CONTINUE TO STRUGGLE WITH THIS PERIOD KEPT THE
PRECIPITATION CHANCES IN THE 20 TO 40 PERCENT RANGE.

FROM TUESDAY INTO THURSDAY...THE MODELS CONTINUE TO STRUGGLE WITH
THE EVOLUTION OF A LONG WAVE TROUGH OVER THE WESTERN UNITED
STATES. THE MODELS SHOW THAT A COUPLE SHORT WAVE TROUGHS WILL BE
EJECTED OUT OF THE LONG WAVE TROUGH DURING THE TIME PERIOD. THE
FIRST ONE COMES OUT ON TUESDAY FOLLOWED BY A MUCH STRONGER ONE FOR
WEDNESDAY AND WEDNESDAY NIGHT. EXPECT SOME LIGHT SNOW WITH THE
FIRST WAVE. WITH THE MODELS BECOMING A BIT MORE CONSISTENT OVER
THE PAST 24 HOURS...THERE IS SLIGHTLY MORE CONFIDENCE THAT THERE
WILL BE MIXED PRECIPITATION WITH THE SECOND WAVE. THE
PRECIPITATION WOULD LIKELY START OFF AS SNOW...THEN TRANSITION
OVER RAIN...AND THEN BACK TO SNOW AS A COLD FRONT MOVES THROUGH
THE REGION. WITH THIS SCENARIO...THERE WOULD BE LITTLE SNOW
ACCUMULATIONS ACROSS THE AREA. HOWEVER IF THIS SYSTEM HAPPENS TO
TRACK A BIT FURTHER EAST LIKE THE GEM...WE WOULD SEE GREATER SNOW
ACCUMULATIONS. WITH A BIT MORE CONFIDENCE IN THE TIME PERIOD...THE
PRECIPITATION CHANCES WERE RAISED SOME MORE.

IN THE WAKE OF THIS SYSTEM...THE DETERMINISTIC GFS AND ECMWF BRING
VERY COLD AIR INTO THE REGION FOR FRIDAY AND SATURDAY. HIGH
TEMPERATURES MAY STRUGGLE TO GET OUT OF THE SINGLE DIGITS.
HOWEVER 9 OF THE 12 GFS ENSEMBLE MEMBERS ARE NOT AS COLD AS THE
OPERATIONAL GFS AND ECMWF MODELS. THEY SHOW THAT THE WAVE ON
WEDNESDAY AND WEDNESDAY IS MUCH WEAKER...THUS...THE REALLY COLD
AIR REMAINS OVER THE DAKOTAS AND MONTANA. DUE TO THIS...JUST
STAYED CLOSE TO THE MODEL CONSENSUS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 540 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...PERSISTING TIL 09-
12Z TIME FRAME. SFC PRESSURE GRADIENT STAYS UP...AND WITHOUT MUCH
DECOUPLING INDICATED VIA BUFKIT SOUNDINGS...CLOSE TO 10 KTS ARE
EXPECTED FOR MUCH OF THE NIGHTTIME HOURS. STILL...THE NEAR SFC JET
WILL RESULT IN A LLWS THREAT...AND WILL CONTINUE MENTION IN THE
TAFS.

4-5KFT CLOUD DECK HAS DEVELOPED OVER CENTRAL MN PER LATEST
FOG/STRATUS SATELLITE IMAGERY AND SFC OBS. ITS LOOKS ASSOCIATED WITH
THE NOSE OF 850 MB MOISTURE TRANSPORT AND SOME LOW LEVEL ISENTROPIC
UPGLIDE. QUESTION IS WHETHER THESE WILL EXPAND SOUTHWARD TOWARD THE
TAF SITES...AND LOWER INTO THE MVFR CATEGORY. RAP/NAM FAVOR SOME
INCREASE IN THE LOW LEVEL MOISTURE...BUT ALSO SOME LOW LEVEL
WARMING. THIS COULD EFFECTIVELY PREVENT SATURATION...AND THUS CLOUD
DEVELOPMENT WITH THE LOW LEVEL MOISTURE. WILL SIDE WITH KEEPING ANY
LOWER CLOUD SHIELD TO THE NORTH FOR NOW.

&&

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

$$

SHORT TERM...BOYNE
LONG TERM....BOYNE
AVIATION.....RIECK