Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 230440
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1140 PM CDT MON SEP 22 2014

.SHORT TERM...(TONIGHT)
ISSUED AT 240 PM CDT MON SEP 22 2014

WEAK SURFACE TROUGH SPARKED A BAND OF FAIR WEATHER CU ACROSS
CENTRAL. THESE WILL DIE OFF QUICKLY AROUND SUNSET. HIGH PRESSURE TO
THE SOUTH AND A LIGHT WIND FIELD SETS THE STAGE FOR SOME VALLEY FOG
IN THE RIVER VALLEYS.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 240 PM CDT MON SEP 22 2014

MODELS REMAIN IN VERY GOOD AGREEMENT WITH AMPLIFYING AN UPPER LEVEL
RIDGE ACROSS THE CENTRAL U.S. THIS WEEK. NAEFS 500 MB HEIGHT
ANOMALIES INTO THE WEEKEND AVERAGE +2-3 ACROSS THE NORTHERN PLAINS-
UPPER MISSISSIPPI RIVER VALLEY. MEANWHILE...850 MB TEMP ANOMALIES
HOVER FROM 0-1...NOT RECORD TERRITORY...BUT CERTAINLY SUGGEST ABOVE
NORMAL TEMPERATURES INTO THE WEEKEND. ALL IN ALL...LOOKS LIKE A
FABULOUS EARLY FALL WEEK/WEEKEND WITH WARM TEMPERATURES AND DRY
CONDITIONS.

THAT SAID...IT MAY NOT BE COMPLETELY DRY. YESTERDAY...MODELS WERE
MOVING A SHORTWAVE TROUGH FROM THE WEST COAST...ACROSS THE
NORTHERN/CENTRAL PLAINS TUE/WED. SOLUTIONS THEN SUGGESTED THIS BIT
OF UPPER LEVEL ENERGY WOULD SPLIT...WITH A PIECE MOVING INTO
NORTHERN MN AND SOUTHERN CANADA...AND THE SOUTHERN PIECE
RETROGRADING BACK TO THE WEST. THIS WOULD HAVE LEFT THE LOCAL
FORECAST AREA DRY.

LATEST MODEL RUNS TREND BACK TO A PREVIOUS ECMWF SOLUTION WHICH KEPT
THE SHORTWAVE TOGETHER...AND SPUN IT ACROSS THE REGION. LITTLE IF
ANY FRONTOGENETIC CONVERGENCE WITH THE FEATURE...BUT WEAK WARM AIR
ADVECTION AND MOISTURE TRANSPORT WOULD HELP FUEL SCATTERED RAIN
SHOWERS. MOST OF THIS WOULD HOLD WEST OF THE MISSISSIPPI RIVER. THE
STRONG RIDGE EVENTUALLY KILLS THE FEATURE AS IT TRIES TO WORK
FARTHER EAST...AND KICKS IT BACK WEST AS IT DIES OUT. HAVE HAD A DRY
FORECAST GOING FOR THE WED/WED NIGHT PORTION OF THE FORECAST...WITH
ONLY SMALL CHANCES IN THE FAR WEST TUE NIGHT. GOING TO HOLD THIS FOR
NOW. HOWEVER...SMALL CHANCES MAY HAVE TO BE EXPANDED EAST FOR
WED/WED NIGHT IF TRENDS CONTINUE TO SUGGEST THE SHORTWAVE WILL HOLD
TOGETHER AS IT MOVES IN.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1140 PM CDT MON SEP 22 2014

LOOKS LIKE ANOTHER NIGHT WITH FOG IN THE RIVER VALLEYS. ALREADY
SEEING SOME FOG FORMING IN THE MISSISSIPPI RIVER CHANNEL WITH KONA
DOWN TO 4SM AT 23.04Z. FAVORABLE CONDITIONS IN PLACE FOR A DENSE
FOG EVENT AT KLSE WITH A 3 DEGREE TEMP/DEW POINT SPREAD AT 04Z
WITH A LIGHT UP CHANNEL FLOW OUT OF THE SOUTHEAST. THE 23.00Z NAM
CONTINUES TO SHOW A DEEP LIGHT WIND PROFILE THROUGH THE NIGHT WITH
SATURATION OCCURRING AT THE SURFACE. WITH SOME FOG ALREADY
DEVELOPING IN THE MISSISSIPPI RIVER CHANNEL...MOVED THE TIMING OF
THE FOG DEVELOPMENT UP A LITTLE BIT FROM THE PREVIOUS
FORECAST...BUT NOT BY MUCH AS NO SIGNS OF A HAZE LAYER OVER THE
CITY YET. ONCE THE FOG BURNS OFF...SHOULD BE ANOTHER DAY WITH VFR
CONDITIONS AS THE SURFACE HIGH SLIDES OFF TO THE SOUTHEAST WITH
SOUTH WINDS AT 5 TO 10 KNOTS. UPPER LEVEL MOISTURE STARTS TO
INCREASE TUESDAY EVENING AND WILL PROBABLY SEE A HIGH VFR CEILING
AT BOTH SITES...BUT WITH A LACK OF SIGNIFICANT CHANGES TO THE KLSE
TAF DID NOT INCLUDE ANOTHER GROUP TO SHOW THIS OCCURRING.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...04


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