Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 271138
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
638 AM CDT SAT SEP 27 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 230 AM CDT SAT SEP 27 2014

THE RETROGRADED CUTOFF LOW IS MEANDERING OVER IA EARLY THIS
MORNING...AND IS SPARKING A FEW SHOWERS/STORMS ACROSS SOUTHERN IA.
MODELS FAVOR DRIFTING THE LOW TO THE MN/IA TODAY BEFORE KILLING IT
OFF UNDER THE INFLUENCE OF THE UPPER LEVEL RIDGE. THE GFS AND NAM
DEVELOP AROUND 1K J/KG OF MAKEUP THIS AFTERNOON...RIGHT UNDER THE
LOW. NO BOUNDARY TO FOCUS PCPN CHANCES...SO MOST CONVECTIVE
POTENTIAL WILL HAVE TO REST ON THE INSTABILITY/UPPER LOW
INTERACTION. SOME OF THE MESO MODELS DEVELOP SPOTTY SHOWERS LATER
THIS AFTERNOON...MOSTLY WEST OF THE LOCAL AREA. SEEMS REASONABLE
GIVEN THE POSSIBLE LIFT AND ENVIRONMENT. WILL ADD SMALL CHANCES TO
FAR WEST - SOUTHEAST MN AND NORTHEAST IA.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 230 AM CDT SAT SEP 27 2014

MODELS IN GOOD AGREEMENT WITH DROPPING AN UPPER LEVEL SHORTWAVE
TROUGH ACROSS THE RIDGE AXIS SUN NIGHT-MON NIGHT. TRACK WOULD TAKE
THE SHORTWAVE ACROSS NORTHERN PORTIONS OF THE REGION...INTO THE
EASTERN GREAT LAKES. THE BULK OF THE UPPER LEVEL FORCING AND QG
CONVERGENCE HOLDS NORTH/EAST OF THE FORECAST AREA AS A RESULT.
HOWEVER...SOME LOW LEVEL FRONTOGENETIC LIFT INDICATED WITH THE
SYSTEM/S ACCOMPANYING SFC BOUNDARY...WHICH STRETCHES WEST-EAST AS IT
MOVES AHEAD OF THE SHORTWAVE. MOST OF THE LOW LEVEL MOISTURE RETURN
IS FOCUSED ACROSS THE PLAIN STATES...BUT SOME WEAK INSTABILITY DOES
BUILD AHEAD OF SYSTEM SUN/MON. THE DEEPER SATURATION SITS WELL TO
THE NORTH WITH THE UPPER LEVEL SHORTWAVE. ALL SAID...PROBABLY ENOUGH
LIFT AROUND THE BOUNDARY THAT A FEW SHOWERS COULD SPARK ALONG THE
WESTERN FLANKS OF FRONT...IN THE I-94 CORRIDOR NORTH AND EAST.

NEXT BEST CHANCE FOR RAIN WILL LIKELY HAVE TO WAIT UNTIL LATER IN
THE WORK WEEK. A CUTOFF 500 MB WEST COAST LOW IS EXPECTED TO GET
CAUGHT BACK INTO THE MEAN FLOW...LIFTING NORTHEAST ACROSS THE
NORTHERN PLAINS TUE NIGHT AND SHIFTING INTO SOUTHERN CANADA BY 00Z
THU. WHILE MUCH OF ITS UPPER LEVEL ENERGY WILL MISS THE LOCAL
AREA...IT WILL DRAG ITS NORTH-SOUTH RUNNING SFC FRONT ACROSS THE
REGION. THIS BOUNDARY LOOKS TO SIT ACROSS THE AREA THROUGH
THU...ALLOWING FOR OTHER BITS OF UPPER LEVEL ENERGY TO WORK ON IT.
SOME LOW LEVEL MOISTURE RETURN INTO THE FRONT. WEAK INSTABILITY DOES
WORK NORTHWARD AHEAD OF THE FRONT...AND COULD HELP SPARK A
THUNDERSTORM OR TWO. TIMING OF THE SYSTEM WOULD START TO BRING A
SHOWER THREAT WEST OF THE MISSISSIPPI RIVER OVERNIGHT TUE...WITH
SHOWER CHANCES BECOMING MORE WIDESPREAD WED-THU.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 638 AM CDT SAT SEP 27 2014

UPPER LEVEL LOW CENTERED OVER IA WILL IMPACT THE KLSE/KRST WITH
SOME VFR CLOUDS. ISOLATED THUNDERSTORMS ARE POSSIBLE ACROSS
PORTIONS OF NORTHEAST IA AND SOUTHEAST MN BY THIS AFTERNOON WITH
DAYTIME HEATING AND INCREASING INSTABILITY UNDER THE UPPER LOW.
RIGHT NOW...IT APPEARS THAT THIS CONVECTION WILL REMAIN WEST AND
OUTSIDE THE VICINITY OF KRST...BUT WILL HAVE TO BE WATCHED CLOSELY
AS THE DAY WEARS ON. WITH CLEARING SKIES TONIGHT...COULD SEE SOME
RIVER VALLEY FOG AT KLSE TOWARD SUNDAY MORNING...BUT MODEL
SOUNDINGS APPEAR TO HAVE TOO MUCH WIND JUST OFF THE SURFACE FOR
FAVORABLE FOG FORMATION. FOR NOW...WILL INCLUDE BCFG IN THE 10-12Z
AND CONTINUE MONITORING FOG POTENTIAL WITH THIS MORNINGS MODEL
RUNS.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...DAS



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