Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261726
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1226 PM CDT SUN OCT 26 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 205 AM CDT SUN OCT 26 2014

FORECAST FOCUS ON RAIN POTENTIAL LATE TODAY/TONIGHT. 07Z SURFACE
ANALYSIS SHOWS HIGH PRESSURE CENTERED OVER THE REGION WITH LIGHT
WINDS AND CLEAR SKIES. LARGE LONG WAVE TROUGH OVER THE WESTERN
CONUS EJECTING EAST AND WILL SPREAD CLOUD INTO THE AREA LATER
TODAY. AHEAD OF THIS...EXPECT ADVECTION OF WARMER AND MORE MOIST
AIR INTO THE REGION. THIS WILL LEAD TO CLOUD DEVELOPMENT AND
EVENTUALLY PRECIPITATION BY TONIGHT. MODELS HAVE BEEN SHOWING THIS
POTENTIAL FOR SEVERAL DAYS NOW. PERUSAL OF MODEL SOUNDING DATA
SHOWS THERE IS A GREAT DEAL OF DRY AIR TO OVERCOME INITIALLY...SO
IT MAY TAKE SOME TIME BEFORE SATURATION OCCURS SUFFICIENTLY TO
ALLOW FOR PRECIPITATION PRODUCTION. SOME MODEL SOLUTIONS SUGGEST
RAIN COULD BE DEVELOPING ALREADY BY MID TO LATE AFTERNOON...BUT
FEEL THIS IS TOO EARLY GIVEN THE DRY AIR. HAVE CONTINUED THE IDEA
OF HOLDING OFF UNTIL EVENING. AS THERMODYNAMIC FORCING MAXIMIZES
OVER THE AREA TONIGHT...HAVE THE HIGHEST RAIN CHANCES FROM LATE
EVENING INTO THE OVERNIGHT ALONG THE I-94 CORRIDOR. LOWEST CHANCES
WEST OF THE MISSISSIPPI RIVER.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 205 AM CDT SUN OCT 26 2014

FOCUS OF THE WARM PUSH SHIFTS NORTH OF THE FORECAST AREA EARLY
MONDAY...WITH THE FORECAST AREA INTO THE WARM SECTOR DURING THE
DAY. A BREAK IN THE RAIN THREAT APPEARS LIKELY...ESPECIALLY DURING
THE MORNING. GOOD DYNAMIC FORCING WITH THE APPROACHING WAVE AND
SOME GOOD INSTABILITY FOR LATE OCTOBER. THUNDERSTORMS POSSIBLE
ALONG THE COLD FRONT AS IT MOVES THROUGH...AND SOME COULD BE
SOMEWHAT STRONG WITH SMALL HAIL AND GUSTY WINDS. FRONT WILL BE
MOVING THROUGH THE FORECAST AREA DURING THE DAY...AND IT APPEARS
THE FRONT MAY BE MOST OF THE WAY THROUGH BEFORE STORMS CAN GET
GOING. THUS THE HIGHEST RAIN CHANCES AND GREATEST RISK FOR THE
STRONGER STORMS WILL BE OVER EXTREME NORTHEAST IOWA INTO SOUTHWEST
AND CENTRAL WI BY EVENING. DEEPENING TROUGH HAS A CLOSE
CIRCULATION MOVING THROUGH NORTHERN MN BY TUE MORNING AND WRAP
AROUND SHOWERS IN THE COLD ADVECTION REGIME POSSIBLE FOR A TIME
DURING THE OVERNIGHT HOURS...AND PERHAPS EVEN INTO TUESDAY FOR
PARTS OF THE AREA. DEFINITELY A COOLER PATTERN FROM HERE THROUGH
THE REMAINDER OF THE WEEK AS NORTHWEST FLOW SETS UP. WEAK SHORT
WAVE TROUGH MOVES THROUGH THE FLOW AND MAY RESULT IN A FEW SHOWERS
WED NIGHT INTO THURS. SOME OF THE COLDEST AIR OF THE SEASON THEN
LOOKS TO SETTLE ACROSS THE AREA BY SATURDAY MORNING. THOSE AREAS
THAT ESCAPED A HARD FREEZE UP TO THIS POINT ARE LIKELY TO FINALLY
SEE ONE. BUT LOOKING EVEN FURTHER OUT...A WARM UP IS IN STORE FOR
EARLY NEXT WEEK AS A BROAD LONG WAVE RIDGE BUILDS INTO THE AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1226 PM CDT SUN OCT 26 2014

VFR CONDITIONS WITH SOUTHEAST WINDS 7-14KTS...PLUS G18-20KTS AT
SITES LIKE KRST...TO CONTINUE THIS AFTERNOON INTO EARLY THIS
EVENING. HOWEVER 925-850MB WARM ADVECTION AHEAD OF A LOW AND TROUGH
ADVANCING ACROSS THE PLAINS WILL SPREAD INCREASING LOW LEVEL
MOISTURE ACROSS THE TAF SITES THRU THE LATE AFTERNOON AND INTO MON.
INITIAL CIGS WILL BE VFR LATE THIS AFTERNOON/EARLY THIS EVENING BUT
AS THE DEEPER LOW LEVEL MOISTURE ARRIVES CIGS ARE EXPECTED TO DROP
TO MVFR/IFR...WITH MVFR/IFR VSBY IN BR...AFTER 06Z THRU MON MORNING.
INCREASING LIFT AND INSTABILITY ALOFT ARE EXPECTED TO TRIGGER SOME
SHRA...EVEN TSRA...ACROSS THE AREA IN ROUGHLY THE 03Z-09Z TIME-
FRAME. WITH THE STRONGEST FORCING/DEEPER MOISTURE LOOKING TO COME
TOGETHER NORTHEAST OF THE TAF SITES...LEFT THIS AS A VCSH MENTION IN
THE TAFS FOR NOW. BIGGER CONCERN IS THE SATURATION OF THE SFC TO
ABOUT 800MB LATER TONIGHT/MON MORNING...WITH SOME WEAK CONVERGENCE/
LIFT IN THE 925-850MB LAYER AHEAD OF THE APPROACHING SFC TO 925MB
LOW. A RATHER CLASSIC DRIZZLE SIGNATURE AND ADDED A -DZ MENTION TO
BOTH TAFS FOR LATE TONIGHT INTO MON MORNING.

&&

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

$$

SHORT TERM...MW
LONG TERM....MW
AVIATION.....RRS



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