Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 242351
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
651 PM CDT FRI APR 24 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 222 PM CDT FRI APR 24 2015

AS WAVE EJECTS OUT OF SOUTHWEST U.S. MAIN FOCUS IN SHORT TERM IS
RAIN THREAT...ESPECIALLY ON SATURDAY AS SYNOPTIC SURFACE LOW PASSES
BY TO THE SOUTH.

WEAKER INITIAL SHORT WAVE TROUGH SWINGING THROUGH AREA THIS
AFTERNOON HAS GENERATED BROAD RAIN SHIELD WITH SOME WARM AIR
ADVECTION. CONSIDERABLY DRIER AIR IN CENTRAL AND EASTERN WISCONSIN
WILL BATTLE THIS. AS FORCING SHIFTS EAST THIS EVENING...BULK OF RAIN
SHOULD END BY EARLY EVENING WITH ONLY PATCHY THREAT AFTER THAT. THIS
TREND IS SUPPORTED IN HIGH RESOLUTION MODELS AND HAVE ADJUSTED RAIN
CHANCES DOWNWARD TO ACCOUNT FOR THAT.

AS STRONGER MAIN WAVE EJECTS INTO CENTRAL U.S. TONIGHT...WITH
STRONGER...DEEPER Q-G FORCING...EXTENSIVE AREA OF RAIN AND
THUNDERSTORMS WILL FORM ACROSS PARTS OF THE CORNBELT AND MID
MISSISSIPPI RIVER VALLEY. BETTER AGREEMENT IN 24.12Z MODELS WITH HOW
FAR NORTH PRECIPITATION WILL GET WHILE SOME MODELS HAVE BEEN VERY
CONSISTENT KEEPING RAIN SOUTH OF INTERSTATE 90 CONSISTENTLY. THIS
WILL MEAN A TIGHT NORTH-SOUTH GRADIENT IN RAIN CHANCES MAINLY
SATURDAY MORNING BEFORE SYSTEM EXITS BY LATE AFTERNOON. AS SURFACE
LOW SHIFTS EAST...COULD ALSO SEE INCREASING EAST TO NORTHEAST WINDS
PICK UP DRIER AIR TO THE NORTHEAST WHICH WOULD ALSO BATTLE NORTHWARD
EXTENT OF PRECIPITATION.

HAVE TRIED TO TIGHTEN THIS RAIN THREAT GRADIENT UP WITH UP TO AN
INCH OF RAIN POSSIBLE CLOSER TO HIGHWAY 20 IN IOWA...TO NOTHING
NORTH OF INTERSTATE 90. NIL TO MINIMAL CAPE SUGGEST THUNDER THREAT
TOO LOW TO MENTION THIS FAR NORTH.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 222 PM CDT FRI APR 24 2015

SHORT TERM UPPER RIDGE WILL BUILD IN QUICKLY SATURDAY NIGHT AS RAIN
THREAT ENDS AND SKIES CLEAR OUT. THIS WILL LAST INTO EARLY NEXT WEEK
WITH QUIET WEATHER ON TAP AND WARMING TEMPERATURES...CLOSER TO
NORMALS FOR LATE APRIL.

UPPER FLOW ACROSS U.S. BECOMES FAR MORE MESSY NEXT WEEK WITH LARGE
LOW OFF OF NORTHEAST AND SPLIT FLOW DEVELOPS IN WEST. THIS COULD
LEAVE OUR REGION IN FAIRLY QUIET PATTERN BETWEEN ALL THIS. MEDIUM
RANGE GUIDANCE SUGGESTS WEAK WAVE COULD DRAG COLD FRONT INTO AREA
NEXT TUESDAY WITH MINOR RAIN THREAT BUT BESIDES THAT...MORE SIGNALS
FOR RIDGING AND NICE SPRING WEATHER.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 651 PM CDT FRI APR 24 2015

THE 800 TO 700 MB FRONTOGENESIS WILL GRADUALLY MOVE NORTHEAST AND
WEAKEN THIS EVENING. AS THIS OCCURS...THE RAIN WILL END AT THE TAF
SITES. THIS SHOULD OCCUR AT KRST AROUND 25.01Z AND AT KLSE AROUND
25.03Z. BOTH THE GFS AND NAM SUGGEST THAT AN IFR/MVFR CEILING BE
FOUND AT BOTH TAF SITES. HOWEVER THESE LOW CLOUDS ARE SUPPOSED TO
ALREADY EXIST...AND THEY ARE SCATTERED AT BEST. AS A RESULT...JUST
STAYED VFR CEILINGS /3-5K FEET/. VISIBILITIES SHOULD IMPROVE TO
VFR ONCE THE RAIN END.

&&

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

$$

SHORT TERM...SHEA
LONG TERM...SHEA
AVIATION...BOYNE



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