Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 231127
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
627 AM CDT SAT MAY 23 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 254 AM CDT SAT MAY 23 2015

IN HURRY UP AND WAIT MODE AS UPPER LOW EVER SO SLOWLY LIFTS OUT OF
SOUTHWEST U.S. THROUGH HOLIDAY WEEKEND. TIMING OF RAIN THREATS MAIN
CHALLENGE BUT ALSO WATCHING FOR ANY SEVERE WEATHER RISKS.

ANOTHER QUIET DAY ON TAP AS MAINLY MID LEVEL WARM AIR ADVECTION AND
FRONTOGENESIS WILL SPREAD MORE AND MORE CLOUD COVER IN FROM THE
SOUTHWEST. CONTINUE TO DELAY ONSET OF ANY RAIN THREAT BUT AS
SOUTHWEST FLOW AHEAD OF UPPER LOW CONTINUES TO ADVECT MOISTURE AND
WARMER AIR NORTHWARD...EXPECT THIS FORCING TO SATURATE DRY AIRMASS
WITH RAIN THREAT MOVING IN TONIGHT FROM SOUTHWEST TO NORTHEAST.
AREAS NORTH AND EAST OF LA CROSSE COULD REMAIN DRY WELL INTO SUNDAY
MORNING BASED ON LATEST MODEL TRENDS.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 254 AM CDT SAT MAY 23 2015

BY SUNDAY...UPPER LOW SHOULD BE WORKING THROUGH THE ROCKIES AND MORE
AND MORE SHORT WAVES EJECTING NORTHEAST. INCREASE IN MOISTURE
TRANSPORT BACKS IDEA OF INCREASING RAIN THREAT THROUGH THE DAY AND
INTO SUNDAY NIGHT. INSTABILITY REMAINS LOW BUT SOME SUGGESTIONS IN
MODELS OF AT LEAST SOME MIXED LAYER CAPE /500 J/KG ?/ BY LATE SUNDAY
AS DEW POINTS CONTINUE TO INCREASE. UP TO THAT POINT THUNDER RISK
LIMITED.

AS UPPER LOW BECOMES MORE OF AN OPEN WAVE BY MEMORIAL DAY...
INTERESTING TREND IN 23.00Z MODEL RUNS BRINGING SURFACE LOW FURTHER
NORTH AS BROAD SOUTHWEST FLOW CONTINUES TO ADVECT IN MOISTURE. NOT
SURE IDEA OF A DRY SLOT DEVELOPING WILL MATERIALIZED...BUT PER
COORDINATION WITH SURROUNDING OFFICES...HAVE MADE ADJUSTMENTS IN
FORECAST FOR THAT POSSIBILITY LOWERING RAIN THREATS IN SOUTHERN
AREAS ON MONDAY...ALONG WITH WARMER TEMPERATURES.

AFOREMENTIONED SETUP WILL ALSO INCREASE RISK OF SEVERE THUNDERSTORMS
ON MEMORIAL DAY AFTERNOON AND EVENING WITH LOWER TO MID 60S SURFACE
DEW POINTS POSSIBLE AND MODEST CAPE ADVECTING AHEAD OF FRONT TO THE
WEST. DECENT SHEAR SHOULD BE REALIZED WITH HODOGRAPHS SUPPORTING
IDEA OF A FEW SUPERCELLS IF WE CAN DEVELOP ENOUGH INSTABILITY. STILL
UNCERTAINTIES OF HOW EARLIER CONVECTION COULD MUDDLE SETUP BUT
WOULD NOT BE SURPRISED IF MARGINAL DAY 3 OUTLOOK IS BUMPED UP TO
SLIGHT RISK.

FRONT GRADUALLY PASSES THROUGH AREA ON TUESDAY WITH RAIN THREATS
DROPPING OFF FROM WEST TO EAST. BUT NO BIG AIRMASS CHANGE EXPECTED
AS NEXT UPSTREAM UPPER TROUGH DROPS OUT OF NORTHWEST U.S. INTO
THE ROCKIES. WHILE COULD SEE SOME DRY TIME MID WEEK...SERIES OF
SHORT WAVE TROUGHS IN BROAD SOUTHWEST FLOW WILL CONTINUE TO KEEP A
RAIN RISK UP UNTIL NEXT WEEKEND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 627 AM CDT SAT MAY 23 2015

VFR CONDITIONS WILL PREVAIL AT BOTH RST/LSE TAF SITES THROUGH MUCH
OF THE TAF PERIOD. LOW PRESSURE DEVELOPING OVER THE HIGH PLAINS WILL
CONTINUE TO SPREAD MID TO HIGH CLOUDS INTO THE TAF SITES TODAY AND
MUCH OF TONIGHT...WITH CEILING HEIGHTS AT OR ABOVE 7000 FEET.
SOUTHERLY WINDS ALOFT OUT AHEAD OF THE UPPER LEVEL TROUGH/SURFACE
LOW WILL ADVECT IN LOW TO MID LEVEL MOISTURE AFTER 00Z SUNDAY AND
LOWER CEILING HEIGHTS TO AROUND 7000 FEET AT RST TAF SITE. CEILING
HEIGHTS ARE EXPECTED TO LOWER BELOW 7000 FEET AFTER 12Z
SUNDAY...BEYOND TAF PERIOD. PRECIPITATION CHANCES REMAIN A
POSSIBILITY AT RST TAF SITE AFTER 06Z. HOWEVER...THE COMBINATION
OF DRY AIRMASS NEAR THE SURFACE/ALOFT AND THE DEEPER LIFT/MOISTURE
MOVING INTO SOUTHERN MINNESOTA AFTER 12Z SUNDAY WILL INHIBIT
SHOWER CHANCES AT RST TAF SITE. AT THIS TIME...WILL LEAVE MENTION
OF SHOWERS OUT OF TAF AT RST AND ALSO LSE.

&&

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

$$

SHORT TERM...SHEA
LONG TERM...SHEA
AVIATION...DTJ


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