Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221721
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1221 PM CDT FRI MAY 22 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 213 AM CDT FRI MAY 22 2015

ANOTHER QUIET DAY ON TAP WITH AREA BETWEEN SYSTEMS. SHORT TERM
RIDGING WITH COLD CORE UPPER LOW OVER QUEBEC AND BROAD TROUGH MOVING
INTO THE SOUTHLAND AND SOUTHWEST U.S.  SURFACE RIDGE WILL RETREAT
LATER TODAY AS HEIGHT FALLS IN RESPONSE TO SOUTHWEST LOW BEGIN TO
INCREASE LOW LEVEL RETURN AND INCREASE PRESSURE GRADIENT. SOME MID
AND HIGH LEVEL CLOUDS WILL ALSO BEGIN TO STREAM IN FROM THE
SOUTHWEST.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 213 AM CDT FRI MAY 22 2015

LATER PERIODS ABOUND IN QUESTIONS WITH UNCERTAINTIES ON TIMING OF
RAIN AND ANY POTENTIAL SEVERE WEATHER RISK FOR HOLIDAY WEEKEND.

AS SOUTHWEST U.S. LOW EJECTS INTO ROCKIES THIS WEEKEND...WE WILL
INITIALLY BE UNDER RIDGING AND RELATIVELY DRY AIRMASS. EVEN AS
LATEST GFS RUNS CONTINUE TO PAINT SMALL RAIN THREAT AS WARM AIR
ADVECTION BEGINS TO INCREASE SATURDAY...WILL LEAN TOWARDS OTHER
GUIDANCE SUGGESTING AREA WILL REMAIN DRY UNTIL AT LEAST SATURDAY
NIGHT...EVEN THOUGH CLOUD COVER WILL LIKELY BE INCREASING THROUGH
THE DAY.

LOW LEVEL JET STRENGTHENS SATURDAY NIGHT AS MOISTURE TRANSPORT
INCREASES...SUGGESTING THREAT FOR CONVECTION WILL INCREASE IN
EARNEST WITH ENOUGH FORCING/LIFT TO OVERTAKE INITIAL DRIER LOW
LEVELS. LIMITED MLCAPE OR MUCAPE SUGGESTS THUNDER RISK IS LOW THOUGH
SO WILL CERTAINLY DOWNPLAY STORM THREAT.

WITH UPPER LOW SLOWLY MOVING NORTHEAST AND EVOLVING INTO MORE OF AN
OPEN WAVE TOWARDS END OF HOLIDAY WEEKEND...FORECAST BECOMES MORE
MUDDLED WITH FAIRLY CONSISTENT LOW LEVEL FORCING AND MOISTURE PUSH
NORTHWARD. AMOUNT OF CONVECTION AND ASSOCIATED DEBRIS NOT ONLY COULD
HAVE IMPACT ON TEMPERATURES BUT AMOUNT OF INSTABILITY WHICH WOULD
LIMIT ANY SEVERE WEATHER RISK. GFS CONTINUES TO BE OUTLIER WITH
SEVERE WEATHER THREAT SUGGESTING MORE INSTABILITY...ESPECIALLY JUST
SOUTH OF THE AREA SETTING UP A CAPE GRADIENT OR WARM FRONT. NOT
ENOUGH CONFIDENCE TO MOVE IN THAT DIRECTION BUT WILL HAVE TO MONITOR
HOW SUNDAY AND MONDAY PLAY OUT AS IT GETS CLOSER. AGREE WITH DAY 3
SPC OUTLOOK KEEPING MARGINAL RISK SOUTH OF AREA AT THIS TIME.

SOME SUGGESTION SURFACE LOW COULD MOVE THROUGH THE AREA MONDAY
/MEMORIAL DAY/ WITH PERHAPS SMALL RISK OF SEVERE WEATHER BUT NOT
CONFIDENT THAT FAR OUT TO HIGHLIGHT. BREAKS IN RAIN THREATS AND
CLOUDS WOULD ALSO ALLOW TEMPERATURES TO REBOUND QUICKLY...ESPECIALLY
IN SOUTHERN AREAS WHERE WARM SECTOR COULD SET UP AS SURFACE LOW
PASSES.

WILL ALSO HAVE TO KEEP AN EYE ON HOW MUCH RAIN FALLS LATER IN
WEEKEND IN CASE SOME AREAS ARE HIT REPEATEDLY.

SMALL RAIN THREATS LINGER INTO MID PART OF NEXT WEEK AS WELL WITH
PSEUDO ZONAL FLOW AND NEXT UPSTREAM WAVE TAKING SHAPE OVER MIDWEST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1221 PM CDT FRI MAY 22 2015

EXPECT VFR CONDITIONS AND WINDS TO REMAIN UNDER 10 KT THROUGH
SATURDAY MORNING...DUE TO HIGH PRESSURE OVER THE TAF SITES
DRIFTING OFF TO THE SOUTHEAST.

&&

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

$$

SHORT TERM...SHEA
LONG TERM...SHEA
AVIATION...AJ



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