Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221125
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
625 AM 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 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 625 AM CDT FRI MAY 22 2015

VFR CONDITIONS WILL PREVAIL AT BOTH RST/LSE TAF SITES THROUGH THE
TAF PERIOD...AS HIGH PRESSURE REMAINS IN CONTROL OF THE AREA. A WEAK
WARM FRONT LIFTING NORTHWARD INTO NORTHERN IOWA AND SOUTHERN
WISCONSIN WILL SPREAD SOME MID TO HIGH CLOUDS AFTER 06Z SATURDAY.
CEILING HEIGHTS ARE EXPECTED TO REMAIN AT OR ABOVE 9000 FEET. WINDS
WILL REMAIN LESS THAN 10 KNOTS FROM THE SOUTHEAST THROUGH THE TAF
PERIOD.

&&

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

$$

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


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