000
FXUS63 KARX 231121
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
621 AM CDT THU MAY 23 2013

.SHORT TERM...(TODAY THROUGH SATURDAY)
258 AM CDT THU MAY 23 2013

FORECAST FOCUS IN THE SHORT TERM PERIOD IS ON THE CLEARING TREND
TODAY...COLD TEMPERATURES TONIGHT WITH FROST POTENTIAL...AND THEN
RAIN CHANCES FRIDAY NIGHT INTO THE WEEKEND.

07Z SURFACE ANALYSIS SHOWS THE PESKY LOW PRESSURE SYSTEM HAS FINALLY
MOVED TO NEAR CHICAGO...AND IS PULLING AWAY. REGIONAL RADAR LOOPS
SHOWS THE LIGHT RAIN WRAPPING AROUND THE BACK SIDE AND DIMINISHING
IN COVERAGE FROM NORTHWEST TO SOUTHEAST. HIGH PRESSURE WAS RIDGING
IN FROM THE DAKOTAS AND SOUTHERN CANADA...AND SATELLITE LOOPS SHOW
THE CLOUDS CLEARING LINE MOVING IN AS WELL.

FIRST CONCERN IS THE CLEARING TREND OF BOTH CLOUDS AND RAIN THIS
MORNING. SATELLITE AND RADAR LOOPS CONFIRM WHAT THE MESOSCALE
MODELS ARE SHOWING...DECREASING MOISTURE. TREND IS FOR MAINLY
SUNNY SKIES TODAY ONCE THIS MOVES OUT. HAVE MAINTAINED THIS TREND
FROM THE PREVIOUS FORECAST. NEXT CONCERN IS THE CHILLY TEMPS
TONIGHT. UNDER MAINLY CLEAR SKIES AND LIGHT WINDS WITH THE HIGH
PRESSURE RIDGE MOVING...ANTICIPATE THE MERCURY WILL DROP OUT
ACROSS THE REGION. ANTICIPATING MOST AREAS WILL SEE LOWS IN THE
30S. MOST SPOTS WILL BE IN THE MID TO UPPER 30S...BUT THE TYPICAL
COOL SPOTS OVER NORTHERN AND CENTRAL WI WILL DIP INTO THE LOWER
30S OR PERHAPS EVEN UPPER 20S. THESE COLD TEMPS AND ALL OF THE
RECENT MOISTURE WILL LEAD TO THE POTENTIAL FOR FROST. HIGHEST
LIKELIHOOD FOR WIDESPREAD AND PROLONGED FROST TONIGHT WILL BE IN
NORTHERN AND CENTRAL WI...AND HAVE POSTED A FROST ADVISORY FOR
THOSE LOCATIONS. FROST WILL BE PATCHY ELSEWHERE.

SURFACE HIGH PRESSURE SHIFTS EAST OF THE AREA ON FRIDAY. MEANWHILE
ANOTHER LARGE LONG WAVE TROUGH AND CLOSED CIRCULATION SETTLES INTO
THE PACIFIC NORTHWEST STATES. SEVERAL WEAKER SHORT WAVE TROUGHS
WILL EJECT OUT OF THE BASE OF THE TROUGH AND TRAVEL INTO THE UPPER
MIDWEST ON SOUTHWEST FLOW. A CONTINUED FETCH OF MOIST AIR WILL BE
DRAWN NORTH TOWARD OUR AREA THANKS TO THE MEAN TROUGH POSITION.
AND EACH DISTURBANCE WILL FOCUS AND TAP INTO THIS MOISTURE SUPPLY...
LEADING TO PERIODS OF SHOWERS AND THUNDERSTORMS. THE FIRST OF
THESE WILL ARRIVE LATE FRIDAY NIGHT INTO SATURDAY. MOISTURE
TRANSPORT AND INSTABILITY ARE QUITE LIMITED...SO ANTICIPATE MAINLY
SHOWERS WITH SOME ISOLATED THUNDERSTORMS.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
258 AM CDT THU MAY 23 2013

BLOCKED AND UNSETTLED FLOW CONTINUES ACROSS THE CONUS THROUGH THE
LONG TERM PERIOD. LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST
WOBBLES AROUND ALL THE WAY INTO NEXT WEEK. SEVERAL WAVES EJECT OUT
OF IT...SOME HEADING ACROSS SOUTHERN CANADA AND OTHERS COME AROUND
THE SOUTH SIDE AND HEAD INTO OUR AREA FROM THE INTER-MOUNTAIN WEST.
THE JUXTAPOSITION OF THIS UPPER FLOW PATTERN WILL KEEP A SURFACE
LOW PRESSURE AREA OVER THE HIGH PLAINS...WITH A CONTINUED FEED OF
WARM AND MOIST AIR INTO THE MIDDLE PORTION OF THE COUNTRY. A
FRONTAL BOUNDARY LOOKS TO MEANDER AROUND SD/IA/IL...MOVING NORTH
AND SOUTH AS EACH SUCCESSIVE WAVE EJECTS THROUGH. THIS SETUP WILL
PROVIDE PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS ALL THE WAY
INTO THE MIDDLE OF NEXT WEEK AT A MINIMUM. MODELS ARE SHOWING
INCREASING DIFFERENCES WITH TIME...AND IT WILL BE HARD TO PIN DOWN
EXACT TIMING. BUT IT APPEARS THAT THE THREAT FOR RAIN WILL BE
THERE NEARLY EVERY DAY...AT LEAST FOR A PORTION OF THE DAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 621 AM CDT THU MAY 23 2013

BACK EDGE OF THE CLOUD SHIELD IS PROGRESSING STEADILY SOUTHEAST
HAVING CLEARED KRST ALREADY. THEY WILL BE PAST KLSE SHORTLY AS
WELL...BUT COULD SEE A VFR CEILING FOR A VERY SHORT PERIOD AROUND
12Z...BUT THIS WILL BE TOO SHORT TO TRY TO ACCOUNT FOR AND WILL
JUST CARRY A SCATTERED DECK. OTHERWISE...EXPECT VFR CONDITIONS
WITH LITTLE OR NO CLOUDS HAS HIGH PRESSURE BUILDS IN FROM THE
NORTH. THE GRADIENT THIS MORNING BETWEEN THE DEPARTING TROUGH OF
LOW PRESSURE AND THE INCOMING HIGH WILL BE TIGHT ENOUGH TO PRODUCE
SOME GUSTS BETWEEN 20 AND 25 KNOTS AT BOTH SITES. THESE SHOULD
DIMINISH DURING THE AFTERNOON AS THE HIGH GETS CLOSE ENOUGH TO
RELAX THE GRADIENT. THE WINDS WILL DROP OFF TO LESS THAN 10 KNOTS
SHORTLY BEFORE SUNSET.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 7 AM CDT FRIDAY FOR
     WIZ017-029-034-042>044.

MN...NONE.
IA...NONE.
&&

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...04