000
FXUS63 KARX 150513
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1213 AM CDT WED MAY 15 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 319 PM CDT TUE MAY 14 2013

THE MAIN FOCUS IN THE SHORT TERM IS WITH HOW MUCH CONVECTION THE
PASSING COLD FRONT WILL BE ABLE TO PRODUCE INTO TONIGHT.

TEMPERATURES HAVE SKYROCKETED INTO THE 90S AND LOW 100S IN THE
WARM SECTOR AHEAD AND ALONG OF A COLD FRONT THAT CURRENTLY EXTENDS
SOUTHWEST FROM A SURFACE LOW IN SOUTH CENTRAL MINNESOTA. THE
TRIPLE POINT OF THE SURFACE LOW...WARM FRONT AND DRYLINE/COLD
FRONT IS VISIBLE VIA MPX RADAR AND SURFACE OBS NEAR FARIBAULT
MINNESOTA. A CORRIDOR OF +30C 925MB TEMPERATURES AHEAD OF THIS LOW
COMBINED WITH DEEP MIXING THROUGH 600MB HAS ALLOWED FOR THIS RAPID
WARMING WITH SOME PLACES JUMPING UP 20F IN AN HOUR AFTER THE MID
LEVEL CLOUDS CLEARED. THIS CLOUD COVER AND SPRINKLES THAT CAME
THROUGH THIS AFTERNOON WAS ASSOCIATED WITH AN OVERNIGHT MCS THAT
INITIATED IN THE DAKOTAS AND CONTINUALLY WEAKENED AS IT PROPAGATED
INTO THE REGION.

CONVECTION HAS STARTED TO DEVELOP ACROSS SOUTHEAST MINNESOTA JUST
TO THE SOUTHEAST OF THE LOW...BUT SHOULD REMAIN FAIRLY ISOLATED
THROUGH THIS AFTERNOON AND EVENING. INVERTED V SOUNDINGS AND
FAVORABLE 0-3KM UNIDIRECTIONAL SHEAR OF 30-40 KTS MEAN THAT ANY
SHOWERS/STORMS THAT DO DEVELOP WILL POSE THE THREAT OF DEVELOPING
STRONG DOWNDRAFTS WITH THEM...PARTICULARLY ACROSS THE WARM SECTOR
IN SOUTHEAST MINNESOTA AND NORTHEAST IOWA THROUGH THIS
AFTERNOON/EARLY EVENING. THIS CONVECTION WILL REMAIN FAIRLY
ISOLATED AND SHOULD DIMINISH INTO THE EVENING HOURS.

THE COLD FRONT WILL THEN SETTLE DOWN TO THE SOUTH OF THE FORECAST
AREA WITH A RIDGE OF HIGH PRESSURE BUILDING IN FROM THE NORTHWEST.
THIS SHOULD LEAD TO A MAINLY CLEAR PERIOD FROM OVERNIGHT INTO
TOMORROW WITH HIGH TEMPERATURES STILL IN THE 70S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 319 PM CDT TUE MAY 14 2013

THE COLD FRONT WILL THEN START TRANSITIONING TO A WARM FRONT
THURSDAY NIGHT INTO FRIDAY AS A MID LEVEL SHORT WAVE TROUGH TRACKS
INTO THE REGION AS A DEEPER TROUGH STARTS TO CARVE ITS WAY THROUGH
THE ROCKIES. LOW LEVEL MOISTURE TRANSPORT STARTS NOSING UP THROUGH
WESTERN MINNESOTA/IOWA THURSDAY NIGHT WITH SOME WEAK CONVERGENCE
ALONG THE UPPER MISSISSIPPI RIVER VALLEY. KEPT PRECIPITATION
CHANCES AS IS THROUGH THE WEEKEND BASED ON A 14.12Z GFS/ECMWF
BLEND...BUT THINK THAT THE PRECIPITATION IS LIKELY OVERDONE DUE TO
THE HIGH DEW POINTS BEING OFFERED UP. WITH STRONGER SOUTHERLY FLOW
DUE TO THE DIGGING TROUGH...CAN NOT RULE OUT THESE SIMILAR
SCENARIOS WHERE A SURFACE LOW DRIFTS EAST ACROSS THE PLAINS THIS
WEEKEND WITH CONVECTION DEVELOPING OUT AHEAD OF IT IN THE WARM
SECTOR...WHICH ALSO COULD BE MORE CAPPED THAN IT CURRENTLY IS
SUGGESTING. THE ECMWF IS MORE PROGRESSIVE WITH THE LOW WHILE THE
GFS CUTS IT OFF AND HAS IT LINGERING IN THE REGION INTO TUESDAY.
CONFIDENCE STILL NOT VERY HIGH ON THE SEVERE THREAT...BUT THE
14.12Z ECMWF WOULD SUGGEST THAT SUNDAY WOULD BE THE MAIN PERIOD
WITH THE 14.12Z GFS SAYING SUNDAY NIGHT IS THE MAIN CONCERN FOR
TIMING OF THE FRONTAL PASSAGE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1212 AM CDT WED MAY 15 2013

SKIES WILL BE CLEAR TONIGHT...AND THEN A 12-15K BROKEN DECK OF
CLOUDS WILL MOVE INTO THE AREA AS A WEAK SYSTEM SLIDES SOUTHEAST
ACROSS NORTHERN MINNESOTA AND NORTHERN WISCONSIN ON WEDNESDAY. IN
THE WAKE OF THIS SYSTEM...THE 12-15K DECK OF CLOUDS WILL BECOME
SCATTERED DURING THE LATE AFTERNOON AND THEN CONTINUE THROUGH THE
EVENING. WINDS WILL REMAIN OUT OF THE NORTHWEST AT 10 TO 15 KNOTS
OVERNIGHT...AND THEN GRADUALLY SHIFT TO WEST AND SOUTHWEST ON
WEDNESDAY WITH WIND SPEEDS FALLING TO AROUND 5 KNOTS.

&&

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

$$

SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...BOYNE