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000
FXUS63 KARX 160848
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
348 AM CDT SUN JUN 16 2013

.UPDATE...
ISSUED AT 348 AM CDT SUN JUN 16 2013

HAVE EXPANDED THE DENSE FOG ADVISORY TO INCLUDE MUCH MORE OF
SOUTHWEST WISCONSIN AS WELL AS WINONA AND HOUSTON COUNTIES OF
MINNESOTA. CALLS TO COUNTY LAW ENFORCEMENTS AS WELL AS AUTOMATED
SURFACE OBSERVATIONS ARE SHOWING A LOT MORE VISIBILITIES OF 1/4
MILE OR LESS...INCLUDING VIROQUA...LA CROSSE...BLACK RIVER FALLS AND
WINONA. MOST RIVER VALLEYS OVER THE NORTHERN HALF OF THE FORECAST
AREA ARE ASSUMED TO BE SOCKED IN WITH FOG GIVEN THE CONDITIONS IN THE
MISSISSIPPI RIVER VALLEY. EXPECT ALL FOG TO DISSIPATE BY 9 AM WITH
THE EARLY SUNRISE HELPING TO MIX IT OUT QUICKLY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 307 AM CDT SUN JUN 16 2013

CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED AN UPPER LOW OFF THE PACIFIC NORTHWEST COAST...AND NEARLY
ZONAL FLOW ACROSS MUCH OF THE NORTHERN U.S.. WITHIN THE ZONAL
FLOW...A COLLECTION OF SHORTWAVES...SOME CONVECTIVELY INDUCED...
EXTENDED FROM LOWER MICHIGAN INTO ARKANSAS. THESE SHORTWAVES HELPED
PRODUCE SOME OF THE CONVECTION YESTERDAY AFTERNOON AND EVENING. DRY
AIR HAS ADVECTED INTO THE FORECAST AREA BEHIND THE SHORTWAVES...
NOTED ON WATER VAPOR AS WELL AS THE 00Z MPX SOUNDING WHERE THE
PRECIPITABLE WATER HAS FALLEN TO 0.94 INCHES. FARTHER WEST...THE AIR
GETS EVEN DRIER...WITH THE 00Z ABR SOUNDING AT 0.34 INCHES FOR
PRECIPITABLE WATER. THE DRY AIR HAS EFFECTIVELY CLEARED MUCH OF THE
SKIES OUT. LIGHT WINDS...THE DRY AIR ALOFT AND PRECIPITATION LAST
EVENING HAS LED TO SOME FOG DEVELOPMENT... ESPECIALLY NORTH OF THE
I-94 CORRIDOR AS WELL AS IN THE MS RIVER VALLEY NORTH OF PRAIRIE DU
CHIEN. 850MB TEMPS DID NOT DROP MUCH WITH THE SHORTWAVE PASSAGE...
WITH READINGS GENERALLY 14-17C FROM THE DAKOTAS EAST INTO WISCONSIN.
MEANWHILE...TO THE NORTHWEST...AN UPPER LOW WAS SITTING OVER
SOUTHEAST SASKATCHEWAN. SOME CONVECTION FORMED AHEAD OF THE UPPER
LOW ALONG THE CANADIAN BORDER WITH NORTH DAKOTA AND MN DURING THE
DAYTIME HOURS YESTERDAY. THIS HAS SINCE MOSTLY DISSIPATED.

MAIN FOCUS IS ON THE UPPER LOW IN SOUTHEAST SASKATCHEWAN. MODELS
CONTINUE TO SHOW THE LOW DROPPING SOUTHEASTWARD AS IT BEGINS TO GET
CAUGHT UP IN THE CIRCULATION AROUND TROUGHING IN EASTERN CANADA. AT
THE SAME TIME...THE UPPER LOW IS PROGGED TO SHEAR OUT INTO A
SHORTWAVE. THERE ARE MODEL DIFFERENCES IN HOW FAR SOUTH THE
SHORTWAVE GETS TO AT 12Z MONDAY...RANGING FROM NEAR MINNEAPOLIS FROM
THE 16.00Z GFS TO NEAR BRAINERD MN FROM THE 16.00Z
NAM/UKMET/CANADIAN. THIS DIFFERENCE HAS IMPLICATIONS ON TIMING OF
POTENTIAL PRECIPITATION LATER TONIGHT.

TODAY CONTINUES TO LOOK QUIET AS WEST-NORTHWEST FLOW AHEAD OF THE
APPROACHING UPPER LOW/SHORTWAVE HELPS TO BRING THAT DRIER AIR IN
SEEN ON THE 00Z ABR SOUNDING. ANY CONVECTIVE ACTIVITY AHEAD OF THE
UPPER LOW/SHORTWAVE LIKE SEEN YESTERDAY AFTERNOON AND EVENING WILL
STAY NORTH AND WEST OF THE AREA. WE SHOULD SEE PLENTY OF
SUNSHINE...EASILY ALLOWING MIXING TO 850MB WHERE TEMPS OF 13-14C
WILL ALLOW FOR HIGHS IN THE LOW TO MID 80S. EXPECT ANY FOG THIS
MORNING TO QUICKLY DISSIPATE...LIKELY BY 9 AM OR EVEN EARLIER
GIVEN THE EARLY SUNRISE.

FOR TONIGHT...GOOD AGREEMENT EXISTS AMONGST MODELS THAT A SURGE OF
SOMEWHAT HIGHER PRECIPITABLE WATER WILL ADVECT INTO THE FORECAST
AREA AS THE UPPER LOW/SHORTWAVE DROPS INTO MN. VALUES CLIMB UP TO
AROUND 1 INCH. AT THE SAME TIME...THERE IS A DEFINITE SURGE OF 850MB
MOISTURE TRANSPORT TO HELP SUPPORT PRECIPITATION. BETWEEN THE
MOISTURE ADVECTION AND DPVA AHEAD OF THE UPPER LOW/SHORTWAVE...SOME
SCATTERED SHOWER AND THUNDERSTORM ACTIVITY SHOULD BE PRESENT AND
PERSIST THROUGH THE NIGHT. 16.00Z NAM/GFS/CANADIAN ALL INDICATE
PRECIPITATION...BUT IT IS JUST A MATTER HOW FAR SOUTH IT GETS WHICH
GOES BACK TO THE MODEL TIMING DIFFERENCES MENTIONED EARLIER. HAVE
FOLLOWED THE MAJORITY SOLUTION OF A SLOWER APPROACH...WHICH RESULTS
IN THE HIGHEST CHANCES OF 30-40 OVER THE NORTHERN 1/3 OF THE
FORECAST AREA. DID EXTEND A 20 PERCENT CHANCE DOWN INTO SOUTHEAST MN
IN THE EVENT THE FASTER 16.00Z GFS COMES TRUE. MOST OF THESE CHANCES
ARE ALSO AFTER MIDNIGHT.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 307 AM CDT SUN JUN 16 2013

MONDAY INTO MONDAY NIGHT...SHORTWAVE LURKING UP TO OUR NORTHWEST AT
12Z MONDAY IS WELL AGREED UPON TO REACH THE I-90 CORRIDOR IN THE
FORECAST AREA AT 00Z TUESDAY...DESPITE THE MODEL DIFFERENCES ON
TIMING BEFORE THAT. ACCOMPANYING THE SHORTWAVE WILL BE A COLD FRONT
WHICH SHOULD GRADUALLY MAKE ITS WAY SOUTH THROUGH THE AREA DURING
THE DAY. ANTICIPATING SCATTERED SHOWER/THUNDERSTORM ACTIVITY THAT
WAS DROPPING INTO NORTHERN PORTIONS OF THE AREA LATE SUNDAY NIGHT TO
CONTINUE DROPPING SOUTH AND POSSIBLY WEAKEN AS THE 850MB MOISTURE
TRANSPORT FALLS APART. AS INSTABILITY BUILDS DURING THE DAY...
THUNDERSTORMS MAY FORM BOTH ALONG THE COLD FRONT IN THE SOUTHERN
PORTION OF THE FORECAST AREA...AS WELL AS UNDER THE COLDER CORE OF
AIR ASSOCIATED WITH THE SHORTWAVE. THUS...IT APPEARS MONDAY WILL BE
AN OFF AND ON PRECIP DAY AT THIS TIME. 0-6KM SHEAR IS NOT THE
GREATEST FOR THINKING SEVERE WEATHER...GENERALLY 30-35 KT OVER THE
SOUTHERN TWO THIRDS OF THE AREA IN THE AFTERNOON. THIS WOULD SUGGEST
MOST OF THE CONVECTION TAKING ON A MULTI-CELLULAR APPEARANCE.
HOWEVER...FREEZING LEVELS DO LOWER AT 21Z TO 9000 FT OVER THE NORTH
TO 10500-11000 FT AGL IN THE SOUTH...SO HAIL IS A DEFINITE
POSSIBILITY FROM THE AFTERNOON STORMS. ANY CONVECTION FROM MONDAY
AFTERNOON SHOULD DIMINISH QUICKLY DURING THE EVENING WITH LOSS OF
DAYTIME HEATING...THE SHORTWAVE HEADING INTO NORTHERN ILLINOIS AND
HIGH PRESSURE BUILDING IN FROM THE NORTH.

TUESDAY INTO TUESDAY NIGHT...WHAT LOOKED TO BE A QUIET PERIOD FOR
MANY DAYS IS BECOMING A LITTLE MORE PROBLEMATIC. THE 15.00Z ECMWF
SHOWED A FAIRLY POTENT SHORTWAVE DROPPING THROUGH WESTERN PORTIONS
OF THE FORECAST AREA DURING THE DAYTIME HOURS ON TUESDAY. SO
ALTHOUGH A RIDGE OF HIGH PRESSURE IS IN PLACE AT THE SURFACE...THE
COLDER AIR ALOFT ACCOMPANYING THE SHORTWAVE RESULTED IN
PRECIPITATION. TODAY...THE 16.00Z NAM/UKMET/GFS/ECMWF/CANADIAN
CONTINUE TO SHOW THIS SHORTWAVE BUT ITS TRACK IS ALL OVER THE PLACE.
THE NAM/UKMET/ECMWF DROP IT SOUTHEAST THROUGH CENTRAL WI WHILE THE
GFS AND 15.12Z ECMWF BRING IT THROUGH SOUTHEAST MN AND NORTHEAST
IA. THE CANADIAN LIES BETWEEN THE TWO. FOR REFERENCE...THE SHORTWAVE
RIGHT NOW SITS ALONG THE SOUTHERN ALBERTA/SASKATCHEWAN BORDER.
DESPITE THE TRACK DIFFERENCES...LIGHT MODEL QPF IS MOSTLY CENTERED
WEST OF THE MS RIVER DURING THE TUESDAY DAYTIME HOURS. THIS AREA
APPEARS TO BE THE BEST JUXTAPOSITION OF DIURNAL HEATING/LOW LEVEL
MOISTENING AND THE COOL AIR ALOFT WITH THE SHORTWAVE. DESPITE SEEING
THE LIGHT QPF SIGNAL...HAVE CONTINUED TO STAY WITH THE DRY FORECAST
THINKING THAT THE MODELS MAY BE OVERDOING LOW LEVEL DEWPOINTS. A
NORTHEAST SURFACE FLOW OUT OF HIGH PRESSURE IN UPPER MI SHOULD
PROVIDE A DRY FLOW OF AIR. AFTER THE SHORTWAVE PASSES...A DRY AND
COOL NIGHT IS IN STORE FOR TUESDAY NIGHT AS HIGH PRESSURE SETTLES
IN.

WEDNESDAY THROUGH SATURDAY NIGHT...
THE UPPER LOW CURRENTLY SITTING OFF THE PACIFIC NORTHWEST COAST IS
FORECAST TO SLOWLY PUSH EAST THE NEXT FEW DAYS...ENCOMPASSING MUCH
OF THE PACIFIC NORTHWEST ON WEDNESDAY. DOWNSTREAM RIDGING SHOULD BE
IN PLACE FROM THE NORTHWEST TERRITORIES DOWN INTO THE SOUTHERN
PLAINS...PLACING THE FORECAST AREA IN SUBSIDENCE. MODELS REMAIN IN
GOOD AGREEMENT KEEPING THE AREA DRY WEDNESDAY AND WEDNESDAY
NIGHT...STAYING IN SUBSIDENCE AND DRY AIR WITH HIGH PRESSURE NEARBY
AT THE SURFACE. THE PATTERN THEN BEGINS TO CHANGE ACCORDING TO THE
16.00Z ECMWF/CANADIAN/GFS AND GFS ENSEMBLES...SUGGESTING THE
TROUGHING THAT HAS BEEN PERSISTENT OVER SOUTHEAST CANADA BEGINS TO
LIFT OUT. ADDITIONALLY...THE UPPER LOW IN THE PACIFIC NORTHWEST
SLOWLY EJECTS EAST-NORTHEAST. ALL THESE CHANGES OCCURRING TO THE
UPPER LEVEL PATTERN SETS UP WARM ADVECTION AND A DECENT RETURN OF
GULF OF MEXICO MOISTURE BACK TOWARDS THE UPPER MISSISSIPPI RIVER
VALLEY REGION. AS A RESULT...PRECIPITATION CHANCES BEGIN TO SLOWLY
INCREASE...AS EARLY AS THURSDAY. MUCH OF THE FORECAST FROM THURSDAY
NIGHT THROUGH SATURDAY NIGHT IS BROAD BRUSHED WITH 30-40 PERCENT
CHANCES AS THE FORECAST PATTERN LENDS ITSELF TO MULTIPLE ROUNDS OF
CONVECTION. WILL LIKELY HAVE TO WAIT MANY DAYS TO NAIL DOWN ANY
TIMING OR LOCATION OF THIS CONVECTION. CERTAINLY POTENTIAL HERE FOR
HEAVY RAIN...AND POSSIBLY SEVERE WEATHER TOO...BUT THOSE DETAILS ARE
TOO EARLY TO HASH OUT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 307 AM CDT SUN JUN 16 2013

FG/BR BECOMING A PROBLEM ALONG/EAST OF THE MS RIVER EARLY THIS
MORNING. WIND HAVE TRENDED LIGHTER THAN EARLIER EXPECTED. THESE
LIGHT/VARIABLE/CALM WINDS COMBINED WITH HIGH BOUNDARY LAYER MOISTURE
FROM RAINS SAT/SAT EVENING AND CLEAR/MOSTLY CLEAR SKIES HAVE
RESULTED IN MORE BR/FG FORMATION AT VALLEY SITES LIKE KLSE. EVEN
WITH A LIGHT WEST/NORTHWEST WINDS...SOME BR FORMING AT HIGHER
ELEVATION SITES ACROSS SOUTHEAST MN /KRST/KAUM/KTOB/.

MVFR/IFR CONDITIONS IN BR/FG CAN BE EXPECTED THRU THE MS/WI RIVER
VALLEYS /KLSE/ THRU 13Z...WITH SOME MVFR VSBYS AT KRST THRU THE SAME
TIME FRAME. GIVEN IT/S MID JUNE NEAR THE SUMMER SOLSTICE AND THE SUN
RISES AROUND 530 AM...THE FOG/BR SHOULD BURN OFF VERY QUICKLY THIS
MORNING...AND BE GONE BY 13Z/1330Z. GOOD VFR THEN EXPECTED THRU
SUN/SUN EVENING.

LATER SUNDAY NIGHT...A BOUNDARY TO THE NORTH WILL SINK SOUTH WITH
SOME WEAK MOISTURE TRANSPORT ALONG IT. A FEW SHRA/TS COULD SPARK
ALONG THE BOUNDARY...AND COULD IMPACT KRST/KLSE AFTER 06Z.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR WIZ017-029-
     032>034-041>044-053.

MN...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR MNZ088-096.

IA...NONE.
&&

$$

UPDATE...AJ/RRS
SHORT TERM...AJ
LONG TERM...AJ
AVIATION.....RRS