000
FXUS63 KARX 200450
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1150 PM CDT WED JUN 19 2013

.SHORT TERM...(TONIGHT THROUGH SATURDAY)
ISSUED AT 303 PM CDT WED JUN 19 2013

MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES AND POTENTIAL
SEVERE WITH THUNDERSTORMS THROUGH PERIOD.

LATEST WATER VAPOR SATELLITE IMAGERY INDICATES SHORTWAVE RIDGING OVER
EASTERN HALF OF MINNESOTA AND WESTERN WISCONSIN AND UPPER LEVEL
TROUGH DIGGING OVER THE WESTERN UNITED STATES. LATEST 19Z SURFACE
ANALYSIS SHOW SURFACE RIDGE OVER NORTHERN MICHIGAN AND ALLOWING FOR
PARTLY SUNNY SKIES ACROSS MUCH OF THE FORECAST AREA...PER LATEST
VISIBLE SATELLITE IMAGERY.

THE 19.12Z GFS/NAM ARE IN GOOD AGREEMENT DIGGING UPPER LEVEL TROUGH
OVER WESTERN UNITED STATES AND DEVELOPING SOUTHWESTERLY FLOW ALOFT
OVER THE CENTRAL UNITED STATES. BIG CONCERN WILL BE TIMING OF THE
SERIES OF SHORTWAVE TROUGHS EJECTING OUT INTO THE UPPER MIDWEST
TONIGHT INTO SATURDAY. THE 19.12Z GFS/NAM HANDLE THE FIRST COUPLE OF
SHORTWAVES THROUGH 00Z FRIDAY OKAY...THEN AFTER 00Z FRIDAY FLOW
BECOMES MUDDLED WITH MESOSCALE COMPLEX VORTICIES AND CONFIDENCE IN
TIMING OF SHORTWAVE TROUGHS BECOMES VERY LOW.

TONIGHT INTO THURSDAY...FIRST IMPULSE TO PUSH OVER THE AREA
AFTER 06Z THURSDAY. THE 19.12Z GFS/NAM SHOW WEAK MOISTURE TRANSPORT
IN ASSOCIATION WITH THE SHORTWAVE TROUGH AND THE LATEST 19.12Z
ARW/19.17Z HRRR PRODUCE CONVECTION OVER PARTS OF MINNESOTA AFTER 06Z
THURSDAY. THIS CONVECTION MOVES EAST OVER  PARTS OF THE FORECAST
AREA. EXPECT SOME SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE
BY 12Z THURSDAY AND CONTINUE DURING THE DAYTIME HOURS.

THE LATEST 19.12Z GFS/NAM INDICATE SEVERAL IMPULSES TO EJECT OUT
INTO THE UPPER MIDWEST THURSDAY NIGHT INTO SATURDAY AND TO AFFECT
PORTIONS OF THE FORECAST AREA. THE CONCERN WILL BE TIMING AND
PLACEMENT OF EACH INDIVIDUAL IMPULSE INTO THE REGION DURING THIS
TIMEFRAME. THE 19.12Z DETERMINISTIC MODELS SHOW DECENT SURGE OF
MOISTURE TRANSPORT AND LIFT IN ASSOCIATION WITH EACH SHORTWAVE
TROUGHS. CONFIDENCE IS INCREASING THE FORECAST AREA WILL RECEIVE
SHOWERS AND THUNDERSTORMS...HENCE HAVE INCREASED PRECIPITATION
CHANCES ESPECIALLY THURSDAY NIGHT.

THE LATEST 19.12Z GFS/NAM CONTINUE TO SHOW LACK OF DEEP SHEAR WITH
UP TO 30 KNOTS OF 0-6KM WIND SHEAR FROM THURSDAY INTO SATURDAY.
THE DETERMINISTIC MODELS INDICATE AROUND 30 KNOTS OF 0-3KM SHEAR...
WITH INCREASING LOW LEVEL MOISTURE...INSTABILITY WILL INCREASE OVER
THE AREA. THIS WILL ALLOW FOR THE POTENTIAL OF SOME OF THE COMPLEX
OF THUNDERSTORMS TO BECOME SEVERE WITH DAMAGING WINDS THE MAIN
THREAT. PRECIPITABLE WATER VALUES WILL INCREASE TO 1.5 TO 2 INCHES
ACROSS THE FORECAST AREA THURSDAY INTO SATURDAY. IF ANY OF THE
THUNDERSTORMS MOVE OVER THE SAME AREA...FLASH FLOODING WILL BE A
CONCERN.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 303 PM CDT WED JUN 19 2013

MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES AND TEMPERATURES
THROUGH THE PERIOD. THE 19.12Z GFS/ECMWF/GEM ARE IN GOOD AGREEMENT IN
CARVING OUT UPPER LEVEL TROUGH OVER THE WESTERN UNITED STATES AND
CONTINUE SOUTHWESTERLY FLOW ALOFT OVER THE CENTRAL UNITED STATES
THROUGH 00Z TUESDAY. THEN...THE DETERMINISTIC MODELS BEGIN TO BUILD
UPPER LEVEL RIDGE OVER THE WESTERN UNITED STATES FOR TUESDAY AND
WEDNESDAY. BIGGEST DIFFERENCE BETWEEN THE MODELS IS TIMING THE
EMBEDDED SHORTWAVE TROUGHS IN THE SOUTHWESTERLY FLOW ALOFT INTO THE
REGION THROUGH THE PERIOD. THIS WILL HAVE IMPACTS ON THE STRENGTH OF
THE UPPER LEVEL RIDGE...AS THE DETERMINISTIC MODELS SUGGEST RIDGE
FLATTENING OUT OVER THE NORTHERN TIER STATES TUESDAY AND WEDNESDAY.
WITH THE UNCERTAINTY ON TIMING OF SHORTWAVE TROUGHS INTO THE
FORECAST AREA...WILL CONTINUE WITH CHANCES OF PRECIPITATION
THROUGH THE PERIOD. NEXT CONCERN ARE TEMPERATURES THROUGH PERIOD...
THE 19.12Z DETERMINISTIC MODELS SHOW 925MB PLUS 20 TO PLUS 25 DEGREES
CELSIUS OVER FORECAST AREA THROUGH MUCH OF THE PERIOD...WITH THE
WARMEST AIR FILTERING INTO THE FORECAST AREA TUESDAY...WHERE THE
19.12Z ECMWF INDICATES PLUS 26 DEGREES CELSIUS OVER FORECAST AREA AT
00Z WEDNESDAY. THIS WOULD SUGGEST AROUND 90 DEGREE HIGH TEMPERATURES
ACROSS FORECAST AREA TUESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1150 PM CDT WED JUN 19 2013

CONVECTION THAT DEVELOPED THIS EVENING OVER SOUTH DAKOTA HAS BEEN
WEAKENING OVER SOUTHWEST MINNESOTA IN FAVOR OF NEW DEVELOPMENT
FARTHER NORTH ACROSS SOUTH DAKOTA INTO NORTH DAKOTA. THIS IS WHERE
THE BEST LOW LEVEL MOISTURE FEED IS OCCURRING AND THE 20.00Z NAM
NOW SHOWS LITTLE TO NO EASTWARD MOVEMENT THROUGH THE NIGHT. THE
20.02Z HRRR SEEMS TO HAVE A DECENT HANDLE ON THE CURRENT ACTIVITY
AND SHOWS A SLOW NORTHEAST MOVEMENT AS IT STAYS IN THE MEAN LOW
LEVEL FLOW. THIS SEEMS REASONABLE BASED ON CURRENT TRENDS AND HAVE
OPTED TO REMOVE THE VCSH FROM BOTH TAF SITES FOR THE LATE NIGHT
INTO THURSDAY MORNING. ALSO PULLED THE VCTS FOR THURSDAY AFTERNOON
AS THE NEW NAM SLOWED THE ARRIVAL OF THE NEXT SHORT WAVE TROUGH
SLIGHTLY TO POINT THAT THERE MAY BE A LITTLE BIT OF SHORT WAVE
RIDGING OCCURRING DURING THE AFTERNOON. STILL WOULD NOT BE TOTALLY
SURPRISED IF SOME STRAY CONVECTION DEVELOPED WITH THE EASTERN
CONVERGENT SIDE OF THE LOW LEVEL MOISTURE TRANSPORT STILL COMING
INTO THE AREA. CONVECTION EXPECTED TO DEVELOP OVER NORTH DAKOTA
AND WESTERN MINNESOTA THURSDAY AFTERNOON AND POSSIBLY MOVE
SOUTHEAST TOWARD THE AREA DURING THE EVENING. THE NAM WOULD
SUGGEST THAT SOME OF THIS ACTIVITY COULD BEGIN TO AFFECT THE TAF
SITES AROUND 21.06Z BUT CONFIDENCE IS NOT HIGH ENOUGH IN THAT
TIMING TO INCLUDE IN THE FORECAST AT THIS TIME.

&&

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

$$

SHORT TERM...DTJ
LONG TERM....DTJ
AVIATION...04