Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 010812
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
312 AM CDT MON JUN 1 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 312 AM CDT MON JUN 1 2015

LATEST WATER VAPOR SATELLITE IMAGERY SHOWS UPPER LEVEL TROUGH OVER
THE WEST COAST AND UPPER LEVEL RIDGE OVER THE ROCKY MOUNTAINS. A
COUPLE OF SHORTWAVE TROUGHS EMBEDDED IN THE NORTHWEST FLOW ALOFT
OVER EASTERN IOWA/SOUTHERN WISCONSIN AND EASTERN SOUTH DAKOTA
PRODUCED MID TO HIGH CLOUDS ACROSS SOUTHERN WISCONSIN/WESTERN
MINNESOTA AND EASTERN SOUTH DAKOTA PER INFARED SATELLITE IMAGERY.
LATEST 08Z SURFACE ANALYSIS INDICATES HIGH PRESSURE OVER SOUTHERN
ONTARIO AND LAKE SUPERIOR.

THE 01.00Z GFS/NAM ARE IN GOOD AGREEMENT IN BUILDING UPPER LEVEL
RIDGE INTO THE NORTHERN PLAINS AND GREAT LAKES REGION AND ALSO
KEEPING SURFACE RIDGE ENTRENCHED OVER THE GREAT LAKES REGION. THIS
WILL BE THE DOMINANT WEATHER FEATURE TODAY INTO TUESDAY. MID TO
HIGH CLOUDS IN ASSOCIATION WITH A SHORTWAVE TROUGH OVER WESTERN
MINNESOTA AND EASTERN SOUTH DAKOTA WILL ERODE/EVAPORATE TODAY...AS
THE MOISTURE ENCOUNTERS THE DRY AIRMASS OVER THE GREAT LAKES
REGION PER THE 00Z UPPER AIR SOUNDINGS.

TEMPERATURES WILL REMAIN BELOW NORMAL TODAY AND BEGIN TO MODERATE
TUESDAY...AS SOUTHERLY WINDS ON BACKSIDE OF RIDGE WILL ADVECT
WARMER TEMPERATURES INTO THE FORECAST AREA.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 312 AM CDT MON JUN 1 2015

NEXT FORECAST CONCERNS ARE PRECIPITATION CHANCES TUESDAY NIGHT INTO
WEDNESDAY NIGHT. THE 01.00Z GFS/NAM AND 31.12Z ECMWF INDICATE
SHORTWAVE RIDGE BEGINS TO FLATTEN OUT...AS EMBEDDED PIECES OF ENERGY
EJECT OUT OF THE UPPER LEVEL TROUGH OVER THE WEST COAST AND INTO THE
NORTHERN PLAINS AND GREAT LAKES REGION. DIFFERENCES OCCUR BETWEEN
THE 01.00Z GFS/NAM AND 31.12Z ECMWF WEDNESDAY INTO WEDNESDAY
NIGHT...AS THE NAM SUGGEST A FASTER FRONTAL PASSAGE WEDNESDAY NIGHT.
WHILE...THE 01.00Z GFS WEAKENS FIRST IMPULSE AND PUSHES THE DEEPER
FORCING/MOISTURE CONVERGENCE NORTHWEST AND SOUTHWEST OF FORECAST
AREA LATE WEDNESDAY INTO WEDNESDAY NIGHT. THE 31.12Z ECMWF SUGGEST
FORECAST AREA WILL BE IN CORRIDOR OF MOISTURE TRANSPORT/CONVERGENCE
ALONG SURFACE COLD FRONT. DPROG/DT OF THE ECMWF/GFS SHOW RUN TO RUN
INCONSISTENCIES WEDNESDAY INTO WEDNESDAY NIGHT THE LAST SEVERAL
RUNS. HOWEVER...THE ECMWF/GFS DPROG/DT SUGGEST THE WESTERN PORTION
OF THE FORECAST AREA WILL BE ON THE EASTERN PERIPHERY OF THE 925-
850MB MOISTURE CONVERGENCE/TRANSPORT BY 00Z THURSDAY. CONFIDENCE
IN FORECAST WEDNESDAY INTO WEDNESDAY NIGHT REMAINS LOW...BASED ON
THE DIFFERENCES BETWEEN THE MODELS ON TIMING AND PLACEMENT OF
SURFACE FEATURES/SHORTWAVE TROUGH. AT THIS TIME...THERE IS A
SIGNAL THE WESTERN HALF OF THE FORECAST AREA WILL BE IMPACTED BY
THE SHORTWAVE TROUGH/SURFACE FRONT LATE WEDNESDAY INTO WEDNESDAY
NIGHT AND WILL CONTINUE WITH CHANCE OF SHOWERS/THUNDERSTORMS.

WITH LIMITED INSTABILITY AND WEAK SHEAR AROUND 20 KNOTS IN THE 0-3KM
LAYER PER THE 01.00Z NAM LATE WEDNESDAY INTO WEDNESDAY
NIGHT...SEVERE RISK OVER THE WESTERN HALF OF THE FORECAST AREA IS
LOW.

MAIN FORECAST CONCERNS THURSDAY INTO SUNDAY ARE PRECIPITATION
CHANCES THROUGH THE PERIOD. THE 01.00Z GFS/GEM AND 31.12Z ECMWF DIG
UPPER LEVEL TROUGH/LOW OVER WESTERN UNITED STATES THROUGH THE
PERIOD. THE 01.00Z GFS/GEM AND 31.12Z ECMWF SHOW A SERIES OF
IMPULSES EMBEDDED IN THE SOUTHWESTERLY FLOW ALOFT TO PUSH INTO THE
UPPER MIDWEST AND GREAT LAKES REGION. BIGGEST DIFFERENCES BETWEEN
THE MODELS IS TIMING OF EACH IMPULSE INTO THE FORECAST AREA AND
STRENGTH OF UPPER LEVEL TROUGH DIGGING OVER THE OHIO RIVER VALLEY
SATURDAY INTO SUNDAY. ENOUGH MOISTURE AND LIFT ASSOCIATED WITH EACH
IMPULSE...WARRANTS CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH MUCH
OF THE FORECAST PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1144 PM CDT SUN MAY 31 2015

SHORT WAVE RIDGING IN THE WAKE OF A DEPARTING SHORT WAVE WILL
PROVIDE GENERALLY CLEAR SKIES THROUGH THE PERIOD. WINDS WILL BE
PRIMARILY EAST AND SOUTHEAST. WIND SPEEDS WILL BE LESS THAN 10
KNOTS.


&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...BOYNE


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