Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 011203
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
703 AM CDT WED JUL 1 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 303 AM CDT WED JUL 1 2015

LATEST WATER VAPOR SATELLITE IMAGERY SHOWS UPPER LEVEL RIDGE AXIS
OVER THE WEST COAST OF THE UNITED STATES AND UPPER LEVEL TROUGH OVER
THE EASTERN UNITED STATES. SEVERAL SHORTWAVE TROUGHS OVER-TOPPING
THE RIDGE AND EMBEDDED IN THE NORTHWEST FLOW ALOFT OVER THE NORTHERN
PLAINS PER WATER VAPOR SATELLITE IMAGERY. LATEST INFRARED
SATELLITE IMAGERY INDICATES MID TO HIGH LEVEL CLOUDS OVER MUCH OF
MINNESOTA AND WESTERN WISCONSIN FROM UPSTREAM SHOWER/THUNDERSTORMS
ACROSS THE NORTHERN PLAINS AND THE HIGH PLAINS. LATEST SURFACE
ANALYSIS SHOWS SURFACE RIDGE OVER SOUTHERN ONTARIO AND LAKE
SUPERIOR.

THE 01.00Z GFS/NAM ARE IN GOOD AGREEMENT WITH THE PLACEMENT OF THE
UPPER LEVEL RIDGE OVER THE WESTERN UNITED STATES AND THE MOVEMENT OF
THE INDIVIDUAL IMPULSES OVER-TOPPING THE RIDGE AXIS INTO THE
NORTHERN PLAINS TODAY INTO TONIGHT. WITH THE PLACEMENT OF THE UPPER
LEVEL RIDGE AXIS OVER THE WEST COAST/SURFACE RIDGE BUILDING INTO
EASTERN WISCONSIN TODAY INTO TONIGHT. THIS SHOULD KEEP TRACK OF SHORTWAVE
TROUGHS WEST OF THE FORECAST AREA. DUE TO THE NORTHERLY FLOW
ALOFT OVER THE FORECAST AREA...COOLER AIR FILTERS INTO THE GREAT
LAKES REGION...WITH 850MB TEMPERATURES AROUND PLUS 10 DEGREES
CELSIUS BY 00Z THURSDAY. HIGH TEMPERATURES WILL REMAIN BELOW
NORMAL ACROSS THE FORECAST AREA TODAY.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 303 AM CDT WED JUL 1 2015

THE 01.00Z GFS/NAM/ECMWF CONTINUE TO SHOW SURFACE RIDGE AXIS AND DRY
EAST TO NORTHEASTERLY FLOW ABOVE THE SURFACE OVER THE FORECAST AREA
THURSDAY INTO FRIDAY NIGHT. THE BIGGEST DIFFERENCE BETWEEN THE
MODELS IS THE 01.00Z GFS TRACKS SHORTWAVE TROUGH FARTHER EAST THAN
THE NAM/ECMWF THURSDAY AND THIS WOULD IMPACT THE FAR WESTERN
FORECAST AREA...WITH THE POSSIBILITY OF SHOWERS AND THUNDERSTORMS.
DUE TO THE DRIER NORTHERLY FLOW ALOFT AND BUFKIT SOUNDINGS
INDICATING WEAK LIFT OVER THE WESTERN PART OF THE FORECAST AREA.
WILL CONTINUE TREND OF DRY WEATHER THURSDAY THROUGH FRIDAY NIGHT.
COOL AIRMASS REMAINS OVER THE GREAT LAKES REGION DURING THIS
PERIOD...TEMPERATURES ARE EXPECTED TO REMAIN SLIGHTLY TO NEAR NORMAL
ACROSS THE FORECAST AREA.

SATURDAY INTO TUESDAY...MAIN FORECAST CONCERNS ARE PRECIPITATION
CHANCES SUNDAY INTO MONDAY NIGHT. THE 01.00Z GFS/ECMWF/GEM ARE IN
AGREEMENT IN DEVELOPING WEST TO EAST ZONAL FLOW ACROSS THE NORTHERN
TIER STATES SATURDAY...THEN SLIGHTLY DIVERGE ON THE STRENGTH OF THE
UPPER LEVEL TROUGH DIGGING ACROSS THE NORTHERN PLAINS SUNDAY INTO
MONDAY...AND TIMING OF THE SURFACE FEATURES IN ASSOCIATION WITH
THE UPPER LEVEL TROUGH. THE 01.00Z GFS/ECMWF/GEM SUGGEST DECENT
MOISTURE CONVERGENCE ALONG SURFACE FRONT LATE SUNDAY INTO MONDAY
NIGHT. WILL CONTINUE TREND OF PRECIPITATION CHANCES...WITH HIGHER
CHANCES OCCURRING ACROSS THE FORECAST AREA SUNDAY NIGHT. SURFACE
FRONT/UPPER LEVEL TROUGH PUSHES SOUTH AND EAST OF THE FORECAST
AREA BY 12Z TUESDAY AND SUBSIDENCE BEHIND SURFACE FRONT/UPPER
LEVEL TROUGH WILL ALLOW FOR PRECIPITATION TO EXIT THE FORECAST
AREA. HAVE REMOVED SMALL PRECIPITATION CHANCES ACROSS THE FORECAST
AREA TUESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 703 AM CDT WED JUL 1 2015

VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A WEAK UPPER
LEVEL DISTURBANCE WILL MOVE ACROSS WESTERN MINNESOTA/WESTERN IOWA
THIS MORNING INTO THIS AFTERNOON PRODUCING A FEW RAIN SHOWERS
MAINLY WEST OF INTERSTATE 35. THE MAIN IMPACT TO THE TAF SITES
WILL BE AN INCREASE IN MID LEVEL CLOUDS AS THE WAVE MOVES THROUGH.
HIGH PRESSURE WILL BE IN CONTROL TONIGHT WITH MOSTLY CLEAR SKIES
EXPECTED. LIGHT WINDS AND THE MOSTLY CLEAR SKIES WILL SET THE
STAGE FOR PATCHY TO AREAS OF VALLEY FOG AT KLSE. FORECAST
SOUNDINGS SHOW A LIGHT WIND LAYER FROM THE SURFACE THROUGH AROUND
3 KFT WITH TEMPERATURE/DEWPOINT SPREADS APPROACHING 0...BASED ON
THE NAM. HAVE INTRODUCED MVFR CONDITIONS IN BR. GIVEN THE DRIER
FLOW FROM THE EAST/NORTHEAST DID NOT FEEL CONFIDENT ENOUGH TO
INTRODUCE LIFR CONDITIONS IN FOG. IF FORECAST MODEL TRENDS
CONTINUE LIFR CONDITIONS MAY NEED TO BE ADDED TO THE TAF AFTER
09Z.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...WETENKAMP


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