Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 180734
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
230 AM CDT FRI JUL 18 2014

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 230 AM CDT FRI JUL 18 2014

HIGH PRESSURE WILL END THE WORK WEEK ON A MOSTLY SUNNY AND DRY NOTE.
THE HIGH WILL EASE EASTWARD OVER THE WEEKEND ALLOWING FOR A BIT OF
UPPER LEVEL ENERGY TO SPIN ACROSS FAR NORTHERN PARTS OF THE REGION
REGION SATURDAY NIGHT. THERE WILL BE A SFC REFLECTION OF THIS
FEATURE...BUT NOT OVERLY CONVERGENT WITH A RATHER BAGGY PRESSURE
GRADIENT. THE GFS AND NAM DEVELOP AN AXIS OF INSTABILITY FROM THE
CENTRAL PLAINS...BENDING NORTHEAST INTO CENTRAL MN SAT. SOME 850 MB
MOISTURE TRANSPORT RIDES AHEAD OF THE FRONT/SHORTWAVE...BUT WEAKENS
THROUGH THE DAY ON SATURDAY AND BECOMES STRONGER-MORE FOCUSED INTO
THE CENTRAL/NORTHERN PLAINS SAT EVENING. ALL SAID...SHOULD STILL BE
ENOUGH FORCING/INSTABILITY TO FIRE OFF SOME SHOWERS/STORMS ACROSS
SOUTHERN-CENTRAL MN INTO NORTHWEST WI SAT AFTERNOON-NIGHT. TRENDS
WOULD KEEP THE CHANCES JUST WEST/NORTH OF THE FORECAST AREA FOR THE
TIME BEING.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 230 AM CDT FRI JUL 18 2014

THE SAT SFC BOUNDARY WILL LIKELY HANG JUST WEST ON SUNDAY...WITHOUT
MUCH IMPETUS TO MOVE. THAT PUSH SHOULD COME AT THE START OF THE NEW
WORK WEEK AS THE GFS AND ECMWF TAKE AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE NORTHERN PLAINS AND OVER NORTHERN PARTS OF THE UPPER
MISSISSIPPI RIVER VALLEY BY 12Z TUE. SOME STRENGTHENING IN THIS
TROUGH AS IT MOVES ACROSS THE EASTERN GREAT LAKES BY 12Z WED. THE
SYSTEM WILL HAVE THE INSTABILITY AXIS TO WORK ON...AS IT SLOWLY
SHIFTS FROM MN INTO WESTERN WI TUE EVENING. STEADY FLOW OF LOW LEVEL
MOISTURE FOR THE FORCING TO FEED ON...VIA 850 MB MOISTURE TRANSPORT.
BEST PCPN CHANCES FROM THE GFS/EC FOCUS ON TUE/TUE NIGHT. THE BULK
OF THE RAIN WOULD SHIFT EAST WED MORNING.

SOME THREAT FOR RAIN SUN-MON AS THE SFC BOUNDARY HANGS JUST TO THE
WEST...ALONG WITH THE BETTER INSTABILITY AND LOW LEVEL MOISTURE FEED.
IF THIS BOUNDARY-INSTABILITY AXIS SHIFTS JUST A BIT EAST...SO WILL
THOSE RAIN CHANCES. WILL CONTINUE TO LEAN TOWARD A DRY
FORECAST...WITH INCREASING CHANCES ON THE WESTERN/NORTHERN EDGES.

THE GFS AND EC BOTH SUPPORT ZONAL TO BROAD UPPER LEVEL RIDGING FOR
MUCH OF NEXT WEEK. OUTSIDE OF MON/TUE...THIS WOULD SUPPORT DRY AND
SEASONAL CONDITIONS. ITS NOT A STRONG RIDGE...SO SOME SHORTWAVE
RUNNERS ACROSS IT COULD RESULT IN PCPN CHANCES. GFS/EC SUGGEST THIS
COULD HAPPEN IN THE FRI/SAT TIME FRAME...ALTHOUGH HAVE DIFFERENCES
IN TIMING/PLACMENT/STRENGTH OF THE FEATURES. WILL LEAN TOWARD A DRY
FORECAST FOR NOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT) ISSUED AT
1152 PM CDT THU JUL 17 2014

THE MAIN FOCUS AT THE TAF SITES IS WITH THE POTENTIAL FOR VALLEY FOG
THIS MORNING AT LSE. DESPITE SURFACE WINDS GENERALLY BEING ON THE
LIGHT SIDE...WINDS JUST OFF THE SURFACE ARE INCREASING AND SHOULD BE
GUSTY ENOUGH TO KEEP VALLEY FOG FROM BECOMING WIDESPREAD THIS
MORNING. WILL KEEP BCFG IN THE TAFS AS CONFIDENCE IS NOT HIGH THAT
ANY OF THE LOWER CONDITIONS WILL OCCUR AT LSE. OTHERWISE...WINDS
WILL REMAIN OUT OF THE SOUTH THROUGH FRIDAY NIGHT WITH ANOTHER FAIR
WEATHER CUMULUS FIELD TO DEVELOP BY AFTERNOON.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION.....HALBACH


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