Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 020812
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
312 AM CDT THU JUL 2 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 312 AM CDT THU JUL 2 2015

LATEST 07Z SURFACE ANALYSIS SHOWS HIGH PRESSURE CENTERED OVER
NORTHERN WISCONSIN AND LAKE SUPERIOR. LATEST METARS INDICATE PATCHY
FOG IN THE MISSISSIPPI TRIBUTARIES AND PARTS OF CENTRAL WISCONSIN.

THE 02.00Z GFS/NAM/ECMWF ARE IN GOOD AGREEMENT IN SLOWLY BUILDING
SURFACE RIDGE INTO EASTERN WISCONSIN AND NORTHERN IOWA TODAY INTO
TONIGHT. WITH SURFACE RIDGE ENTRENCHED OVER THE AREA AND MAIN
SHORTWAVE ENERGY REMAINING JUST TO THE WEST OF THE FORECAST AREA
TODAY INTO TONIGHT...THIS WILL ALLOW FOR DRY WEATHER ACROSS THE
FORECAST AREA.

WITH MOSTLY CLEAR SKIES...LIGHT WINDS AND THE 02.00Z BUFKIT
SOUNDINGS SUGGEST INVERSION DEVELOPING IN RIVER VALLEYS TONIGHT...HAVE
INTRODUCED PATCHY FOG IN THE MISSISSIPPI RIVER/TRIBUTARIES AND
PARTS OF CENTRAL WISCONSIN.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 312 AM CDT THU JUL 2 2015

NEXT CONCERN ARE SMALL PRECIPITATION CHANCES FRIDAY AND SATURDAY
ACROSS THE CENTRAL WISCONSIN. THE 02.00Z GFS/NAM/ECMWF ARE IN DECENT
AGREEMENT IN DIGGING UPPER LEVEL TROUGH OVER THE NORTHERN GREAT
LAKES REGION AND SOUTHERN CANADA FRIDAY. WEAK IMPULSE EMBEDDED IN
THE NORTHWEST FLOW ALOFT/WEAK SURFACE FRONT MOVES INTO NORTHERN
WISCONSIN AFTER 18Z FRIDAY. THE 02.00Z GFS/NAM/ECMWF SHOW WEAK 925-
850MB MOISTURE TRANSPORT IN ASSOCIATION WITH THE WEAK SURFACE
FRONT/IMPULSE AND THE 02.00Z GFS/NAM BUFKIT SOUNDINGS SUGGEST STEEP
LOW LEVEL LAPSE RATES AFTER 18Z FRIDAY. AN ISOLATED
SHOWER/THUNDERSTORM WILL BE POSSIBLE ACROSS NORTH CENTRAL WISCONSIN
FRIDAY AFTERNOON INTO THE EVENING HOURS.

SATURDAY...THE 02.00Z GFS/ECMWF/NAM SUGGEST WEAK 850-700MB MOISTURE
CONVERGENCE ALONG A WEAK SURFACE FRONT OVER NORTHERN WISCONSIN.
THE BIGGEST QUESTION WILL BE PLACEMENT OF SURFACE FRONT...AS THE
02.00Z GFS IS FARTHER SOUTH THAN THE 02.00Z NAM/ECMWF. THE NAM/GFS
SUGGEST A LITTLE MORE INSTABILITY THAN FRIDAY PER BUFKIT SOUNDINGS
ACROSS THE NORTHERN SECTIONS OF THE FORECAST AREA. HOWEVER...WHAT
COULD PREVENT ANY WIDESPREAD CONVECTION...WILL BE SHORTWAVE
RIDGING ALOFT OVER THE FORECAST AREA. WITH THE 02.00Z
GFS/NAM/ECMWF SHOW WEAK MOISTURE CONVERGENCE ALONG THE FRONT AND
STEEP LOW LEVEL LAPSE RATES...ISOLATED SHOWERS/THUNDERSTORMS ARE
ONCE AGAIN POSSIBLE ACROSS THE NORTHERN PARTS OF THE FORECAST
AREA.

MAIN FORECAST CONCERNS SATURDAY NIGHT INTO WEDNESDAY ARE
PRECIPITATION CHANCES SUNDAY INTO TUESDAY. THE 02.00Z
GFS/ECMWF/ECMWF ARE IN AGREEMENT DIGGING UPPER LEVEL TROUGH OVER
THE NORTHERN PLAINS AND MOVING UPPER LEVEL TROUGH INTO THE GREAT
LAKES REGION SUNDAY INTO MONDAY. THE BIGGEST DIFFERENCE BETWEEN
THE MODELS IS THE STRENGTH OF THE UPPER LEVEL TROUGH...AS THE
02.00Z ECMWF SLIGHTLY STRONGER THAN THE 02.00Z GFS/GEM...HENCE A
SLOWER PROGRESSION WITH SURFACE FEATURES/UPPER LEVEL TROUGH. THE
02.00Z GFS/ECMWF/GEM SHOW DECENT MOISTURE CONVERGENCE IN
ASSOCIATION WITH SURFACE FRONT/UPPER LEVEL TROUGH. WILL CONTINUE
WITH SHOWER AND THUNDERSTORM CHANCES ACROSS THE FORECAST AREA LATE
SUNDAY INTO TUESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1150 PM CDT WED JUL 1 2015

MODEL SOUNDINGS CONTINUE TO SHOW A VERY DEEP LAYER OF LIGHT WINDS
UP TO 10K FEET OVERNIGHT. THIS CAUSES BOTH THE NAM AND RAP
SOUNDINGS TO DEVELOP A VERY SHALLOW SATURATED LAYER NEAR THE
GROUND. MEANWHILE THE GFS SOUNDING STILL DOES NOT SHOW THIS
DEVELOPING. WITH KLSE ALREADY AT 3 DEGREES TEMPERATURE/DEW POINT
SPREAD SOMEWHAT CONCERNED THAT VALLEY FOG COULD DEVELOP.
HOWEVER AT THE SAME TIME...WE HAVE HAVE NOT SEEN PRECIPITATION IN
A COUPLE OF DAYS AND THE NIGHTS STILL ARE RELATIVELY SHORT. BOTH
OF THESE ARE NEGATIVES TO FOG FORMATION. DUE TO THIS...STILL THINK
THAT THE BEST CHANCES FOR FOG FORMATION WILL BE ACROSS CENTRAL
WISCONSIN AND IN THE KICKAPOO AND WISCONSIN RIVER VALLEYS. HOWEVER
CANNOT COMPLETELY RULE IT POSSIBLY DEVELOPING IN THE MISSISSIPPI
TRIBUTARIES AND THEN MIGRATING INTO THE MAIN CHANNEL BY MORNING.
DUE TO THIS...WILL JUST LEAVE THE 4SM REDUCTION CAUSED BY BR AND
LA CROSSE BETWEEN 02.10Z AND 02.14Z.

OTHER THAN THE FOG CHANCES OVERNIGHT...THERE ARE NO OTHER CONCERNS
WITH CEILINGS OR VISIBILITIES.


&&

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

$$

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



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