Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KARX 111958
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
258 PM CDT THU SEP 11 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 258 PM CDT THU SEP 11 2014

MAIN FORECAST CONCERNS TONIGHT INTO FRIDAY ARE PRECIPITATION CHANCES.

LATEST WATER VAPOR SATELLITE IMAGERY SHOWING VIGOROUS SHORTWAVE
TROUGH OVER MONTANA AND NORTHERN WYOMING AND WESTERLY FLOW OVER
UPPER MIDWEST AND GREAT LAKES REGION. LATEST VISIBLE SATELLITE
IMAGERY INDICATING CUMULUS CLOUDS DEVELOPING OVER MINNESOTA...AND
WESTERN WISCONSIN AND NORTHEAST IOWA. ALSO...VISIBLE SATELLITE
IMAGERY SHOWING MID LEVEL CLOUDS STREAMING EASTWARD IN ADVANCE OF
VIGOROUS SHORTWAVE TROUGH INTO NEBRASKA...SOUTH DAKOTA AND SOUTHWEST
MINNESOTA. NORTHERLY FLOW NEAR THE SURFACE...COOLER AIRMASS HAS
FILTER INTO THE FORECAST AREA...WITH TEMPERATURE READINGS IN
THE UPPER 40S TO UPPER 50S PER LATEST 20Z METARS.

THE LATEST 11.12Z GFS/NAM CONTINUE TO BE IN GOOD AGREEMENT IN MOVING
VIGOROUS SHORTWAVE TROUGH INTO THE UPPER GREAT LAKES REGION TONIGHT
INTO FRIDAY. THE 11.12Z GFS/NAM SHOW STRONG PV ADVECTION/ISENTROPIC
LIFT AND QG FORCING INTO THE FORECAST AREA AFTER 09Z FRIDAY IN
ASSOCIATION WITH SHORTWAVE TROUGH AND FOCUS THE STRONGEST
FORCING/LIFT TO BE OVER THE SOUTHERN FORECAST AREA DURING THE DAY
FRIDAY. WITH THE MODELS INDICATING GOOD RUN TO RUN CONSISTENCY WITH
THE SHORTWAVE TROUGH...CONFIDENCE IS INCREASING A FRONTOGENETICAL
BAND OF PRECIPITATION WILL DEVELOP AND MOVE OVER THE SOUTHERN
FORECAST AREA AFTER 09Z FRIDAY. HAVE INCREASED POPS AFTER 09Z
FRIDAY.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 258 PM CDT THU SEP 11 2014

NEXT CONCERN IS THE POTENTIAL FOR FROST AND FOG IN RIVER VALLEYS
FRIDAY NIGHT INTO SATURDAY MORNING. THE 11.12Z GFS/NAM CONTINUE TO
PROG COOLER AND DRIER AIR TO ADVECT INTO THE UPPER GREAT LAKES
REGION FRIDAY NIGHT BEHIND DEPARTING SHORTWAVE TROUGH. THE BIG
QUESTION WILL BE HOW FAST SKIES WILL CLEAR OUT FRIDAY EVENING/NIGHT
TO ALLOW FOR A RADIATIONAL COOLING NIGHT. THE LATEST 11.12Z NAM/GFS
BUFKIT SOUNDINGS ARE IN AGREEMENT CLOUDS WILL REMAIN OVER CENTRAL
WISCONSIN THROUGH 06Z SATURDAY...AND SKIES SHOULD BE CLEAR WEST OF
THE MISSISSIPPI RIVER BY 06Z SATURDAY...AS SURFACE RIDGE AXIS BUILDS
INTO WESTERN WISCONSIN. WITH THE COLDEST AIRMASS OVER THE FORECAST
AREA AND LIGHT WINDS...TEMPERATURES WILL FALL INTO THE 30S ACROSS
MUCH OF THE FORECAST AREA. AREAS TO PATCHY FROST CAN BE EXPECTED
WEST OF THE MISSISSIPPI RIVER AND EAST OF THE MISSISSIPPI RIVER. IN
ADDITION...THE 11.12Z GFS/NAM CONTINUE TO SHOW LIGHT WINDS BELOW
1000 FEET FRIDAY NIGHT/SATURDAY MORNING PER BUFKIT SOUNDINGS. WILL
CONTINUE MENTION OF PATCHY FOG AFTER 06Z SATURDAY.

SLIGHTLY WARMER TEMPERATURES ARE EXPECTED SUNDAY...AS THE LATEST
11.12Z GFS/NAM/ECMWF INDICATE 850MB TEMPERATURES WARMING TO PLUS 6
TO PLUS 8 DEGREES CELSIUS...DUE TO SOUTHERLY FLOW ADVECTING WARMER
AIR INTO THE REGION.

MAIN FORECAST CONCERN ARE SMALL PRECIPITATION CHANCES SUNDAY NIGHT
INTO MONDAY...THEN TEMPERATURES TUESDAY INTO FRIDAY. THE 11.12Z
GFS/GEM/ECMWF ARE IN GOOD AGREEMENT IN DIGGING UPPER LEVEL TROUGH
OVER THE NORTHEAST UNITED STATES AND GREAT LAKES REGION THROUGH
THE PERIOD. ALL THE MODELS ARE ALSO IN DECENT AGREEMENT IN PUSHING
STRONG SHORTWAVE TROUGH INTO THE AREA SUNDAY NIGHT INTO
MONDAY...WITH MINOR DIFFERENCES IN PLACEMENT OF SURFACE FRONT. THE
11.12Z GFS SHOWS DECENT QG FORCING AND LIFT WITH SHORTWAVE
TROUGH...HOWEVER GFS BUFKIT SOUNDINGS CONTINUE TO INDICATE ZERO
INSTABILITY. WILL CONTINUE CHANCE OF SHOWERS ACROSS MUCH OF THE FORECAST
AREA. SURFACE RIDGE BUILDS INTO THE UPPER MIDWEST AND GREAT LAKES
REGION AND DOMINATES THE FORECAST AREA TUESDAY INTO THURSDAY.
A SLIGHT DIFFERENCE IS NOTED ON THE STRENGTH OF THE RIDGE BETWEEN
THE GFS AND ECMWF...AS GFS MORE AMPLIFIED THAN THE ECMWF BY 12Z
WEDNESDAY. THIS RIDGE SHOULD PROVIDE DRY WEATHER CONDITIONS AND
NEAR SEASONABLE TEMPERATURES WITH THE 11.12Z GEFS SHOWING ZERO TO
MINUS 0.5 DEGREE CELSIUS STANDARD ANOMALIES ACROSS THE GREAT LAKES
REGION TUESDAY INTO THURSDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1201 PM CDT THU SEP 11 2014

THE MVFR CLOUDS HAVE MOVED SOUTH OF BOTH TAF SITES AS SOME
CLEARING DEVELOPED OVER CENTRAL MINNESOTA AND NORTHWEST WISCONSIN.
HOWEVER....THIS CLEARING IS NOW FILLING BACK IN AS THE DAYTIME
HEATING IS CAUSING SOME DIURNAL CUMULUS TO FORM. LOOKING AT
SATELLITE...EXPECT THAT VFR CEILINGS WILL BE OVER THE AREA THIS
AFTERNOON FROM THESE CUMULUS CLOUDS. LOOKING AT THE 11.12Z NAM
BUFKIT SOUNDINGS...THESE LOWER CLOUDS SHOULD DISSIPATE THIS
EVENING AND THERE ARE MIXED SIGNALS AS TO WHETHER THERE WILL BE A
MID LEVEL VFR CEILING IN PLACE OR NOT. WILL CONTINUE THE TRENDS OF
THE PREVIOUS FORECASTS AND SHOW A MID LEVEL VFR CEILING THROUGH
THE NIGHT. THE NEXT SHORT WAVE TROUGH IS WORKING ACROSS THE
NORTHERN ROCKIES AND WILL START TO APPROACH THE REGION LATE FRIDAY
MORNING. MOST OF THE FORCING LOOKS TO INITIALLY BE IN THE MID
LEVELS WHICH SHOULD RESULT IN LOWERING VFR CEILINGS AFTER 12Z
FRIDAY. SOME RAIN WILL FALL WITH THIS SYSTEM BUT SOME UNCERTAINTY
ON HOW FAST IT WILL ADVANCE IN GIVEN THAT IT WILL BE FIGHTING SOME
DRY AIR IN THE LOW LEVELS. BOTH THE NAM AND 11.06Z GFS SUGGEST
THERE IS A POSSIBILITY THAT THE RAIN WILL NOT GET TO THE
INTERSTATE 90 CORRIDOR UNTIL LATE FRIDAY MORNING OR EARLY IN THE
AFTERNOON. BASED ON THIS...WILL ONLY HAVE A VCSH FOR BOTH TAF
SITES STARTING LATE FRIDAY MORNING.


&&

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

$$

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.