Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Text Only | 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 241721
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1221 PM CDT SUN AUG 24 2014

.UPDATE...
ISSUED AT 1221 PM CDT SUN AUG 24 2014

VISIBLE SATELLITE SHOWING STRATUS ERODING FROM WEST TO EAST ACROSS
THE FORECAST AREA AS SOUTHERLY FLOW INCREASES AND DAYTIME HEATING MIXES
OUT THE LOWER BOUNDARY LAYER MOISTURE. RAP SHOWING AXIS OF 26-30C
AIR NOSING INTO THE AREA THIS AFTERNOON IN ADVANCE OF A COLD FRONT
PUSHING INTO CENTRAL MN/WESTERN IA. WILL HOLD STEADY ON HIGHS
TOPPING OFF IN THE MIDDLE 80S ACROSS CENTRAL WISCONSIN AND UPPER
80S/AROUND 90 ALONG AND WEST OF THE MISSISSIPPI RIVER. WITH DEW
POINTS IN THE 70S...PLAN ON MAXIMUM HEAT INDICES IN THE 95-100
DEGREE RANGE IN THE 2-6PM TIME FRAME.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 230 AM CDT SUN AUG 24 2014

HOT AND HUMID TODAY. 850 MB SREF TEMP ANOMALIES PEGGING +1.5 TODAY
WHILE 925 MB TEMPS RANGE FROM 26-28 C. HIGHS SHOULD REACH 90 FOR
MANY LOCATIONS. MEANWHILE...SFC DEWPOINTS WILL LIKELY HOLD IN THE
LOW 70S THROUGH THE DAY. THE MIX OF HOT/HUMID AIR WILL PLACE HEAT
INDICES AROUND 100 DEGREES FOR MUCH OF THE FORECAST AREA THIS
AFTERNOON. HOWEVER...SOME UNCERTAINTY TO HOW MUCH CLOUD COVER WILL
BE AROUND TODAY. LOW STRATUS COULD LINGER ACROSS WESTER/CENTRAL WI
THROUGH THE MORNING...WHILE SOME HIGH CLOUDS START TO TRACK INTO
AREAS WEST OF THE RIVER THIS AFTERNOON. ALL WOULD TEMPER TEMPS BACK
A FEW DEGREES...AND THUS DROP THE HEAT INDICES DOWN. AT THIS
TIME...DON/T FEEL A HEAT ADVISORY WILL BE NEEDED. IF TEMPS WARM A
DEGREE OR TWO MORE THAN EXPECTED...ONE MAY BE NECESSARY.

TONIGHT...AN UPPER LEVEL SHORTWAVE TROUGH WILL LIFT NORTHEAST ACROSS
THE NORTHERN PLAINS AND INTO SOUTHERN CANADA. AN ASSOCIATED COLD
FRONT WILL LEAD WELL AHEAD OF THE TROUGH...MOVING INTO WESTERN WI
TOWARD 06Z. A RIBBON OF LOW LEVEL MOISTURE WILL RUN AHEAD OF THE
FRONT...WITH MUCAPES FROM 1-2K J/KG. PLENTY OF FUEL FOR THE BOUNDARY
TO FIRE SHOWERS/STORMS. THE DEEPER SHEAR IS WEST OF THE INSTABILITY
AXIS...BUT ENOUGH 0-3KM SHEAR THAT SOME STORM ORGANIZATION COULD
OCCUR AND POTENTIALLY A STRONG WIND THREAT. MOSTLY...HEAVY RAIN AND
LARGE HAIL WOULD BE THE MAIN THREATS.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 230 AM CDT SUN AUG 23 2014

NAM/GFS/ECMWF CONTINUE TO POINT TO THE SAME SOLUTION THEY HAVE BEEN
SUGGESTING FOR THE PAST FEW DAYS...ONE THAT WILL BRING ROUNDS OF
PCPN WITH THE POTENTIAL FOR HEAVY RAIN AND STRONGER STORMS.

SEVERAL FACTORS WILL PLAY ROLES IN THE PRECIPITATION CHANCES OVER
THE NEXT FEW DAYS.

1) COLD FRONT. THE COLD FRONT THAT TRACKS ACROSS THE REGION LATE
TONIGHT WILL GRADUALLY ORIENTATE ITSELF AS A WEST-EAST STATIONARY
FRONT ACROSS CENTRAL IA-NORTHERN ILL FOR THE FIRST HALF OF THE NEW
WORK WEEK. ESSENTIAL...IT GETS STUCK UNDER THE BROAD UPPER LEVEL
RIDGE...AND IS NOT EXPECTED TO GET A NUDGE OUT OF THE REGION UNTIL
LATER ON THU WHEN A SHORTWAVE TROUGH DRIVES EASTWARD ACROSS THE MID
MISSISSIPPI RIVER VALLEY.

WHERE THE FRONT RESTS WILL BE THE MAIN REGION FOR STORM DEVELOPMENT.

2) LOW LEVEL JET/MOISTURE TRANSPORT. MODELS POINT TO THE NOSE OF THE
850 MB JET AND MOISTURE TRANSPORT FOCUSING INTO WESTERN/SOUTHERN IA
MON-THU NIGHTS...IMPINGING ON AND ACROSS THE STATIONARY FRONT. NIGHT
TIME MCS/S ARE LIKELY IN THIS REGION ALL THESE NIGHTS...TRACKING
EAST OVERNIGHT. ASSOCIATED MCVS WILL LIKELY BE ANOTHER SOURCE FOR
FORCING.

3) INSTABILITY.  NAM AND GFS BUILD UPWARDS OF 4000+ J/KG OF SBCAPE
ALONG AND SOUTH OF THE BOUNDARY. ELEVATED INSTABILITY DOES SLOPE
NORTH ACROSS THE BOUNDARY. FOR THE FORECAST AREA...THE BULK OF THE
INSTABILITY WOULD STAY SOUTH...BUT ENOUGH IN THE VICINITY TO SUPPORT
STORM DEVELOPMENT.

4) WIND SHEAR. THE DEEPER-STRONGER SHEAR IS EXPECTED TO LIE WELL
NORTH OF THE STATIONARY FRONT...IN THE COLDER AIR. THERE COULD BE
ENOUGH OVERLAP OF FAVORABLE SHEAR INTO THE INSTABILITY AXIS TO
FURTHER SUPPORT STORM DEVELOPMENT AND UPDRAFTS. STABLE SFC LAYER
NORTH OF THE FRONT WILL INHIBIT THE GUST POTENTIAL...BUT WON/T
COMPLETELY RULE IT OUT. ALONG AND SOUTH OF THE FRONT THE STRONG WIND
POTENTIAL INCREASES. HEAVY RAIN WILL OCCUR. HAIL WILL BE POSSIBLE
BOTH SIDES OF THE BOUNDARY.

WITH SEVERAL FACTORS FAVORING HEAVY RAIN...ALONG WITH DAILY/NIGHTLY
CHANCES FOR STORMS...THE HYDRO CONCERNS ARE INCREASING. MORE ON THE
THREAT FOR RIVER AND FLASH FLOOD IMPACTS IN THE HYDRO SECTION BELOW.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1221 PM CDT SUN AUG 24 2014

VISIBLE SATELLITE SHOWING STRATUS MIXING OUT NICELY FROM WEST TO
EAST AS INCREASING SOUTHERLY FLOW/DAYTIME HEATING SCOURS OUT THE
LOWER BOUNDARY LAYER. LOOK FOR VFR CONDITIONS GOING INTO THE
AFTERNOON HOURS WITH SOUTH WINDS IN THE 10-20KT RANGE. A FEW
HIGHER GUST AROUND 25KT CAN BE EXPECTED AT KRST.

A COLD FRONT WILL THEN PUSH INTO THE AREA LATER THIS
EVENING...SPARKING OFF A LINE OF SHRA/TSRA. MODELS IN PRETTY GOOD
AGREEMENT THAT THE SOUTHERN END OF THIS LINE OF SHRA/TS WILL
BEGIN AFFECTING KRST AROUND 03-04Z AND KLSE 05-06Z. PLAN ON A FEW
HOUR WINDOW OF SHRA/TSRA ACTIVITY. LOOKS LIKE CIGS SHOULD STAY IN
THE VFR RANGE WITH VIS POSSIBLY DIPPING INTO MVFR FOR A LITTLE
BIT IN TSRA/BR. MODELS INDICATING A BAND OF STRATUS WITH THE
PASSAGE OF THE COLD FRONT IN THE 13-18Z TIMEFRAME. NOT CONFIDENT
YET AT THIS POINT IF THIS WILL CONSTITUTE A CEILING OR NOT. WILL
KEEP AN EYE ON IT.

&&

.HYDROLOGY...
ISSUED AT 230 AM CDT SUN AUG 23 2014

WARM CLOUD DEPTHS CONTINUE TO APPROACH 4 KFT ALONG AND SOUTH OF THE
FRONT WITH PWS UPWARDS OF 1.5 - 1.75 INCHES. STORMS IN THIS
ENVIRONMENT WILL BE EFFICIENT RAIN PRODUCERS...AND HEAVY RAIN WILL BE
LIKELY WITH ANY STRONGER STORM.

STORM TRACKS LOOKS MOSTLY EAST ALONG AND AROUND THE FRONT...FAVORING
TRAINING THUNDERSTORMS AND REPEATED ROUNDS OF SOAKING RAINS. THERE
COULD BE IMPACTS TO RIVER SYSTEMS IF MCS/S IMPACT THE SAME AREAS
NIGHT AFTER NIGHT. THE FLASH FLOOD THREAT WOULD ALSO INCREASE AS
GROUNDS BECOME SATURATED.

OVERALL - CURRENT MODEL SOLUTIONS WOULD KEEP THE BULK OF THE
POTENTIAL HYDRO ISSUES SOUTH OF I-90...MOSTLY NORTHEAST IA AND
SOUTHWEST WI.

A HYDROLOGIC OUTLOOK MIGHT BE NEEDED IN THE NEXT COUPLE DAYS TO
FURTHER OUTLINE THE RAINFALL-RIVER THREATS. WOULD NOT BE SURPRISED
IF FLASH FLOOD WATCHES EVENTUALLY BECOME NECESSARY LATER IN THE
WEEK.

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

&&

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

$$

UPDATE...DAS
SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...DAS
HYDROLOGY....RIECK


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