Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 052259
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
559 PM CDT THU MAY 5 2016

.SHORT TERM...(TONIGHT THRU FRIDAY NIGHT)
ISSUED AT 255 PM CDT THU MAY 5 2016

MAIN FORECAST CONCERNS THIS PERIOD...SMALL -SHRA CHANCES OVER WI
LATE TONIGHT...WARM HIGHS FRIDAY...SHRA/TSRA CHANCES SPREADING IN
FRI NIGHT.

18Z DATA ANALYSIS HAD A RIDGE OF HIGH PRESSURE SLOWLY SINKING SOUTH
OF THE UPPER MIDWEST. SOUTH/SOUTHWEST WINDS ON THE INCREASE ACROSS
THE NORTHWEST HALF OF THE REGION AT MID-DAY...WHILE WIND REMAIN
LIGHT/VARIABLE OR NORTHERLY OVER THE SOUTHEAST HALF OF THE REGION.
BIT OF MOISTURE TRANSPORT/THETA-E CONVERGENCE ON THE LEADING EDGE OF
THE STRONGER LOWER LEVEL WARM ADVECTION CONTINUED TO PRODUCE A FEW
-SHRA OVER FAR NORTHWEST WI AND EAST-CENTRAL MN. OTHERWISE...SKIES
GENERALLY SUNNY ACROSS MN/IA/WI TODAY. WARMEST EARLY AFTERNOON TEMPS
/NEAR 90F/ ACROSS FAR NORTHWEST MN WHILE COOLEST READINGS /MID 50S/
WERE OVER EASTERN WI.

NO ISSUES NOTED WITH 05.12Z MODEL INITIALIZATIONS. MODELS OFFERING A
RATHER TIGHT CONSENSUS TONIGHT THRU FRI NIGHT. THIS AS HGTS RISE/
SHORTWAVE RIDGING ALOFT BUILDS OVER THE UPPER MIDWEST TONIGHT/FRI
THEN AS A NORTHERN STREAM SHORTWAVE DROPS SOUTH INTO THE REGION FRI
NIGHT. TREND FAVORS A COMPROMISE OF THE EARLIER RUNS ON THE HGT
RISE/RIDGING TONIGHT/FRI THEN STRONGER OF THE EARLIER RUNS ON THE
TROUGHING DROPPING IN FRI NIGHT. SHORT-TERM FORECAST CONFIDENCE
REMAINS GOOD THIS CYCLE.

IN THE SHORT TERM...SFC-850MB WARM FRONT CONTINUES TO PUSH EAST
ACROSS THE REGION TONIGHT. STRONGEST OF THE 925-700MB WARM
ADVECTION MOVES ACROSS THE FORECAST AREA LATE THIS EVENING THRU
THE OVERNIGHT HOURS. THIS WITH SOME 850-700MB MOISTURE
TRANSPORT/THETA-E CONVERGENCE...PW VALUES AROUND 0.75 INCH AND
800-550MB LAPSE RATES IN THE 8 TO 8.5 C/KM RANGE. IF 850-800MB
PARCELS CAN BE LIFTED TO 750-700MB WITH THE STRONGER LOW LEVEL
WARM ADVECTION ISOLATED/SCT -SHRA POSSIBLE AS THE STRONGER THERMO-
DYNAMIC FORCING MOVES ACROSS THE EAST SIDE OF THE FORECAST AREA
LATE THIS EVENING INTO THE OVERNIGHT HOURS. WILL CONTINUE WITH A
SMALL -SHRA CHANCE ACROSS THE EAST/ SOUTHEAST ENDS OF THE FORECAST
AREA IN THE 04Z-12Z TIME- FRAME. WITH THE CONTINUED LOW LEVEL WARM
ADVECTION AND SOUTHWEST WINDS 5-10 MPH FOR BOUNDARY LAYER
MIXING...LOWS TONIGHT TO BE SOME 10F TO 20F WARMER THAN THOSE OF
THIS MORNING. LOW LEVEL WARM ADVECTION CONTINUES ON FRI...AHEAD OF
THE NEXT APPROACHING COLD FRONT. COLUMN DRIES IN THE 850-700MB
PORTION...BEHIND THE LOWER LEVEL WARM FRONT. 925MB TEMPS AT 00Z
SAT PROGGED TO BE IN THE 22-24C RANGE...SUPPORTING HIGHS FRI
AFTERNOON IN THE 80-85F RANGE. TIGHTER PRESSURE GRADIENT IS OVER
THE AREA AS WELL ON FRI...FOR SOUTHWEST WINDS 10-20 MPH AND WHAT
SHOULD BE STRONGER BOUNDARY LAYER MIXING. WITH POTENTIAL FOR
DRYING/ LOWERING DEW POINTS FRI ...EVAPO-TRANSPIRATION JUST
GETTING STARTED AND NO CROPS IN THE FIELDS...WILL CONTINUE TO SIDE
WITH WARMER OF GUIDANCE HIGHS FRI. COLD FRONT...MOISTURE/FORCING
INCREASE AHEAD OF/WITH IT DROPS QUICKLY INTO THE AREA FRI NIGHT.
SFC COLD FRONT PROGGED TO BE ALREADY EXITING THE SOUTH END OF THE
FORECAST AREA BY 12Z SAT. MDT BUT WEAKENING 1000-700MB FN
CONVERGENCE TO ACCOMPANY THE FRONT INTO/ACROSS THE AREA. MODEL
SOUNDINGS INDICATING 250 TO AS MUCH AS 1250 J/KG CAPE WHEN LIFTING
800MB PARCELS LATE FRI EVENING INTO THE OVERNIGHT HOURS. EVEN WITH
ALL THIS...BULK OF MODELS INCLUDING HI-RES/WRF MODELS...ONLY
PRODUCING A BAND OF SCT -SHRA/ TSRA AS THE FRONT MOVES SOUTH
ACROSS THE AREA AND WILL LEAVE FRI NIGHT RAIN CHANCES IN THE 20-30
PERCENT RANGE. USED A BLEND OF THE GUIDANCE LOWS TONIGHT/FRI NIGHT
THEN CONTINUED TO TREND TOWARD WARMER OF GUIDANCE HIGHS FRI.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 255 PM CDT THU MAY 5 2016

FOR SATURDAY THRU SUNDAY NIGHT...

MAIN FORECAST CONCERNS THIS PERIOD...SHRA/TSRA CHANCES SAT
MORNING AND AGAIN SUN NIGHT...TEMPERATURES THRU THE PERIOD.

MODEL RUNS OF 05.12Z IN GOOD AGREEMENT SAT/SAT NIGHT AS THE NORTHERN
STREAM SHORTWAVE TROUGH SWINGS SOUTHEAST THRU THE GREAT LAKES.
IMPROVING AGREEMENT AS THIS TROUGH MOVES EAST SUN/SUN NIGHT...HGTS
RISE OVER THE UPPER MIDWEST AND THE MID LEVEL LOW OVER THE ROCKIES
LIFTS INTO THE CENTRAL PLAINS. TREND FAVORS MORE NORTHERLY OF
EARLIER RUNS WITH THE LOW LIFTING INTO THE PLAINS...BEING DRIVEN BY
MODELS TRENDING STRONGER WITH A NORTHERN STREAM SHORTWAVE DIGGING
INTO THE NORTHERN ROCKIES BEHIND IT.

WITH THE COLD FRONT AND THE MOISTURE/FORCING/LIFT WITH IT ALREADY
EXITING THE FORECAST AREA AT 12Z SAT...LIMITED BULK OF ANY
-SHRA/TSRA CHANCES SAT MORNING TO THE 12-15Z PERIOD. TRENDED RAIN
CHANCES SOUTH AND OUT OF THE FORECAST AREA THRU THE REST OF SAT
MORNING AS SUBSIDENCE/ COOLER/DRIER AIR SPREADS SOUTH ACROSS THE
AREA BEHIND THE FRONT. 925MB TEMPS BY SAT AFTERNOON IN THE 12C-14C
RANGE. EVEN UNDER PARTLY CLOUDY/MOSTLY SUNNY SKIES...HIGHS SAT
LOOKING TO BE NEAR NORMAL IN THE 65-70F RANGE. NEXT RIDGE OF CAN
HIGH PRESSURE DRIFTS ACROSS THE UPPER MIDWEST SAT NIGHT...FOR WHAT
SHOULD BE MOSTLY CLEAR/CLEAR SKIES AND LIGHT WINDS...WITH ANOTHER
DRY AIRMASS SETTLING OVER THE REGION. ROLLER-COASTER TEMPERATURE
RIDE CONTINUES...WITH LOWS SAT NIGHT DIPPING INTO THE 35F-45F
RANGE...AND POTENTIAL FOR PATCHY FROST AGAIN IN FAVORED LOW-LAYING
LOCATIONS ALONG/NORTHEAST OF I-94. DID NOT ADD THIS TO GRIDS JUST
YET BUT WILL HAVE TO KEEP AN EYE ON CHILLY LOWS SAT NIGHT. LOW
LEVEL RIDGE AXIS REMAINS OVER THE REGION SUN...WITH GRADUAL
MODIFICATION/WARMING OF THE LOW LEVEL AIRMASS. MOTHERS DAY
CONTINUED TO TREND MOSTLY SUNNY...LIGHT WINDS AND HIGHS ABOUT A
CATEGORY ABOVE NORMAL. GIVEN THE MORE NORTHERLY CONSENSUS OF THE
ROCKIES SYSTEM MOVING INTO THE PLAINS SUN/SUN NIGHT...LEADING
LOWER LEVEL THERMO-DYNAMIC FORCING/LIFT AND INCREASE OF MOISTURE
AHEAD OF IT NOW SPREADS NORTHEAST INTO THE FORECAST AREA LATER SUN
NIGHT. CARRIED MOST OF THE RETURNING -SHRA/TSRA CHANCES IN THE
OVERNIGHT HOURS OF SUN NIGHT. WITH BULK OF ANY MUCAPE NOW LOOKING
TO REMAIN JUST SOUTHWEST OF THE FORECAST AREA SUN NIGHT...LIMITED
TSRA CHANCE TO THE SOUTHWEST HALF HALF OF THE FORECAST AREA
OVERNIGHT SUN NIGHT AS WELL. USED A BLEND OF THE GUIDANCE HIGHS
SAT/SUN AND LOWS SUN NIGHT. TRENDED TOWARD COOLER OF GUIDANCE LOWS
SAT NIGHT UNDER THE SFC RIDGE AXIS AND DRIER BOUNDARY LAYER
AIRMASS.

FOR MONDAY THRU THURSDAY...DAYS 4 TO 7...

MAIN FORECAST CONCERNS THIS PERIOD...SHRA/TSRA CHANCES THRU MOST
OF THE PERIOD...TEMPERATURES.

MEDIUM RANGE MODEL RUNS 05.00Z/05.12Z IN RATHER GOOD AGREEMENT MON
AS THE ROCKIES MID LEVEL LOW OPENS UP AND LIFTS INTO THE CENTRAL
PLAINS. TREND FAVORS FASTER/FURTHER NORTH OF THE EARLIER RUNS WITH
THIS FEATURE...AS THE NORTHERN STREAM WAVE BEHIND IT DIGS MORE
STRONGLY INTO THE NORTHERN ROCKIES. PLENTY OF DETAIL DIFFERENCES BY
TUE BUT LOOSE CONSENSUS FOR REMNANTS OF THE ROCKIES/PLAINS SYSTEM TO
MOVE ACROSS THE UPPER MIDWEST TUE WHILE THE NORTHERN ROCKIES ENERGY
CARVES OUT A DEEPER TROUGH/LOW OVER THE MT/WY/DAKOTAS AREA. LOOSE
CONSENSUS THEN DRIFTS THIS TROUGH/LOW SLOWLY EASTWARD TOWARD/INTO
THE UPPER MIDWEST WED/THU. PLENTY OF DETAIL DIFFERENCES WED/THU TOO.
FORECAST CONFIDENCE IS ABOVE AVERAGE MON THEN AVERAGE FOR TUE
THRU THU.

INCREASING LOWER LEVEL MOISTURE/MOISTURE TRANSPORT AHEAD OF THE
LOW/TROUGH LIFTING INTO THE PLAINS TO SPREAD NORTHEAST ACROSS THE
AREA MON. THIS WITH ROUNDS OF LOW LEVEL WARM ADVECTION/ISENTROPIC
LIFT...MUCAPES AS HIGH AS 250-750 J/KG AND GENERAL DIVERGENCE ALOFT
AHEAD OF THE TROUGH. THIS FORCING/LIFT/INSTABILITY TO THEN CONTINUE
ACROSS THE AREA MON NIGHT/TUE AS THE SFC THRU MID LEVEL TROUGH LIFTS
TOWARD/ACROSS THE UPPER MIDWEST. SHRA/TSRA CHANCES MOSTLY IN THE 40-
60 PERCENT RANGE MON THRU TUE LOOK GOOD. POTENTIAL FOR SOME 1 TO 2
INCH RAINFALLS IN THE MON THRU TUE PERIOD. WED WOULD BE THE BETWEEN-
SYSTEMS PERIOD AS ONE TROUGH EXITS AND THE NEXT ONE TRACKS EAST
ACROSS THE NORTHERN PLAINS. GIVEN ALL THE DETAIL DIFFERENCES...SOME
20-30 PERCENT SHRA/TSRA CHANCES TUE NIGHT THRU WED NIGHT REASONABLE
FOR NOW. THE NEXT LOW/TROUGH WOULD THEN MOVE INTO THE UPPER MIDWEST
THU...BRINGING RENEWED MOISTURE ADVECTION/FORCING/LIFT INTO THE AREA
FOR MORE SHRA/TSRA CHANCES. AGAIN...WITH ALL THE DETAIL DIFFERENCES
AMONG THE MODELS...CONSENSUS 20-40 PERCENT CHANCES OUT ON DAY 7 OKAY
FOR NOW. 925MB TEMPS THRU THE PERIOD GENERALLY SUPPORT HIGHS NEAR
NORMAL...WHILE WHAT WOULD BE MORE CLOUDS WOULD HELP LOWS ABOVE
NORMAL. MODEL/ENSEMBLE CONSENSUS OF HIGHS/LOWS FOR MON THRU THU
LOOKING REASONABLE AT THIS TIME.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 559 PM CDT THU MAY 5 2016

THE AREA OF HIGH PRESSURE AT THE SURFACE WAS CENTERED OVER
NORTHERN MISSOURI LATE THIS AFTERNOON WITH THE RIDGE AXIS
EXTENDING NORTHWARD ACROSS LAKE MICHIGAN INTO ONTARIO. THIS
FEATURE WILL CONTINUE TO DRIFT SOUTH THROUGH THE PERIOD AS A COLD
FRONT ADVANCES ACROSS THE DAKOTAS AND INTO MINNESOTA FRIDAY. GOOD
LOW LEVEL LAPSE RATES WILL DEVELOP AHEAD OF THE COLD FRONT FRIDAY
AFTERNOON BUT WIND SPEEDS IN THE MIXED LAYER DO NOT LOOK ALL THAT
STRONG. STILL ENOUGH FOR SOME GUSTS TO AROUND 20 KNOTS TO OCCUR AT
BOTH SITES. THE LOWER AND MID LEVELS OF THE ATMOSPHERE LOOK TO BE
VERY DRY...SO NOT EXPECTING MUCH IF ANY CLOUDS THROUGH THE PERIOD.

&&

.FIRE WEATHER...FRIDAY
ISSUED AT 255 PM CDT THU MAY 5 2016

THE TEMPERATURES WILL CLIMB INTO THE LOWER AND MID 80S ON FRIDAY
AFTERNOON. THIS ALONG WITH SOUTHWEST WINDS INCREASING TO 10-20MPH
WITH THE STRONGER AND GUSTIER WINDS MAINLY ACROSS THE OPEN COUNTRY
AREAS OF SOUTHEAST MN/NORTHEAST IA. BIGGER QUESTION FRI IS HOW DEEP
WILL THE BOUNDARY LAYER MIX AND HOW DRY/LOW WILL THE AFTERNOON
HUMIDITIES GO. INDICATIONS IN MODEL SOUNDINGS FOR A WEAK/MDT
INVERSION NEAR 850MB ON FRI AS STRONGER WARMING ABOVE 850MB OUTPACES
THE WARMING BELOW 850MB. THIS WOULD TEND TO KEEP AFTERNOON DEW
POINTS MORE IN THE MID-UPPER 40S AND MINIMUM HUMIDITIES MORE IN THE
25-30 PERCENT RANGE. IF THE AIRMASS MIXES DEEPER...AFTERNOON
HUMIDITIES ON FRI WOULD DROP MORE IN THE THE 15-25 PERCENT RANGE.
EITHER WAY...THE WARM TEMPS/WINDS/LOW RH/S WILL MAKE FOR AN ELEVATED
FIRE DANGER DAY ON FRIDAY.

&&

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

$$

SHORT TERM.....RRS
LONG TERM......RRS
AVIATION...04
FIRE WEATHER...RRS


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