Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 300807
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
307 AM CDT SAT APR 30 2016

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 307 AM CDT SAT APR 30 2016

CHALLENGE TODAY THROUGH SUNDAY WILL BE TIMING AND COVERAGE OF
SHOWERS AS WELL AS OVERALL RAINFALL AMOUNTS. 30.00Z GLOBAL MODEL
SUITE IN GOOD AGREEMENT WITH SHORT-RANGE RAP/HRRR THROUGH TODAY
LENDING HIGH CONFIDENCE IN PRECIP FORECAST. HOWEVER...SOME
DIFFERENCES DO EMERGE BY SUNDAY WITH COVERAGE OF LINGERING
SHOWERS. WILL FOLLOW A BLENDED SOLUTION BETWEEN THE WETTER
GFS/ECMWF AND DRIER NAM/GEM SUNDAY AND BEYOND.

30.08Z WATER VAPOR LOOP SHOWS A STRONG CLOSED LOW SPINNING ALONG
THE CO/KS BORDER WITH A LEADING SHORT-WAVE ROUNDING ITS SOUTHERN
PERIPHERY INTO THE CENTRAL PLAINS. THIS SHORT-WAVE WILL UNDERCUT
A HIGHLY AMPLIFIED RIDGE FROM THE OHIO VALLEY INTO THE SOUTHERN
CANADIAN PRAIRIES AND THEN EVENTUALLY MERGE WITH A SECONDARY
TROUGH CURRENTLY DIVING SOUTH ACROSS ONTARIO. NORTHWEST TO
SOUTHEAST ORIENTED BAND OF ENHANCED 850 TO 700 HPA FRONTOGENESIS
AND MOISTURE TRANSPORT ASSOCIATED WITH THE CENTRAL PLAINS SYSTEM
WILL LIFT NORTHWARD THROUGH TODAY...BRINGING SHOWERS INTO THE
FORECAST AREA. EASTERLY SURFACE WINDS...GUSTING AT TIMES TO 25 MPH
WILL ADVECT DRY LOW-LEVEL AIR INTO THE AREA...PROVIDING A SHARP
GRADIENT IN RAINFALL AMOUNTS. LATEST RAP/HRRR SUGGEST THE HEAVIEST
PRECIP WILL ADVANCE NORTHWARD TO WITHIN THE VICINITY OF THE I-90
CORRIDOR BY MID TO LATE AFTERNOON BEFORE GETTING CHOKED OFF BY
THE DRY AIR. WILL KEEP LIKELY/CATEGORICAL POPS ALONG AND SOUTH OF
I-90 WITH CHANCE POPS EXTENDING NORTHWARD TO JUST SOUGH OF HWY 29.
TEMPERATURES TODAY WILL BE DEPENDENT ON RAINFALL...RANGING FROM
THE UPPER 40S ACROSS NORTHEAST IA TO NEAR 60 DEGREES ACROSS NORTH
CENTRAL WI.

FOR TONIGHT...SHOWERS SHOULD SLOWLY DISSIPATE AS PRIMARY FORCING/
MOISTURE TRANSPORT MOVE EAST OF THE AREA. HOWEVER...THE GFS AND
ECMWF TO A LESSER EXTENT NOW SUGGEST SOME LINGERING LIGHT SHOWERS
ALONG A TRAILING MID-LEVEL DEFORMATION AXIS FOR MUCH OF THE NIGHT
INTO SUNDAY MORNING MAINLY ACROSS THE SOUTHEASTERN TWO THIRDS OF
THE FORECAST AREA. IF SHOWERS PERSIST...THINK THEY WILL BE MORE
SCATTERED TO ISOLATED IN NATURE AND THIS IS REFLECTED IN
DECREASING POPS THROUGH THE NIGHT. ALL SAID...RAIN AMOUNTS TO
RANGE FROM AROUND THREE QUARTERS OF AN INCH ACROSS THE SOUTH TO NO
ACCUMULATION ACROSS NORTH-CENTRAL WI. TEMPERATURES TO DROP INTO
THE 40S TONIGHT.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 307 AM CDT SAT APR 30 2016

ADDED SOME LINGERING SLIGHT CHANCE POPS SOUTH OF I-90 TO ACCOUNT
FOR WEAKENING DEFORMATION PRECIP ON SUNDAY...BUT MOST OTHER AREAS
SHOULD BE DRY. THAT SAID...WILL NEED TO WATCH MODEL TRENDS FOR A
POSSIBLE UPTICK IN MORE SCATTERED SHOWERS IF DEFORMATION AXIS IS
SLOWER TO EXIT AND/OR A BIT STRONGER. EITHER WAY...SUNDAY DOES
APPEAR TO BE MORE CLOUDY THAN PREVIOUS FORECAST AND ADJUSTED
TEMPERATURES DOWNWARD A FEW DEGREES INTO THE UPPER 50S TO LOWER
60S.

HIGH PRESSURE BUILDS ACROSS THE REGION ON MONDAY INTO TUESDAY WITH
MORE SUN COMPARED TO MUCH OF LAST WEEK. TEMPERATURES MONDAY WARM
INTO THE MID 60S...CLIMBING FURTHER INTO UPPER 60S TO LOWER 70S
ON TUESDAY AS 925 HPA TEMPERATURES RISE TO BETWEEN +13 AND +18
CELSIUS. A WEAKENING COLD FRONT WILL DROP SOUTH ACROSS THE REGION
TUESDAY NIGHT...BRINGING A SLIGHT CHANCE FOR LIGHT SHOWERS.
BIGGER IMPACT LIKELY TO BE COOLER TEMPERATURES...DROPPING AT
LEAST 10 DEGREES (POSSIBLY MORE) FROM TUESDAY/S HIGHS. FOR THE
LATTER HALF OF THE WEEK...EXPECT DRY CONDITIONS WITH TEMPERATURES
RISING GRADUALLY AS OMEGA BLOCK SYNOPTIC PATTERN BEGINS TO SET-
UP ACROSS THE CONUS WITH THE RIDGE AXIS ACROSS THE GREAT PLAINS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1105 PM CDT FRI APR 29 2016

STRATO-CU HAVE DECREASED THRU THE EVENING...WITH FEW/SCT EXPECT AT
THE TAF SITES INTO THE OVERNIGHT HOURS. HOWEVER...SOME RENEWED LOWER
LEVEL MOISTURE/2500-3500 FT CLOUDS AROUND THE SOUTHERN END OF LK MI
WERE ADVECTING TOWARD THE AREA ON SOUTHEAST 925-850MB FLOW. THIS
WOULD ARRIVE AFTER 12Z...AND CONTINUED WITH A SCT025-030 MENTION AT
BOTH KLSE/KRST THRU MUCH OF SAT MORNING. MODEL SOUNDINGS/X-SECTIONS
SHOW THIS TO RISE TO 4K-5K FT BY MID-DAY WITH DIURNAL WARMING/MIXING
AND THE CONTINUED DRY EAST-NORTHEAST SFC-925MB FLOW. NOW APPEARS THE
NORTHERN EDGE OF THE PRECIP WITH THE SYSTEM MOVING ACROSS THE
CENTRAL PLAINS IS GOING TO SPREAD INTO THE I-90 CORRIDOR DURING THE
LATE AFTERNOON/EARLY EVENING HOURS OF SAT. WITH THE TAF SITES ON THE
NORTH EDGE OF THIS PRECIP AND BRISK/GUSTY/DRY EAST/NORTHEAST LOWER
LEVEL FLOW CONTINUING...CIGS/VSBYS EXPECTED TO REMAIN VFR AS THE
BAND OF -SHRA MOVES THROUGH THE AREA. A SHIFT NORTHWARD OF THE
PRECIP BY AS LITTLE AS 25-50 MILES COULD BRING MVFR VSBYS IN SHRA
INTO THE TAF SITES DURING THE 21Z-02Z PERIOD. MAIN FORCING/LIFT OVER
THE AREA WEAKENS RATHER QUICKLY DURING THE MID/LATE EVENING HOURS
WITH ONLY A VCSH MENTION AFTER 01-02Z. GRADIENT RELAXES FOR LIGHTER
NORTHEAST WINDS BY MID EVENING AS WELL.

&&

.HYDROLOGY...
ISSUED AT 307 AM CDT SAT APR 30 2016

RECENT RAINFALLS THIS PAST WEEK WILL PRODUCE MINOR RISES ON THE
MISSISSIPPI RIVER. THOSE WITH INTERESTS OR PLANS ALONG THE RIVER
SHOULD MAY WANT TO KEEP AN EYE ON WATER LEVELS AND INCREASED FLOW
RATES.

&&

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

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION.....RRS
HYDROLOGY...DAS



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