Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 252010
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
310 PM CDT MON APR 25 2016

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 310 PM CDT MON APR 25 2016

PRIMARY CHALLENGE IN THE VERY NEAR TERM WITH COVERAGE/INTENSITY OF
SCATTERED SHOWERS AND THUNDERSTORMS NORTH OF I-94...THEN DECREASING
PRECIP CHANCES THIS EVENING AND OVERNIGHT. WILL FOLLOW RAP/HRRR
GUIDANCE OVER THE NEXT 6-12 HOURS.

25.020Z ANALYSIS SHOWS A WEAKENING SURFACE LOW CENTERED OVER LA
CROSSE WITH AN IMPRESSIVE NORTHWEST-SOUTHEAST FRONTAL BOUNDARY
ALONG A LINE FROM JUST NORTH OF BLACK RIVER FALLS TO WISCONSIN
DELLS. TEMPERATURES TO THE SOUTH OF THIS BOUNDARY HAVE SOARED INTO
THE 70S...WHILE READINGS FURTHER NORTH ARE IN THE 40S TO MID 60S.
PRIMARY INSTABILITY AXIS WITH MOST UNSTABLE CAPES OF 500 TO 1000
J/KG IS NOSING INTO SOUTHERN WI WITH A FEW HUNDRED J/KG TRYING TO
WRAP BACK TO THE NORTHWEST OF THE SURFACE LOW. EFFECTIVE BULK
SHEAR IN THIS AREA ALSO IN THE 30 TO 40 KT RANGE. MOST CONCERNED
ABOUT WEAK SHOWERS DEVELOPING ACROSS JACKSON COUNTY AND THEN
LIFTING NORTHWARD ACROSS THE STRONG SURFACE BOUNDARY AND INTO
CLARK COUNTY. COULD SEE SOME FUNNELS OR EVEN A TORNADO IN THESE
AREAS OVER THE NEXT FEW HOURS. MORE WIDESPREAD SEVERE WEATHER IS
EXPECTED FARTHER EAST INTO SOUTHEAST WI/NORTHERN IL WHERE A SEVERE
THUNDERSTORM WATCH IS IN EFFECT.

FOR THE REST OF TONIGHT...SHOWERS/THUNDERSTORMS WILL LIFT NORTH
AND EAST OF THE FORECAST AREA AS THE OCCLUDED SYSTEM FINALLY
WOBBLES ACROSS SOUTHERN WI AND INTO MI. UPSTREAM LOW STRATUS WILL
RUSH INTO THE AREA WITH THE POSSIBILITY OF SOME PATCHY DRIZZLE IN
THE VICINITY OF A TRAILING SURFACE TROUGH. WINDS WILL DECREASE AND
SHIFT TO THE NORTHWEST WITH TEMPERATURES FALLING INTO THE 40S.

WHILE TUESDAY WILL BE MOSTLY CLOUDY...EXPECT DRY CONDITIONS AS A
STRONG HUDSON BAY SURFACE HIGH NOSES INTO THE REGION. SURFACE
PRESSURE GRADIENT TIGHTENS AS THE DAY PROGRESSES...RESULTING IN
INCREASING EASTERLY WINDS. TEMPERATURES WILL ALSO BE NOTICEABLY
COOLER THAN TODAY...RANGING FROM THE LOW 50S ACROSS NORTH CENTRAL
WI TO THE MID 60S ACROSS NORTHEAST IA AND FAR SOUTHWEST WI.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 310 PM CDT MON APR 25 2016

SHOWERS INCREASE LATE TUESDAY AND ESPECIALLY WEDNESDAY AS ANOTHER
500 HPA CLOSED LOW ACROSS THE FOUR CORNERS REGION EJECTS INTO THE
CENTRAL PLAINS. PWATS RISING TO NEAR ONE INCH...COMBINED WITH
INCREASING 850 TO 700 HPA FRONTOGENESIS AND WARM AIR ADVECTION
WILL RESULT IN SHOWERS MOVING FROM SOUTHWEST TO NORTHEAST THROUGH
THURSDAY MORNING. NO THUNDER EXPECTED WITH MAJORITY OF INSTABILITY
SOUTH OF THE FORECAST AREA. RAINFALL TOTALS THROUGH THIS PERIOD
LIKELY TO RANGE FROM LESS THAN A TENTH OF AN INCH ACROSS NORTH
CENTRAL WI TO OVER AN INCH ACROSS PORTIONS SOUTHERN MN AND
NORTHERN IA. THIS SHARP GRADIENT IS A RESULT OF DRY EASTERLY FLOW
FROM CANADIAN SURFACE HIGH FIGHTING THE NORTHWARD PUSH OF MOISTURE
FROM THE SOUTH. CLOUD COVER AND PERIODS OF SHOWERS WILL KEEP
TEMPERATURES WEDNESDAY/THURSDAY IN THE UPPER 40S TO MID 50S.

FRIDAY WILL BE DRY AND WARMER WITH SHORT-WAVE RIDGING OVERHEAD.
LOOKING INTO THE WEEKEND...ANOTHER ROUND OF SHOWERS IS POSSIBLE AS
YET ANOTHER CLOSED LOW MOVES INTO THE CENTRAL PLAINS. WILL CAP
POPS AT 50 PERCENT WITH SUBSTANTIAL DIFFERENCES BETWEEN THE
LATEST DRY GFS/WET EC. TIMING/COVERAGE/AMOUNTS OF PRECIP LIKELY
RELATED TO INTERACTION OF LOW AND PERSISTENT CANADIAN HIGH.
OVERALL...EXPECT MORE CLOUDS THAN SUN WITH TEMPERATURES FROM THE
UPPER 50S TO LOWER 60S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 104 PM CDT MON APR 25 2016

A LOW PRESSURE SYSTEM...CURRENTLY LOCATED JUST WEST OF THE TWIN
CITIES...WILL MOVE EAST ACROSS THE AREA. A MVRF CEILING WILL MOVE
INTO KRST AROUND 25.19Z AND KLSE AROUND 26.05Z. THE CEILINGS AT
KRST WILL THEN LOWER THE CEILINGS TO IFR AT KRST AROUND 26.01Z...
AND IMPROVE BACK TO MVFR BY 26.15Z.

THERE WILL BE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THIS
AFTERNOON...BUT THE CHANCES WERE TOO LOW TO BE INCLUDED IN THE
TAFS.

AS FAR AS THE FOG TONIGHT...THE MODELS ARE NOW SHOWING A
TEMPERATURE AND DEW POINT SPREAD OF 2 TO 4 DEGREES. DUE TO
THIS...REMOVED THE IFR/MVFR RESTRICTIONS DUE TO FOG.

&&

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

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...BOYNE



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