Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 250446
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1146 PM CDT SUN APR 24 2016

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 302 PM CDT SUN APR 24 2016

IMMEDIATE CHALLENGES INCLUDE PRECIP CHANCES AND THREAT FOR STRONG/
MARGINALLY SEVERE STORMS LATE THIS AFTERNOON THROUGH MONDAY. RAP/
HRRR HAVE DONE A FANTASTIC JOB SO FAR TODAY WITH TIMING/PLACEMENT
OF SHOWER ACTIVITY AND WILL CONTINUE TO FOLLOW ITS OUTPUT THROUGH
TONIGHT.

24.20Z ANALYSIS SHOWS A STRONG SURFACE LOW ACROSS CENTRAL SD WITH
AN EAST-WEST STATIONARY FRONT DRAPED ACROSS SOUTHERN MN AND INTO
WESTERN WI JUST NORTH OF THE I-90 CORRIDOR. MOST SIGNIFICANT
SHOWER ACTIVITY TODAY HAS BEEN ALONG AND NORTH OF THIS BOUNDARY
WITH PORTIONS OF NORTH-CENTRAL WI ALREADY RECEIVING OVER AN INCH
OF RAIN. FROM NOW THROUGH MOST OF THE EVENING...EXPECT AN OVERALL
LULL/DECREASE IN SHOWER ACTIVITY AS PRIMARY SHORT-WAVE ENERGY
ASSOCIATED WITH STRONG 500 HPA CLOSED LOW OVER THE WY/SD/NE BORDER
REGION INTERACTS WITH HIGHEST INSTABILITY PLUME FROM NORTH-CENTRAL
KS INTO EASTERN NE/SD.

FARTHER EAST ACROSS THE FORECAST AREA...OVERCAST SKIES AND SFC
DEW POINTS IN THE LOWER TO MID 50S THIS AFTERNOON HAVE LIMITED
ELEVATED INSTABILITY TO MAYBE 100 TO 200 J/KG AND THAT/S BEING
GENEROUS. EVEN IF WE SEE SOME PEAKS OF SUN PRIOR TO SUNSET...
ALLOWING CAPES TO RISE A FEW HUNDRED MORE J/KG...LATEST RAP/HRRR
SHOW VERY LITTLE CONVECTIVE ACTIVITY ACROSS THE AREA UNTIL CLOSER
TO MIDNIGHT WHEN LINE OF STORMS FROM SD/NE/KS MOVE ACROSS WESTERN
MN/IA AND APPROACH THE FORECAST AREA. BY THIS TIME...INSTABILITY/
DEEP SHEAR IS WEAK. CONSIDERING ALL OF THIS...WILL REMOVE STRONG/
MARGINALLY SEVERE THUNDERSTORM WORDING FROM LATEST MESSAGING AND
FOCUS ON SCATTERED SHOWERS/STORMS INTO THE OVERNIGHT PERIOD.
PRIMARY THREATS WILL BE BRIEF HEAVY RAIN...LIGHTNING AND PERHAPS
SOME GUSTY WINDS.

BETTER CHANCE FOR STRONG/LOW-END SEVERE STORMS WILL BE MID MONDAY
MORNING UNTIL 3-4 PM IN THE AFTERNOON MAINLY ALONG AND EAST OF THE
MS RIVER. WEAKENING 500 HPA CLOSED LOW MOVES INTO CENTRAL MN BY
18Z WITH A 50-60 KT JET STREAK MOVING ACROSS THE FORECAST AREA...
PROVIDING BETTER OVERALL DEEP LAYER SHEAR. HOWEVER...STRENGTH OF
STORMS WILL BE HIGHLY DEPENDENT ON WHETHER OR NOT SUFFICIENT
INSTABILITY CAN BUILD AHEAD OF THE LOW. NAM IS MOST ROBUST SHOWING
A PLUME OF 0-3KM MUCAPE VALUES FROM 1000 TO 2000 J/KG BY 18Z ALONG
AND EAST OF THE MS RIVER...WHEREAS THE GFS IS IN THE 700 TO 1000
J/KG RANGE. PERSISTENT CLOUD COVER/ONGOING MORNING SHOWERS MAY
LIMIT POTENTIAL INSTABILITY...BUT BOTH MODELS MOVE PLUME OF
HIGHEST INSTABILITY SOUTH AND EAST OF THE FORECAST AREA IN THE
21-00Z PERIOD. SPC DAY 2 OUTLOOK HIGHLIGHTS A MARGINAL RISK FOR
SEVERE STORMS MAINLY ACROSS FAR EASTERN IA/SOUTHERN WI/NORTHERN
IL AND THIS SEEMS REASONABLE. PRIMARY THREATS WITH ANY STRONGER
STORMS ARE HAIL AND GUSTY WINDS.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 302 PM CDT SUN APR 24 2016

WHILE TUESDAY WILL BE DRY/COOLER UNDER THE INFLUENCE OF HIGH
PRESSURE...PARTS OF THE WEEK MAY BE POTENTIALLY ACTIVE WITH A
COUPLE OF PACIFIC TROUGHS DROPPING INTO THE GREAT BASIN AND
EVENTUALLY EJECTING NORTHEASTWARD ACROSS THE UPPER MIDWEST IN
SOUTHWEST FLOW ALOFT. BEST MODEL AGREEMENT FOR MORE WIDESPREAD
PRECIPITATION IS LATE TUESDAY NIGHT THROUGH WEDNESDAY. MOST
INSTABILITY REMAINS SOUTH OF THE FORECAST AREA...SO WILL NOT
MENTION ANY THUNDER AT THIS TIME. SHOWERS MAY HAVE TROUBLE LIFTING
NORTHEAST WITH TIME AS THEY BATTLE AGAINST LOW LEVEL DRY EASTERLY
FLOW ALONG SOUTHERN PERIPHERY OF STRONG HUDSON BAY HIGH. FOR NOW
50 TO 70 POPS INCREASING FROM SOUTHWEST TO NORTHEAST SEEMS
REASONABLE.

THURSDAY/FRIDAY LOOK MOSTLY DRY AT THIS TIME WITH THE NEXT BEST
CHANCE FOR PRECIPITATION LATE FRIDAY THROUGH SUNDAY DEPENDING ON
WHICH MODEL SOLUTION IS FOLLOWED. FOR NOW...ENOUGH DIFFERENCES
BETWEEN MEDIUM-RANGE SOLUTIONS TO KEEP POPS CAPPED AT 50 PERCENT.
WITH LARGE SCALE TROUGHING FOR THE LATTER HALF OF THE FORECAST
PERIOD...TEMPERATURES WILL BE ON THE COOL SIDE WITH DAILY HIGHS
MAINLY IN THE 50S AND LOWS IN THE MID 30S AND 40S...ALTHOUGH
CANNOT RULE OUT SOME NEAR FREEZING READINGS IN FAVORED COLD SPOTS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1146 PM CDT SUN APR 24 2016

SCATTERED SHOWERS AND PERHAPS A FEW THUNDERSTORMS WILL MOVE
THROUGH THE AREA TONIGHT. A FEW STORMS COULD PRODUCE GUSTY WINDS
TO AROUND 30 KTS. OTHERWISE...PERIOD OF MVFR CONDITIONS ARE
POSSIBLE TONIGHT UNDER THE STEADIER SHOWERS AND CANNOT RULE OUT
SOME BRIEF IFR CONDITIONS. VFR TO MVFR CONDITIONS ARE THEN
EXPECTED TOMORROW AS A FRONT PUSHES THROUGH THE REGION WITH WINDS
SWITCHING TO THE SOUTHWEST AND BECOMING GUSTY. A FEW AFTERNOON
THUNDERSTORMS ARE POSSIBLE...BUT ITS LOOKING LIKE THESE WOULD
DEVELOP MAINLY EAST OF THE TAF SITES. LOW STRATUS LOOKS TO MOVE IN
MONDAY EVENING WITH CONDITIONS LOWERING TO IFR.

&&

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

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...WETENKAMP



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