Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261738
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1238 PM CDT SUN JUL 26 2015

.UPDATE...
ISSUED AT 1235 PM CDT SUN JUL 26 2015

IT HAS TURNED INTO A MESSY FORECAST TODAY ACROSS THE AREA AS THERE
IS SOME DESTABILIZATION AND A STACKED SURFACE TO 700MB TROUGH /
ELONGATED LOW OVER THE SOUTHWESTERN FORECAST AREA. THIS FEATURE
DOESNT REALLY MOVE AND WITH GROWING INSTABILITY COULD SPAWN
SHOWERS AT ANY TIME.

SPC 17Z MESOSCALE ANALYSIS INDICATED MLCAPE TO 3 KM REALLY
JUMPING UP JUST TO THE WEST OF KAEL TO KALO /200 J/KG/ AND LAPS
LOCAL ANALYSIS SYSTEM CONFIRMS THIS...BUT HAS SBCAPE TO 3KM VALUES
NEAR 250 J/KG. THUS...LAPSE RATES ARE ALREADY GETTING CLOSE TO
SUPPORTIVE OF NON-SUPERCELL TORNADOES /NST/. THE BIG PARAMETER WE
ARE WATCHING IS THE CONVERGENT BOUNDARY FOR MISOVORTEX ACTIVITY.
NEAR THE SURFACE...THIS APPEARS TO BE FROM SC MN /KFRM/ TO SW OF
KMCW...TO SW OF KALO AT 17Z. SO...IT IS CLOSE BUT SOUTHWEST OF
THE FORECAST AREA AT THIS TIME. RAP SEEMS TO SHIFT THIS SLIGHTLY
SOUTHWEST WITH TIME THROUGH THE AFTERNOON.

BOTTOM LINE IS INSTABILITY AND SFC-700MB TROUGH HANGING OVER THE
AREA MEANS SHRA AND ISOLATED TSRA COULD HAPPEN OVER SERN MN...NERN
IA...AND SWRN WI THIS AFTERNOON AT ANY TIME. WHILE THE NST
BOUNDARY AT THE SURFACE APPEARS TO BE JUST SW/W OF THE FORECAST
AREA...HAVE INCLUDED NST FUNNELS INTO THE HAZ WEATHER OUTLOOK FOR
A FEW COUNTIES BASED ON INSTABILITY GROWING RAPIDLY AND PROXIMITY
TO THE BOUNDARY. MEAN WIND WOULD CARRY SHRA/TSRA ACTIVITY
EASTWARD WOULD THINK...AWAY FROM THE BOUNDARY DIMINISHING NST
THREAT.

BEING CAREFUL WITH HIGH TEMPERATURES TODAY AS WE ARE ONLY 10F
AWAY IN THE CLOUDS. CLEARING COULD EASILY PROVIDE 10F AND HIT THE
HIGHS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 350 AM CDT SUN JUL 26 2015

EARLY THIS MORNING...A CONVECTIVE COMPLEX ACROSS SOUTH-CENTRAL MN
INTO NORTHWEST IA WILL TRACK EAST-SOUTHEAST IMPACTING AREAS
PRIMARILY WEST OF THE MS RIVER. THE STRONGEST STORMS WITHIN THIS
COMPLEX ARE ACROSS WEST-CENTRAL IA NEAR THE HIGHEST MID-LEVEL
MOISTURE TRANSPORT AND SURFACE WARM FRONT. FARTHER NORTH...SEVERE
THUNDERSTORMS ARE NOT EXPECTED ACROSS THE FORECAST AREA WITH THE
PRIMARY THREATS BEING BRIEF HEAVY RAIN AND LIGHTNING. THESE
THUNDERSTORMS SHOULD BE OUT OF THE AREA NO LATER THAN NOON...BUT
SOME CONVECTIVE RE-DEVELOPMENT IS POSSIBLE MAINLY WEST OF THE
RIVER THIS AFTERNOON. WILL KEEP 20 TO 30 POPS FOR THIS AREA...BUT
SEVERE WEATHER IS NOT EXPECTED.

925 HPA TEMPERATURES TODAY RISE 1 TO 2 CELSIUS COMPARED TO
YESTERDAY...SO EXPECT AFTERNOON HIGHS IN THE MID TO UPPER 80S WITH
SOME 90 DEGREE READINGS ACROSS WESTERN WI. BOUNDARY LAYER MIXES TO
NEAR 700 HPA BY MID-AFTERNOON EAST OF THE MS RIVER AND THIS SHOULD
PROMOTE DRYING AT THE SURFACE WITH RELATIVE HUMIDITY BRIEFLY
DIPPING BELOW 40 PERCENT. LIGHT SOUTH-SOUTHEAST WINDS WILL
CONTINUE THROUGH THE DAY. TONIGHT WILL BE WARM BUT DRY WITH LOW
TEMPERATURES FROM THE MID 60S TO NEAR 70 DEGREES.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 350 AM CDT SUN JUL 26 2015

THERMAL PROFILE CHANGES LITTLE ON MONDAY...BUT NEAR SURFACE MOISTURE
CONTINUES TO INCREASE WITH DEWPOINTS RISING INTO THE LOWER 70S. WITH
AFTERNOON HIGHS AGAIN IN THE UPPER 80S TO NEAR 90 DEGREES...MUCAPE
EASILY RISES INTO THE 2000 TO 4000 J/KG RANGE. HOWEVER...PRIMARY
MID-LEVEL MOISTURE TRANSPORT IS WELL WEST OF THE FORECAST AREA AND
A WEAK SURFACE BOUNDARY REMAINS ACROSS IA. AS A RESULT...WILL KEEP
DRY FORECAST FOR MONDAY...ALTHOUGH IT WILL BE MUGGY WITH HEAT
INDICES RISING INTO THE MID 90S.

SURFACE WARM FRONT FINALLY BEGINS TO LIFT NORTHWARD MONDAY NIGHT
INTO TUESDAY MORNING IN RESPONSE TO APPROACHING EASTERN PACIFIC
TROUGH. MODELS SHOW A 40 TO 50 KT 850 HPA NOCTURNAL JET MONDAY
NIGHT IN THE VICINITY OF THE FRONT ACROSS CENTRAL MN. WITH THIS
SET-UP WITHIN A MOIST/UNSTABLE AIR MASS...SOME KIND OF CONVECTIVE
COMPLEX IS LIKELY BUT ITS TIMING AND LOCATION ARE UNCERTAIN. AT
THIS TIME...WILL KEEP HIGHEST CHANCE POPS MONDAY NIGHT INTO
TUESDAY ACROSS THE NORTHWEST HALF OF THE FORECAST AREA.

CONVECTIVE EVOLUTION TUESDAY MORNING MAY HAVE AN IMPACT ON
TEMPERATURES/HEAT INDICES...AS WELL AS ADDITIONAL THUNDERSTORM
CHANCES LATER IN THE DAY. FOR NOW...GENERAL IDEA THAT
STRENGTHENING CAP WITH 700 HPA TEMPERATURES RISING INTO THE 11 TO
13 CELSIUS RANGE WILL SQUASH ADDITIONAL CONVECTION UNTIL COLD
FRONTAL PASSAGE TUESDAY NIGHT STILL HOLDS. IN THIS SCENARIO...
SURFACE TEMPERATURES RISE INTO THE LOWER 90S TUESDAY AFTERNOON
WITH DEWPOINTS INTO THE MID 70S...RESULTING IN HEAT INDICES ABOVE
100 DEGREES. THUNDERSTORMS SHOULD IGNITE NEAR THE COLD FRONT
TUESDAY NIGHT. SOME OF THESE STORMS COULD BECOME STRONG TO SEVERE
AS DEEP LAYER SHEAR/FORCING FOR ASCENT INCREASES OVERNIGHT.

MUCH COOLER/DRIER AIR MASS MOVES INTO THE REGION WEDNESDAY THROUGH
FRIDAY IN THE WAKE OF TUESDAY NIGHT/S FRONTAL PASSAGE. DAILY HIGHS
WILL RANGE FROM THE UPPER 70S TO LOWER 80S WITH DEWPOINTS
GENERALLY IN THE 50S TO LOWER 60S. DRY CONDITIONS WILL BE THE RULE
THE LATTER HALF OF THE WEEK WITH BROAD SURFACE HIGH PRESSURE
FIRMLY IN CONTROL ACROSS THE NATION/S MID-SECTION.

THE NEXT BEST CHANCE FOR THUNDERSTORMS WILL BE FRIDAY NIGHT INTO
SATURDAY AS WEAK WAVES MOVE THROUGH NORTHWEST FLOW ALOFT. HOWEVER...
MODEL CONSENSUS IS POOR THIS FAR OUT LENDING TO LOW OVERALL
CONFIDENCE FOR PRECIPITATION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1235 PM CDT SUN JUL 26 2015

LOW CONFIDENCE FORECAST FOR THIS SET OF TAFS. INSTABILITY WILL BE
INVOF KRST THIS AFTERNOON AND TSRA COULD FORM AS WELL NEARBY.
THERE IS NOT A STRONG SIGNAL FOR TSRA TO BE NUMEROUS ENOUGH TO
INCLUDE IN THE AIR SPACE THERE.

OVERNIGHT IT APPEARS LIGHT LIFT WILL KEEP SOME VFR CLOUDS AT THE
TAF SITES OVERNIGHT. MORE ABUNDANT LOW-LEVEL MOISTURE THROUGH SRN
MN INTO IA LOOKS TO GENERATE A NEAR IFR CLOUD DECK BY SUNRISE.
DRIER AIR TOWARD KLSE AND FURTHER EAST SEEMS TO INHIBIT THIS
CLOUD DECK A BIT. HOWEVER...IF THE SKIES ARE CLEAR ENOUGH...THERE
COULD BE SOME RIVER VALLEY FOG THAT COULD PULL KLSE TO IFR FOG IN
THE MORNING.

IFR VSBY/CIG ARE POSSIBLE AT BOTH TAF SITES BY SUNRISE. AT THIS
TIME...CONFIDENCE WAS NOT HIGH ENOUGH TO LOWER FLIGHT CONDITIONS
TO SUCH...BUT THE FOLLOWING FORECASTS MAY NEED TO INCLUDE IT.

&&

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

$$

UPDATE...BAUMGARDT
SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...BAUMGARDT


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