Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 272314
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
614 PM CDT SAT JUN 27 2015

.SHORT TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 250 PM CDT SAT JUN 27 2015

GOOD MODEL CONSENSUS WITH DROPPING AN UPPER LEVEL SHORTWAVE TROUGH
OUT OF SOUTHERN CANADA TO ACROSS THE UPPER MISSISSIPPI RIVER VALLEY
OVERNIGHT. DECENT QG CONVERGENCE THROUGH THE LAYERS WITH THE
FEATURE...FAVORING MN/IA. SWATH OF 925-700 MB LEADS THE SHORTWAVE
IN...ALSO TAKING A MORE MN-IA TRACK. UPPER LEVEL JET STREAK WILL
ENHANCE THE AVAILABLE LIFT. AT THE SFC...AN ASSOCIATED NORTH-SOUTH
RUNNING FRONTAL BOUNDARY MOVES ACROSS EASTERN MN/IA BY 18Z SUN. NO
TAP TO GULF MOISTURE...BUT SOME 850 MB MOISTURE TRANSPORT - ALBEIT
FROM THE NORTHWEST - COMES WITH THE SHORTWAVE...WHILE PWS APPROACH
1.5 INCHES. CERTAINLY ENOUGH SATURATION TO FUEL THE LIKELY
SHOWER/STORMS CHANCES.

AS FOR ANY SEVERE RISK...THE GFS/NAM CONTINUE TO BUILD A THIN RIDGE
OF ABOUT 1500 SBCAPE ALONG/AHEAD OF THE FRONT. HOWEVER...THIS IS CO-
LOCATED WITH WHAT IS EXPECTED TO BE AN ACTIVE REGION OF
SHOWERS/STORMS. ITS UNCERTAIN WHETHER THESE VALUES ARE REALISTIC
GIVEN THIS LIKELIHOOD. WHATEVER INSTABILITY DOES DEVELOP WILL
ENHANCE THE COVERAGE...BUT BUFKIT SOUNDINGS PAINT A REALLY SKINNY
PROFILE TO THE CAPE...AND NOT SUPPORTIVE OF STRONG UPDRAFTS. SHEAR
IS ALSO MEAGER...MOSTLY IN THE 0-3KM LAYER AND AROUND 20 KTS.
THUS...SEVERE RISK LOOKS VERY LOW.

THE SHORTWAVE TROUGH WILL TAKE A RIGHT TURN EAST TOWARD THE EASTERN
GREAT LAKES AFTER IT SLIDES ACROSS THE FORECAST AREA...BUT ANOTHER
WEAKER RIPPLE FOLLOWS IN ITS WAKE FOR MONDAY. SBCAPES CLIMB TO
AROUND 1000 J/KG FOR THE AFTERNOON...WITH FAVORABLE LOW LEVEL LAPSE
RATES. SHOULD BE ENOUGH TO FIRE SCATTERED SHOWERS/STORMS...MOSTLY
AFTERNOON/EVENING. A SFC TROUGH COULD LINK THE SFC LOW FROM THE
SUNDAY CONVECTION WITH THE SFC LOW WITH THIS NEXT RIPPLE IN THE
FLOW. IF SO...THE BOUNDARY WOULD PROVIDE ANOTHER FOCUS FOR
SHOWER/STORMS DEVELOPMENT...WHICH COULD LINGER LONGER INTO MONDAY
NIGHT.

FOR TUESDAY...HIGH PRESSURE WILL BUILD IN FROM THE NORTH...AND LOOKS
TO BRING A MOSTLY DRY AND SUNNY DAY TO A BULK OF THE REGION. THAT
SAID...A COUPLE THINGS TO WATCH. FIRST IS HOW QUICKLY THE MONDAY
SYSTEM EXITS. IF ITS A BIT SLOWER...SOME RAIN CHANCES COULD LINGER
ACROSS THE FAR SOUTH/EAST. MEANWHILE...ANOTHER SHORTWAVE TROUGH
COULD STREAK IN FROM THE NORTHWEST LATER IN THE DAY. THE NAM FAVORS
SPINNING THIS ACROSS THE FORECAST AREA...WHILE THE GFS/EC KEEP IT TO
THE WEST. SIDING WITH THE GFS/EC IN THIS STEAD.

.LONG TERM...(WEDNESDAY THROUGH SATURDAY)
ISSUED AT 250 PM CDT SAT JUN 27 2015

NORTHWEST FLOW REMAINS IN CONTROL OF THE REGION/S WEATHER INTO NEXT
WEEKEND. THE GFS AND ECMWF BRING VARIOUS RIPPLES THROUGH THE
FLOW...ALTHOUGH THERE ARE SOME DIFFERENCES IN PLACEMENT AND TIMING.
THAT/S EXPECTED. THERE IS A GENERAL CONSENSUS IN THEIR LATEST RUNS
THAT THE BETTER RAIN CHANCES MAY SKIRT NORTH/SOUTH OF THE FORECAST
AREA. WEAK INSTABILITY EACH DAY TO TAP INTO...SO ANY BOUNDARY OR
SHORTWAVE SHOULD BE ABLE TO SPARK SOME SHOWER/STORMS. THAT
SAID...ORGANIZED SEVERE WEATHER DOES NOT LOOK LIKELY AT THIS TIME.
IN ADDITION...WHILE CONTINUING SMALL RAIN CHANCES EACH DAY DUE TO
MODEL DIFFERENCES ON WHERE/WHEN ON THE VARIOUS PERTURBATIONS COULD
SLIDE IN...THERE LOOKS TO BE A BETTER CHANCE THAN NOT FOR MOST AREAS
STAYING DRY INTO THE WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 614 PM CDT SAT JUN 27 2015

A SHORT WAVE TROUGH DROPPING SOUTH THROUGH MANITOBA WAS PRODUCING
A CONVECTIVE COMPLEX AHEAD OF IT OVER NORTHERN MINNESOTA INTO THE
EASTERN DAKOTAS. THIS ACTIVITY WILL CONTINUE TO MOVE SOUTHEAST
THROUGH THE NIGHT WITH SOME WEAKENING EXPECTED AS THE CAPE
DIMINISHES AFTER SUNSET. STILL ENOUGH FORCING FROM THE SHORT WAVE
TO MAINTAIN THIS COMPLEX AND LOOKING AT THE MESO MODELS...THE
27.18Z HRRR AND 27.12Z HI-RES ARW ARE THE QUICKEST TO BRING THE
COMPLEX IN WITH IT REACHING KRST BY 08Z. THE 27.12Z CR-NAM NEST
AND HI-RES NMM ARE 2-3 HOURS SLOWER. PLAN TO ACKNOWLEDGE THE
FASTER SOLUTIONS WITH A VCSH FOR BOTH TAF SITES AND THEN GO WITH
CATEGORICAL SHOWERS AND VCTS BY 10Z AT KRST AND 12Z AT KLSE. THIS
INITIAL ACTIVITY SHOULD MOVE THROUGH BY THE MID TO LATE MORNING
WITH A BREAK EXPECTED BEFORE MORE ACTIVITY DEVELOPS AS THE SHORT
WAVE TROUGH AND UPPER LEVEL LOW MOVE ACROSS DURING THE AFTERNOON.
THE MESO SCALE MODELS ALL SHOW THIS SECONDARY DEVELOPMENT
OCCURRING BUT HAVE DIFFERENT IDEAS ON THE TIMING AND COVERAGE.
LOOKING AT THE BUFKIT SOUNDINGS FROM THE 27.18Z NAM...THERE LOOKS
TO BE BETWEEN 500 AND 1000 J/KG OF CAPE WHICH WILL BE MORE THAN
ENOUGH TO SUPPORT ADDITIONAL THUNDERSTORMS. FOR NOW...WILL GO BACK
TO A VCTS FOR BOTH TAF SITES AFTER THE INITIAL ROUND OF RAIN AND
CARRY THIS FOR THE REMAINDER OF THE AFTERNOON. FOR THE MOST
PART...EXPECTING VFR CONDITIONS WITH ALL THIS ACTIVITY...BUT MVFR
CONDITIONS POSSIBLE WITH THE HEAVIER RAIN AND CONFIDENCE IS ONLY
HIGH ENOUGH TO INCLUDE THIS FOR A WHILE AT KRST WITH THE INITIAL
ACTIVITY LATE TONIGHT INTO SUNDAY MORNING.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...04



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