Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 031708
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1208 PM CDT FRI JUL 3 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 215 AM CDT FRI JUL 3 2015

AN UPPER LEVEL SHORTWAVE TROUGH WAS DROPPING SOUTHEAST ACROSS
SOUTHERN CANADA EARLY THIS MORNING...AND IS SLATED TO SPIN ACROSS
NORTHERN PORTIONS OF THE GREAT LAKES THIS AFTERNOON/EVENING.
ACCOMPANYING IT...A MOSTLY WEST-EAST RUNNING SFC FRONT WILL SINK
SOUTHWARD AHEAD OF IT...MOVING OVER NORTHERN WI THIS AFTERNOON. SOME
CONVERGENCE ALONG THE BOUNDARY...WITH AS MUCH AS 2000 J/KG OF SBCAPE
ALONG/AHEAD OF IT AND 1000-700 MB LAPSE RATES IN THE 7-8.5 C/KM
RANGE. NOT A LOT OF SATURATION WITH IT...BUT ENOUGH TO TRIGGER
AFTERNOON/EVENING SHOWERS AND STORMS. MESO MODELS SHOW THIS LIKELY
OUTCOME WELL...QUICKLY DIMINISHING THE ACTIVITY WITH THE LOSS OF THE
DAYTIME HEATING /INSTABILITY/ IN THE EVENING. THE BETTER CHANCES FOR
SCATTERED PCPN WILL HOLD ACROSS NORTHERN WI...BUT COULD WORK FAR
ENOUGH SOUTH TO BRING AN ISOLD/SCT SHOWER OR STORM TO TAYLOR/CLARK
COUNTIES IN NORTH-CENTRAL WI. WILL CONTINUE CHANCES FOR THE LATE
AFTERNOON/EARLY EVENING. NOTE - SOME SUGGESTIONS VIA SOME MESO
MODELS INCLUDING THE NAM12 THAT THE RAIN THREAT COULD LINGER FARTHER
INTO TONIGHT - POTENTIALLY WORKING TOWARD THE I-90 CORRIDOR.

ON SAT...WHILE ITS PARENT SHORTWAVE WILL BE HEADED TOWARD THE NEW
ENGLAND STATES...THE SFC FRONT WILL HOLD UP WEST TO EAST ACROSS
SOUTHERN MN-CENTRAL WI. WEAK CONVERGENCE PERSISTS...WITH THE NAM
PRODUCING WELL OVER 2000 J/KG OF SBCAPE. SEEMS A BIT AMBITIOUS WITH
OTHER MODELS SUGGESTING CLOSER TO 1000 J/KG. STILL...ADD IN
FAVORABLE LOW LEVEL LAPSE RATES AND ENOUGH SATURATION AND A FEW MORE
AFTERNOON SHOWERS/STORMS SHOULD POP UP IN THE VICINITY OF THE FRONT.
IN ADDITION...THE BOUNDARY COULD GET SOME AID FROM A WEAK UPPER
LEVEL RIPPLE APPROACHING FROM THE NORTHERN PLAINS. UNFORTUNATELY CAN/T
GUARANTEE A DRY 4TH HOLIDAY FOR ALL...BUT THE PCPN THAT COULD
DEVELOP SHOULD BE OF THE ISOLATED/SCATTERED NATURE.

BOUNDARY EXITS/WEAKENS ON SUNDAY...AND IT SHOULD BE A DRY DAY.

FOR TEMPS...LOOKS LIKE A SEASONABLY WARM HOLIDAY WEEKEND AFTER
TODAY. SFC FLOW BECOMES MORE SOUTHERLY WITH SOME PUSH OF LOW LEVEL
WARMING FROM THE WEST. HIGHS IN THE UPPER 70S TO AROUND 80 LOOK TO
WARM INTO THE LOW TO MID 80S FOR SAT/SUN.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 215 AM CDT FRI JUL 3 2015

MODELS IN GOOD AGREEMENT WITH DRIVING AN UPPER LEVEL TROUGH OUT OF
WESTERN CANADA SOUTHEAST TO ACROSS NORTHERN PLAINS/UPPER MISSISSIPPI
RIVER VALLEY OVERNIGHT SUN. AN ACCOMPANYING COLD FRONT WILL LEAD THE
WAY INTO THE REGION...WITH A SLUG OF 850 MB MOISTURE TRANSPORT JUST
OUT AHEAD OF IT. INSTABILITY BUILDS AHEAD OF THE FRONT...BUT CURRENT
TIMING OF OVERNIGHT THROUGH MON MORNING WOULD PUT IT AT A MINIMUM.
WIND SHEAR IS LOCATED BEHIND THE FRONT - AWAY FROM THE BULK OF THE
INSTABILITY. FORCING/MOISTURE SHOULD PRODUCE A SWATH OF
SHOWERS/STORMS EITHERWAY...WITH MONDAY LOOKING LIKE A
RELATIVELY WET DAY.

TIMING IS IMPORTANT WITH THIS SYSTEM. IF IT SHOULD SLOW DOWN EVEN BY
6 HOURS...INSTABILITY COULD BUILD ACROSS THE FORECAST AREA...AND THE
POTENTIAL FOR STRONGER STORMS ON MONDAY COMES INTO THE PICTURE.
DISCONNECT BETWEEN SHEAR-INSTABILITY HELPS KEEP A SEVERE RISK
TEMPERED...BUT CAN/T SAY NO TO THAT QUESTION YET. WHAT IT MAY LACK
IN FAVORABLE SEVERE PARAMETERS AT THIS MOMENT...IT DOES SHOW THE
POTENTIAL FOR HEAVY RAIN. GFS HAS NEARLY 2 INCHES OF PW WITH A WARM
CLOUD DEPTH IN EXCESS OF 4000 KM. MONDAY IS CERTAINLY A DAY TO
WATCH.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1208 PM CDT FRI JUL 3 2015

A WEAK COLD FRONT EXTENDED ACROSS NORTHERN MINNESOTA LATE THIS
MORNING. THIS FRONT WILL SAG SOUTH TOWARD THE AREA THROUGH THE
NIGHT WITH THE 03.12Z NAM SUGGESTING IT WILL ONLY MAKE IT TO ABOUT
CENTRAL MINNESOTA AND WISCONSIN BEFORE STALLING OUT SUNDAY MORNING
AND STARTING TO RETREAT BACK TO THE NORTH. ANY CONVECTIVE ACTIVITY
THAT FORMS ALONG THE FRONT THIS AFTERNOON IS SHOWN BY THE NAM AND
03.15Z HRRR TO DRIFT OFF TO THE SOUTHEAST STAYING WELL EAST OF
EITHER TAF SITE. THIS SCENARIO WILL ALLOW FOR VFR CONDITIONS
THROUGH THE PERIOD WITH JUST SOME AFTERNOON CUMULUS CLOUDS TODAY
AND THEN POSSIBLY SOME SCATTERED MID LEVEL CLOUDS OVERNIGHT AHEAD
OF THE FRONT. THE SMOKE FROM THE CANADIAN WILDFIRES WAS BEGINNING
TO PRODUCE SOME VISIBILITY RESTRICTIONS ALONG AND NORTH OF THE
WEAK COLD FRONT. FOR NOW...DO NOT PLAN TO SHOW ANY VISIBILITY
RESTRICTIONS DUE TO THIS SMOKE WITH THE FRONT NOT EXPECTED TO MAKE
IT THIS FAR SOUTH...BUT WILL MONITOR TRENDS FOR POSSIBLE INCLUSION
WITH LATER FORECASTS.

&&

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

$$

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



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