Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 202100
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
400 PM CDT SUN JUL 20 2014

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 400 PM CDT SUN JUL 20 2014

MAIN FORECAST CONCERNS ARE ON HEAT INDEX VALUES MONDAY AFTERNOON
THEN FOCUS TURNS TO SEVERE THUNDERSTORM POTENTIAL MONDAY NIGHT INTO
TUESDAY MORNING.

QUIET AND PLEASANT CONDITIONS ARE EXPECTED ACROSS THE REGION THIS
EVENING INTO THE OVERNIGHT HOURS WITH WARM SOUTHERLY FLOW EXPECTED.
YOU MAY HAVE FELT A LITTLE MORE HUMIDITY IN THE AIR THIS AFTERNOON.
THIS IS THANKS TO A MORE HUMID AIRMASS MAKING ITS WAY IN FROM THE
WEST. IN FACT...DEW POINTS IN WESTERN MINNESOTA AND EASTER SOUTH
DAKOTAS WERE IN THE LOWER 70S WITH THIS AIRMASS EXTENDING SOUTH INTO
THE CENTRAL PLAINS. THIS MUGGY AIRMASS WILL CONTINUE TO PUSH INTO
THE REGION TONIGHT INTO MONDAY. A STEAMY AIRMASS MOVES INTO THE
REGION ON MONDAY WITH TEMPERATURES CLIMBING INTO THE UPPER 80S TO
APPROACHING 90. THESE TEMPERATURES COMBINED WITH DEWPOINTS IN THE
70S WILL PRODUCE HEAT INDEX VALUES OF 95 TO 100 MAINLY WEST OF THE
MISSISSIPPI RIVER. EVEN THOUGH HEAT INDEX VALUES WON/T BE AS HIGH
OVER WESTERN INTO CENTRAL WISCONSIN IT WILL STILL FEEL UNCOMFORTABLE
WITH HEAT INDEX VALUES APPROACHING THE LOWER TO MID 90S. HAVE
DECIDED TO ISSUE A HEAT ADVISORY OVER PORTIONS OF SOUTHEAST
MINNESOTA INTO PORTIONS OF NORTHEAST IOWA WHERE THE HEAT INDEX
VALUES WILL BE RIGHT AROUND 100.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 400 PM CDT SUN JUL 20 2014

FOCUS QUICKLY TURNS TO THE POTENTIAL FOR SEVERE THUNDERSTORMS MONDAY
NIGHT INTO TUESDAY MORNING. A MESOSCALE CONVECTIVE COMPLEX IS
EXPECTED TO DEVELOP OVER WEST CENTRAL MINNESOTA INTO SOUTHEAST NORTH
DAKOTA MONDAY AFTERNOON THEN RACES EAST. BASED ON THE 12 AND 18Z NAM
THE MCS LOOKS TO SPLIT WITH A BRANCH GOING EAST AND TRACKING ACROSS
NORTHERN WISCONSIN AND ANOTHER BRANCH DIVING SOUTHEAST INTO THE
FORECAST AREA. HIGH RESOLUTION MODELS SHOW A LARGE SQUALL LINE
TRACKING ACROSS AREAS MAINLY ALONG AND NORTH OF INTERSTATE 90 MONDAY
NIGHT INTO EARLY TUESDAY MORNING. CAPE VALUES ARE RATHER IMPRESSIVE
WITH 0-3KM MUCAPE VALUES APPROACHING 3500 J/KG OVER CENTRAL
MINNESOTA WITH 0-3KM CAPE VALUES CLIMBING TO AROUND 2250 J/KG ACROSS
MUCH OF THE FORECAST AREA. CORFIDI VECTORS ARE POINTING
SOUTH/SOUTHEAST MONDAY NIGHT SO THIS WOULD TAKE ANY THUNDERSTORM
COMPLEX OVER CENTRAL INTO EAST CENTRAL MINNESOTA SOUTH INTO THE
FORECAST AREA. GIVEN SHEAR PROFILES...DAMAGING WINDS LOOK TO THE BE
THE MAIN HAZARD WITH THE THUNDERSTORMS. ALSO...GIVEN THE HIGH CAPE
VALUES CANNOT RULE OUT LARGE HAIL. LOOKING AT WHERE THE LOW LEVEL
JET ALIGNS MONDAY NIGHT...BASICALLY POINTED RIGHT INTO WESTERN AND
CENTRAL WISCONSIN...PROVIDING AMPLE SUPPORT TO SUSTAIN A LONG LIVED
MCS THAT WOULD LIKELY GROW UPSCALE AS IT PROGRESSES EAST OUT OF
CENTRAL MINNESOTA INTO THE JET. WILL HAVE TO KEEP A VERY CLOSE EYE
ON THIS SITUATION.  DEPENDING ON HOW QUICKLY THE SYSTEM CLEARS THE
REGION TUESDAY MORNING...ANOTHER ROUND OF SHOWERS AND STORMS IS
POSSIBLE TUESDAY AFTERNOON AS A COLD FRONT SLIDES ACROSS THE AREA. A
FEW OF THESE STORMS COULD ALSO BE STRONG.  HEAT INDEX VALUES WILL
ONCE AGAIN BE A CONCERN ON TUESDAY AHEAD OF THE COLD FRONT...MAINLY
OVER NORTHEAST IOWA. TEMPERATURES LOOK TO COOL BACK INTO THE MID 70S
TO AROUND 80 ON WEDNESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1220 PM CDT SUN JUL 20 2014

SURFACE MAP AROUND NOON SHOWED HIGH PRESSURE OVER THE EASTERN
CONUS WHILE A TROUGH OF LOW PRESSURE WAS MOVING EAST ACROSS THE
NORTHERN PLAINS. BREEZY SOUTHERLY WINDS WERE RESULTING BEWTEEN
THESE TWO SYSTEMS ACROSS THE AREA THIS AFTERNOON WITH GUSTS
EXPECTED IN THE 20-25KT RANGE AT TIMES. THESE WINDS WILL DIE OFF
TOWARD SUNSET WITH LOSS OF SURFACE HEATING AND BOUNDARY LAYER
MIXING. OTHERWISE...JUST A FEW CUMULUS THROUGH THIS AFTERNOON WITH
BASES AROUND 5KFT. THESE TOO EXPECTED TO DIMINISH BY SUNSET.
OVERNIGHT HOURS LOOK RELATIVELY QUIET WITH SOME PASSING CIRRUS.
VFR CONDITIONS/SOUTH WINDS CONTINUE INTO MONDAY.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR MNZ079-086-087-
     094-095.

IA...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR IAZ008-009-018-
     019.

&&

$$

SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...DAS



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