Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 201720
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1220 PM CDT SUN JUL 20 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 305 AM CDT SUN JUL 20 2014

SHOULD BE A NICE END TO THE WEEKEND WITH SEASONABLE TEMPS AND SOME
SUNSHINE. THE UPPER LEVEL FLOW WILL KEEP ANY PERTURBATIONS TO THE
NORTH...WITH NO NOTABLE SFC BOUNDARIES. THE INSTABILITY AXIS HANGS
ACROSS THE EASTERN DAKOTAS/WESTERN MN ALTHOUGH THE 850 MB MOISTURE
TRANSPORT ANGLES FROM THE SOUTHERN PLAINS INTO NORTHERN MN/NORTHWEST
WI. LOW LEVEL INVERSION AROUND 800 MB PER BUFKIT SOUNDINGS SHOULD
KEEP ANY CONVECTION IN CHECK - OUTSIDE OF A FORCING MECHANISM.

TONIGHT...THE 850 MB MOISTURE TRANSPORT/40 KTS LOW LEVEL JET POINT
INTO WESTERN IOWA. SOME WARM AIR ADVECTION IN THE 925-700 MB LAYER
IN THIS REGION...WHICH STRETCHES NORTHEAST INTO WI. HIGHWAY OF 850
MB THETA-E ADVECTION IN THIS REGION. FAIRLY BROAD AND NOT OVERLY
CONVERGENT...OUTSIDE OF THE LOW LEVEL JET FORCING. COULD SEE SOME
CONVECTION OVER IA LATER TONIGHT...BUT UNCERTAIN HOW FAR NORTHEAST
THIS POTENTIAL EXTEND. BETTER CHANCE FOR SOME SHOWERS FARTHER NORTH
ACROSS NORTHERN MN - BUT THIS SHOULD STAY NORTH.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 305 AM CDT SUN JUL 20 2014

MONDAY AND TUESDAY STILL SHAPING UP TO BE RATHER STEAMY AS SOUTHERLY
FLOW KICKS IN IN EARNEST. 925MB TEMPS IN THE NAM/GFS WARM INTO THE
MID 20S...WHILE SREF 850 MB TEMP ANOMALIES HOVER NEAR +2. HIGHS IN
THE MID-UPPER 80S ARE EXPECTED...WITH A FEW LOCATIONS REACHING 90.
MEANWHILE...DEWPOINTS ARE EXPECT TO REACH INTO THE LOW 70S...MAKING
FOR A VERY STICKY/HUMID COUPLE DAYS. THE COMBO OF THE HIGH HEAT AND
HUMIDITY WILL RESULT IN HEAT INDICES NEARING 100 FOR A FEW HOURS
MON/TUE AFTERNOONS ACROSS PARTS OF SOUTHEAST MN/NORTHEAST IA. A HEAT
ADVISORY COULD BE NECESSARY FOR THESE LOCATIONS MON/TUE
AFTERNOONS...IF THE DANGEROUS HEAT CAN BE REACHED FOR MORE THAN A
COUPLE OF HOURS.

AN UPPER LEVEL TROUGH WILL SLIDE EAST ACROSS CANADA FOR THE START TO
THE NEW WORK WEEK...AND WHILE ALL ITS FORCING WILL STAY NORTH...IT
WILL HELP DRAG A COLD FRONT INTO THE NORTHERN PLAINS...EASING IT
OVER THE UPPER MISSISSIPPI RIVER VALLEY MONDAY NIGHT. A SHORTWAVE
TROUGH WILL DRIVE ACROSS THE NORTHERN PLAINS MONDAY
NIGHT...INTERACTING WITH THE SFC FRONT AND FORCING IT SOUTHEAST ON
TUE. THE INSTABILITY AXIS WILL BEND WITH THIS SYSTEM...BECOMING MORE
WEST-EAST ORIENTATED ACROSS IA-NORTHERN ILL BY 00Z WED. ABOUT 30-40
KTS OF 0-6 KM SHEAR. ENOUGH FORCING ALONG THE BOUNDARY...AND AMPLE
INSTABILITY WITH ENOUGH SHEAR THAT SHOWERS/STORMS SHOULD FIRE ALONG
IT...WITH SOME THREAT FOR STRONGER-SEVERE STORMS. HOWEVER...THE
THREAT HAS SOME CAVEATS...MOSTLY WHAT HAPPENS WITH A STORM COMPLEX
MONDAY NIGHT. NOSE OF THE MOISTURE TRANSPORT AND SHORTWAVE SHOULD
RESULT IN A THUNDERSTORM COMPLEX DEVELOPING IN THE ND/MN
REGION...MOVING EAST INTO NORTHERN WI OVERNIGHT. SOME OF THESE
STORMS COULD BE SEVERE...AND DEPENDING ON THEIR TRACK...COULD POSE A
RISK FOR THE LOCAL AREA. MEANWHILE...HOW DEBRIS CLOUDS-BOUNDARIES
FROM THIS SYSTEM INTERACT AND MOVE THE FRONT IS UNCERTAIN. THE
SHOWER/STORM THREAT REMAINS HIGH FOR LATE MON THROUGH TUE
NIGHT...BUT THE SEVERE RISK WILL HAVE TO BE MONITORED CLOSELY.

BROAD RIDGING TO ZONAL FLOW STILL A GO FOR THE UPPER LEVEL FLOW PER
THE GFS AND ECMWF FOR THE LATER PART OF THE WORK WEEK. PRETTY GOOD
AGREEMENT IN DRIVING A CLOSED 500 MB LOW ACROSS SOUTHERN
CANADA...THEN DROPPING IT OVER THE NORTHERN PLAINS AND INTO THE
UPPER MISSISSIPPI RIVER VALLEY BY THE END OF THE WEEKEND.
DIFFERENCES IN SPEED...TIMING AND POSITIONING THOUGH...WITH THE EC
FASTER BY ABOUT 12 HOURS...AND SHIFTED FARTHER EAST. WHILE BOTH
POINT TO PCPN...WHEN...LOCATION AND TIMING VARY. WILL TREND TOWARD A
CONSENSUS SOLUTION FOR THE MOMENT...LETTING LATER MODEL RUNS ADD
SOME CLARITY.

&&

.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...NONE.
IA...NONE.
&&

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...DAS


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