Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 221147
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
647 AM CDT FRI AUG 22 2014

.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 245 AM CDT FRI AUG 22 2014

LARGE AREA OF STRATUS AND FOG ACROSS MN AND NORTHERN/EASTERN WI
EARLY THIS MORNING...WITH SATELLITE TRENDS SAGGING IT SOUTH. MAY
NEED A DENSE FOG ADVISORY FOR PARTS OF THE FORECAST AREA EARLY THIS
MORNING. WILL MONITOR AND ISSUE IF NECESSARY.

WARM FRONT CURRENTLY RUNNING FROM SOUTH CENTRAL MN INTO WESTERN
WI...JUST NORTH OF I-90. WEAK MOISTURE TRANSPORT INTO THE FRONT HAS
RESULTED IN ISOLATED SHOWERS/STORMS OVER NORTHERN WI. MOISTURE
TRANSPORT WANES THROUGH THE EARLY MORNING HOURS...AND EXPECT A
DECREASE IN THE ALREADY SPOTTY ACTIVITY AROUND THE WARM FRONT A
RESULT.

TO THE SOUTH...A WEST TO EAST BOUNDARY WAS RUNNING FROM SOUTHERN IA
INTO CENTRAL ILL. MOISTURE TRANSPORT HELPING TO FEED SOME
PRECIPITATION IN THIS REGION...AND THIS FOCUS WILL PERSIST THROUGH
THE DAY. INCREASING INSTABILITY WILL AID THE STORM PRODUCTION TO THE
SOUTH...ALONG THAT FRONT. NOT A LOT OF REASON FOR IT TO MOVE
NORTH...SITTING UNDER AN UPPER LEVEL TROUGH. HOWEVER...A BIT OF
UPPER LEVEL ENERGY COULD MOVE OUT OF THE PLAINS AND WORK ON THIS
BOUNDARY THIS AFTERNOON. SHOWERS/STORMS SHOULD REDEVELOP ALONG THE
SOUTHERN BOUNDARY...BUT UNLESS IT GETS AN UNEXPECTED PUSH
NORTH...THESE CHANCES SHOULD STAY SOUTH OF THE LOCAL FORECAST AREA.

THAT SAID...BUFKIT SOUNDINGS POINT TO PLENTY OF INSTABILITY
DEVELOPING THROUGH THE AFTERNOON ACROSS THE ENTIRE FORECAST AREA.
SOME MESO MODELS HINT THAT THE FRONT COULD INCH A BIT FARTHER
NORTH...WHICH WOULD PUT SOME RAIN CHANCES ACROSS THE FAR SOUTH. WILL
LEAVE SMALL CHANCES IN THIS AREA FOR NOW.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 245 AM CDT FRI AUG 22 2014

THE WEST-EAST SOUTHERN BOUNDARY WILL LIFT NORTH LATE FRIDAY NIGHT
THROUGH SATURDAY...PER LATEST GFS/NAM/EC...AS AN UPPER LEVEL
SHORTWAVE TROUGH MOVES NORTH/NORTHEAST ACROSS THE PLAINS. SLOPING
FRONTOGENETIC ALONG THE BOUNDARY...COUPLED WITH INCREASING
INSTABILITY AND WEAK WIND SHEAR SHOULD RESULT IN A FEW SHOWERS/STORMS
DEVELOPING AROUND THE FRONT. CURRENT TIMING VIA THE GFS/NAM SUGGEST
THAT SHOWERS/STORMS COULD BE WORKING IN ALREADY BY MORNING. MODELS
ARE STEADFAST IN PUSHING THE WARM FRONT INTO CENTRAL MN/NORTHERN WI
BY 00Z SUN. HOWEVER...IF PCPN IS WIDESPREAD IN THE MORNING...RAIN
COOLED AIR COULD SLOW THIS ADVANCEMENT DOWN. SOMETHING TO WATCH.

A SHOT OF SUMMER HEAT/HUMIDITY ON SUNDAY WITH THE WARM FRONT TO THE
NORTH AND 925 MB TEMPS AROUND 28 C. SREF 850 MB ANOMALIES HOVER
AROUND +1. EXPECTING HIGHS TO REACH OR EXCEED 90 FOR A LARGE CHUNK
OF THE AREA. WITH DEWPOINTS IN THE LOW 70S...HEAT INDICES COULD
REACH 100+ DEGREES DURING THE AFTERNOON. A HEAT ADVISORY MAY BE
NEEDED.

THE UPPER LEVEL TROUGH WILL MOVE INTO CANADA SUNDAY NIGHT...DRAGGING
ITS SURFACE COLD FRONT ACROSS THE UPPER MISSISSIPPI RIVER VALLEY.
THE SOUTHERN/WESTERN EXTENT OF THE BOUNDARY WILL LIKELY LAY UP WEST-
EAST ACROSS THE REGION MONDAY...AND PROVIDE A FOCUS FOR
SHOWERS/STORMS. BUFKIT SOUNDINGS POINT TO A LOW LEVEL CAP...BUT
THERE SHOULD BE ENOUGH FORCING AROUND THE FRONT FOR A PCPN RISK.
HIGHER THREAT FOR STORMS CURRENTLY LOOKS TO BE SUNDAY NIGHT.

DECENT AGREEMENT BETWEEN THE GFS AND EC WITH TRACKING AN UPPER LEVEL
SHORTWAVE TROUGH FROM THE ROCKIES TO ACROSS THE NORTHERN PLAINS BY
THE MIDDLE OF NEXT WEEK. STRONG PUSH OF LOW LEVEL MOISTURE TRANSPORT
AHEAD OF THE TROUGH...WITH A SFC WARM FRONT LIFTING INTO AND ACROSS
THE AREA TUE. THIS COULD BE A REMNANT OF THE FRONT FROM MONDAY. THE
GFS DEVELOPS AMPLE INSTABILITY AND WIND SHEAR FOR STORM DEVELOPMENT.
PWS NEAR 1.75 WITH WARM CLOUD DEPTH JUST UNDER 4 KFT SUGGEST THE
POTENTIAL FOR HEAVY RAIN. SOME DISCREPANCIES WITH TIMING/STRENGTH
AND PLACEMENT...BUT OVERALL THEY AGREE THAT SHOWERS/STORMS ARE
LOOKING LIKELY FOR THE REGION IN THE TUE-WED TIME FRAME. WILL LEAN
ON CONSENSUS FOR THE RAIN CHANCES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 646 AM CDT FRI AUG 22 2014

AREAS TO WIDESPREAD DENSE FOG AND LIFR/IFR CEILINGS WILL PERSIST
THROUGH 22.15Z...AND THEN QUICKLY DISSIPATE. WITH WINDS OF 10 TO
15 KNOTS AT THE OFFICE...A STRATUS DECK INSTEAD OF DENSE FOG
FORMED IN THE MISSISSIPPI RIVER VALLEY.

A WEAK COLD FRONT WILL MOVE THROUGH THE TAF SITES THIS MORNING.
THE PRESSURE GRADIENT IS NOT THAT GREAT...SO EXPECT THE WINDS TO
REMAIN 5 KNOTS OR LESS AS THEY SHIFT FROM THE SOUTH TO NORTHWEST.

FOR TONIGHT...THE LIGHT WINDS LOOK EVEN DEEPER THAN THEY WERE THIS
MORNING...SO INTRODUCED A TEMPO GROUP OF DENSE FOG AFTER 23.10Z.
&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR WIZ017-029-
     034-042>044-053>055-061.

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...BOYNE



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