Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 231701
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1201 PM CDT SAT AUG 23 2014

.UPDATE...
ISSUED AT 954 AM CDT SAT AUG 23 2014

BASED ON THE 23.12Z RAP...NOT REALLY EXPECTING THE COMPLEX OF
SHOWERS AND STORMS TO DISSIPATE ANY TIME SOON. A SHORT WAVE TROUGH
WILL CONTINUE TO SLOWLY MOVE NORTHEAST THROUGH THE AREA PROVIDING
WEAK TO MODERATE PV ADVECTION IN THE 500-300 MB LAYER. IN THE LOW
LEVELS...THE WARM FRONT WILL BE ADVANCING TOWARD THE AREA WITH
WEAK FRONTOGENESIS IN THE 1000-850 MB LAYER THROUGH THE DAY. WARM
AIR ADVECTION OVER THIS FRONT WILL PROVIDE 4 TO 6 UBAR/S OF UP
GLIDE ON THE 310K ISENTROPIC SURFACE. THE MOISTURE TRANSPORT AT
850 MB SHOULD CONTINUE TO BE INTO AND OVER THE WARM FRONT. BASED
ON ALL THIS...HAVE INCREASED THE RAIN CHANCES TO 80 PERCENT OR
HIGHER FOR THE REMAINDER OF THE MORNING WEST OF THE MISSISSIPPI
RIVER AND THEN ALLOWED FOR A SLOW WEAKENING TREND WHILE SPREADING
THE RAIN CHANCES ACROSS MOST OF WISCONSIN DURING THE AFTERNOON.

WILL LET THE DENSE FOG ADVISORY EXPIRE AS SCHEDULED AT 10 AM. MOST
OF THE VISIBILITY HAS IMPROVED TO 2 MILES OR BETTER AND THE
INCOMING RAIN SHOULD ALSO HELP TO CLEAN THE ATMOSPHERE UP A LITTLE
BIT.

UPDATE ISSUED AT 737 AM CDT SAT AUG 23 2014

A SHORT WAVE TROUGH CONTINUES TO MOVE NORTHEAST TOWARD THE
FORECAST AREA THIS MORNING. THE HRRR SEEMS TO HAVE THE BEST HANDLE
ON ITS PRECIPITATION...SO TRENDED THE FORECAST TOWARD IT. AS THE
SYSTEM MOVES INTO OUR AREA THIS EXPECT TO SEE A GRADUAL SPLIT AS
THE 850 TO 700 MB MOISTURE TRANSPORT BREAKS APART AND ONE PART
GOES ACROSS NORTHEAST IOWA AND SOUTHWEST WISCONSIN...AND THE OTHER
PIECE MOVES TO THE WEST OF OUR AREA. SO EXPECT THE AREA WHICH
MOVES INTO SOUTHEAST MINNESOTA TO DISSPATE. MEANWHILE THE BETTER
CHANCES OF PRECIPITATION WILL BE SOUTH OF INTERSTATE 90 AS THAT
JET VEERS THROUGH THAT AREA. THERE MAY BE A REMNANT MCV THAT
KEEPS SOME PRECIPITATION ACROSS WESTERN WISCONSIN THIS AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 330 AM CDT SAT AUG 23 2014

SFC BOUNDARY LIES...MORE OR LESS...WEST EAST ACROSS SOUTHERN IA INTO
CENTRAL ILL EARLY THIS MORNING. AN UPPER LEVEL TROUGH WILL LIFT
NORTHEAST ACROSS THE NORTHERN PLAINS TODAY...AND SHOULD HELP GIVE
THIS BOUNDARY A SHOVE NORTH. MEANWHILE...THERE ARE SUGGESTIONS IN
THE MESO MODELS THAT AN MCV ASSOCIATED WITH THE CURRENT CONVECTION
OVER NEB WOULD TAKE NORTHEAST TRACK TODAY...AND COULD SERVE AS A
FOCUS FOR SHOWER/STORMS DEVELOP AS IT AND THE BOUNDARY SLIDE
NORTH/NORTHEAST ACROSS THE REGION.

HEAT AND HUMIDITY WILL ROUND OUT THE WEEKEND...AND HEAT ADVISORIES
LOOK LIKELY FOR PORTIONS OF THE REGION. 850 MB SREF TEMP ANOMALIES
AROUND +1.5 FOR SUNDAY WHILE 950 MB TEMPS ARE EXPECTED TO WARM TO 26-
28 C. HIGHS SHOULD REACH 90 ACROSS MUCH OF THE FORECAST AREA. ADD IN
DEW POINTS IN THE LOWER 70S AND AFTERNOON HEAT INDICES SHOULD REACH
100 FOR A LARGE PORTION OF THE FORECAST AREA.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 330 AM CDT SAT AUG 23 2014

MODELS IN PRETTY GOOD AGREEMENT WITH THE OVERALL PATTERN THROUGH
THE MIDDLE PART OF THE NEW WORK WEEK.

SOLUTIONS SUGGEST AN UPPER LEVEL SHORTWAVE WILL TRACK OUT OF THE
CENTRAL ROCKIES...ACROSS THE NORTHERN PLAINS AND INTO SOUTHERN
CANADA SUNDAY NIGHT. ITS ASSOCIATED SFC COLD FRONT WILL DRAG ACROSS
THE REGION LATE SUNDAY NIGHT INTO MONDAY...WITH THE SOUTHERN EXTENT
LIKELY LINGERING IN A SOUTHWEST-NORTHEAST ORIENTATION OVER THE
REGION. RIPPLES IN THE UPPER LEVEL FLOW WILL KICK OUT OF THE MEAN
TROUGH...AND WORK ON THIS BOUNDARY MON-TUE. THIS NEXT TROUGH THEN
SLIDES ACROSS THE UPPER MISSISSIPPI RIVER VALLEY WED
NIGHT/THU...CONTINUING TO WORK ON THAT SFC BOUNDARY...BUT ALSO
PUSHING IT EAST/SOUTHEAST AS THE SYSTEM EXITS INTO THE EASTERN GREAT
LAKES ON THU NIGHT.

THERE ARE SOME DISCREPANCIES IN THE MODELS WITH PLACEMENT...TIMING
AND STRENGTH OF THIS TROUGH...BUT THE TRENDS ARE SIMILAR AND ALL
POINT TO SEVERAL DAYS WITH RAIN CHANCES.

NOT OVERLY STRONG...BUT FAIRLY PERSISTENT FETCH OF 850 MB MOISTURE
TRANSPORT INTO THE REGION FOR THE EARLY PART OF THE UPCOMING WEEK.
WARM CLOUD DEPTHS CONTINUE TO HOVER NEAR 4 KFT WHILE PWS RANGE FROM
1.5 TO 1.75 INCHES. SO...HEAVY RAIN WOULD BE LIKELY WITH ANY
THUNDERSTORMS...ESPECIALLY THE STRONGER ONES.

AS FOR SEVERE POTENTIAL...AFTERNOON SBCAPES PROGGED FROM 2000-3000
J/KG PER THE GFS INTO WED...MOSTLY AROUND AND SOUTH OF THE SFC
BOUNDARY. HOWEVER...WITH LOW/MID LEVEL WARMING PERSISTING...AND 700
MB TEMPS AROUND 10 C...THERE WILL BE A CAP TO DEAL WITH...AND SOME
OF THIS LOW LEVEL INSTABILITY WILL NOT BE REALIZED. BUFKIT SOUNDINGS
INDICATE THIS TOO. THE DEEPER...STRONGER SHEAR IS EXPECTED TO BE
WELL INTO THE COLD AIR NORTH OF THE BOUNDARY...DISPLACED FROM THE
STRONGER INSTABILITY. THERE IS SOME OVERLAP...SO SOME ENHANCED
UPDRAFTS COULD BE SUPPORTED. OVERALL...NOT SURE THERE IS A TIME
PERIOD THAT STANDS OUT FOR AN ORGANIZED SEVERE THREAT AT THIS TIME.
THERE CERTAINLY COULD BE SOME SEVERE TO MARGINAL SEVERE
STORMS...PERHAPS MORE PULSEY IN NATURE. MUCH DEPENDS ON
BOUNDARY/SHORTWAVE INTERACTION AND TIME OF DAY. LOOK FOR UPDATES IN
THE HWO FOR THE LATEST THOUGHTS ON THE DAY TO DAY SEVERE POTENTIAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1201 PM CDT SAT AUG 23 2014

THE SHOWERS AND STORMS CONTINUE TO ADVANCE NORTHEAST ACROSS THE
AREA BUT ARE NOW SHOWING A DIMINISHING TREND. EXPECT THAT THESE
WILL BE PAST KRST BY 18Z BUT WILL LINGER INTO THE EARLY AFTERNOON
WITH SOME MVFR CONDITIONS AT KLSE. ONCE THESE MOVE
THROUGH...EXPECT THAT BOTH SITES WILL HAVE VFR CONDITIONS AS A
WARM FRONT APPROACHES AND THEN MOVES THROUGH SWINGING THE WINDS
AROUND TO THE SOUTHEAST. HOWEVER...NO DECREASE IN THE LOW LEVEL
HUMIDITY LEVELS WILL OCCUR WHICH SHOULD PRESENT THE POSSIBILITY OF
IFR CEILINGS WITH LOW STRATUS AGAIN TONIGHT. THE FORECAST
SOUNDINGS FROM THE 23.12Z NAM AND 23.15Z RAP BOTH INDICATING THE
STRATUS SHOULD FORM AND HAVE INCLUDED IT IN BOTH FORECASTS. NOT
OVERLY CONCERNED ABOUT FOG FOR TONIGHT AS BOTH THE SURFACE WINDS
AND WINDS JUST ABOVE THE SURFACE SHOULD BE TOO STRONG WITH TOO
MIXING TO ALLOW IT TO FORM.

&&

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

$$

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


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