Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 260447
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1147 PM CDT SAT OCT 25 2014

.SHORT TERM...(TONIGHT THRU SUNDAY NIGHT)
ISSUED AT 307 PM CDT SAT OCT 25 2014

MAIN FCST CONCERNS THIS PERIOD...SHRA/TSRA CHANCES SUN NIGHT...
TEMPERATURES.

DATA ANALYSIS AT 18Z HAD 1021MB HIGH PRESSURE CENTERED OVER THE
DAKOTAS. THE HIGH WAS BRINGING SUNNY SKIES AND DRIER AIR TO THE
NORTHERN PLAINS/UPPER MIDWEST. GRADIENT BETWEEN THE HIGH AND A
987MB LOW WEST OF JAMES BAY ALONG WITH DIURNAL WARMING/MIXING
RESULTING IN NORTHWEST WINDS 10-20KT G20-25KTS ACROSS MUCH OF
MN/WI/EASTERN IA EARLY THIS AFTERNOON. TEMPS AGAIN ABOVE NORMAL IN
THE MID 50S TO UPPER 60S ACROSS MUCH OF MN/IA/WI. WV IMAGERY
SHOWED THE NEXT SYSTEM TO IMPACT THE UPPER MIDWEST COMING ON SHORE
OVER WA/OR/NORTHERN CA.

25.12Z MODELS INITIALIZATIONS QUITE GOOD THIS CYCLE. SOLUTIONS VERY
SIMILAR FOR TONIGHT/SUN AS HGTS RISE AND THE MID LEVEL RIDGE AXIS
MOVES OVER THE UPPER MIDWEST. TREND FAVORS STRONGER OF EARLIER RUNS
WITH THE RIDGE AXIS AND A COMPROMISE ON THE TROUGHING/ENERGY MOVING
THRU THE ROCKIES. GOOD CONSENSUS AS THE TROUGH MOVES IN THE CENTRAL/
NORTHERN PLAINS SUN NIGHT. SUN NIGHT TREND FAVORS FASTER/STRONGER
OF THE EARLIER RUNS WITH THE TROUGH/ENERGY AT 12Z MON. GIVEN THE
TIGHT CONSENSUS...SHORT-TERM FCST CONFIDENCE REMAINS GOOD THIS CYCLE.

FOR THE SHORT TERM...QUIET WEATHER CONTINUES TONIGHT AS THE SFC
RIDGE AXIS SLIDES OVER THE AREA. CLEAR SKIES/LIGHT WINDS/DRY
BOUNDARY LAYER AIRMASS FAVORABLE FOR STRONG RADIATIONAL COOLING WITH
LOWS DIPPING INTO THE LOW-MID 30S...NEAR THE NORMALS. THE HIGH SLIPS
OFF QUICKLY ON SUN WITH SOUTHEAST TO SOUTHWEST SFC-850MB GRADIENT
FLOW INCREASING ACROSS THE AREA. SOUNDINGS SHOW MIXING TO 925-900MB
SUN AFTERNOON WITH AROUND 20KTS OF WIND IN THE TOP OF THE MIXED
LAYER...ESPECIALLY WEST OF THE MS RIVER. AFTER BRISK NORTHWEST WINDS
TODAY...BRISK/GUSTY SOUTHEAST WINDS EXPECTED ACROSS THE HIGHER
TERRAIN OF SOUTHEAST MN/NORTHEAST IA SUN AFTERNOON. STRONGER OF THE
925-850MB WARM ADVECTION AND INCREASE OF SFC-850MB MOISTURE REMAINS
SOUTH/WEST OF THE FCST AREA SUN...UNTIL VERY LATE IN THE DAY. BULK
OF MOISTURE INCREASE SUNDAY IS AT/ABOVE 700MB IN THE INCREASING
SOUTHWEST FLOW AHEAD OF THE MID LEVEL TROUGH. BULK OF THE LEADING
LOW LEVEL WARM ADVECTION GOES INTO WARMING WITH 850MB TEMPS CLIMBING
SOME 5C TO 6C ON SUNDAY. HOWEVER WARMER LOW LEVELS SUNDAY WILL BE
OFFSET BY THE INCREASING MID/HIGH CLOUDS IN THE AFTERNOON WITH
HIGHS SIMILAR TO THOSE OF TODAY.

WILL CONTINUE TO LEAVE SUNDAY DRY FOR NOW BUY MAY YET NEED A SMALL
SHRA/TSRA CHANCE OVER THE FAR WEST/NORTHWEST END OF THE FCST AREA
LATE IN THE AFTERNOON IF MORE ROBUST MODELS WITH MOISTURE/LIFT ARE
MORE CORRECT. SFC-850MB MOISTURE INCREASE SPREADS ACROSS THE AREA
SUN NIGHT ALONG WITH STRONGER OF THE 925-850MB WARM ADVECTION/
ISENTROPIC LIFT. STRONGER OF THE LIFT/GREATER LOW LEVEL SATURATION
SPREAD ACROSS THE NORTHEAST HALF OF THE FCST AREA CENTERED ON ABOUT
06Z MON...AHEAD OF THE APPROACHING SFC-850MB FRONT/TROUGH. THIS WITH
MUCAPE PROGGED TO BE AT LEAST 500 J/KG LIFTING ELEVATED PARCELS.
RAISED SHRA/ISOLATED TSRA CHANCES IN THE 03Z-09Z MON TIMEFRAME INTO
THE 50-75 PERCENT RANGE OVER THE NORTHEAST HALF OF THE FCST AREA AND
MOSTLY 20-50 PERCENT ACROSS THE SOUTHWEST HALF. USED A BLEND OF THE
NUMERICAL GUIDANCE LOWS/HIGHS FOR TONIGHT THRU SUN NIGHT.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 307 PM CDT SAT OCT 25 2014

MAIN CONCERNS FOR THE MON THRU TUE NIGHT PERIOD...SHRA/TSRA CHANCES
MON INTO MON NIGHT...LINGERING SHRA CHANCES TUE...TEMPERATURES THRU
THE PERIOD.

25.12Z MODELS OFFER A SLOWLY IMPROVING CONSENSUS MON/MON NIGHT AS
THE TROUGH/ENERGY LIFTS TOWARD/INTO THE UPPER MIDWEST. TREND FAVORS
FASTER OF THE EARLIER RUNS WITH MORE OF A POSITIVE TILT TROUGH AS
IT MOVES IN. THE FASTER TREND CONTINUES TUE AS THE MID LEVEL
TROUGH AXIS MOVES EAST OF THE AREA AND TUE NIGHT AS HGTS RISE/
SHORTWAVE RIDGING BUILDS INTO THE UPPER MIDWEST. FCST CONFIDENCE
IS AVERAGE TO GOOD IN THE MON THRU TUE NIGHT PERIOD.

MORE POSITIVE TILT OF THE TROUGH SHEARS MORE OF THE SHORTWAVE ENERGY
WEST/NORTH OF THE FCST AREA MON. THE SFC-850MB TROUGH AXIS AND
STRONGER LOW LEVEL THERMO-DYNAMIC FORCING STILL PUSHES EAST OF THE
AREA BY MID-DAY MON...WITH DRYING WESTERLY 850-500MB FLOW SPREADING
ACROSS THE FCST AREA. SOME WEAK MUCAPE LINGERS MON MORNING...BUT
GIVEN THE LACK OF ANY FOCUSED FORCING SIGNALS...APPEARS MON MORNING
WILL BE DRY ACROSS MUCH OF THE FCST AREA. SOME INCREASE OF DEEPER
LAYERED FORCING/LIFT MON AFTERNOON/EVENING WITH APPROACH OF THE 700-
500MB TROUGH AXIS AND SOME SHORTWAVE ENERGY/PV ADVECTION. THIS WITH
AN INCREASE OF MOISTURE IN THE SFC-500MB COLUMN CENTERED ON 00Z
TUE. SOME MUCAPE OF 200-500 J/KG STILL INDICATED OVER FCST AREA AT
18Z MON THEN OVER THE SOUTHEAST HALF AT 00Z TUE. INCREASED -SHRA
CHANCES THRU MON AFTERNOON THEN CARRIED 30-50 PERCENT CHANCES TUE
EVENING WITH THE DEEPER MOISTURE SIGNAL AND PASSAGE OF SOME OF
THE STRONGER PV ADVECTION. 850-500MB SUBSIDENCE/DRYING RATHER
QUICKLY SPREADS ACROSS THE AREA LATER MON NIGHT. TRENDED -SHRA
DOWN AND OUT FOR MUCH OF THE FCST AREA AFTER MIDNIGHT MON NIGHT
AND REMOVED ANY TSRA MENTION WITH CAPE PUSHED WELL SOUTH/EAST OF
THE AREA. CONTINUED TO TREND MUCH OF THE AREA DRY TUE MORNING WITH
FASTER EASTWARD MOVEMENT OF THE MID LEVEL TROUGH AND ANY FORCING.
QUESTION TUE IS WILL ANY DEFORMATION BAND -SHRA CLIP THE NORTH
END OF THE FCST AREA TUE AFTERNOON. CONSENSUS SHOWS AN INCREASE OF
925-700MB MOISTURE TO WRAP SOUTH INTO THE NORTH END OF THE FCST
AREA TUE AFTERNOON BUT FORCING/LIFT SIGNALS WEAK. WILL CONTINUE A
SMALL -SHRA CHANCE NORTH OF HWY 10 TUE AFTERNOON FOR NOW...MAINLY
TO BLEND WITH NEIGHBORING GRIDS. MID LEVEL HGTS RISE WITH SHORTWAVE
RIDGING TUE NIGHT. HOWEVER LOW LEVEL RIDGE AXIS REMAINS WEST OF
THE AREA WITH SOME WEAK 925-850MB CYCLONIC FLOW AND MOISTURE
REMAINING OVER MAINLY THE WI PORTION OF THE FCST AREA. LOWER
CLOUDS MAY BE TOUGH TO GET RID OF OVER THE NORTHEAST 1/3 OF THE
FCST AREA TUE NIGHT BUT WILL REMAIN OPTIMISTIC IN THE FCST GRIDS.
USED A BLEND OF THE GUIDANCE HIGHS LOWS FOR MON THRU TUE. WITH
POTENTIAL FOR A DRIER DAY AND SOME SUNSHINE MON...HIGHS STILL
LOOKING TO BE SOME 10-15F ABOVE NORMAL TO START THE WORK WEEK.

FOR WEDNESDAY THROUGH SATURDAY.../DAYS 4 TO 7/...

MEDIUM RANGE MODEL RUNS OF 25.00Z/25.12Z IN GOOD AGREEMENT WED AS
ONE TROUGH EXITS AND HGTS FALL AGAIN ACROSS THE NORTHERN PLAINS WITH
THE NEXT TROUGH/ENERGY. IMPROVING SIGNAL FOR A STRONGER SECONDARY
PIECE OF NORTHERN STREAM ENERGY TO DROP INTO/ACROSS THE WESTERN
GREAT LAKES THU INTO FRI. 25.12Z ECMWF BACK IN LINE WITH OTHER
MODELS/PREVIOUS RUNS AT 12Z FRI VS. ITS STRONG...OUTLIER LOOKING
25.00Z RUN. GOOD CONSENSUS FOR RISING HGTS/MID LEVEL RIDGING TO
BUILD INTO THE UPPER MIDWEST SAT. FCST CONFIDENCE IS AVERAGE TO
GOOD FOR THE WED-SAT PERIOD.

THE REGION IS GENERALLY BETWEEN SYSTEMS WED WITH SFC HIGH PRESSURE
AND WEAK SHORTWAVE RIDGING ALOFT MOVING ACROSS MN/IA/WI. WEAK LOW
LEVEL WARM ADVECTION SPREADS OVER THE AREA WED AFTERNOON BUT 925MB
TEMPS ONLY IN THE +4C TO +8C RANGE AT 00Z THU. ROUND OF LOWER
LEVEL WARM ADVECTION AHEAD OF A SFC LOW THRU MID LEVEL TROUGH/
SHORTWAVE ENERGY TO SLIDE ACROSS THE AREA WED NIGHT/THU. BULK OF
THE MOISTURE WITH THE STRONGER/DEEPER OF THE FORCING/LIFT WED
NIGHT LOOKS TO BE AT/ABOVE 700MB...WITH MORE SFC-700MB MOISTURE/
SATURATION ARRIVING THU AFTER THE STRONGER/DEEPER OF THE LIFT HAS
PASSED. SMALL RAIN CHANCES WED NIGHT/THU PER THE MODEL CONSENSUS
REASONABLE UNTIL DETAILS BECOME CLEARER. COLUMN TOO WARM TO
SUPPORT -SN LATER WED NIGHT/THU MORNING AND REMOVED THAT MENTION.
ANOTHER CHANCE OF LIGHT PRECIP WOULD SPREAD SOUTH ACROSS THE EAST
SIDE FCST AREA THU NIGHT WITH THE SHORTWAVE ENERGY DROPPING THRU
THE WESTERN GREAT LAKES. COLUMN BY LATE THU NIGHT WOULD BE COLD
ENOUGH TO SUPPORT PRECIP AS -RA/-SN OR -SN. SYSTEM WOULD EXIT
SOUTH/EAST OF THE AREA BY LATE FRI...WITH FRI EVENING STILL
LOOKING DRY BUT COOL FOR THE TRICK-OR-TREATERS. COLD/DRY CAN HIGH
PRESSURE LOOKING TO SETTLE INTO MN/IA/WI FRI NIGHT/SAT EAST OF THE
BUILDING LONGWAVE RIDGE AXIS. SOME OF THE COLDEST AIR OF THE
SEASON LOOKS TO SETTLE ACROSS THE AREA FRI NIGHT. THOSE LOCATIONS
THAT HAVE ESCAPED A HARD FREEZE SO FAR...THAT IS LOOKING TO COME
TO AN END SAT MORNING. DRY/QUIET/COOL DAY SAT UNDER THE CAN HIGH
PRESSURE. MODEL/ENSEMBLE CONSENSUS OF THE HIGHS/LOWS FOR WED THRU
SAT LOOKS WELL TRENDED AT THIS TIME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1147 PM CDT SAT OCT 25 2014

HIGH PRESSURE OVER MINNESOTA AND IOWA WILL CONTINUE TO MOVE
SOUTHEAST AND REACH THE OHIO RIVER VALLEY BY LATE SUNDAY
AFTERNOON. VFR CONDITIONS THROUGH THE DAY SUNDAY WITH THE WINDS
COMING AROUND TO THE SOUTHEAST ON THE BACK SIDE OF THE HIGH. A
SHORT WAVE TROUGH WILL START TO APPROACH FROM THE SOUTHWEST SUNDAY
EVENING. THE 26.00Z NAM SHOWS STRONG ISENTROPIC UP GLIDE OCCURRING
ON THE 300K SURFACE AHEAD OF THE WAVE WITH 3 TO 9 UBAR/S POSSIBLE.
THERE SHOULD ALSO BE GOOD MOISTURE TRANSPORT ON THIS SURFACE INTO
THE AREA WHICH SHOULD ALLOW FOR A VFR CEILING TO QUICKLY FORM
DURING THE EVENING. SHOWERS ARE ALSO EXPECTED TO DEVELOP WITH THE
BEST CHANCE FOR SATURATION TO OCCUR ALONG AND EAST OF THE
MISSISSIPPI RIVER. WILL INCLUDE A VCSH FOR KLSE BUT LEAVE KRST DRY
FOR NOW THINKING MOST OF THESE SHOULD REMAIN TO THE EAST.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION...04



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