Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KARX 120529
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1129 PM CST THU FEB 11 2016

.SHORT TERM...(TONIGHT THRU FRIDAY NIGHT)
ISSUED AT 312 PM CST THU FEB 11 2016

MAIN FCST CONCERNS THIS PERIOD...SMALL -SN CHANCES ACROSS THE
SOUTHWEST END OF THE FCST AREA TONIGHT...BITTER COLD TEMPS/WIND
CHILLS FRI NIGHT.

DATA ANALYSIS AT 18Z HAD HIGH PRESSURE CENTERED NEAR THE WI/IL/IA
BORDER WITH RIDGING TO ANOTHER HIGH OVER SASKAT/ALB. A SOUTHEAST
MOVING LOW WAS OVER WESTERN SD...ASSOCIATED WITH A RATHER VIGOROUS
LOOKING SHORTWAVE SEEN IN WV IMAGERY...ALSO OVER WESTERN SD. VIS/
FOG PRODUCT IMAGERY SHOWING CLEAR/MOSTLY CLEAR SKIES OVER THE FCST
AREA AND LOCATIONS EAST/SOUTH...NEAR THE CENTER OF THE SFC HIGH.
MID CLOUDS WITH THE SD LOW/SHORTWAVE SPREADING SOUTHEAST ACROSS
MN. SNOW BAND WITH THESE FEATURES WAS ABOUT 150 MILES WIDE...
CENTERED ON KFSD AND HEADED TOWARD KDMX EARLY THIS AFTERNOON.
ANOTHER COLDER DAY ACROSS THE REGION WITH MOST MID-DAY TEMPS AGAIN
IN THE 5F TO 20F ABOVE RANGE.

MODEL RUNS OF 11.12Z GENERALLY INITIALIZED QUITE WELL. ONE EXCEPTION
IS ALL WERE ABOUT 2MB TOO HIGH WITH SFC PRESSURES OVER MUCH OF
THE NORTH-CENTRAL CONUS THIS MORNING. SOLUTIONS VERY SIMILAR THRU
TONIGHT BUT DO TREND TO TRACK THE WESTERN SD SHORTWAVE A BIT
FURTHER SOUTHWEST THAN THE PREVIOUS RUNS. TREND FAVORS STRONGER
OF THE EARLIER MODELS WITH THE SHORTWAVE DROPPING SOUTH INTO
NORTHERN MN/LK SUPERIOR BY 12Z FRI THEN THRU THE WESTERN GREAT
LAKES SAT. GOOD CONSENSUS FOR THE TROUGH TO BE PROGRESSIVE AND
HGTS TO START RISING FRI NIGHT. SHORT-TERM FCST CONFIDENCE REMAINS
GOOD THIS CYCLE.

FOR THE SHORT TERM...SHORTWAVE...LOW AND BAND OF -SN WITH IT
TRANSLATES RATHER QUICKLY SOUTHEAST TONIGHT. SLIGHT SOUTHWESTWARD
SHIFT OF THE SHORTWAVE KEEPS THE BULK OF LOWER LEVEL THERMO-DYNAMIC
FORCING/LIFT AND GREATER SATURATION OF THE SFC-700MB PORTION OF THE
COLUMN SOUTHWEST OF THE FCST AREA. SOME DEEPER SATURATION CLIPS THE
SOUTHWEST END OF THE FCST AREA THIS EVENING...THEN EXITS RATHER
QUICKLY DURING THE OVERNIGHT HOURS. LEFT SOME SMALL -SN/FLURRY
CHANCES OVER THE SOUTHWEST END OF THE FCST AREA MAINLY THIS
EVENING...WHICH BLEND WELL WITH THE NEIGHBORING GRIDS. SOUNDINGS/X-
SECTIONS SHOWING STRONG DRYING ABOVE 900MB FOR FRI...WITH THE WAVE
DROPPING SOUTHEAST ACROSS THE WESTERN GREAT LAKES HAVING LITTLE
MOISTURE TO WORK WITH. LEFT FRIDAY DRY EVEN OVER THE EAST END OF
THE FCST AREA. TIGHTER SFC-850MB PRESSURE GRADIENT AND MDT/STRONG
LOW LEVEL COLD ADVECTION SPREADS ACROSS THE AREA BEHIND THE
PASSING SHORTWAVE. BRISK NORTHWEST WINDS 15-25 MPH GUSTING 25-30
MPH EXPECTED FOR MUCH OF FRI AS THE NEXT CAN/ARCTIC HIGH BUILDS
IN. PREVIOUS SHIFT INTRODUCED SOME BLOWING SNOW INTO THE GRIDS FOR
FRI AFTERNOON/EVENING AND CONTINUED THIS MENTION. HOWEVER...THIS
LIKELY TO BE MORE DRIFTING SNOW IN THE OPEN COUNTRY AREAS VS.
BLOWING SNOW. LOW LEVEL COLD ADVECTION CONTINUES FRI NIGHT WITH
925MB TEMPS IN THE -18C TO -23C BY 12Z SAT AND NAEFS 850MB TEMP
ANOMALIES IN THE -1 TO -2 STD DEVIATION RANGE. LOWS FRI NIGHT
TRENDING TO MOSTLY BE IN THE -10F TO -20F RANGE...BUOYED SOME BY
NORTHWEST 5-10KT GRADIENT WINDS FOR BOUNDARY LAYER MIXING. HOWEVER
THESE WINDS AND THE BITTER COLD TEMPS SET TO PRODUCE WIND CHILLS
IN THE -20 TO -35 RANGE LATER FRI NIGHT AND MUCH OF SAT MORNING.
MID CREW TONIGHT OR DAY CREW ON FRI WILL HANDLE ISSUING A WIND
CHILL ADVISORY FOR THAT PERIOD. USED A BLEND OF THE GUIDANCE
LOWS/HIGHS FOR TONIGHT/FRI THEN FAVORED COLDER OF GUIDANCE LOWS
FRI NIGHT.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 312 PM CST THU FEB 11 2016

FOR SATURDAY THRU SUNDAY NIGHT...

MAIN FCST CONCERNS THIS PERIOD...WIND CHILLS SAT MORNING...SNOW
CHANCES/AMOUNTS CENTERED ON SUNDAY...TEMPERATURES THRU THE PERIOD.

11.12Z MODEL RUNS IN GOOD AGREEMENT FOR RISING HGTS/SOME SHORTWAVE
RIDGING ALOFT TO BUILD OVER THE UPPER MIDWEST SAT INTO SAT NIGHT.
IMPROVING CONSENSUS ON THE NEXT STRONGER SHORTWAVE TO DROP INTO/
ACROSS THE REGION LATE SAT NIGHT INTO SUN NIGHT. TREND FAVORS
STRONGER OF EARLIER SOLUTIONS WITH THIS SHORTWAVE INTO/ACROSS
MN/IA/WI LATER SAT NIGHT/SUN. TREND IS STRONGER WITH SOME SECONDARY
SHORTWAVE ENERGY TO DROP INTO THE WEST SIDE OF THE TROUGH OVER THE
REGION SUN NIGHT...HOLDING MORE TROUGHING/CYCLONIC FLOW OVER THE
REGION THRU AT LEAST 12Z MON. GIVEN A GOOD AND IMPROVING CONSENSUS
FCST CONFIDENCE FOR SAT THRU SUN NIGHT IS ON THE GOOD SIDE.

PERIOD STARTS OFF WITH SUB-ZERO TEMPS AND WIND CHILLS IN THE -20 TO
-35 RANGE SAT MORNING. PLENTY OF SUNSHINE EXPECTED OVER THE AREA SAT
WITH THE SFC-850MB RIDGE AXIS DRIFTING ACROSS THE AREA. WINDS
DIMINISH RATHER QUICKLY SAT MORNING WITH WIND CHILLS QUICKLY
IMPROVING AS TEMPS CLIMB TOWARD 0F. THIS ALSO MEANS LITTLE GRADIENT
FLOW FOR ADVECTIONS TO SHOVE THE COLD AIRMASS QUICKLY OUT OF THE
AREA. 925MB TEMPS STILL IN THE -15C TO -18C AT 00Z SUN...ONLY
SUPPORTING HIGHS IN THE 5F TO 15F RANGE. ATTENTION THEN QUICKLY
TURNS TO THE APPROACHING SFC-500MB TROUGH FOR LATER SAT NIGHT INTO
SUN NIGHT. RATHER CONSISTENT SIGNAL FOR A ROUND OF DEEPER LAYERED
FORCING/LIFT TO SPREAD WEST TO EAST ACROSS THE FCST AREA IN THE
LATER SAT NIGHT INTO SUN EVENING PERIOD. THIS WITH DEEP SATURATION
OF THE COLUMN DURING THIS TIME AND AT LEAST MODEST LIFT THRU THE
-10C TO -15C LAYER. APPEARS SOME SNOW IS GOING SPREAD WEST TO
EAST ACROSS THE FCST AREA FROM LATER SAT NIGHT INTO SUN NIGHT.
GIVEN THE CONSISTENT SIGNAL...RAISED SNOW CHANCES INTO THE 60-85
PERCENT RANGE FOR SUNDAY...HIGHEST IN THE WEST HALF SUN MORNING.
AT THIS TIME 1 TO LOCALLY 4 OR 5 INCHES APPEAR POSSIBLE...WITH THE
HIGHEST AMOUNTS ACROSS NORTHEAST IA. STILL CONSIDERABLE SPREAD
AMONG THE MODELS ON THE SNOWFALL POTENTIAL WITH THIS SYSTEM...AND
CONFIDENCE NOT ALL THAT HIGH ON SNOWFALL AMOUNTS JUST YET. A
WINTER WEATHER ADVISORY MAY BE NEEDED FOR PORTIONS OF THE FCST
AREA CENTERED ON SUNDAY...BUT PLENTY OF TIME TO HONE IN ON THE
DETAILS AND IMPROVE THE CONFIDENCE ON THE SNOWFALL POTENTIAL.
USED A BLEND OF THE GUIDANCE HIGHS/LOWS FOR SAT THRU SUN NIGHT.

FOR MONDAY THRU THURSDAY...DAYS 4 TO 7...

MAIN FCST CONCERNS THIS PERIOD...WARMING TEMPERATURES...SMALL MAINLY
-SN CHANCES MUCH OF MON THRU WED.

11.00Z/11.12Z MEDIUM RANGE MODEL RUNS IN RATHER GOOD AGREEMENT AT
THE START OF THIS PERIOD WITH TROUGHING/DEEP CYCLONIC FLOW OVER THE
UPPER MIDWEST MON. TREND IS TO LAG MORE TROUGHING OVER THE REGION
MON. IMPROVING AGREEMENT FOR NORTHWEST FLOW ALOFT TO REMAIN OVER THE
REGION TUE/WED...WITH VARIOUS PIECES OF SHORTWAVE ENERGY TO RIPPLE
SOUTHEAST THRU THIS FLOW. HOWEVER...PLENTY OF DETAIL/TIMING
DIFFERENCES ON THESE FEATURES IN THE DAY 5/6 TIME-FRAME. REASONABLE
AGREEMENT FOR HGTS TO RISE OVER THE CENTRAL CONUS WED NIGHT/THU...AS
THE WESTERN NOAM RIDGING IS PUSHED EAST BY STRONG TROUGHING/ENERGY
INTO THE WEST COAST. GIVEN BETTER MODEL AGREEMENT THRU THE PERIOD
BUT DETAIL DIFFERENCES...DAY 4-7 FCST CONFIDENCE IS GENERALLY
AVERAGE THIS CYCLE.

WITH DEEP CYCLONIC FLOW/TROUGH AXIS NEAR OVER THE AREA...SOME
SHORTWAVE ENERGY IN THIS FLOW AND LINGERING LOWER LEVEL MOISTURE...
SMALL -SN CHANCES MON/MON NIGHT GOOD FOR NOW. ADDITIONAL NORTHWEST
FLOW SHORTWAVES RIPPLING SOUTHEAST THRU THE FLOW TUE/WED SPREADING
ROUNDS OF INCREASING MOISTURE AND PERIODS OF STRONGER LIFT ACROSS
THE AREA. GIVEN THE MODEL TIMING/DETAIL DIFFERENCES AT THIS
POINT...CONSENSUS 20-30 PERCENT MAINLY -SN CHANCES THESE PERIODS
APPEAR REASONABLE. MORE WESTERLY COMPONENT TO THE FLOW NEXT WEEK
ALLOWS FOR MODIFICATION OF THE LOWER LEVEL AIRMASS AND
TEMPERATURES CLOSER TO NORMAL FOR MON-WED. EVEN STRONGER LOW LEVEL
WARMING INTO THE REGION THU AS STRONGER MID LEVEL RIDGING WOULD
BUILD EAST ACROSS THE NORTH-CENTRAL CONUS. FOR NOW TEMPS WED
NIGHT/THU TRENDING ABOVE NORMAL. RIDGING ALOFT WOULD GENERALLY SHUT
OFF THE PRECIP CHANCES FOR WED NIGHT/THU AS WELL. MODEL/ENSEMBLE
CONSENSUS OF THE HIGHS/LOWS FOR MON-THU APPEARS REASONABLE AT THIS
TIME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1129 PM CST THU FEB 11 2016

VERY LIGHT SNOW WILL MOVE ACROSS THE TAF SITES THROUGH AROUND 10Z
THIS MORNING. THE MAIN IMPACT TO THE TAFS WILL BE MVFR STRATUS
MOVING THROUGH THIS MORNING. VISIBILITY COULD FALL TO AROUND 4SM
IN STEADIER SNOW EARLY THIS MORNING. OTHERWISE...LOOK FOR
NORTHWEST WINDS TO INCREASE OUT OF THE NORTHWEST TO 15 TO 20 KTS
BY MID FRIDAY MORNING WITH GUST TO AROUND 28 KTS POSSIBLE AT
TIMES. PATCHY BLOWING AND DRIFTING SNOW IS POSSIBLE...ESPECIALLY
ON KRST. THE STRATUS WILL SCATTER OUT ON FRIDAY AND EVENTUALLY
CLEAR BY LATE FRIDAY AFTERNOON AS ARCTIC HIGH PRESSURE EDGES IN.
PLAN ON VFR CONDITIONS FOR FRIDAY EVENING.

&&

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

$$

UPDATE...WETENKAMP
SHORT TERM...RRS
LONG TERM....RRS
AVIATION...WETENKAMP


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.