Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 140538
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1138 PM CST SAT FEB 13 2016

.SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)
ISSUED AT 315 PM CST SAT FEB 13 2016

MAIN FCST CONCERNS THIS PERIOD...SNOW CHANCES/AMOUNTS LATE TONIGHT
INTO SUNDAY NIGHT...TEMPERATURES.

DATA ANALYSIS AT 18Z HAD THE SFC RIDGE AXIS FROM NEAR KINL TO KRST
TO KSTL...DRIFTING STEADILY EAST/SOUTHEAST ACROSS THE UPPER MIDWEST.
PLENTY OF SUNSHINE ALONG/EAST OF THIS RIDGE AXIS WHILE MAINLY MID
CLOUDS WERE INCREASING OVER THE WEST/SOUTHWEST PORTION OF THE
REGION. TEMPS CLIMBING OUT OF THE DEEP-FREEZE...WITH MOST MID-DAY
READINGS ACROSS THE REGION IN THE 0F TO 15F ABOVE RANGE. A FEW WIND
CHILLS +5 TO -10 YET...BUT WINDS RATHER LIGHT IN/NEAR THE RIDGE
AXIS. SHORTWAVE OF INTEREST FOR LATER TONIGHT/SUN COULD BE SEEN IN
WV IMAGERY CROSSING THE ID/MT ROCKIES.

NO MAJOR ERRORS NOTED ON 13.12Z MODEL INITIALIZATIONS. ALL AGAIN
ABOUT 2MB TOO HIGH ON SFC PRESSURES OVER THE NORTH-CENTRAL CONUS.
MODELS OFFERING A TIGHTER CONSENSUS AS THE SHORTWAVE CROSSING THE
NORTHERN ROCKIES THIS AFTERNOON MOVES TO SOUTHWEST IA BY 12Z SUN
THEN TO NEAR/EAST OF CHICAGO BY 00Z MON. TREND CONTINUES TO FAVOR
STRONGER OF EARLIER MODEL RUNS WITH THIS FEATURE AND A SECONDARY
SHORTWAVE TO DROP SOUTHEAST ACROSS MN SUNDAY. IMPROVING AGREEMENT
FOR THIS WAVE TO CROSS THE AREA SUN NIGHT AND THE MAIN MID LEVEL
TROUGH AXIS TO BE NEARING LK MI BY 12Z MON. SHORT-TERM FCST
CONFIDENCE IS GOOD THIS CYCLE.

FOR THE SHORT TERM...WITH THE NORTHERN ROCKIES SHORTWAVE MOVING
QUICKLY TO SOUTHWEST IA BY 12Z SUN...LOWER LEVEL THERMO-DYNAMIC
FORCING AND PV ADVECTION AHEAD OF THE WAVE ITSELF SPREADS QUICKLY
TOWARD/INTO THE FCST AREA TONIGHT. INITIAL FORCING/LIFT WILL WORK TO
SATURATE THE COLUMN. THIS WILL BE A BIG TASK AS KMPX/KGRB/KDVN
SOUNDINGS THIS MORNING ONLY HAD ABOUT 0.05 INCH PW IN THE COLUMN.
HOWEVER...CONSISTENT SIGNAL AMONG MODELS AND RUN-TO-RUN THAT SNOW WILL
DEVELOP AND SPREAD ACROSS ROUGHLY THE SOUTHWEST HALF OF THE FCST
AREA BY SUNRISE SUNDAY. ALL MODELS NOW TRACK THE SHORTWAVE AND
THE DEEPER/STRONGER LIFT WITH IT ACROSS IA/NORTHERN IL...AND HAVE
SHIFTED THE SWATH OF HEAVIER PRECIP WITH IT MORE ACROSS SOUTHWEST
MN TO EAST CENTRAL IA AND NORTHWEST IL. WITH WEAKER LIFT NOW
PROGGED OVER MUCH OF THE FCST AREA...THE INITIAL DRY AIR TO WORK
AGAINST AND MUCH OF THE EARLIER/STRONGER LIFT WORKING TO SATURATE
THE COLUMN...HAVE LOWERED SNOW AMOUNTS OVER MUCH OF THE FCST AREA
LATE TONIGHT INTO SUNDAY EVENING. SNOW-WATER RATIOS REMAIN A
CONCERN...STRONGLY IMPACTING HOW MUCH SNOW IS LIKELY TO
ACCUMULATE. HIGHEST RATIOS APPEAR LIKELY OVER THE SOUTHWEST HALF
OF THE FCST AREA WHERE THE LIFT OVERCOMES THE DRIER AIRMASS FOR A
LONGER TIME. NORTH/EAST OF I-94 SFC-850MB PORTION OF THE COLUMN
MAY STRUGGLE TO SATURATE...AND THESE LOCATIONS MAY WELL END UP
WITH LESS THAN AN INCH OF SNOW THRU SUN NIGHT. LEFT SNOW TOTALS OF
1 TO 1.5 INCHES OVER THE NORTHEAST END OF THE FCST AREA FOR
NOW...WHICH BLENDS WELL WITH NEIGHBORING GRIDS. 3 TO LOCALLY 5
INCHES OF SNOW STILL LOOKING LIKELY ACROSS THE SOUTHWEST 1/3 OF
THE FCST AREA...AND LINES UP QUITE WELL WITH WHERE THE WINTER
WEATHER ADVISORY HAS BEEN ISSUED. WILL ADD OLMSTED AND HOUSTON
COUNTIES TO THE ADVISORY WHERE AROUND 3 INCHES OF SNOW IS A
REASONABLE BET...ESPECIALLY ACROSS THE SOUTHWEST HALF OF THOSE
COUNTIES. SOUTHEAST WINDS OF 15-20MPH GUSTING 20-25MPH WILL ALSO
OCCUR ACROSS OLMSTED AND WESTERN HOUSTON COUNTIES...TO BLOW/DRIFT
THE SNOW AROUND...MAKING FOR A LESS THAN PLEASANT TRAVEL DAY EVEN
IF ONLY 2 TO 3 INCHES OF SNOW FALL. THIS WIND ALSO ACROSS THE
REST OF THE OPEN COUNTRY LOCATIONS OF SOUTHEAST MN/NORTHEAST IA.
ADDED A MENTION OF BLOWING/DRIFTING SNOW TO MUCH OF THE SOUTHWEST
HALF OF THE FCST AREA FOR LATER TONIGHT THRU MID AFTERNOON SUNDAY.

MAIN SNOWFALL TAPERS OFF SUN AFTERNOON WITH PASSAGE OF THE LEAD
WAVE. SECONDARY WAVE DROPPING ACROSS MN KEEPS SOME WEAK LIFT AND
ENHANCED SFC-500MB CYCLONIC FLOW OVER THE AREA THRU MUCH OF SUN
NIGHT. CONTINUED -SN CHANCES ACROSS MUCH OF THE FCST AREA THRU SUN
NIGHT...HIGHEST EAST/NORTH AND HIGHEST DURING THE EVENING. MAIN
SNOWFALL NORTHEAST OF I-94 LIKELY TO BE FROM THIS FORCING SUN
NIGHT. USED A BLEND OF THE GUIDANCE LOWS/HIGHS FOR TONIGHT THRU
SUN NIGHT. LOWS TONIGHT TO BE DURING THE LATE EVENING...WITH
STEADY/SLOWLY RISING TEMPS AFTER MIDNIGHT.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 315 PM CST SAT FEB 13 2016

FOR MONDAY THRU TUESDAY NIGHT...

MAIN FCST CONCERNS THIS PERIOD...WARMER TEMPERATURES...NEXT STRONGER
NORTHWEST FLOW SHORTWAVE TO PASS WEST/SOUTH OF THE FCST AREA MON
NIGHT/TUE.

13.12Z MODELS CONTINUE WITH IMPROVING AGREEMENT ON THE NEXT BUNDLE
OF SHORTWAVE ENERGY DOWN THE WEST SIDE OF EASTERN NOAM TROUGHING
MONDAY...AND FOR THE BULK OF THIS TO PASS WELL SOUTH/WEST OF THE
FCST AREA. BETTER AGREEMENT ON A STRONGER SHORTWAVE DROP SOUTHEAST
THRU THIS FLOW MON NIGHT/TUE...CLOSER TO THE FCST AREA THAN THE
MONDAY ENERGY. AGREEMENT FOR HGTS OVER THE UPPER MIDWEST TO START
RISING TUE NIGHT AS STRONGER TROUGHING APPROACHING THE WEST COAST
STARTS TO PUSH THE WESTERN NOAM RIDGING EASTWARD. FCST CONFIDENCE
AVERAGE TO GOOD THRU THIS PERIOD.

WEAK HIGH PRESSURE TO SETTLE OVER THE REGION MON WITH 925-700MB
WARM ADVECTION BEHIND THE TROUGH FROM SUN NIGHT SPREADING ACROSS
THE AREA. 925MB TEMPS BY 00Z TUE WOULD SUPPORT HIGHS AROUND 32F ON
MON IF WE CAN MIX THAT DEEP. LOWER LEVEL MOISTURE/CLOUDS TRAPPED
IN/UNDER AND INVERSION NEAR 925MB MAY WELL TEMPER THE WARMUP ON
MON...AND TRENDED TOWARD COOLER OF THE GUIDANCE HIGHS. 13.12Z
MODEL CONSENSUS TRACKS A VIGOROUS SHORTWAVE TO NEAR THE NE/IA/MO
BORDER BY 12Z TUE THEN INTO THE OH VALLEY BY 00Z WED. 13.18Z NAM
SHIFTS THE TRACK OF THIS SHORTWAVE ABOUT 200 MILES TO THE
NORTH/EAST MON NIGHT/TUE. 13.12Z CONSENSUS WOULD TRACK THE MAIN
FORCING/LIFT WITH THIS FEATURE JUST SOUTHWEST OF THE FCST AREA
CENTERED ON 12Z TUE...CLOSE ENOUGH THAT SOME OF IT AND DEEPER
SATURATION MAY PASS ACROSS MAINLY THE SOUTHWEST 1/3 OF THE FCST
AREA. GIVEN THE 13.18Z NAM TREND AND POTENTIAL FOR A NORTHEAST
SHIFT OF THIS WAVE...CONSENSUS 20-30 PERCENT -SN CHANCES MAINLY
OVER THE SOUTHWEST 1/2 OF THE FCST AREA LATE MON NIGHT/TUE MORNING
OKAY FOR NOW. TUE NIGHT WOULD HAVE WEAK BUT COOLER HIGH PRESSURE
BUILDING INTO THE REGION UNDER THE HGTS ALOFT THAT ARE STARTING
TO RISE...FOR WHAT WOULD BE A DRY PERIOD. USED A BLEND OF THE
GUIDANCE LOWS/HIGHS FOR MON NIGHT THRU TUE NIGHT.

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

MAIN FCST CONCERNS THIS PERIOD...TEMPERATURES THRU THE PERIOD...
SMALL MAINLY -RA CHANCES CENTERED ON FRI.

13.00Z/13.12Z MEDIUM RANGE MODEL RUNS IN GOOD AGREEMENT ON WHAT
SHOULD BE QUIET NORTHWEST FLOW ALOFT OVER THE REGION WED...THEN
RIDGING ALOFT OVER THE REGION THU AS STRONGER PAC ENERGY MOVES INTO
THE WESTERN CONUS. IMPROVING CONSENSUS FOR THE WESTERN CONUS
TROUGHING TO THEN MOVE INTO/ACROSS THE MID/UPPER MS VALLEY FRI...
QUICKLY BEING REPLACED BY RIDGING ALOFT FOR SAT. PLENTY OF DETAIL
DIFFERENCES BY FRI/SAT WITH RUN-TO-RUN CONSISTENCY LEAVING QUITE A
BIT TO BE DESIRED BY LATE NEXT WEEK. FCST CONFIDENCE IS AVERAGE
WED/THU THEN BELOW AVERAGE FRI/SAT.

THE NORTHWEST FLOW ALOFT BEHIND THE TUESDAY SYSTEM IS SET TO SPREAD
COOLER CAN HIGH PRESSURE SOUTHEAST ACROSS THE UPPER MIDWEST WED. DRY
WED WITH TEMPS A BIT BELOW NORMAL APPEARS TO BE A GOOD TREND. FOR
WED NIGHT INTO THU NIGHT...STRONG SOUTHERLY FLOW/LOW LEVEL WARM
ADVECTION PROGGED TO RETURN UNDER THE BUILDING RIDGING ALOFT AND
AHEAD OF THE NEXT TROUGHING INTO THE PLAINS. 850MB TEMPS LOOKING TO
WARM WELL ABOVE 0C ON THU. THESE WARM TEMPS ALOFT TO THEN REMAIN
OVER THE AREA THRU FRI AS THE STRONGER SFC-MID LEVEL LOW/TROUGHING
WOULD SWING THRU THE REGION. QUESTIONS/DIFFERENCES REMAIN ON HOW
MUCH MOISTURE IS AVAILABLE AHEAD OF/WITH THIS TROUGH AS IT MOVES
THRU THE REGION. PRESENT CONSENSUS PLACES THE GREATER SATURATION AND
STRONGER FORCING/LIFT SIGNALS NORTH OF OR OVER THE NORTH END OF THE
FCST AREA AS THIS TROUGH APPROACHES/PASSES. THE CONSENSUS 20-30
PERCENT PRECIP CHANCES /HIGHEST NORTH/ THU NIGHT INTO FRI NIGHT OKAY
FOR NOW. WITH WHAT WOULD BE 850MB TEMPS WELL ABOVE 0C AND BOUNDARY
LAYER TEMPS AT LEAST IN THE 30S...MUCH OF THESE CHANCES WOULD BE
-RA. WITH THE PATTERN TO BE PROGRESSIVE AND RIDGING BUILDING IN FROM
THE WEST FOR SAT...AIRMASS OVER THE REGION WOULD REMAIN ON THE MILD
SIDE SAT AS HIGH PRESSURE MOVES IN FROM THE PLAINS VS. CANADA.
MODEL/ENSEMBLE CONSENSUS OF HIGHS/LOWS FOR WED THRU SAT...TRENDING
ABOVE TO MUCH ABOVE NORMAL FOR THU/FRI...REASONABLE AT THIS TIME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1138 PM CST SAT FEB 13 2016

SNOW WILL OVERSPREAD THE TAF SITES TONIGHT INTO SUNDAY MORNING
WITH CONDITIONS GRADUALLY LOWERING TO IFR AS LOW LEVELS SATURATE.
PLAN ON VISIBILITIES FALLING INTO THE 1-3 SM RANGE WITH CEILINGS
FALLING TO AROUND 900 FT AT TIMES. ALSO...SOUTHEAST WINDS WILL
INCREASE SUNDAY MORNING INTO THE 13 TO 18 KT RANGE...WITH GUSTS
TO AROUND 25 KTS. THE SNOW AND PERIODS OF IFR CONDITIONS WILL
PERSIST INTO SUNDAY AFTERNOON...THEN SNOW TAPERS OFF DURING THE
MID TO LATE AFTERNOON HOURS. A SECONDARY SHORTWAVE MOVES IN AND WE
COULD SEE ANOTHER ROUND OF LIGHT SNOW LATE THIS AFTERNOON INTO
THIS EVENING.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY UNTIL 6 PM CST SUNDAY FOR WIZ054-061.

MN...WINTER WEATHER ADVISORY UNTIL NOON CST SUNDAY FOR MNZ086-087-
     094>096.

IA...WINTER WEATHER ADVISORY UNTIL 6 PM CST SUNDAY FOR IAZ008>011-018-
     019-029-030.

&&

$$

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


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