National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KARX 110403
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1100 PM CDT MON MAR 10 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 321 PM CDT MON MAR 10 2014

THE MAIN FOCUS INTO TOMORROW IS WITH THE PRECIPITATION
CHANCES...TYPE AND AMOUNTS LATE TONIGHT INTO TOMORROW.

THE LOCALS REJOICED TODAY AS MUCH OF THE REGION REACHED
TEMPERATURES THAT ARE CONSIDERED TO BE ABOVE NORMAL. WITH THE
WARMER START THIS MORNING IN THE LOW 30S...HIGH TEMPERATURES
REACHED THE MID 40S TO MID 50S DESPITE HAVING A FOOT OR HIGHER
SNOW PACK AND A WEAK COLD FRONT/TROUGH MOVE THROUGH. TEMPERATURES
WILL TAKE A GRADUAL DROP OVERNIGHT AS COLDER LOW LEVEL AIR GETS
ADVECTED INTO THE REGION.

A MID LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL PROPAGATE EAST
ACROSS THE ROCKIES TONIGHT AS A SURFACE LOW DEVELOPS IN CENTRAL
NEBRASKA. AS THE COLDER LOW LEVEL AIR CONTINUES TO PUSH SOUTH
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY...THE THERMAL GRADIENT
WILL TIGHTEN UP ALONG A WEST TO EAST BAND FROM IOWA TOWARD THE
SOUTHERN GREAT LAKES. THIS WILL CREATE A NORTHWARD SLANTING BAND
OF FRONTOGENESIS THAT RUNS FROM THE SURFACE ON UP THROUGH THE MID
LEVELS. AS THE SURFACE LOW AND MID LEVEL TROUGH ENTER THE PLAINS
OVERNIGHT...PRECIPITATION WILL START TO FORM FROM CENTRAL
MINNESOTA INTO CENTRAL WISCONSIN. 10.12Z NAM/GFS SOUNDINGS SHOW
ABOUT A 100MB DRY LAYER NEAR THE SURFACE AS THIS PRECIPITATION
BEGINS TO FALL THROUGH THE COLUMN...SO CONFIDENCE IN WHETHER IT
WILL ACTUALLY BE ABLE TO MAKE IT TO THE GROUND IS SOMEWHAT LOW
THROUGH THE 6-12Z PERIOD. WITH A PORTION OF THE THERMAL PROFILE AT
+4C OR HIGHER...THE PRECIPITATION IS EXPECTED TO START OFF AS RAIN
WITH IT POSSIBLY CHANGING OVER TO A MIX AS THE COLUMN COOLS BELOW
ZERO.

STILL SOME UNCERTAINTY WITH THIS EVENT DESPITE IT BEING LESS THAN
24 HOURS AWAY. THE MAIN TRENDS THAT HAVE BEEN TAKEN WITH THIS
FORECAST IS TO SLOW DOWN THE SOUTHWARD PROGRESSION OF THE BAND AND
CHANGE IT BACK TO BEING MORE OF A SNOW PRODUCER THAN A MIX. IN
REGARD TO THE TIMING/LOCATION OF THE BAND...THE 10.12Z
NAM/GFS/ECMWF/GEM ARE ALL IN FAIRLY DECENT AGREEMENT WITH
DEVELOPING THE BAND ACROSS SOUTHERN MINNESOTA /WESTERN-CENTRAL
WISCONSIN TUESDAY MORNING AND THEN SHIFTING IT SOUTH INTO
NORTHEAST IOWA/SOUTHERN WISCONSIN IN THE AFTERNOON/EARLY EVENING.
AS FOR PRECIPITATION TYPE...10.12Z NAM/GFS SOUNDINGS BOTH SHOW A
SIMILAR TREND WITH THE WARM/DRY LAYER BEING IN THE LOW LEVELS AND
STARTING OUT WELL ABOVE FREEZING BEFORE IT DROPS DOWN TO THE WET
BULB TEMPERATURE WHICH IS BELOW 0C THROUGH THE ENTIRE PROFILE. AS
TIME GOES ON...THE WARM LAYER DROPS TO THE SURFACE AND THE P-TYPE
IS ALL DEPENDENT UPON HOW WARM IT IS AT THE GROUND. 10.12Z MOS
GUIDANCE SUGGESTS THAT TEMPERATURES WILL DIURNALLY CLIMB BACK INTO
THE MID 30S...WHICH STILL WOULD BE COLD ENOUGH TO ALLOW SNOW TO
REACH THE GROUND...PARTICULARLY IF WE ARE HAVING SOME HIGHER
SNOWFALL RATES.

FELT CONFIDENT ENOUGH TO GO BACK TOWARD A SNOWIER FORECAST GIVEN
THE DRY AIR THAT IS IN PLACE WHICH WILL KEEP THAT WET BULB
TEMPERATURE BELOW 0C THROUGH MOST OF THE SOUNDING. 10.12Z
GUIDANCE SHOWS ABOUT 0.10 TO 0.20 OF QPF WITH SNOW RATIOS RANGING
FROM 12:1 TO 17:1. THIS LEADS TO ABOUT 1 TO 3 INCHES OF SNOW
ACCUMULATIONS. 10.15Z SREF PLUMES HAVE MEAN AMOUNTS OF AROUND 1 TO
3 AS WELL...BUT ALSO HAVE A NUMBER OF MEMBERS THAT JUMP UP INTO
THE 3 TO 5 INCH RANGE WHICH IS PLAUSIBLE BASED ON THE AMOUNT OF
FRONTOGENETIC FORCING THAT WILL BE TAKING PLACE. CONSIDERED GOING
HIGHER ON SNOW TOTALS THAN THE 1 TO 3 INCH RANGE DUE TO THE
AMOUNT OF LIFT PRESENT...BUT THINK THAT SOME OF THE QPF WILL GO
TOWARD THE RAIN/MIX BEFORE IT CHANGES OVER TO SNOW. THE
PRECIPITATION BAND SHIFTS SOUTHWARD AND DOES NOT STAY IN PLACE
LONG AS WELL...BUT TRENDS WILL HAVE TO BE MONITORED OVERNIGHT.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 321 PM CDT MON MAR 10 2014

KNOCKED TEMPERATURES DOWN ON WEDNESDAY A BIT AS 850MB TEMPERATURES
DROP DOWN TO AROUND -15C. THIS COLD AIR ADVECTION LEADS TO SOME
STEEP LOW LEVEL LAPSE RATES AND SOME POTENTIAL SNOW
SHOWERS/FLURRIES AS AN INVERTED SURFACE TROUGH SWINGS FROM EAST TO
WEST ACROSS THE REGION.

TEMPERATURES WILL CLIMB BACK UP TOWARD NORMAL ON THURSDAY AS A
SYSTEM DROPS DOWN FROM CENTRAL CANADA THROUGH THE NORTHWESTERLY
FLOW ALOFT. 850MB TEMPERATURES WILL JUMP BACK TO AROUND +2/+4C AS
THIS SYSTEM REACHES SOUTHWEST ONTARIO. BEFORE THE WARM FRONT COMES
THROUGH...SOME LIGHT SNOW WILL BE POSSIBLE LATE WEDNESDAY NIGHT
INTO EARLY THURSDAY...PARTICULARLY IN NORTH CENTRAL WISCONSIN.

BEYOND THAT...THE 10.12Z GFS/ECMWF START TO HAVE DIFFERING
OPINIONS ON HOW COLD IT WILL BE IN THE LOW LEVELS WITH THE GFS
SHOWING A COOLER PERIOD. COULD HAVE ANOTHER SYSTEM CLIP NORTHERN
WISCONSIN ON FRIDAY TO BRING SOME LIGHT SNOW/RAIN IN WITH IT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1100 PM CDT MON MAR 10 2014

BAND OF PCPN CONTINUES TO DEVELOP WEST-EAST ACROSS THE NORTHERN
PLAINS LATE THIS EVENING...IN A REGION OF FRONTOGENETIC FORCING.
MESO MODEL TRENDS CONTINUE TO SUGGEST THE PCPN WILL MOVE IN A BIT
FARTHER NORTH THAN PREVIOUS FORECASTS...AND HAVE NUDGED THE FORECAST
THIS WAY. THIS DELAYS PCPN ONSET AT KRST/KLSE BY AN HOUR OR TWO.
BUFKIT SOUNDINGS POINT TO A LOW LEVEL WARM/DRY LAYER THAT WILL MAKE
-RA/-RASN MORE LIKELY INITIALLY...WITH QUICK COOLING/SATURATION
CHANGING PTYPE OVER TO -SN WITHIN 3 HOURS OR SO. VSBYS WILL DROP
FROM MVFR TO IFR WITH THE CHANGE OVER. STRONG ENOUGH FORCING THAT A
NARROW BAND OF 1/2SM SN WOULD BE POSSIBLE. MODEL TRENDS SUGGEST THE
BAND OF PCPN WILL SINK SOUTH OF KRST/KLSE BY 00Z...AND SHOULD BE
BREAKING BACK INTO VFR SHORTLY AFTER IT DOES. LOW CLOUDS COULD
QUICKLY RETURN OVERNIGHT TUE AS A SHORTWAVE TROUGH SCOOTS ACROSS THE
UPPER MISSISSIPPI RIVER VALLEY. CONFIDENCE NOT HIGH IN THIS
POTENTIAL AT THIS MOMENT. ANTICIPATE THERE WILL BE REFINEMENTS TO
TIMING/EXITING OF THE PCPN AS TRENDS BECOME CLEARER.

&&

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

$$

SHORT TERM...HALBACH
LONG TERM....HALBACH
AVIATION.....RIECK