Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 280804
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
304 AM CDT SAT MAR 28 2015

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 304 AM CDT SAT MAR 28 2015

WATER VAPOR SATELLITE THIS MORNING SHOWS A STRONG TROUGH MOVING
ONSHORE FROM THE PACIFIC. THE EXPECTATION IS STILL THAT THERE WILL
BE TWO SEPARATE SHORT WAVE TROUGHS THAT EMERGE FROM THIS TROUGH
WITH ONE TRACKING ACROSS THE NORTHERN ROCKIES AND THE OTHER GOING
SLIGHTLY FARTHER NORTH ACROSS SOUTHERN CANADA. THE SOUTHERN WAVE
WILL THEN MOVE ACROSS THE UPPER MIDWEST LATE TONIGHT AND SUNDAY
MORNING. THE WAVE THAT GOES ACROSS SOUTHERN CANADA WILL TURN
SOUTHEAST AND MOVE ALONG THE CANADIAN BORDER INTO THE GREAT LAKES
SUNDAY AFTERNOON. THE FIRST WAVE IS EXPECTED TO BE THE DOMINANT
WEATHER MAKER FOR THE LOCAL REGION AS IT BRINGS IN A ROUND OF
STRONG PV ADVECTION IN THE 500-300 MB LAYER SUNDAY MORNING ALONG
WITH MODERATE AND DEEP QG CONVERGENCE IN THE 1000-300 MB LAYER.
THIS DYNAMICAL FORCING LOOKS TO GET A BOOST WITH SOME JET DYNAMICS
COMING INTO PLAY SUNDAY MORNING AS THE LEFT EXIT REGION OF THE JET
MOVES ACROSS THE REGION.

IN THE LOW LEVELS...THE AREA OF SURFACE LOW PRESSURE IS EXPECTED
TO MOVE ACROSS SOUTHERN CANADA WITH A TRAILING COLD FRONT COMING
ACROSS THE AREA SUNDAY. THE BAROCLINIC ZONE WITH THE COLD FRONT
DOES NOT LOOK TO BE ALL THAT STRONG WHICH RESULTS IN ONLY SOME
WEAK FRONTOGENESIS OCCURRING IN THE 1000-850 MB LAYER WITH THE
PASSAGE OF THE FRONT. GOOD WARM AIR ADVECTION IS EXPECTED AHEAD OF
THE FRONT WHICH SHOULD HELP TO PRODUCE 2 TO 4 UBAR/S OF UP GLIDE
ON THE 290K ISENTROPIC SURFACE LATE SATURDAY NIGHT INTO SUNDAY
MORNING. THERE SHOULD ALSO BE SOME DECENT MOISTURE TRANSPORT INTO
THE AREA AHEAD OF THE FRONT. WITH THE WARM AIR ADVECTION AND THE
INCREASING SOUTH WINDS AHEAD OF THE FRONT...TEMPERATURES ARE
EXPECTED TO REACH THEIR LOWS EARLY TONIGHT AND SLOWLY RISE THROUGH
THE REST OF THE NIGHT WITH READINGS OF 32 OR ABOVE EXPECTED ALONG
AND WEST OF THE MISSISSIPPI RIVER BY 12Z SUNDAY. THIS BECOMES
IMPORTANT IN THE TYPE OF PRECIPITATION THAT IS EXPECTED LATE
TONIGHT INTO SUNDAY MORNING. THE 28.00Z MODELS CONTINUE TO
INDICATE A WARM LAYER ALOFT ALONG WITH SOME CONCERNS ABOUT WHETHER
ICE WILL BE PRESENT IN THE CLOUDS OR NOT. AS A RESULT...EXPECTING
A WINTRY MIX OF SNOW...SLEET AND SOME FREEZING RAIN/DRIZZLE BEFORE
GOING OVER TO ALL RAIN. FORTUNATELY...WITH THE RISING SURFACE
TEMPERATURES...ONLY EXPECTING A COUPLE HOURS OR SO OF THE MIX
BEFORE GOING OVER TO RAIN. THIS MAY STILL BE LONG ENOUGH TO
PRODUCE A LITTLE BIT OF ICE ACCUMULATION...BUT THINK THIS REALLY
SHOULD NOT CAUSE TOO MANY PROBLEMS AND NOT ANTICIPATING THE NEED
FOR A WINTER WEATHER ADVISORY AT THIS TIME.

ONCE THE FRONT GOES THROUGH SUNDAY...THERE WILL BE A PERIOD OF
WINDY WEST TO NORTHWEST WINDS AS STRONG SUBSIDENCE DEVELOPS ALONG
WITH LOW LEVEL LAPSE RATES ON THE ORDER OF 7-8 C/KM UP THROUGH
ABOUT 850 MB. THIS IS EXPECTED TO PRODUCE SUSTAINED WINDS OF 20 TO
30 MPH WITH GUSTS APPROACHING 40 MPH IN THE WINDY AREAS OF
SOUTHEAST MINNESOTA AND NORTHEAST IOWA...WHICH IS CLOSE BUT JUST
BELOW ADVISORY LEVELS.

STILL SOME DIFFERENCES AMONG THE MODELS WITH THE NEXT SYSTEM
COMING IN ON THE NORTHWEST FLOW ALOFT FOR MONDAY. THE 28.00Z ECMWF
HAS SHIFTED THE TRACK OF ITS SHORT WAVE TROUGH FARTHER NORTH...BUT
STILL NOT AS FAR AS THE 28.00Z GFS OR NAM. WITH THESE
DIFFERENCES...THE NAM AND GFS ARE DRY FOR MONDAY WHILE THE ECMWF
PRODUCES A LITTLE BIT OF LIGHT PRECIPITATION ACROSS THE NORTHERN
SECTIONS. WITH THE ECMWF TRENDING TOWARD A MORE NORTHERN TRACK AND
SLIGHTLY SLOWER TIMING...WILL TAKE THE PRECIPITATION CHANCES OUT
AND GO DRY FOR MONDAY.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 304 AM CDT SAT MAR 28 2015

THE DIFFERENCES WITH THE TRACK OF THE SHORT WAVE TROUGH AND
PRECIPITATION CONTINUE INTO MONDAY NIGHT. THE ECMWF WOULD SUGGEST
THAT MOST AREAS ALONG AND EAST OF THE MISSISSIPPI RIVER WOULD HAVE
A CHANCE FOR SOME LIGHT PRECIPITATION WHILE THE NAM AND GFS TAKE
IT NORTH OF THE AREA. PLAN TO SHOW JUST SOME 20 TO 30 PERCENT
CHANCES ACROSS THE AREA WITH THIS SYSTEM. THE CHANCES FOR
ADDITIONAL PRECIPITATION RETURN STARTING WEDNESDAY. THE NEXT
PACIFIC SHORT WAVE TROUGH IS EXPECTED TO MOVE ACROSS THE UPPER
MIDWEST WITH A SURFACE LOW TRACKING ALONG THE CANADIAN BORDER. THE
PRECIPITATION CHANCES WILL BE TIED TO THE COLD FRONT THAT COMES
ACROSS THE AREA LATE WEDNESDAY AND WEDNESDAY NIGHT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1148 PM CDT FRI MAR 27 2015

VFR CONDITIONS TO CONTINUE AT KRST/KLSE THROUGH 29.06Z. PERIODS OF
MID-HIGH LEVEL CLOUDS OVERNIGHT WILL MOVE SOUTH OF THE REGION BY
SATURDAY MORNING WITH MOSTLY SUNNY SKIES THROUGH THE DAY. EXPECT
A RETURN OF HIGH CLOUDS LATE IN THE PERIOD AHEAD OF THE NEXT LOW
PRESSURE SYSTEM. WINDS WILL BE LIGHT AND VARIABLE OVERNIGHT...
INCREASING SLIGHTLY FROM SOUTH-SOUTHEAST BY 28.15Z...BUT STILL
AROUND 10 KTS OR LESS. LATE IN THE PERIOD...THE SURFACE PRESSURE
GRADIENT WILL STRENGTHEN AS HIGH PRESSURE SLIDES TO THE SOUTHEAST...
ALLOWING FOR SOME SOUTHERLY GUSTS INTO THE LOW 20 KT RANGE AT KRST
AFTER 29.01Z.


&&

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

$$

SHORT TERM...04
LONG TERM...04
AVIATION...ROGERS



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