Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 160922
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
322 AM CST SUN NOV 16 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 322 AM CST SUN NOV 16 2014

MAIN FORECAST CONCERNS THIS PACKAGE...LINGERING -SN CHANCES THIS
MORNING...-SHSN CHANCES WITH THE NEXT TROUGH/FRONT TONIGHT...
CONTINUED COLD TEMPERATURES.

06Z DATA ANALYSIS HAD A WEAK SFC TROUGH/FRONT ACROSS EASTERN MN TO
CENTRAL IA...MAKING STEADY PROGRESS EAST EARLY THIS MORNING. WV
IMAGERY SHOWED THE STRONG SHORTWAVE MOVING EAST/NORTHEAST NEAR THE
MN/IA BORDER WITH THE HIGHER/COLDER CLOUD TOPS AHEAD OF THIS FEATURE
NOW OVER WI. AREA RADARS SHOWED THE SNOW MOVING STEADILY EAST...WITH
THE TRAILING EDGE LINING UP QUITE WELL WITH THE SFC TROUGH/FRONT
POSITION. CLOUDS ALREADY DECREASING IN SOUTHWEST MN IN THE WAKE OF
THE SHORTWAVE. EARLY MORNING TEMPS UNDER THE CLOUDS/-SN REMAINED IN
THE UPPER TEENS TO MID 20S.

NO PROBLEMS NOTED WITH 16.00Z MODEL INITIALIZATIONS. SOLUTIONS OFFER
A TIGHT CONSENSUS TODAY/TONIGHT AS ONE SHORTWAVE TROUGH EXITS
QUICKLY NORTHEAST THIS MORNING THEN THE NEXT ONE DROPS INTO THE
REGION THIS AFTERNOON/TONIGHT. TREND FAVORS STRONGER OF THE EARLIER
RUNS WITH THE TROUGH/ENERGY TO DROP IN THIS AFTERNOON/TONIGHT. SHORT
TERM FCST CONFIDENCE REMAINS GOOD THIS CYCLE.

IN THE SHORT TERM...THE FIRST SHORTWAVE WAS ALREADY LIFTING
NORTHEAST OF THE FCST AREA EARLY THIS MORNING...TAKING THE DEEPER
MOISTURE/LIFT AND -SN WITH IT. DECREASE OF CLOUDS WAS ALREADY
SPREADING ACROSS SOUTH CENTRAL MN/NORTH CENTRAL IA IN THE POST
SHORTWAVE SUBSIDENCE. WILL USE THE DISTANCE-SPEED TO TIME THE EXIT
OF THE -SN AND DECREASE OF CLOUDS THIS MORNING. POST SHORTWAVE
CLEARING/DECREASE OF CLOUDS WORKS ACROSS THE FCST AREA TODAY...BUT
THIS IS SHORT-LIVED. THE STRONG SHORTWAVE DROPPING INTO NORTHERN MN
THIS AFTERNOON QUICKLY SPREADS INCREASING 850-500MB MOISTURE
SOUTHEAST INTO THE FCST AREA LATER THIS AFTERNOON. INCREASING CLOUDS
IN ORDER AGAIN FROM NORTHWEST TO SOUTHEAST ACROSS THE FCST AREA
LATER THIS AFTERNOON/EVENING. STRONGEST OF THE DYNAMIC FORCING/LIFT
WITH THE SHORTWAVE STILL LOOKS TO PASS NORTHEAST OF THE FCST AREA
TONIGHT AS A DEEP TROUGH FORMS OVER THE REGION. LOWER LEVELS
GENERALLY DOMINATED BY COLD ADVECTION TONIGHT...BUT SOME WEAK LIFT
INDICATED IN THE SFC-700MB LAYER...IN STRONG/DEEP CYCLONIC FLOW AS
THE SFC-500MB TROUGH AXIS ROTATES THRU THE AREA. GIVEN THE SFC-700MB
MOISTURE...THE WEAK LIFT AND MUCH OF THIS LAYER PROGGED TO BE IN THE
-12C TO -18C RANGE...A 20-30 PERCENT CHANCE OF -SHSN ACROSS THE AREA
QUITE REASONABLE FOR LATER TONIGHT.

LITTLE BIT WARMER START THIS MORNING...BUT EVEN WITH SOME SUNSHINE
THE FRESH SNOW COVER WILL HOLD TEMPS BACK. BLEND OF GUIDANCE HIGHS
IN THE UPPER TEENS TO MID 20S LOOKS GOOD FOR TODAY. 925MB TEMPS IN
THE -13C TO -15C RANGE BY 12Z MON...HOWEVER THE CLOUDS AND
TIGHTENING GRADIENT/INCREASING NORTHWEST WINDS WILL KEEP THE
BOUNDARY LAYER STIRRED AND LOWS FROM HEADING BELOW ZERO TONIGHT.
BLEND OF GUIDANCE LOWS A FEW DEGREES EITHER SIDE OF +10F LOOKS GOOD.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 322 AM CST SUN NOV 16 2014

MAIN CONCERNS FOR MON THRU TUE NIGHT...WINDS/BLOWING SNOW/-SHSN
MON...-SHSN CHANCES AGAIN TUE NIGHT...COLD TEMPERATURES THRU THE
PERIOD.

16.00Z MODELS IN GOOD AGREEMENT AS THE TROUGH DEEPENS OVER THE MID/
UPPER VALLEY MON THEN PROGRESSES EAST MON NIGHT/TUE. TIGHTENING
CONSENSUS ON THE NEXT NORTHERN STREAM SHORTWAVE TO DROP INTO MN/WI
TUE NIGHT. TREND FAVORS A COMPROMISE OF THE EARLIER RUNS WITH THE
STRENGTH OF THE TUE NIGHT SHORTWAVE WHILE FAVORING SLOWER OF THE
EARLIER RUNS AT 12Z WED. FCST CONFIDENCE FOR MON THRU TUE NIGHT
REMAINS QUITE GOOD.

DEEP CYCLONIC FLOW REMAINS OVER THE AREA MON AS THE COLD MID LEVEL
TROUGH DEEPENS/BOTTOMS OUT OVER THE REGION. COLDEST OF THE 700-500MB
AIRMASS WITH 700MB TEMPS IN THE -27C RANGE IS OVER THE FCST AREA
MON. THIS WITH 70 TO 100 PERCENT RH AND SOME WEAK LIFT PROGGED IN
THE 925-700MB LAYER. MODEL SOUNDINGS SHOWING STEEP LOW LEVEL LAPSE
RATES DURING THE AFTERNOON WITH MIXING AS DEEP AT 850MB. SCT -SHSN
SEEM ALMOST CERTAIN FOR MON AFTERNOON...SOME OF WHICH COULD HAVE
BRIEF HEAVY BURSTS OF FLUFFY SNOW WITH THEM. 25-50 PERCENT -SHSN
CHANCE...HIGHEST NORTHEAST OF I-94...ON MON LOOK GOOD FOR NOW.
LINGERED A SMALL -SHSN CHANCES ALONG/NORTHEAST OF I-94 INTO MON
EVENING. TIGHTER PRESSURE GRADIENT OVER THE AREA MON AND 925MB WINDS
IN THE 25-30KT RANGE. WITH THE STEEP LOW LEVEL LAPSE RATES/MIXING TO
900-850MB...NORTHWEST WINDS 15-20MPH GUSTING 30-35MPH IN ORDER FOR
MON. GIVEN THE FRESH 1 TO 4 INCHES OF FROM SAT/SAT NIGHT...
CONTINUED/EXPANDED BLSN MENTION IN THE 10Z MON THRU 03Z TUE PERIOD.
WINDS DIMINISH MON NIGHT BUT APPEAR TO REMAIN STRONG ENOUGH TO KEEP
THE BOUNDARY LAYER STIRRED AND LOWS FROM BOTTOMING OUT WELL BELOW
ZERO AS THE COLDEST OF THE 925MB AIRMASS MOVES ACROSS THE AREA. SOME
LINGERING CLOUDS TO PROVIDE A BLANKET AS WELL MON NIGHT. STILL
APPEARS MOST LOWS MON NIGHT WILL BE IN THE 0F TO +5F RANGE. MDT TO
STRONG 850-700MB WARM ADVECTION IN ADVANCE OF THE NEXT NORTHERN
STREAM SHORTWAVE SPREADS ACROSS THE AREA TUE. HOWEVER LITTLE WARMING
OF THE 925MB TEMPS TUE WITH MID/HIGH LEVEL MOISTURE/CLOUDS INCREASE
AGAIN LATER IN THE DAY. EVEN WITH WINDS BECOMING SOUTHWEST TUE
AFTERNOON...TUE HIGHS LOOKING TO STRUGGLE TO GET ABOVE THE TEENS AT
MOST LOCATIONS. SFC-700MB MOISTURE WITH THIS FEATURE SPREADS
SOUTHEAST ACROSS THE AREA TUE NIGHT. WITH THE TREND TOWARD A
STRONGER SHORTWAVE AND PV ADVECTION TO MOVE ACROSS THE AREA TUE NIGHT
AND SOME LOWER LEVEL WARM ADVECTION/ISENTROPIC LIFT...RAISED -SHSN
CHANCES ACROSS THE NORTHEAST 2/3 OF THE FCST AREA INTO THE 20-30
PERCENT RANGE. GENERALLY USED A BLEND OF THE GUIDANCE HIGHS/LOWS FOR
MON THRU TUE NIGHT.

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

MAIN FCST CONCERNS IN THE WED THRU SAT PERIOD...TEMPERATURES.

16.00Z MODELS IN GOOD AGREEMENT FOR RENEWED COLD TROUGHING OVER THE
UPPER MIDWEST FOR WED...WITH THE REGION TO THEN REMAIN UNDER
NORTHWEST FLOW ALOFT THU INTO FRI. MODEL DIFFERENCES BEGIN TO IMPACT
THE REGION LATE FRI THRU SAT. THIS AS MODELS INDICATE THE WESTERN
NOAM RIDGING TO BREAK DOWN AS ENERGY UNDERCUTS IT INTO THE WESTERN
CONUS AND THE COLD EASTERN NOAM TROUGHING LIFTS TOWARD THE CAN
MARITIMES. FCST CONFIDENCE REMAINS GOOD WED/THU...BECOMING AVERAGE
BY SAT.

ANOTHER COLD AIRMASS WITH 925MB TEMPS IN THE -10C TO -14C RANGE
EXPECTED TO SETTLE ACROSS THE UPPER MIDWEST FOR WED/THU AS THE
NEXT CAN/ARCTIC HIGH PRESSURE BUILDS SOUTHEAST THRU THE PLAINS.
GENERALLY DRY WED/THU /MAY YET NEED MORE OF A FLURRY MENTION WED/
WITH TEMPERATURES REMAINING AROUND 20F BELOW NORMAL. LOWER LEVEL
MODEL DIFFERENCES START FRI. ECMWF MAINTAINS THE LOW LEVEL COLD
AIRMASS OVER MN/IA/WI WHILE GFS SPREAD MDT/STRONG 925MB WARM
ADVECTION ACROSS THE AREA. SOME 10C DIFFERENCE OF 925MB TEMPS
BETWEEN THE TWO PROGGED OVER THE AREA BY 00Z. IF GFS IS MORE
CORRECT...TEMPS START TO WARM NICELY BY FRI...IF ECMWF IS MORE
CORRECT WE STAY IN THE WINTER PREVIEW THRU THE END OF THE WEEK. BOTH
GFS/ECMWF SPREAD LOW LEVEL WARM ADVECTION ACROSS THE AREA BY SAT BUT
HAVE DIFFERENT WAYS OF GETTING THERE. IT DOES LOOK LIKE TEMPS WILL
START TO MODERATE ON SAT BUT REMAIN BELOW NORMAL. LOW LEVEL FLOW FRI
NIGHT/SAT IS OFF THE CENTRAL/NORTHERN PLAINS SO WOULD EXPECT SAT TO
REMAIN DRY AT THIS TIME. STAYED WITH THE MODEL/ENSEMBLE CONSENSUS
HIGHS/LOWS FOR WED THRU SAT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1104 PM CST SAT NOV 15 2014

SNOW CONTINUES TO FALL ACROSS THE TAF SITES...WITH VISIBILITIES
OSCILLATING BETWEEN MVFR AND IFR AS HEAVIER BANDS MOVE THROUGH.
CEILINGS ARE ALSO OSCILLATING BETWEEN VFR AND MVFR. MEANWHILE...
THE BACK EDGE OF THE SNOW WAS PROGRESSING QUICKLY EASTWARD ACROSS
MN AND IA. MUCH OF THE VISIBILITY REDUCTION DUE TO THE SNOW SHOULD
BE THROUGH BY 08-09Z WITH MAYBE A FEW ADDITIONAL TENTHS OF
ACCUMULATION. CEILINGS REMAIN TRICKY...BUT ANTICIPATING THEM TO
SETTLE AROUND MVFR AS LOWER STRATUS UNDER/WEST OF THE BACK EDGE OF
THE SNOW MOVES IN. SKIES HAVE CLEARED OUT ALONG I-29 AND THIS
CLEARING IS ALSO PUSHING EASTWARD AT A GOOD CLIP. SPED UP THE
SCATTERING OUT TIME IN THE TAFS TO 16-17Z. VFR CONDITIONS THEN
LOOK TO CONTINUE UNTIL LATE EVENING WHEN AN ARCTIC COLD FRONT
APPROACHES THE TAF SITES. IT APPEARS A BAND OF SNOW SHOWERS SHOULD
FORM ALONG THE FRONT...BRINGING AT LEAST CEILINGS DOWN TO MVFR.
VISIBILITIES COULD FALL TO MVFR OR EVEN IFR FOR A BRIEF TIME TOO.

EXPECT SOUTHERLY WINDS LESS THAN 10 KT TO VEER SOUTHWESTERLY THIS
AFTERNOON AND PICK UP SLIGHTLY AS THE ARCTIC FRONT APPROACHES.
STRONGER NORTHWEST WINDS ARE ON TRACK FOR MONDAY.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION.....AJ



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