Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 092028
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
328 PM CDT WED APR 9 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 328 PM CDT WED APR 9 2014

SHORT TERM FORECAST FOCUSED ON PRECIPITATION CHANCES ASSOCIATED
WITH FRONTAL PASSAGE OVERNIGHT.

LATEST WATER VAPOR IMAGERY OVERLAID WITH 500MB RAP HEIGHTS SHOWS
DEEP TROUGH MARCHING OFF THE SOUTHEAST US COAST WITH UPSTREAM
RIDGING EXTENDING WEST OF THE MISSISSIPPI RIVER TO THE WEST
COAST. IN THE PAST 24 HOURS THIS RIDGE HAS BROKEN
DOWN...INDICATING A CHANGE IN OUR WEATHER PATTERN IN THE DAYS TO
COME. TWO SHORTWAVE TROUGHS OF INTEREST ARE SKIRTING ACROSS THE
US/CANADIAN BORDER FROM NORTH DAKOTA WESTWARD TO NORTHWEST
MONTANA. AT THE SURFACE...A COLD FRONT IS PUSHING ACROSS THE
NORTHWEST HALF OF NORTH DAKOTA. ITS A WARM...BREEZY AFTERNOON AS
READINGS HAVE PUSHED INTO THE 60S...BRUSHING 70 DEGREES ACROSS
SOUTHERN MN / NORTHERN IA.

MILD SOUTHWESTERLY FLOW ON TAP THIS EVENING AHEAD OF THE
AFOREMENTIONED COLD FRONT. WITH INCREASED CLOUD COVER AND THE MILD
AIRMASS...LOWS TONIGHT LOOK TO RANGE FROM MIDDLE 40S TO NEAR 50.

EXCELLENT MODEL AGREEMENT IN THE COLD FRONTAL PASSAGE...BETWEEN
06Z AND 12Z ACROSS THE AREA. COMBINATION OF UPPER LEVEL PV
ADVECTION AND MID LEVEL FRONTOGENESIS WILL SUPPORT THE CHANCE OF
SHOWERS. THE GREATEST FORCING EXISTS FROM CENTRAL MINNESOTA INTO
CENTRAL AND NORTH CENTRAL WISCONSIN. A LOOK AT THE HI-RES MODELS
SUGGESTS LIGHT ACTIVITY ALONG THE MN/IA BORDER AS WELL. THE MAIN
LIMITING FACTOR IS THE DRIER AIRMASS IN PLACE...AND FEEL THAT A
LOT OF THE FORCING/LIFT WILL GO INTO SATURATION
INITIALLY...LIMITING QPF. AT THE SAME TIME...ITS PASSAGE DURING
THE NIGHT WILL LIMIT ANY TSTORM POTENTIAL LOCALLY...WITH
INSTABILITY WANING AND MAINLY LIMITED NORTHWEST OF THE AREA FOR
THIS EVENING. WILL MAINTAIN HIGHER POPS ALONG AND NORTHEAST OF
I-94.

BY THURSDAY MORNING...THE NORTHWEST HALF OF THE FORECAST AREA
LOOKS TO BE DRY WITH ANY REMAINING SHOWERS CONFINED TO SOUTHWEST
INTO CENTRAL WISCONSIN. COOL CANADIAN HIGH PRESSURE QUICKLY BUILDS
IN...THOUGH ITS AIRMASS WILL BE MODIFIED A BIT. NOT EXPECTING TOO
MUCH OF A TEMPERATURE DROP TOMORROW...AND SHOULD BE A PLEASANT
AFTERNOON FOR MOST. HIGHS MIDDLE 50S TO LOWER 60S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 328 PM CDT WED APR 9 2014

MANY FEATURES TO FOCUS ON IN THE LONG TERM...BUT THE BIG PICTURE
IS THAT PRECIPITATION CHANCES WILL BE ON THE INCREASE STARTING
SATURDAY FOLLOWED BY A RETURN TO MUCH BELOW NORMAL TEMPERATURES
INTO EARLY NEXT WEEK. LOOKS LIKE AN ACTIVE WEATHER
PATTERN...ESPECIALLY FOR THE SOUTHERN HALF OF THE FORECAST AREA.

ANOTHER SHORTWAVE TROUGH MOVES THROUGH DURING THE DAY
FRIDAY...YET MODEL DIFFERENCES ARE MORE PRONOUNCED WITH THIS
FEATURE. MAINLY STRENGTH AND TIMING DIFFERENCES...WITH THE
GFS/NAM/GEM CAMP A FASTER AND DRIER SOLUTION. THIS WOULD RESULT IN
PRECIPITATION CHANCES CONFINED ALONG AND NORTH OF I-90 WHILE THE
09.12Z ECMWF HAS BETTER SATURATION WHICH PAINTS LIGHT QPF ACROSS
MUCH OF THE AREA. LOOKS TO BE ENOUGH WEAK INSTABILITY TO WARRANT
AN ISOLATED THUNDER MENTION. PUSHED HIGHER CHANCES IN THE
NORTHWEST HALF...MAINLY IN THE 12-18Z TIME FRAME.

NEXT SHORTWAVE TROUGH SLATED TO ARRIVE SATURDAY MORNING AS AN
AREA OF LOW PRESSURE DEVELOPS ACROSS THE NORTHERN PLAINS. THIS
FEATURE IS MUCH STRONGER WITH ITS UPPER LEVEL SUPPORT AND LOW
LEVEL MOISTURE RETURN FROM THE GULF OF MEXICO. 09.12Z GUIDANCE IN
REASONABLE AGREEMENT WITH HIGHER CHANCES SATURDAY MORNING WEST OF
THE AREA...BUT MOVE IN DURING THE DAY. THE GFS IS A FAST OUTLIER
WHILE THE GEM/ECMWF AND THE NAM TO SOME DEGREE HOLD THE COLD FRONT
BACK THROUGH 00Z SUNDAY WITH CONVECTION REDEVELOPING ON THE
BOUNDARY. AS THIS NORTHERN / INITIAL WAVE MOVES OFF SATURDAY
NIGHT...A SECONDARY SOUTHERN LOW PRESSURE DEVELOPS ACROSS
OKLAHOMA AND KANSAS SUNDAY INTO SUNDAY NIGHT...THEN LIFTING
THROUGH MID MISSISSIPPI RIVER VALLEY. PREVIOUS RUNS HAD
DIFFERENCES IN WHERE THE WAVE EJECTS...PUTTING THE LOCAL AREA ON
THE COLDER...NORTHWEST FRINGE. THIS TREND SEEMS TO HAVE CONTINUED
IN THE 09.12Z GUIDANCE. THE HIGHER CHANCES FOR THE LATTER HALF OF
THE WEEKEND INTO MONDAY MORNING WILL BE CONFINED SOUTHEAST OF A
CHARLES CITY IOWA TO LA CROSSE TO NEILLSVILLE WISCONSIN LINE.
SOME REPEATED ROUNDS OF SHOWERS AND THUNDERSTORMS COULD PRODUCE
HEALTHY QPF AMOUNTS /0.75 TO 1.5 IN/ ACROSS NORTHEAST IOWA INTO
SOUTHWEST WISCONSIN...RESULTING IN SOME MINOR RISES ON AREA
RIVERS...CREEKS...AND TRIBUTARIES.

TEMPERATURE WISE...DESPITE THE CLOUD COVER AND THREAT OF
PRECIPITATION FRIDAY AND SATURDAY READINGS ARE EXPECTED TO CLIMB
INTO THE 60S. FRIDAY WILL LIKELY BE A TAD WARMER...MIDDLE TO
UPPER 60S AND THEN A FEW DEGREES LESS ON SATURDAY.

THE CORE OF THE COLD AIR ARRIVES MONDAY MORNING AS 850 MB
TEMPERATURES CRASH TO THE -5 TO -7C RANGE...FALLING TO AROUND -10C
TUESDAY THROUGH WEDNESDAY. THIS SUPPORTS HIGHS IN THE MIDDLE 40S
AND LOWS IN THE 20S TO LOWER 30S. NORMAL HIGHS/LOWS ARE MID TO
UPPER 50S/MID 30S...SO GET EXCITED FOR ANOTHER STRETCH OF
UNSEASONABLY COOL DAYS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1227 PM CDT WED APR 9 2014

A TIGHT PRESSURE GRADIENT AHEAD OF A COLD FRONT CROSSING THE
DAKOTAS HAS LED TO INCREASING SOUTHERLY WINDS AT THE TAF
SITES...ESPECIALLY AT RST. BOTH SITES BY 20Z...THE TIME OF PEAK
HEATING...SHOULD SEE SUSTAINED WINDS OF 15-20 KT WITH GUSTS OF
25-30 KT. AS NOCTURNAL COOLING SETS IN THIS EVENING...PLAN ON
WINDS TO DIMINISH SOME...PARTICULARLY AT LSE BEING IN THE VALLEY.
WITH A 45-50 KT JET CORE DEVELOPING THIS EVENING BETWEEN 1500-2000
FT ABOVE THE GROUND AT BOTH TAF SITES...ADDED LOW LEVEL WIND SHEAR
TO THE LSE TAF. THE COLD FRONT IS SLATED TO PASS THROUGH THE TAF
SITES BETWEEN 06-07Z...ENDING THE LOW LEVEL WIND SHEAR AND
SHIFTING WINDS TO THE NORTHWEST WITHIN A FEW HOURS AFTER PASSAGE.
LOOK FOR THESE NORTHWEST WINDS TO PICK UP LATE THURSDAY
MORNING...ESPECIALLY AT RST WHERE MORE SUN OCCURS. GUSTS OF 20-25
KT SEEM LIKELY FOR THURSDAY AFTERNOON AT BOTH SITES.

DRY AIR IN THE LOWER LAYERS OF THE TROPOSPHERE AHEAD OF AND BEHIND
THE COLD FRONT WILL HELP MAINTAIN VFR CONDITIONS THROUGH THE TAF
PERIOD AND BEYOND. A COUPLE HOURS OF LIGHT RAIN WITH A 4000 FT
CEILING LOOKS LIKELY AT BOTH TAF SITES...BETWEEN 09-13Z...
ASSOCIATED WITH THE COLD FRONT. NO VISIBILITY RESTRICTION IS
EXPECTED.

&&

.FIRE WEATHER...THIS EVENING
ISSUED AT 328 PM CDT WED APR 9 2014

TEMPERATURES HAVE NOT WARMED UP TO THIS POINT AS MUCH AS
EXPECTED...RESULTING IN HIGHER DEWPOINT AND RELATIVE HUMIDITY
VALUES WEST OF THE MISSISSIPPI RIVER. MEANWHILE...DEWPOINTS HAVE
STAYED LOWER IN CENTRAL WISCONSIN...CAUSING LOWER RELATIVE
HUMIDITY VALUES THERE. THESE CURRENT CONDITIONS WOULD SUGGEST THE
RED FLAG WARNING COULD BE DROPPED WEST OF THE MISSISSIPPI RIVER
AND ISSUED OVER CENTRAL WISCONSIN. HOWEVER...FUELS SUPPORT THE
CURRENT RED FLAG WARNING WEST OF THE MISSISSIPPI RIVER. IN
ADDITION...TEMPERATURES SHOULD CLIMB A FEW MORE DEGREES OVER THE
NEXT FEW HOURS...RESULTING IN LOWERING RELATIVE HUMIDITIES.
THEREFORE...HAVE ALLOWED THE CURRENT RED FLAG WARNING TO CONTINUE.

RAINFALL WITH THE COLD FRONTAL PASSAGE TONIGHT LOOKS
MINIMAL...MAYBE A 0.10 OF AN INCH AT BEST. THIS LACK OF RAIN
COMBINED WITH INCREASING NORTHWEST WINDS AND CANADIAN DRY AIR ON
THURSDAY BRINGS UP CONCERN OF FIRE CONDITIONS AGAIN. ONE POSITIVE
IS THAT HIGHS MAY STRUGGLE TO CLIMB MUCH ABOVE 60. THIS SHOULD
HELP KEEP RELATIVE HUMIDITY VALUES FOR THE MOST PART ABOVE 25
PERCENT. THE LONE EXCEPTION TO THIS IS OVER CENTRAL WISCONSIN.
HOWEVER...FUEL FORECASTS FOR CENTRAL WISCONSIN SUGGEST ONLY
ELEVATED CONDITIONS AT THIS TIME...THUS DID NOT CONSIDER ANY FIRE
WEATHER WATCH/RED FLAG WARNING AT THIS TIME.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...RED FLAG WARNING UNTIL 7 PM CDT THIS EVENING FOR MNZ079-086>088-
     094>096.

IA...RED FLAG WARNING UNTIL 7 PM CDT THIS EVENING FOR IAZ008>011-018-
     019-029-030.

&&

$$

SHORT TERM.....ZT
LONG TERM......ZT
AVIATION.......AJ
FIRE WEATHER...AJ



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