Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 102346
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
646 PM CDT THU APR 10 2014

.UPDATE...
ISSUED AT 646 PM CDT THU APR 10 2014

HAVE LOWERED DEWPOINTS FRIDAY...ESPECIALLY IN THE AFTERNOON
HOURS...WITH LAV GUIDANCE SUGGESTING POTENTIAL FOR UPPER TEENS /
LOW 20S OVER CENTRAL WISCONSIN. THE RESULT CAUSES RELATIVE
HUMIDITY VALUES TO FALL TO 20 TO 25 PERCENT. THEREFORE...ANOTHER
DAY OF NEAR-CRITICAL FIRE WEATHER CONDITIONS EXISTS TOMORROW. SEE
THE FIRE WEATHER SECTION BELOW FOR MORE DETAILS.

&&

.SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)
ISSUED AT 300 PM CDT THU APR 10 2014

MAIN FORECAST CONCERNS THIS PACKAGE...SMALL -SHRA/TSRA CHANCES FRI
AND AGAIN LATE FRI NIGHT...TEMPERATURES.

18Z DATA ANALYSIS HAD A COLD FRONT FRONT FROM LOWER MI THRU NORTHERN
IL TO OK...WITH A WEAK RIDGE OF HIGH PRESSURE LOCATED OVER SD/NEB TO
IA. COOLER/DRIER AIR WAS SPREADING INTO MN/IA/WI IN THE WAKE OF THE
FRONT WITH VIS IMAGERY SHOWING DECREASING CLOUDS/CLEARING SKIES OVER
MUCH OF THE UPPER MIDWEST. PER VIS IMAGERY...SURPRISING HOW MUCH ICE
COVER REMAINS ON LK SUPERIOR FOR APRIL 10TH. TEMPS IN THE 40S/50S
BEHIND THE FRONT WITH NORTHWEST WINDS 10-20 MPH AND GUSTY.

10.12Z MODELS LOOK TO HAVE INITIALIZED WELL...BUT FOR GFS TOO HIGH
ON SFC DEW POINTS. EVEN WITH SOME MINOR STARTING DIFFERENCES...
SOLUTIONS QUITE SIMILAR FOR TONIGHT THRU FRI NIGHT AS A WEAKER
SHORTWAVE MOVES ACROSS THE REGION FRI THEN A STRONG TROUGH BEGINS TO
APPROACH FRI NIGHT. CHECK OF OBS VS. MODEL DATA AT 18Z SHOWED MODELS
WERE ALL QUITE GOOD WITH THE COLD FRONT PUSHING SOUTH AND THE RIDGE
OF HIGH PRESSURE OVER SD/NEB INTO IA. PER WV IMAGERY...MODELS ALL
APPEARED REASONABLE ON THE SHORTWAVE DETAILS ACROSS NOAM/EASTERN
PAC. NO ONE MODEL FAVORITE AND WITH THE TIGHTENING CONSENSUS...
FAVORED A MODEL/ENSEMBLE COMPROMISE THIS CYCLE. SHORT-TERM FCST
CONFIDENCE IS GOOD.

FOR THE SHORT TERM...QUIET/DRY WEATHER PREVAILS THIS EVENING AS A
WEAK RIDGE OF HIGH PRESSURE SLIDES QUICKLY ACROSS THE REGION. 850-
500MB MOISTURE INCREASE AHEAD OF THE FRI SHORTWAVE ALREADY ARRIVES
LATE TONIGHT...WITH SOME MDT 925-700MB WARM ADVECTION/ISENTROPIC
LIFT. STRONGEST OF THE LOWER LEVEL FORCING/MID LEVEL LIFT WITH THE
SHORTWAVE/MOISTURE INCREASE SPREAD ACROSS THE NORTH HALF OF THE FCST
AREA LATE TONIGHT/FRI. PW VALUES WITH THIS SYSTEM SIMILAR TO THOSE
AHEAD OF THE FRONT THIS MORNING...IN THE 0.50 INCH RANGE AND MAINLY
ABOVE 850MB. BULK OF PRECIP LATE TONIGHT/FRI MAY END UP SPRINKLES
AND LEFT PRECIP CHANCES IN THE 20-40 PERCENT RANGE ACROSS THE NORTH.
MODEL CONSENSUS CONTINUES TO INDICATE SOME WEAK CAPE ACROSS THE
NORTH END OF THE FCST AROUND MID-DAY FRI AND WILL CONTINUE AN
ISOLATED -TSRA MENTION ACROSS THE NORTH END. STRONGER OF THE LOWER
LEVEL FORCING/PV ADVECTION WITH THE SHORTWAVE MOVE EAST OF THE FCST
AREA BY LATE AFTERNOON AND PREVIOUS GRID SET ALREADY HAD PRECIP
CHANCES TRENDED DOWN AND OUT BY LATE AFTERNOON.

QUIET FRI EVENING WITH THE FCST AREA BETWEEN SHORTWAVES AND THEIR
IMPACTS. STRONGER ENERGY DROPPING INTO THE NORTHERN PLAINS FRI NIGHT
DEVELOPS A ROUGHLY 1000MB LOW OVER EASTERN SD BY 12Z SAT. INCREASING
LOWER LEVEL WARM ADVECTION/ISENTROPIC LIFT SPREADS INTO THE AREA
LATER FRI NIGHT...ALONG WITH INCREASING MOISTURE. THIS SYSTEM WILL
HAVE SOME GULF OF MEX MOISTURE TO TAP INTO...WITH PW VALUES INTO THE
WESTERN SIDE OF THE FCST AREA IN THE 0.75 TO 1 INCH RANGE BY 12Z
SAT. THIS WITH SOME STEEP 700-500MB LAPSE RATES AND 50-200 J/KG OF
MUCAPE WHEN LIFTING 800-700MB PARCELS BY 12Z SAT. LEFT FRI EVENING
DRY THEN CONTINUED TO INCREASE PRECIP CHANCES AFTER MIDNIGHT TOWARD
SAT MORNING. ADDED A TSRA MENTION LATE FRI NIGHT WEST OF THE MS
RIVER GIVEN THE WEAK CAPE IN THE ELEVATED AIRMASS.

A COOLER NIGHT TONIGHT WITH A PERIOD OF MOSTLY CLEAR SKIES/LIGHT
WINDS THIS EVENING AND THE DRIER BOUNDARY LAYER AIRMASS. WARMER
AGAIN FRI WITH WEST-SOUTHWEST FLOW AND 925MB TEMPS IN THE +8C TO
+12C RANGE...THOUGH HIGHS MAY BE TEMPERED BY CLOUD COVER. DEPENDING
ON HOW DEEP THE COLUMN MIXES FRI AND CLOUD COVER...RH/S FRI
AFTERNOON MAY DIP INTO THE 25-30 PERCENT RANGE. SEE FIRE WEATHER
DISCUSSION BELOW FOR MORE DETAILS. A WARMER NIGHT AGAIN FRI NIGHT
WITH THE INCREASING LOWER LEVEL WARM ADVECTION AND THICKENING CLOUDS.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 300 PM CDT THU APR 10 2014

MAIN FORECAST CONCERNS FOR SAT THRU SUN NIGHT...-SHRA/TSRA CHANCES
AND RAIN AMOUNTS.

MODEL RUNS OF 10.12Z IN GOOD AND IMPROVING AGREEMENT SAT THRU SUN
NIGHT AS STRONG/COLD TROUGHING DIGS INTO THE CENTRAL/NORTHERN PLAINS
THRU THE PERIOD. CONSENSUS FAVORS SLOWER/STRONGER OF THE EARLIER
RUNS WITH THIS TROUGHING SAT/SUN AND ONE SFC LOW/TROUGH TO MOVE
ACROSS THE REGION SAT THEN THE SECOND LOW TO LIFT NORTHEAST ACROSS
MO/IL SUN INTO LOWER MI SUN NIGHT. TREND IS TOWARD THE ECMWF
SOLUTION WITH A MORE NORTHERLY EXTENT OF THE RAIN SUN/SUN NIGHT.
GIVEN THE TIGHTENING MODEL CONSENSUS...FCST CONFIDENCE IMPROVING IN
THE SAT-SUN NIGHT PERIOD AND IS ABOVE AVERAGE THIS CYCLE.

LEAD PIECE OF ENERGY IN THE DEVELOPING PLAINS TROUGH SENDS A SFC-
700MB LOW/TROUGH ACROSS THE REGION SAT. MDT/STRONG 925-700MB WARM
ADVECTION/ISENTROPIC WITH/AHEAD OF THIS TROUGH LIFTS AN INFLOW
AIRMASS WITH PW VALUES IN THE 1 INCH RANGE INTO/OVER THE SFC-925MB
WARM FRONTAL TROUGH/BOUNDARY LAYING ACROSS THE AREA SAT. HIGHEST
PRECIP CHANCES SAT LOOK TO REMAIN OVER THE NORTH HALF OF THE FCST
AREA...ALONG/NORTH OF THE WARM FRONT. HOWEVER...WITH MUCAPE VALUES
IN THE INFLOW AIRMASS LOOKING TO BE IN THE 500-1000 J/KG SAT...GIVEN
THE DEEPER FORCING/LIFT AND HIGHER CAPE OVER THE SOUTH HALF OF THE
FCST AREA...SHRA/TSRA APPEAR LIKELY THERE AS WELL. SAT SHRA/TSRA
CHANCES IN THE 50-80 PERCENT RANGE QUITE REASONABLE...WITH CONSENSUS
FOR AROUND 1/2 INCH OF AN INCH OF RAIN POSSIBLE. WITH ENOUGH SFC
HEATING SAT...CANNOT RULE OUT A SVR HAIL OR WIND THREAT ACROSS THE
SOUTH END OF THE FCST AREA LATER SAT AFTERNOON/EARLY SAT EVENING.

BRIEF BREAK FROM THE PRECIP SAT NIGHT WITH THE AREA BETWEEN
SHORTWAVES AND SFC LOWS/WAVES. FIRST ROUND OF FORCING/LIFT SLIDES
EAST OF THE AREA THRU SAT EVENING WITH THE NEXT ROUND ARRIVING LATE
SAT NIGHT OR SUN MORNING. BY LATE SAT NIGHT/SUN MORNING SFC-850MB
COLD FRONT/TROUGH IS SOUTH OF THE AREA...WITH NORTHERLY FLOW IN THAT
LAYER AND ANY CAPE SOUTH OF THE AREA. BULK OF FORCING LIFT SUN/SUN
NIGHT IS 290K-310K MOISTURE TRANSPORT/ISENTROPIC LIFT AT AND ABOVE
700MB...OVER-RUNNING THE SOUTHWARD ADVANCING LOWER LEVEL COLD DOME
WITH A 0.75 TO 1 INCH OF PW AIRMASS. THIS AIDED BY DIVERGENCE/PV
ADVECTION ABOVE 500MB AHEAD OF THE MID LEVEL SHORTWAVE/TROUGH. MODEL
CONSENSUS SPREADS MORE OF A STEADY LIGHT-MDT RAIN NORTHEAST ACROSS
THE FCST AREA SUN INTO SUN EVENING. RAISED RAIN CHANCES INTO THE 50-
70 PERCENT RANGE ACROSS MUCH OF THE FCST AREA BY SUN AFTERNOON.
RAISED RAIN SUN NIGHT RAIN CHANCES INTO THE 40-70 PERCENT RANGE
MAINLY FOR THE EVENING...AS THE 290-310K ISENTROPIC UPGLIDE MOVES
EAST OF THE AREA LATER SUN NIGHT. GIVEN PLENTY OF CLOUDS THRU THE
SAT-SUN NIGHT PERIOD...TRENDED HIGHS DOWN A BIT BOTH SAT/SUN.

FOR MONDAY THRU THURSDAY.../DAYS 4 TO 7/...

MAIN CONCERNS ARE BELOW/MUCH BELOW NORMAL TEMPS THRU THE PERIOD.

10.00Z/10.12Z MEDIUM RANGE MODELS IN GOOD AND IMPROVING AGREEMENT
FOR A COLD-CORE MID LEVEL TROUGH TO SETTLE ACROSS THE NORTH-CENTRAL
CONUS FOR MON/TUE. LESS CONSISTENCY BY WED WITH THIS TROUGHING OVER
THE REGION BUT SIGNAL FOR THE FLOW TO BECOME MORE WESTERLY WED AS
TROUGHING MOVES INTO THE WESTERN CONUS. LOOSE CONSENSUS FOR
SOUTHWEST FLOW ALOFT OVER THE REGION THU AS BROAD TROUGHING MOVES
INTO THE CENTRAL CONUS/PLAINS. FCST CONFIDENCE IS GOOD AND IMPROVING
FOR THE COLDER/BELOW NORMAL TEMPS MON-WED...THEN AVERAGE WITH TEMPS
THU AND ANY PRECIP CHANCES FOR MON THRU THU.

IMPROVING SIGNAL FOR THE SFC-700MB TROUGH FROM SUN TO BE PASSING
WELL EAST/SOUTH OF THE AREA MON...WITH A WEAK RIDGE OF DRIER/COLDER
CAN HIGH PRESSURE BUILDING IN UNDER THE MID LEVEL TROUGH. BOTH GFS/
ECMWF SWING A STRONGER SECONDARY SHORTWAVE SOUTHEASTWARD THRU THE
COLD TROUGH AND ACROSS THE AREA MON NIGHT/TUE. SFC REFLECTION OF A
TRAILING INVERTED TROUGH OR SECONDARY FRONTAL BOUNDARY TO PUSH
ACROSS THE AREA MON NIGHT/TUE. AN INCREASE OF PW IN THE 925-600MB
LAYER PROGGED TO ACCOMPANY THE LOWER LEVEL THERMODYNAMIC FORCING AND
MID LEVEL DYNAMICS/DIVERGENCE AS THE WAVE PASSES. SMALL PRECIP
CHANCES MON NIGHT/TUE MORNING REASONABLE...AND COLUMN WOULD BE COLD
ENOUGH FOR THE BULK OF THIS TO BE -SN. MODELS AT ODDS WITH SPEED OF
SHORTWAVES THRU THE FLOW AND ACROSS THE REGION WED/THU AS WELL AS
HOW QUICKLY MOISTURE WOULD RETURN ACROSS THE AREA. SMALL MODEL/
ENSEMBLE CONSENSUS -RA/-SN CHANCES FOR WED/THU REASONABLE FOR NOW
UNTIL BETTER AGREEMENT IS SEEN IN THE DETAILS. 850MB TEMPS IN THE 1
TO 2 STANDARD DEVIATIONS BELOW NORMAL RANGE FOR THE 14.12Z TO 16.12Z
PERIOD...WITH TEMPS THIS PERIOD TRENDING SOME 10F-20F BELOW NORMAL.
MODEL/ENSEMBLE CONSENSUS OF BELOW/MUCH BELOW NORMAL HIGHS/LOWS FOR
MON-THU LOOKS WELL TRENDED AT THIS TIME.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 646 PM CDT THU APR 10 2014

GUSTY NORTHWEST WINDS WILL SETTLE DOWN QUICKLY OVER THE NEXT 1-2
HOURS DUE TO A COMBINATION OF NIGHTTIME COOLING AND HIGH PRESSURE
BUILDING INTO THE TAF SITES. GENERALLY LIGHT WINDS LOOK TO PERSIST
THROUGH FRIDAY MORNING. THE HIGH SHIFTS OFF TO THE EAST IN THE
AFTERNOON...AND WITH DEEP DAYTIME MIXING FORECAST...EXPECT
SOUTHWEST TO WEST WINDS TO INCREASE. GUSTS OF 20-25 KT APPEAR
LIKELY AGAIN.

PLENTIFUL DRY AIR ASSOCIATED WITH THE HIGH BUILDING IN WILL KEEP
CONDITIONS VFR THROUGH FRIDAY.

&&

.FIRE WEATHER...
ISSUED AT 646 PM CDT THU APR 10 2014

WINDS LOOK TO RAPIDLY DIMINISH DURING THE NEXT 1-2 HOURS...ALLOWING
TEMPERATURES TO COOL AND RELATIVE HUMIDITY VALUES TO CLIMB. THIS
WILL HELP END THE FIRE WEATHER CONCERNS FOR TODAY.

THE POTENTIAL EXISTS FOR MORE FIRE WEATHER CONCERNS TOMORROW. SOME
OF THE LATEST LAV GUIDANCE SUGGESTS DEWPOINTS COULD FALL INTO THE
UPPER TEENS / LOWER 20S OVER CENTRAL WISCONSIN DURING THE
AFTERNOON...THE SAME AREA WHERE DEWPOINTS MIXED OUT MORE THAN
FORECAST TODAY. THIS SEEMS VERY PLAUSIBLE SO LOWERED DEWPOINTS
TOWARDS BUT NOT ALL THE WAY TO LAV GUIDANCE. THE TEMPERATURE
FORECAST STILL LOOKS REASONABLE...RESULTING IN RELATIVE HUMIDITY
VALUES FALLING TO 20-25 PERCENT. AT THE SAME TIME...WINDS ARE
PROGGED TO COME UP AS MIXING INTENSIFIES. AFTER COMMUNICATION WITH
FIRE WEATHER USERS...LOOKING AT THE FUELS AND NEW FORECAST
INFORMATION...THIS IS STILL A NEAR-CRITICAL SITUATION. SIMILAR TO
TODAY...WINDS WILL RAPIDLY DIMINISH DURING THE EVENING...ENDING
THE FIRE WEATHER CONCERNS.

&&

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

$$

UPDATE...AJ
SHORT TERM.....RRS
LONG TERM......RRS
AVIATION...AJ
FIRE WEATHER...AJ



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