Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 142304
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
600 PM CDT TUE APR 14 2015

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY NIGHT)
ISSUED AT 307 PM CDT TUE APR 14 2015

MAIN FCST CONCERNS THIS PERIOD...ELEVATED FIRE WEATHER CONCERNS
WED...SMALL -SHRA CHANCE WED NIGHT...TEMPERATURES.

18Z DATA ANALYSIS HAD HIGH PRESSURE CENTERED OVER SOUTHERN WI WITH
RIDGING TO THE EAST...NORTH AND SOUTHWEST. A 999MB LEE LOW WAS
LOCATED OVER CENTRAL MT. THE HIGH WAS BRINGING LIGHT WINDS AND VERY
DRY BOUNDARY LAYER AIR TO MUCH OF WI/MN/IA. EARLY AFTERNOON TEMPS
ACROSS MUCH OF MN/IA/WI A RATHER UNIFORM UPPER 50S TO MID 60S. SFC
DEW POINTS IN THE TEENS COMBINED WITH THESE TEMPS PRODUCING VERY LOW
RH/S OF 12 TO 22 PERCENT ACROSS MUCH OF WI/MN/EASTERN IA EARLY THIS
AFTERNOON. SOME HIGH LEVEL MOISTURE/CLOUDS WELL NORTH OF SHORTWAVE
ENERGY IN THE SOUTHERN PLAINS WAS SPREADING NORTHWARD ACROSS IA AND
SOUTHERN WI/MN.

14.12Z MODELS INITIALIZED WELL. SOLUTIONS QUITE SIMILAR FOR TONIGHT
THRU WED NIGHT AS THE WEST COAST TROUGH DIGS INTO THE CENTRAL/
SOUTHERN ROCKIES AND SOME OF THE SOUTHERN PLAINS ENERGY LIFTS INTO
THE MID/UPPER MS VALLEY BE LATER WED/WED NIGHT. TREND TENDS TO FAVOR
A COMPROMISE OF THE EARLIER RUNS ON THE ROCKIES TROUGHING/DEVELOPING
LOW...WHILE FAVORING STRONGER OF EARLIER RUNS ON THE ENERGY LIFTING
TOWARD/INTO THE MID/UPPER MS VALLEY WED/WED NIGHT. OVERALL SHORT-
TERM FCST CONFIDENCE IS GOOD THIS CYCLE.

IN THE SHORT TERM...QUIET TONIGHT AS HIGH PRESSURE AND A DRY LOW
LEVEL AIRMASS REMAINING OVER THE REGION. NOT AS COOL TONIGHT WITH THE
CENTER OF THE HIGH OVER THE GREAT LAKES AND SOME SOUTHEAST GRADIENT
WINDS OF 5-10KTS FOR BOUNDARY LAYER MIXING. SOME HIGH LEVEL
MOISTURE/CIRRUS AHEAD OF THE SOUTHERN PLAINS ENERGY TO SPREAD NORTH
ACROSS THE AREA AS WELL LATER TONIGHT...ALSO HELPING KEEP LOWS A BIT
WARMER FOR MANY LOCATIONS. HGTS FALL OVER THE AREA WED AS SHORTWAVE
ENERGY CONTINUES TO LIFT NORTHEAST THRU THE MID MS VALLEY TOWARD THE
AREA. MID/HIGH LEVEL MOISTURE CONTINUES TO INCREASE AHEAD OF THIS
SOUTHWEST FLOW SHORTWAVE TROUGH WHILE THE HIGH PRESSURE TRIES TO
HOLD STRONG OVER MN/WI/IA. SFC PRESSURE GRADIENT TIGHTENS OVER THE
AREA ON WED AS LOW PRESSURE/TROUGHING SLOWLY ADVANCES ACROSS THE
CENTRAL/NORTHERN PLAINS. MODEL SOUNDINGS SHOWING MIXING TO 850MB ON
WED WITH AROUND 20KTS OF WIND IN THE 925-850MB PORTION OF THE MIXED
COLUMN. AIRMASS REMAINS QUITE DRY BELOW 500MB AS THE SFC-700MB RIDGE
AXIS HANGS ON. FIRE WEATHER CONCERNS ON WED WITH CONTINUED LOW
HUMIDITIES AND MORE WIND. SEE FIRE WEATHER SECTION BELOW FOR MORE
DETAILS. LEFT WED DRY WITH THE DRY SFC-500MB AIRMASS HOLDING OVER
THE AREA. MODEL SOUNDINGS/X-SECTIONS SHOW MOISTENING IN THE 850-
500MB LAYER WED NIGHT...ESPECIALLY AFTER MIDNIGHT. HOWEVER...EVEN
WITH APPROACH OF THE MID LEVEL SHORTWAVE...FORCING/LIFT REMAIN ON
THE WEAK SIDE. WILL LEAVE A 15-20 PERCENT -SHRA CHANCE FOR MUCH OF
THE FCST AREA...MAINLY AFTER MIDNIGHT WED NIGHT...FOR NOW. WITH MORE
CLOUDS/WINDS...USED A BLEND OF THE GUIDANCE LOWS/HIGHS FOR TONIGHT
THRU WED NIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 307 PM CDT TUE APR 14 2015

MAIN FCST CONCERNS FOR THU THRU FRI NIGHT...-SHRA CHANCE CENTERED ON
FRI...TEMPERATURES THRU THE PERIOD.

14.12Z MODEL SOLUTIONS SHOW GOOD CONSISTENCY WITH THE WED NIGHT
SHORTWAVE ENERGY TO EXIT QUICKLY EAST THU MORNING. HOWEVER MODELS
BEGIN TO DIVERGE ON THE ROCKIES TROUGH THU...WITH GFS FASTER TO
OPEN/MOVE THE TROUGH EASTWARD. THIS TREND CONTINUES FRI...WITH GFS
OFFERING A SOLUTION OF MORE NORTH-SOUTH STREAM PHASING OVER THE
UPPER MIDWEST FOR LATE FRI/FRI NIGHT. THIS WHILE NAM/GEM/ECMWF HOLD
A MID LEVEL LOW OVER THE SOUTHERN ROCKIES THRU FRI INTO FRI NIGHT
AND MAINTAIN A NORTH-SOUTH STREAM SPLIT. ECMWF EVEN HOLDS SHORTWAVE
RIDGING ALOFT OVER THE UPPER MIDWEST FRI/FRI NIGHT. FCST CONFIDENCE
IS AVERAGE THU/THU NIGHT THEN AVERAGE TO BELOW FOR FRI/FRI NIGHT.

SHORTWAVE TROUGH EXITS THU MORNING WITH DRYING IN THE 850-500MB
PORTION OF THE COLUMN. WITH MINIMAL FORCING/LIFT AND THIS
DRYING...WILL LEAVE THU DRY AS WEAK SHORTWAVE RIDGING MOVES ACROSS
THE REGION. DIVERGING MODELS WITH PROGRESSIVENESS OF ENERGY LIFTING
OUT OF THE ROCKIES TROUGH HAS LARGE IMPACTS ON THE SENSIBLE WEATHER
FOR THE AREA LATER THU NIGHT INTO FRI NIGHT. FASTER...MORE
PROGRESSIVE GFS WITH SOME ROCKIES TROUGH ENERGY PHASES THIS WITH
SOME NORTHERN STREAM ENERGY OVER THE UPPER MIDWEST FRI/FRI NIGHT.
GFS AND TO SOME EXTENT THE NAM WITH STRONGER 850-500MB FN/QG
CONVERGENCE TO SPREAD INTO/ACROSS THE FCST AREA LATER THU NIGHT INTO
FRI EVENING WITH APPROACH/PASSAGE OF THE SFC-MID LEVEL TROUGH AXIS.
GFS WITH ITS STRONGER TROUGH PULLS UPWARDS OF 1 INCH OF PW INTO THE
FCST AREA BY 18Z FRI AND PRODUCES 1/2 TO 1 INCH OF RAIN ACROSS MUCH
OF THE FCST AREA. ALL THIS WHILE GEM/ECMWF HOLD SOME DRIER HIGH
PRESSURE OVER THE UPPER MIDWEST. WITH GFS GETTING LITTLE IF ANY
SUPPORT FROM THE OTHER MODELS...WILL NOT WEIGH HEAVY ON ITS
SOLUTION. GIVEN THE AMOUNT OF AVAILABLE MOISTURE IS ONE OF THE
BIGGER QUESTIONS WITH THIS POTENTIAL LATE-WEEK SYSTEM...WILL ONLY
CARRY 20 PERCENT -SHRA CHANCES FROM LATE THU NIGHT INTO FRI EVENING
FOR NOW. OVERALL FAVORING A MODEL/ENSEMBLE CONSENSUS FOR THU THRU
FRI NIGHT...USED A BLEND OF THE NUMERICAL GUIDANCE HIGHS/LOWS THIS
PERIOD.

FOR SAT THRU TUE...DAYS 4 TO 7...

MAIN FCST CONCERNS THIS PERIOD...-SHRA CHANCES SUN THRU TUE...
COOLING FOR EARLY NEXT WEEK.

14.00Z/14.12Z IN REASONABLE AGREEMENT FOR WEAK SHORTWAVE RIDGING TO
MOVE ACROSS THE UPPER MIDWEST OR BE BEHIND TROUGHING ON SAT...AHEAD
OF NORTHERN STREAM ENERGY DROPPING INTO MT. REASONABLE AGREEMENT
CONTINUES SUN/MON AS THE MT ENERGY AND SOME REMNANT ENERGY FROM THE
ROCKIES TROUGHING PHASE AND CARVE OUT A RATHER SHARP/DEEP MID LEVEL
TROUGH CENTERED OVER THE MID/UPPER MS VALLEY BY 00Z TUE. GFS REMAINS
THE MORE PROGRESSIVE MODEL WITH FEATURES IN THE SAT-TUE TIME-FRAME.
NAEFS MEAN SHOWS 00MB HGTS OF 1 TO 2 STANDARD DEVIATIONS BELOW
NORMAL ACROSS THE UPPER MIDWEST AT 00Z TUE. SIGNAL FOR MORE NORTHERN
STREAM ENERGY TO DROP IN AND HOLD THE COLD TROUGH OVER THE UPPER
MIDWEST/GREAT LAKES THRU AT LEAST TUE. PLENTY OF SHORTWAVE DETAIL
DIFFERENCES IN THE FLOW/TROUGH /IMPACTING -SHRA CHANCES/ BY SUN THRU
TUE...BUT THIS MORE OR LESS EXPECTED IN THE DAY 5-7 TIME-FRAME. FCST
CONFIDENCE IN THIS PERIOD IS GOOD FOR COOLER TEMPERATURES BY NEXT
WEEK...BUT AVERAGE TO BELOW AVERAGE FOR SUN THRU TUE SHRA CHANCES.

HIGH PRESSURE BEHIND THE FRIDAY TROUGH TO SLIDE ACROSS THE REGION ON
SAT UNDER THE MID LEVEL SHORTWAVE RIDGING. SOME VARIABILITY AMONG
MODELS ON 925MB TEMPS OVER THE AREA SAT BUT APPEARS SAT HIGHS WILL
STILL BE A CATEGORY OR 2 ABOVE NORMAL IN UPPER 50S TO MID 60S.
PHASING ENERGY AND DEEPENING TROUGH OVER THE REGION SUN/MON LOOKING
TO INCREASE THE MOISTURE/FORCING/LIFT OVER THE AREA THESE DAYS.
GIVEN THE SHORTWAVE DETAIL DIFFERENCES...20-40 PERCENT -SHRA CHANCES
FROM LATER SAT NIGHT INTO MON REASONABLE FOR NOW. ANY CAPE APPEARS
QUITE LIMITED AND WILL LEAVE TSRA MENTION OUT OF SAT NIGHT THRU MON
PERIOD AT THIS TIME. STRONGER SHOT OF 925-850MB COOLING DROPS IN FOR
SUN NIGHT/ MON UNDER THE MID LEVEL TROUGH AXIS. THIS AND MORE CLOUDS
AROUND... MONDAY HIGHS TRENDING CLOSER TO THE NORMALS. SECONDARY
SHOT OF LOWER LEVEL COOLING DROPS IN TUE WITH THE NORTHERN STREAM
ENERGY DROPPING INTO THE WEST SIDE OF THE TROUGH TUE. THIS ENERGY
WOULD SEND ANOTHER LOWER LEVEL/SFC TROUGH/FRONT ACROSS THE REGION
TUE WITH CONTINUED -SHRA CHANCES. WITH LOWER CONFIDENCE IN THE DAY 5-
7 SHORTWAVE DETAILS...STAYED WITH THE MODEL/ENSEMBLE PRECIP CHANCES
THESE DAYS. MODEL/ENSEMBLE CONSENSUS HIGHS/LOWS FOR SAT THRU TUE
APPEAR WELL TRENDED AT THIS TIME.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 600 PM CDT TUE APR 14 2015

CIGS/WX/VSBY...
VFR CONDITIONS ABOUND WITH SCT/SKC SKIES INTO WED
EVENING. INCREASING MID LEVEL DECK LATER WED NIGHT. NO IMPACTS TO
VSBY.

WINDS...
DECOUPLING WILL RESULT IN LIGHT SOUTHEAST WINDS TONIGHT...THEN
INCREASING BUT STAYING SOUTHEAST BY MID/LATE WED MORNING. COULD SEE
SOME GUSTINESS TO AROUND 20 KTS.

&&

.FIRE WEATHER...WEDNESDAY
ISSUED AT 307 PM CDT TUE APR 14 2015

MINIMUM AFTERNOON RH/S WED WILL AGAIN BE IN THE 20 TO 30 PERCENT
RANGE...MORE IN THE 20-25 PERCENT RANGE EAST OF THE MS RIVER. THIS
WITH SOUTHEAST WINDS 10-15 MPH GUSTING TO AROUND 20 MPH. GIVEN THE
NOW DRY FUELS AND MAXIMUM RH/S OF ONLY 60-70 PERCENT EXPECTED
TONIGHT...ANOTHER DAY/AFTERNOON OF ELEVATED FIRE WEATHER
CONDITIONS EXPECTED ON WED. APPEARS A VEIL OF CIRRUS WILL SPREAD
ACROSS MUCH OF THE FCST AREA WED...THICKENING THRU THE DAY. SOME
UNKNOWNS ON HOW THICK THIS CIRRUS WILL BE...BUT ANY AMOUNT OF
CIRRUS WILL HAVE AN IMPACT ON THE HIGH TEMPS...DEPTH OF MIXING AND
HOW GUSTY THE WINDS MAY BE. GIVEN THE CIRRUS UNKNOWNS AND PER
COORDINATION WITH OUR FIRE WEATHER USERS...WILL ISSUE A FIRE
WEATHER WATCH FOR MOST OF THE WI PORTION OF THE FCST FROM NOON TO
8PM WED WERE MINIMUM RH/S...EVEN WITH THE CIRRUS...LOOKING TO BE
IN THE 20-25 PERCENT RANGE. WITHOUT THE CIRRUS STRONG POTENTIAL
FOR RED- FLAG CONDITIONS ACROSS MUCH OF WI PORTION OF THE FCST
AREA CENTERED ON WED AFTERNOON.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY
     EVENING FOR WIZ029-032>034-041>044-053>055-061.

MN...NONE.
IA...NONE.
&&

$$

SHORT TERM.....RRS
LONG TERM......RRS
AVIATION.......RIECK
FIRE WEATHER...RRS


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