Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 220921
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
421 AM CDT WED APR 22 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 421 AM CDT WED APR 22 2015

MAIN FCST CONCERNS THIS PERIOD...ANY LINGERING -SHRA/-SHSN CHANCES
TODAY...CLOUD TRENDS/TEMPERATURES.

DATA ANALYSIS AT 06Z HAD A BROAD AREA OF LOW PRESSURE CENTERED OVER
JAMES BAY WITH TROUGHING TO THE SOUTHWEST INTO THE WESTERN GREAT
LAKES. HIGH PRESSURE WAS CENTERED OVER THE DAKOTAS INTO MAN/SASKAT.
TIGHTER PRESSURE GRADIENT BETWEEN THE 2 REMAINED OVER THE REGION
WITH NORTHWEST WINDS OF 10-20 MPH PERSISTING ACROSS MUCH OF THE
REGION. COMBINED WITH TEMPS IN THE UPPER 20S AND 30S...ANOTHER
BLUSTERY/CHILLY LATE NIGHT ACROSS THE REGION. CLOUDS/SCT -SHSN/
FLURRIES PERSISTED ACROSS MUCH OF WI/EASTERN MN/ NORTHEAST IA...EAST
OF YET ANOTHER SHORTWAVE ROTATING AROUND THE UPPER LOW OVER EASTERN
ONT AND EAST OF THE MID/UPPER LEVEL TROUGH AXIS.

INITIALIZATIONS OF 22.00Z MODELS LOOK QUITE GOOD. SOLUTIONS VERY
SIMILAR FOR TODAY/TONIGHT AS THE MID LEVEL LOW OVER EASTERN ONT
MOVES EVER SO SLOWLY EAST. AREA REMAINS UNDER COOL NORTHWEST FLOW
WITH ONE CHANNELED SHORTWAVE TO MOVE BY TODAY AND YET ANOTHER TO
COME ACROSS THE AREA TONIGHT. TREND WITH THESE FEATURES FAVORS A
TIGHTER COMPROMISE/CONSENSUS OF THE EARLY RUNS. SHORT-TERM FCST
CONFIDENCE IS GOOD THIS CYCLE.

FOR THE SHORT TERM...CHANNELED SHORTWAVE ENERGY CONTINUING TO DROP
ACROSS THE REGION ON THE WEST SIDE OF THE LOW/TROUGH TRENDING TO
HOLD THE LOWER LEVEL CLOUDS/MOISTURE /SLOWER CLEARING/ OVER THE FCST
AREA TODAY INTO THIS EVENING. HAVE INCREASED CLOUD COVER OVER THE
CENTRAL/EAST PARTS OF THE FCST AREA FOR MUCH OF TODAY AND MAY YET
NEED TO INCREASE/LINGER CLOUDS EVEN MORE OVER THE SOUTHWEST SIDE OF
THE FCST AREA THIS MORNING. DEEPER MOISTURE/SFC-700MB CYCLONIC FLOW
AND WEAK CONVERGENCE/LIFT LINGERS OVER THE NORTHEAST END OF THE
FCST AREA INTO EARLY AFTERNOON...EAST OF THE MID LEVEL SHORTWAVE
AND TROUGH AXIS. ADDED/LINGERED SOME SPRINKLES/FLURRIES
ALONG/NORTHEAST OF I-94 INTO THE EARLY AFTERNOON HOURS. DEEPER
MIXING PROGGED TO 850- 800MB AGAIN TODAY...WITH 25-30KTS OF WIND
AT 925-850MB. BRISK/GUSTY WINDS AGAIN LATE THIS MORNING/AFTERNOON
BUT BELOW ADVISORY CRITERIA. CLOUDS OVER THE NORTHEAST SIDE OF THE
FCST AREA WILL CONTINUE TO HOLD TEMPS DOWN TODAY. EVEN WITH SOME
SUNSHINE IN THE AFTERNOON HIGHS OVER THE WESTERN SIDE OF THE FCST
AREA ONLY LOOKING TO BE IN THE UPPER 40S TO NEAR 50F. SFC-700MB
TROUGH AXIS SLIDES EAST WITH INCREASED SUBSIDENCE/DRYING IN THE
LOWER LAYERS. CLOUDS SHOULD PUSH EAST/EXIT THE FCST AREA TONIGHT
AS THE SFC RIDGING FROM THE DAKOTAS MOVES INTO MN/IA. WEAKER
GRADIENT TONIGHT BUT APPEARS TO BE SOME NORTHWEST WINDS 4-8KTS
MOST LOCATIONS TONIGHT TO KEEP THE BOUNDARY LAYER STIRRED AND LOWS
FROM BOTTOMING OUT TOO FAR. EVEN SO...MOST LOWS TONIGHT EXPECTED
TO BE IN THE MID-UPPER 20S UNDER CLEAR/ CLEARING SKIES AS THE HIGH
BUILDS IN. WITH THE SPRING SEASON AND GREEN-UP HAVING NOT ADVANCED
ALL THAT FAR YET...NO FROST/FREEZE HEADLINES PLANNED FOR LATE
TONIGHT/THU MORNING BUT DAY CREW MAY NEED TO RE-EVALUATE THIS.
USED A BLEND OF THE GUIDANCE HIGHS/LOWS FOR TODAY/TONIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 421 AM CDT WED APR 22 2015

MAIN FCST CONCERNS FOR THU THRU FRI NIGHT...RAIN CHANCES FRI/FRI
NIGHT...TEMPERATURES THRU THE PERIOD.

22.00Z MODELS OFFERING BETTER AGREEMENT IN THE THU THRU FRI NIGHT
PERIOD. THIS ESPECIALLY AS SHORTWAVE TROUGHING/ENERGY COMES OUT OF
THE ROCKIES THU NIGHT...DEVELOPS MORE ORGANIZED/STRONGER TROUGHING
IN THE CENTRAL PLAINS FRI THEN LIFTS IT TOWARD THE MID/UPPER MS
VALLEY FRI NIGHT. GFS MORE IN LINE WITH EARLIER ECMWF/GEM RUNS WITH
MORE SHORTWAVE RIDGING/SOUTHWEST FLOW AHEAD OF THIS FEATURE AND
BRINGING MORE MOISTURE FURTHER NORTHWARD FRI/FRI NIGHT. FCST
CONFIDENCE IN THE THU THRU FRI NIGHT PERIOD IS AVERAGE TO GOOD THIS
CYCLE.

PERIOD STARTS OUT WITH COOL/DRY CAN HIGH PRESSURE DRIFTING EAST
ACROSS THE UPPER MIDWEST THU/THU NIGHT. THU SHOULD BE A SUNNY DAY
WITH THE SFC RIDGE AXIS OVER THE REGION. DEEPER MIXING AGAIN WITH
925-850MB TEMPS SUPPORTING HIGHS MOSTLY IN THE 50S. SFC RIDGE AXIS
SLIPS EAST THU NIGHT...WITH WINDS BECOMING SOUTHEAST AND INCREASING
ESPECIALLY WEST OF THE MS RIVER. ANOTHER COLDER NIGHT WITH STRONGER
RADIATIONAL COOLING OVER THE NORTHEAST HALF OF THE FCST
AREA...WHILE WEST OF THE MS RIVER THE SOUTHEAST WINDS AFTER
MIDNIGHT TO HELP KEEP LOWS NEAR/ABOVE FREEZING. SOUTH/SOUTHEAST
FLOW CONTINUES TO INCREASE FRI AS LOW PRESSURE STRENGTHENS IN THE
CENTRAL PLAINS...BRINGING INCREASING MOISTURE INTO THE AREA. PW
VALUES OF 3/4 INCH INTO THE SOUTHWEST HALF OF THE FCST AREA BY 00Z
SAT...WITH INCREASING FORCING/LIFT OVER THE AREA IN STRONGER LOW
LEVEL WARM ADVECTION AND FALLING HGTS/PV ADVECTION AHEAD OF THE
MID LEVEL TROUGH. CONSENSUS 20-40 PERCENT RAIN CHANCES OVER THE
WEST HALF OF THE FCST AREA BY FRI AFTERNOON LOOK REASONABLE. ANY
CAPE APPEARS LIMITED AND LEFT ANY MENTION OF TSRA OUT OF THE GRIDS
FOR NOW. MOISTURE CONTINUES TO SPREAD OVER MAINLY THE
CENTRAL/SOUTH PARTS OF THE FCST AREA FRI NIGHT AS THE SFC LOW AND
MAIN MID LEVEL SHORTWAVE TROUGH/ENERGY MOVES INTO MO/IA. STRONGEST
OF THE LIFT/DEEPER OF THE MOISTURE TRENDING TO BE OVER THE SOUTH
HALF OF THE FCST AREA. CONSENSUS RAIN CHANCES IN THE 30-50 PERCENT
RANGE OVER THE SOUTHWEST 2/3 OF THE FCST AREA...LESSER CHANCES
NORTHEAST OF I-94...LOOKING WELL TRENDED. THICKENING CLOUDS AND
SOME SOUTHEAST TO EAST WINDS TO KEEP MOST LOWS FRI NIGHT ABOVE
FREEZING. TRENDED TOWARD WARMER OF GUIDANCE HIGHS WITH PLENTY OF
SUNSHINE EXPECTED ON THU. USED A BLEND OF THE GUIDANCE LOWS/HIGHS
FOR THU NIGHT THRU FRI NIGHT.

FOR SATURDAY THRU TUESDAY...DAYS 4 TO 7...

MAIN FCST CONCERNS THIS PERIOD...LINGERING RAIN CHANCES SOUTH
SAT...RAIN CHANCES MON/TUE...TEMPERATURES.

MEDIUM RANGE MODEL RUNS OF 22.00Z OFFERING BETTER AGREEMENT SAT AS
MID LEVEL TROUGHING MOVES ACROSS THE MID MS VALLEY AND THE NEXT
TROUGH/ENERGY MOVES INTO THE ROCKIES. LATEST RUN CONSISTENCY REMAINS
QUITE GOOD SUN AS RIDGING BUILDS OVER THE MID/UPPER MS VALLEY...
AHEAD OF STRONGER TROUGHING DIGGING THRU THE CENTRAL/ SOUTHERN
ROCKIES. HOWEVER RUN-TO-RUN CONSISTENCY WITH THE 20.00Z/21.0Z RUNS
FOR SAT/ON SAT IS LESS THAN DESIRED. BY MON MODELS BEGIN TO DIFFER
ON THE SPEED/EVOLUTION OF THE CENTRAL/SOUTHERN ROCKIES TROUGH AS
IT MOVES/LIFTS INTO THE SOUTH-CENTRAL CONUS...AND A NORTHERN
STREAM SHORTWAVE DROPS INTO MAN/ND. GFS MORE PROGRESSIVE...AND
PHASED WITH THESE FEATURES BY LATER MON AND TUE...WITH SIGNIFICANT
SENSIBLE WEATHER DIFFERENCES BETWEEN ECMWF/GFS BY MON NIGHT/TUE.
FCST CONFIDENCE AVERAGE TO GOOD FOR THE WEEKEND...THEN GOES
DOWNHILL FOR MON/TUE.

GOOD MODEL AGREEMENT ON THE SYSTEM CROSSING THE MID MS VALLEY SAT
WRAPS MOISTURE/LIFT ACROSS THE SOUTH HALF OF THE FCST AREA SAT.
CONSENSUS RAIN CHANCES IN THE 30-55 PERCENT RANGE ALONG/SOUTH OF I-
90 ON SAT QUITE REASONABLE...WITH THESE CHANCES MAINLY IN THE
MORNING. CLOUDS AND AND EAST/NORTHEAST LOW LEVEL FLOW LOOKING TO
HOLD TEMPS DOWN ON SAT. HIGH PRESSURE BUILDS IN UNDER THE SHORTWAVE
RIDGING FOR SAT NIGHT THRU SUN NIGHT. COOLER LOWS AGAIN SAT
NIGHT...BUT HOW COOL WILL DEPEND ON ANY LINGERING CLOUDS/CLEARING
THAT NIGHT. A WARMER DAY SUNDAY WITH MORE SUNSHINE AND 925MB TEMPS
EXPECTED TO BE IN THE +5C TO +10C RANGE. MORE PROGRESSIVE/PHASED GFS
WOULD DEVELOP A STRONG LOW IN THE MID MS VALLEY FOR LATER MON INTO
TUE...SPREADING MOISTURE/FORCING/LIFT...AND RAIN INTO THE FCST AREA
EARLY NEXT WEEK. SLOWER AND MINIMALLY PHASED ECMWF WOULD HOLD WEAK
BUT DRY HIGH PRESSURE OVER THE UPPER MIDWEST EARLY NEXT WEEK. NO
REASON...OR CONFIDENCE TO FAVOR ONE OVER THE OTHER AT THIS POINT AND
SMALL CONSENSUS RAIN CHANCES MON THRU TUE OKAY FOR NOW. MODEL/
ENSEMBLE CONSENSUS OF HIGHS/LOWS FOR SAT THRU TUE LOOKS TO HAVE THEM
WELL TRENDED UNTIL THE DETAIL DIFFERENCES SORT THEMSELVES OUT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1200 AM CDT TUE APR 21 2015

A 5 TO 6K BROKEN DECK OF CLOUDS WILL PERSIST ACROSS THE AREA
THROUGH THE OVERNIGHT AND WEDNESDAY MORNING. SCATTERED SNOW
SHOWERS WILL PERSIST DURING THIS TIME PERIOD...BUT ANY VISIBILITY
RESTRICTIONS WOULD ONLY LAST A FEW MINUTES AT MOST. AS DRIER AIR
MOVES INTO THE REGION AND THE FLOW BECOMES ANTICYCLONIC...EXPECT
SKIES TO QUICKLY CLEAR AT BOTH TAF SITES.

&&

.FIRE WEATHER...TODAY AND THURSDAY
ISSUED AT 421 AM CDT WED APR 22 2015

TODAY CONTINUES TO LOOK LIKE A DRYING DAY ACROSS THE FCST AREA.
RELATIVE HUMIDITIES ARE EXPECTED TO DROP INTO THE 20-30 PERCENT
RANGE THIS AFTERNOON...WITH NORTHWEST WINDS OF 15 TO 25 MPH AND
GUSTY AS DIURNAL WARMING/MIXING OCCURS. HOW QUICKLY FUELS DRY OUT
TODAY AFTER THE RECENT COOL/WET COUPLE OF DAYS IS THE MAIN
CONCERN. MAXIMUM RELATIVE HUMIDITIES TONIGHT EXPECTED TO BE 65 TO
85 PERCENT AS A COOL BUT DRY AIRMASS SETTLES OVER THE REGION.
THURSDAY WOULD STILL APPEAR TO BE THE MORE CONCERNING FIRE WEATHER
DAY AFTER DRYING OF FUELS TODAY/TONIGHT AND MINIMUM AFTERNOON
HUMIDITIES AGAIN IN THE 20-30 PERCENT RANGE ACROSS MUCH OF THE
AREA. HOWEVER...THE SFC RIDGE AXIS IS OVER THE FCST AREA ON
THU...WITH WEST TO NORTHWEST WINDS MOSTLY 8 TO 12 MPH. SOME RAIN
NOW LOOKS TO RETURN TO AT LEAST THE SOUTHERN 2/3 OF THE FCST FOR
LATER FRI/FRI NIGHT.

&&

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

$$

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



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