Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 240901
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
401 AM CDT THU APR 24 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 401 AM CDT THU APR 24 2014

MAIN FORECAST CONCERNS THIS PACKAGE...RAIN CHANCES/AMOUNTS TODAY...
CLOUD TRENDS TONIGHT...TEMPERATURES.

06Z DATA ANALYSIS HAD HIGH PRESSURE OVER THE CENTRAL GREAT LAKES AND
LOW PRESSURE LIFTING NORTHEAST ACROSS KS. STRONGER PRESSURE FALLS
AHEAD OF THIS LOW AND TROUGHING NORTHWARD INTO THE DAKOTAS WERE OVER
EASTERN KS TO MN. BROAD SCALE ASCENT AHEAD OF THIS LOW AND THE
STRONG MID LEVEL TROUGH MOVING ACROSS THE PLAINS WAS PRODUCING
RATHER WIDESPREAD -SHRA/ISOLATED TSRA ACROSS NORTHERN IA/SOUTHERN
MN/WI AS GULF OF MEX MOISTURE SPREAD NORTHWARD INTO THE UPPER
MIDWEST. EVEN WITH ALL THE CLOUDS/DEVELOPING SHRA TEMPS ACROSS THE
REGION WERE ON THE COOL SIDE EARLY THIS MORNING.

NO PROBLEMS NOTED WITH 24.00Z MODEL INITIALIZATIONS. A RATHER TIGHT
CONSENSUS AMONG THE MODELS FOR TODAY/TONIGHT...TOWARD THE EARLIER
ECMWF RUNS...AS THE MID LEVEL TROUGH APPROACHES/PASSES. HOWEVER
TREND IS TOWARD STRONGER/MORE ENERGY IN THE SOUTHERN PORTION OF THE
TROUGH AS IS MOVES THRU THE MID MS VALLEY. THIS STRONGER TREND IS A
BIT SLOWER THAN THE EARLIER RUNS BY 12Z FRI. CHECK OF OBS VS. MODEL
DATA AT 06Z SHOWED MODELS WERE GOOD WITH THE KS LOW AND TROUGHING
INTO THE DAKOTAS. PER WV IMAGERY...ALL APPEARED REASONABLE WITH THE
TROUGH/SHORTWAVE ENERGY FROM THE SOUTHERN PLAINS TO ALB/SASKAT. A
BLEND OF THE MODELS LOOKED BEST WITH THE 00-06Z PRECIP ACROSS THE
PLAINS/UPPER MS VALLEY. WITH THE MODEL/ENSEMBLE CONSENSUS LOOKING
GOOD AT 06Z...FAVORED THE COMPROMISE/BLEND OF THE MODELS. SHORT-TERM
FCST CONFIDENCE REMAINS GOOD THIS CYCLE.

IN THE SHORT TERM...STRONG SURGE OF GULF OF MEX MOISTURE IN THE 925-
700MB LAYER WILL CONTINUE INTO THE AREA THIS MORNING. THIS AN AREA
OF MDT/STRONG LOWER LEVEL THERMO-DYNAMIC FORCING/LIFT AND UNDER
BROAD LIFT/DIVERGENCE ALOFT BETWEEN JET MAXES AND AHEAD OF THE
APPROACHING MID LEVEL TROUGH/SHORTWAVE ENERGY. PW VALUES AROUND 200
PERCENT OF NORMAL COUPLED WITH THE DEEP LAYERED FORCING/LIFT...THE
100 PERCENT OR NEARLY SO RAIN CHANCES THIS MORNING ARE WELL TRENDED.
STRONGER/DEEPER OF THE MOISTURE/LIFT SLOWLY TRANSLATE EAST ACROSS
THE AREA THIS AFTERNOON WITH A DOWNWARD TREND IN THE RAIN CHANCES
WEST OF THE MS RIVER. LATEST MODEL CONSENSUS HAS THE SFC-700MB
TROUGH AXIS NEAR THE MS RIVER AT 00Z FRI. THE SLIGHT SLOWING TREND
AMONG THE MODELS NOW HAS THE MID LEVEL TROUGH AXIS PASSING THIS
EVENING. IN RESPONSE TO THIS...GENERALLY RAISED RAIN CHANCES THIS
AFTERNOON INTO THIS EVENING ESPECIALLY OVER THE EAST HALF OF THE
FCST AREA. CAPE STILL LOOKS TO REMAIN VERY LIMITED TODAY BUT GIVEN
THE DEEP MOISTURE/STRONG LIFT WILL CONTINUE THE ISOLATED/EMBEDDED
TSRA MENTION. ONCE THE SFC-500MB TROUGH AXIS PASSES...STRONG SIGNAL
FOR DEEP SUBSIDENCE AND SHARP/RAPID DRYING IN THE 925-500MB LAYER
OVER THE SOUTHWEST 2/3 OF THE FCST AREA. WILL TREND GRIDS FOR THIS
BUT HAVE TO DELAY IT A BIT DUE TO THE SLIGHT SLOWING TREND.

ALL THE LOWER CLOUDS/RAIN LONGER INTO THE AFTERNOON TODAY WILL LIMIT
TEMPS AND THE DOWNWARD TREND OF HIGHS SEEN IN THE MODEL/ENSEMBLE
CONSENSUS LOOKS GOOD. WITH DECREASING CLOUDS/CLEARING EXPECTED FOR
MUCH OF THE FCST AREA LATER TONIGHT...COOLER LOWS PER THE CONSENSUS
LOOK GOOD. IF WINDS END UP LIGHT/DECOUPLE...WILL HAVE TO WATCH FOR
FOG DEVELOPMENT WITH THE DECREASING CLOUDS/CLEARING LATER TONIGHT
AND PLENTY OF MOISTURE FROM THE RAINS TODAY TO REMAIN IN THE
BOUNDARY LAYER. LEFT LATE NIGHT FOG OUT OF THE GRIDS FOR NOW BUT
WILL PASS ALONG TO DAY CREW TO KEEP AN EYE ON THE POTENTIAL.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 401 AM CDT THU APR 24 2014

MAIN FORECAST CONCERNS FOR FRIDAY THROUGH SATURDAY NIGHT...SMALL
-SHRA POTENTIAL FRI NIGHT/SAT...RETURNING RAIN CHANCES SAT NIGHT...
TEMPERATURES.

RATHER TIGHT CONSENSUS AMONG THE MODELS FOR FRI WITH A FASTER EXIT
OF TODAY/S TROUGH AND ANY SECONDARY SHORTWAVE ON THE BACK SIDE TO
PASS WELL NORTH/EAST OF THE FCST AREA. SIGNAL REMAINS STRONG FOR
RISING HGTS/RIDGING ALOFT TO BUILD INTO THE UPPER MIDWEST FRI
NIGHT/SAT WITH THE AREA EAST OF THE RIDGE AXIS. IMPROVING CONSENSUS
FOR THIS RIDGE AXIS TO PASS SAT NIGHT AS STRONG OVER THE ROCKIES
EJECTS INTO THE CENTRAL/SOUTHERN PLAINS. WITH THE IMPROVING BETWEEN
MODEL AND RUN-TO-RUN CONSISTENCY OUT TO 12Z SUN...ESPECIALLY WITH
THE TROUGHING DIGGING THRU THE ROCKIES...FCST CONFIDENCE FOR FRI
THRU SAT NIGHT IS TRENDING GOOD THIS CYCLE.

GENERALLY DRY/QUIET WEATHER FRI AS A WEAK BACK-DOOR COLD FRONT
SLIDES INTO THE AREA. BULK OF THE LOWER LEVEL COOLING BEHIND THIS
BOUNDARY REMAINS NORTH/EAST OF THE FCST AREA. MODEL SOUNDINGS
SHOWING MIXING TO AROUND 800MB ON FRI...WITH 850MB TEMPS IN THE +2C
TO +10C RANGE. WITH SOME SUNSHINE FOR MUCH OF THE AREA AND MDT WEST
TO NORTHWEST WINDS FOR MIXING...FRI TRENDING TO BE A WARMER DAY WITH
HIGHS SOUTHWEST OF I-94 IN THE 60S. THIS WEAK FRONTAL BOUNDARY SAGS
SOUTH OF THE AREA FRI NIGHT AND BECOMES THE FOCUS FOR LIFT/PRECIP
PRODUCTION LATER IN THE WEEKEND AS A WARM FRONT. CAN HIGH PRESSURE
NOSES INTO THE AREA BEHIND THE FRONT FOR FRI NIGHT/SAT. HOWEVER...
SIGNAL AMONG THE MODELS FOR A WEAK SHORTWAVE TO SNEAK THRU THE MID
LEVEL RIDGE AND ACROSS THE AREA FRI NIGHT. SOME 850-700MB WARM
ADVECTION/MOISTURE INCREASE LOOKS TO ACCOMPANY THIS WAVE...WITH
BAROCLINIC ZONE NORTH OF THE WEAK FRONT HELPING PROVIDE SOME LIFT.
PREVIOUS GRIDS CARRIED A SMALL -SHRA CHANCE ACROSS THE SOUTHEAST END
OF THE FCST AREA FRI NIGHT AND LEFT THIS FOR NOW. NAM/ECMWF TRY TO
PRODUCE SOME LIGHT QPF ACROSS THE NORTHEAST PART OF THE FCST AREA
SAT BUT FORCING FOR THIS NOT WELL FOCUSED AND 850MB LAYER PROGGED ON
THE DRY SIDE. LEFT SAT DRY FOR NOW.

BY SAT NIGHT TREND OF THE TIGHTER MODEL CONSENSUS IS MORE PROGRESSIVE
WITH THE MID LEVEL TROUGHING MOVING INTO THE PLAINS AND MORE
NORTHERLY WITH THE CENTRAL PLAINS SFC LOW. WITH THE MID LEVEL RIDGE
AXIS MOVING EAST OF THE AREA SAT NIGHT...DEEPER SOUTH TO SOUTHWEST
FLOW IS ALLOWED TO SPREAD MORE MOISTURE NORTH/NORTHEAST INTO THE
UPPER MIDWEST...OVER THE NOW WARM FRONTAL BOUNDARY NEAR THE MO/IA
BORDER. PW VALUES OVER THE AREA PROGGED TO QUICKLY INCREASE TO AN
INCH OR MORE SAT NIGHT. WITH MORE CLOUDS/LOW LEVEL WARM ADVECTION
SAT NIGHT...TRENDED LOWS UPWARD. LOWS STILL LOOKS TO SUPPORT A -SN
CHANCE OVER THE NORTHEAST END OF THE FCST AREA LATE SAT NIGHT...
BUT 850MB TEMPS IN THE +4 TO +8C RANGE FOR WHAT WOULD BE A COLD
RAIN LATE SAT NIGHT/EARLY SUN MORNING. REMOVED -SN MENTION FROM
THESE PERIODS. USED THE MODEL/ENSEMBLE CONSENSUS HIGHS/LOWS FOR
FRI THRU SAT NIGHT.

FOR SUNDAY THROUGH WEDNESDAY.../DAYS 4 TO 7/...

MAIN FORECAST CONCERNS ARE RAIN CHANCES AND TEMPERATURES THRU THE
PERIOD.

MODEL RUNS OF 24.00Z TREND MORE PROGRESSIVE/FURTHER NORTH WITH THE
LARGE MID LEVEL TROUGH/LOW IN THE CENTRAL CONUS MUCH OF THE SUN-WED
PERIOD. MOVEMENT OF THIS SYSTEM PROMISES TO BE SLOW WITH IT STILL
LOOKING TO BE THE WESTERN LIMB OF A CENTRAL/EASTERN NOAM OMEGA
BLOCK...WITH GENERALLY COOL AND MOIST PERIOD OF WEATHER FOR THE AREA.
FCST CONFIDENCE IN THE SUN-WED PERIOD IS AVERAGE.

WITH THE BROAD SFC-500MB CIRCULATION LOOKING TO VERY SLOWLY WORK ITS
WAY ACROSS THE MID SECTION OF THE CONUS SUN-WED...THE FCST AREA
REMAINS ON ITS EAST/NORTHEAST SIDE AND UNDER THE MOIST WARM CONVEYOR
BELT THRU AT LEAST SUN/MON AND LIKELY THRU TUE/WED. MODEL SOUNDINGS
SHOW THE COLUMN TO BE TOO WARM FOR ANY -SN THRU MON AND REMOVED THIS
MENTION FROM THE LATE NIGHT/EARLY MORNING GRIDS OF SUN THRU MON.
INCREASING RAIN CHANCES FOR SUN THRU MON PER THE MODEL CONSENSUS
QUITE REASONABLE. SOME 925-850MB COOLING TO OCCUR FOR MON NIGHT INTO
WED AS THE SFC-700MB LOW TRIES TO SLIDE EAST THRU THE MID MS VALLEY
AND SOME DRIER LOW LEVEL AIR...ALLOWING FOR EVAPORATIVE COOLING...
WRAPS SOUTHWEST AROUND THE MID MS VALLEY CIRCULATION. CONTINUED THE
MENTION OF LATE NIGHT/EARLY MORNING -RA/-SN ACROSS MAINLY THE NORTH
PORTIONS OF THE FCST AREA TUE/WED. MAY BE ENOUGH LOWER LEVEL DRY AIR
TO WRAP IN TUE/WED TO LIMIT PRECIP...BUT LEFT THE 20-40 PERCENT
CONSENSUS PRECIP CHANCES AS IS FOR NOW. MODEL/ENSEMBLE CONSENSUS
HIGHS/LOWS GENERALLY 10F BELOW NORMAL APPEAR WELL TRENDED AT THIS
TIME WITH PLENTY OF CLOUDS EXPECTED AND LOW LEVEL FLOW FROM AN EAST
TO NORTHERLY DIRECTION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1100 PM CDT WED APR 23 2014

THE FIRST BAND OF PCPN HAS SHIFTED EAST OF KLSE LATE THIS
EVENING...WHILE ANOTHER BAND IS MOVING NORTHEAST ACROSS IA/NEB. THIS
NEXT BATCH WILL BE SHOWERY IN NATURE AT THE ONSET...BECOMING MORE
WIDESPREAD TOWARD 09Z PER LATEST HRRR/RUC13/NAM12. CIGS WILL FALL
INTO THE IFR/MVFR CATEGORIES OVERNIGHT...AND LIKELY HOLD THERE
THROUGH THU NIGHT. THE RAIN WON/T EXIT UNTIL CLOSE TO 00Z FRI.
MOSTLY FORECASTING MVFR VSBYS WITH THE RAIN...BUT A PERIOD OF 1-2SM
COULD OCCUR.

TIGHT PRESSURE GRADIENT WILL KEEP WINDS FAIRLY BREEZY FROM THE
EAST/SOUTHEAST THROUGH MOST OF THU...WITH A SWING TO THE
WEST/NORTHWEST AS THE LOW PASSES TO THE EAST TOWARD 00Z FRI. BUFKIT
SOUNDINGS ALSO SUGGESTING ABOUT A 3 HOUR WINDOW WHERE LLWS COULD BE
A CONCERN...ROUGHLY IN THE 10-13Z TIME FRAME. ITS BORDERLINE RIGHT
NOW...SO WILL LEAVE OUT OF THE FORECAST. WOULD BE WS020/17048KT.

&&

.HYDROLOGY...
ISSUED AT 401 AM CDT THU APR 24 2014

RAIN AMOUNT OF 1 TO 1.5 INCHES EARLY THIS MORNING AND TODAY HAVE THE
POTENTIAL TO CREATE RUNOFF AND MDT TO STRONG WITHIN BANK RISES ON
MANY RIVERS AND STREAMS ACROSS THE FCST AREA. POTENTIAL FOR SOME
MINOR FLOODING ALONG PORTIONS OF THE KICKAPOO RIVER IF THE RAIN
AMOUNTS/RUNOFF END UP ON THE HEAVIER SIDE OF WHAT IS EXPECTED. WITH
MANY RIVER STILL RUNNING HIGH FROM RECENT RAINS/SNOWMELT...WILL
ISSUE AND ESF FOR THE POSSIBLE RISES/FLOODING FROM THE RAINS TODAY.

ALSO OF CONCERN IS THE NEXT ROUND OF RAIN EXPECTED SAT NIGHT THRU
MON...WITH POTENTIAL FOR 1 TO 2 INCHES OF RAIN DURING THIS
PERIOD. THESE RAINS IF THEY MATERIALIZE/FALL WOULD CREATE
ADDITIONAL RISES AND FLOODING THREATS WELL INTO NEXT WEEK.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION.....RIECK
HYDROLOGY....RRS



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