Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 131734
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1234 PM CDT SUN JUL 13 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 259 AM CDT SUN JUL 13 2014

MAIN SHORT TERM CONCERN IS ON RAIN POTENTIAL TODAY.

CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED STRONG UPPER RIDGING OVER THE WESTERN U.S. INTO WESTERN
CANADA...WHILE AN ANONYMOUSLY DEEP TROUGH OVER MANITOBA AND NORTHERN
ONTARIO WAS SLOWLY SINKING SOUTH. A PROMINENT DRY SLOT AHEAD OF THE
DESCENDING TROUGH HELPED KICKED THE SHOWERS AND STORMS OUT OF THE
FORECAST AREA BY 03Z LAST EVENING. NORTHWEST FLOW OF 20-35 KT FROM
925MB TO 700MB ALSO WAS BRINGING MUCH DRIER AIR INTO THE AREA...
NOTED BY PRECIPITABLE WATER DOWN TO 1 INCH COMPARED TO AS HIGH AS 2
INCHES AT 00Z. SURFACE DEWPOINTS ARE STILL RELATIVELY HIGH...IN THE
LOW 60S...RESULTING MOSTLY FROM MOISTURE TRAPPED UNDER THE NOCTURNAL
INVERSION. THAT TRAPPING HAS LED TO SOME LOW STRATUS AND FOG
DEVELOPMENT OVERNIGHT. ANOTHER SLUG OF EVEN DRIER AIR WAS EVIDENT
OVER NORTH DAKOTA AND NORTHERN MN WITH PRECIPITABLE WATER AT 0.5
INCH...ALONG WITH SURFACE DEWPOINTS IN THE 40S AND 50S. THIS DRIER
AIR WAS LOCATED BEHIND A COLD FRONT STRETCHING FROM NORTHWEST WI
INTO WEST CENTRAL MN. SOME DYING SHOWERS WERE OVER NORTHWEST WI WITH
THIS FRONT...TIED MOSTLY WITH A SHORTWAVE CROSSING WESTERN LAKE
SUPERIOR. OTHERWISE...THE FRONT IS MOSTLY CLOUD FREE. TEMPERATURE
WISE...850MB TEMPS WERE GENERALLY 13-16C FROM NORTH DAKOTA INTO
WISCONSIN AT 00Z. HOWEVER...5C READINGS WERE SEEN LURKING OVER
CENTRAL MANITOBA WITHIN THE DEEP UPPER TROUGH.

MODELS ARE IN GOOD AGREEMENT DROPPING THE COLD FRONT OVER CENTRAL MN
SOUTHEASTWARD THROUGH THE FORECAST AREA THIS MORNING. DAYTIME
HEATING COMBINED WITH THE LINGERING MOISTURE AROUND WILL LIKELY LEAD
TO A DECENT AMOUNT OF CUMULUS AHEAD OF THE FRONT. ALTHOUGH THE
DETERMINISTIC NAM/GFS/CANADIAN SUGGEST A DRY FRONTAL PASSAGE...NEW
13.00Z ECMWF AS WELL AS THE 13.05Z HRRR AND 3 OF THE 4 HOPWRF
MEMBERS RUN BY THE MPX OFFICE SUGGEST A BAND OF SHOWERS WILL OCCUR
WITH THE FRONT. DEVELOPMENT TIME OCCURS AROUND 14Z / 9 AM AND SINKS
TO THE SOUTH OUT OF THE AREA BY 19Z / 2 PM. INCLUDED A 20 PERCENT
CHANCE AND ISOLATED SHOWERS FOR THIS SHOWER POTENTIAL. DID NOT PUT
ANY THUNDER WITH IT AS THE CAPE IS ONLY PROGGED AT 100-200 J/KG AND
ALL OF THE CAPE IS BELOW THE FREEZING LEVEL. AS THE FRONT PASSES AND
THE LOWER PRECIPITABLE WATER ADVECTS IN BEHIND IT...EXPECT THE
CUMULUS TO GRADUALLY DISSIPATE ALONG WITH DEWPOINTS DROPPING THROUGH
THE 50S. NORTHWEST WINDS SHOULD BECOME A BIT BREEZY TOO IN THE WAKE
OF THE FRONTAL PASSAGE GIVEN A FAVORABLE DEEPER MIXING ENVIRONMENT.

ATTENTION TONIGHT TURNS TO A POTENT SHORTWAVE WITHIN THE DEEP TROUGH
LOCATED IN NORTHEAST MANITOBA. MODELS DROPS THIS SHORTWAVE OVER THE
NORTHERN HALF OF MN BY 12Z...WITH AN UPPER LOW ALSO INDICATED AT
500MB. DPVA AHEAD OF THIS FEATURE COMBINED WITH THE MOIST AND MUCH
COOLER AIR WITHIN THE TROUGH IS EXPECTED TO SPREAD SHOWERS INTO
NORTHWEST WI BY 12Z MONDAY. BELIEVE THESE SHOULD STAY AWAY FROM
TAYLOR COUNTY BEFORE 12Z. SOME CLOUD INCREASE IS LIKELY NORTH OF I-
90 AFTER MIDNIGHT...THOUGH. A SECONDARY COLD FRONTAL PASSAGE SHOULD
COME INTO AND POSSIBLY THROUGH THE AREA BY 12Z AS WELL. ADVECTION
BEHIND THIS FRONT WILL ALLOW TEMPERATURES TO DIP INTO THE 50S...WITH
EVEN A FEW UPPER 40S POSSIBLE IN CENTRAL WI.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 259 AM CDT SUN JUL 13 2014

THE MAIN ISSUE HERE IN THE LONG TERM IS WITH THE TRACK OF THE UPPER
LOW IN NORTHERN MN AT 12Z MONDAY. THE ECMWF HAS BEEN PERSISTENT AS A
SLOWER...MORE AMPLIFIED SOLUTION...TAKING THE UPPER LOW ACROSS
CENTRAL AND NORTHERN WI MONDAY EVENING AND ACROSS LOWER MICHIGAN ON
TUESDAY. HOWEVER...THE 13.00Z CANADIAN/NAM/GFS ALL ARE IN STEP WITH
EACH OTHER SHOWING A TRACK ACROSS UPPER MICHIGAN ON MONDAY...AND
INTO EAST CENTRAL ONTARIO ON TUESDAY. THESE DIFFERENCES ARE
SIGNIFICANT AS IT IMPACTS THE LOCATION OF DPVA AND DIURNALLY
ENHANCED SHOWER POTENTIAL...ALONG WITH HOW COLD TEMPERATURES WILL BE
MONDAY AND TUESDAY. IT SHOULD BE NOTED THAT THE 13.00Z ECMWF HAS
TRENDED JUST SLIGHTLY TOWARDS THE CANADIAN/NAM/GFS. TO HANDLE THE
DIFFERENCE BETWEEN THESE TWO SOLUTIONS...HAVE DECIDED TO STAY PRETTY
CLOSE TO THE PREVIOUS FORECAST...WHICH WOULD BE IN-LINE WITH A MODEL
CONSENSUS IDEA.

FOR MONDAY...WE SHOULD GRADUALLY SEE SHOWER COVERAGE INCREASE
THROUGH THE DAY AS THE UPPER LOW AND ASSOCIATED COLD AIR ALOFT
APPROACH. THE MOST NUMEROUS COVERAGE IS ANTICIPATED NORTH OF HIGHWAY
29 CLOSER TO THE UPPER LOW. THESE SHOWERS SHOULD MOSTLY DIMINISH
MONDAY NIGHT DUE TO THE LOSS OF DAYTIME HEATING. TUESDAYS RAIN
CHANCES ARE A BIT MORE QUESTIONABLE NOW AFTER SEEING THE 13.00Z
ECMWF. THE FLOW IS STILL CYCLONIC INTO THE REGION...BUT DRY AIR IS
ADVECTING IN AT THE SAME TIME. THE CANADIAN/GFS/NAM ARE ALL
DRY...AND NOW THE ECMWF ONLY HAS SOME LIGHT QPF BETWEEN 12-18Z
TUESDAY BEFORE DRYING OUT. HAVE THEREFORE TRENDED PRECIPITATION
CHANCES LOWER A BIT AND DRIED OUT LOCATIONS WEST OF THE MISSISSIPPI
RIVER. REGARDING TEMPERATURES...850MB TEMPS PLUMMET TO 4-6C IN THE
MORNING WHICH WILL KEEP HIGHS MOSTLY IN THE 60S. THE LONE EXCEPTION
TO THAT IS IN FAR SOUTHWEST WI WHERE THE COLDER AIR ENTERS LAST AND
HAS MORE SUN POTENTIAL IN THE MORNING. WITH LESS SHOWER POTENTIAL ON
TUESDAY...HAVE RAISED HIGHS SLIGHTLY BUT THEY ARE STILL A FAR CRY
FROM NORMAL.

BENIGN WEATHER CONTINUES TO BE THE RULE AFTER TUESDAY. UPPER
TROUGHING DOMINATES MUCH OF THE EASTERN U.S. WEDNESDAY INTO THURSDAY
WITH THE FORECAST AREA ON THE BACK SIDE OF THE TROUGH. THIS FAVORS
SUBSIDENCE ALOFT AND DRYING HIGH PRESSURE AT THE SURFACE. THE GFS
CONTINUES TO SPLATTER LIGHT QPF AROUND DURING THE AFTERNOON AND
EVENINGS AS A RESULT OF TOO MUCH EVAPOTRANSPIRATION. AS WE HEAD INTO
FRIDAY AND SATURDAY...500MB HEIGHTS LOOK TO RISE ACROSS MUCH OF THE
EASTERN U.S. AS THE TROUGH LIFTS OUT. IN FACT...WE COULD EVEN BE
UNDER UPPER RIDGING BY SATURDAY AS A SHORTWAVE TROUGH SLIDES ACROSS
THE NORTHERN ROCKIES. THIS PATTERN HEADING INTO SATURDAY FAVORS A
CONTINUATION OF DRY CONDITIONS ALONG WITH A NICE WARMING TREND
TOWARDS CLOSER TO NORMAL. MUCH OF THE MORE HUMID AIR LOOKS TO BE
STUCK ACROSS THE SOUTHERN U.S. THANKS TO THE COLD/DRY AIR FROM
EARLIER THIS WEEK DROPPING ALL THE WAY DOWN TO THE GULF COAST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1234 PM CDT SUN JUL 13 2014

SECONDARY COLD FRONT HAS PUSHED THROUGH KRST/KLSE THIS AFTERNOON
WITH SCATTERED CUMULUS DEVELOPING ITS WAKE. EXPECTING MOST OF
THIS...ALONG WITH THE 20KT GUSTS ACROSS SOUTHERN MINNESOTA...TO BE
DIURNAL AND SUBSIDE TOWARD SUNSET. THE MAIN ENERGY ASSOCIATED WITH
THE UPPER LEVEL SHORTWAVE TROUGH ARRIVES MONDAY AFTERNOON...AND
WITH IT ANOTHER ROUND OF SCATTERED TO BROKEN VFR CUMULUS IS
EXPECTED. BASES LOOK TO BE BETWEEN 3 AND 5 KFT...AS OBSERVED TODAY
UPSTREAM. SOME SHOWERS WILL BE POSSIBLE AT THE TAF SITES...BUT
MORE SO AFTER 18Z AND TO THE NORTHEAST...SO HAVE KEPT CURRENT TAF
PERIOD DRY.

&&

.CLIMATE...
ISSUED AT 259 AM CDT SUN JUL 13 2014

RECORD COOL HIGH TEMPERATURES ARE POSSIBLE MONDAY AND TUESDAY AS AN
UNSEASONABLY COLD AIRMASS SETTLES OVER THE UPPER MISSISSIPPI RIVER
VALLEY.

FOR LA CROSSE...
MONDAY....FORECAST HIGH 68.  RECORD 65 IN 1994
TUESDAY...FORECAST HIGH 70.  RECORD 68 IN 1962

FOR ROCHESTER...
MONDAY....FORECAST HIGH 64.  RECORD 64 IN 1952
TUESDAY...FORECAST HIGH 67.  RECORD 67 IN 1962

&&

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

$$

SHORT TERM...AJ
LONG TERM....AJ
AVIATION.....ZT
CLIMATE......AJ



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