Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 062249
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
550 PM CDT SUN JUL 6 2014

.MESOSCALE DISCUSSION...
ISSUED AT 331 PM CDT SUN JUL 6 2014

NUMEROUS SHOWERS AND THUNDERSTORMS CONTINUE TO DEVELOP ALONG AND
NORTH OF INTERSTATE 90...ESPECIALLY IN WISCONSIN. THESE ARE ON THE
NOSE OF 850MB MOISTURE TRANSPORT AND BASICALLY THE FINE LINE BACK
EDGE IS THE 850MB FRONT DEPICTED IN RAP ANALYSIS. THE STRONGEST
CORE HAS BEEN OVER TREMPEALEAU COUNTY...AND DOES HAVE SOME MID-
LEVEL ROTATION...HOWEVER MUCH OF THE CORE APPEARS TO BE RAIN. NOT
ANTICIPATING ANY OF THIS ELEVATED DRIVEN CONVECTION TO TURN
SEVERE. FARTHER TO THE WEST...STILL MONITORING FOR SHOWERS AND
THUNDERSTORMS TO DEVELOP FROM NORTH CENTRAL IOWA TO SOUTH CENTRAL
MN AND WEST CENTRAL WI. SEEING A TOWERING CUMULUS LINE ON VISIBLE
IMAGERY...BUT OVERALL DEEP- MOISTURE AND EVEN SURFACE CONVERGENCE
ALONG THIS TROUGH IS WEAK. LOOKING AT THE SURFACE FLOW...IT GOES
SOUTHWEST AT RST TO NEARLY WEST AT I-35 TO NORTHWEST AT NEW
ULM...A LONG DISTANCE. RAP ANALYSIS DOES SHOW 2500-3500 J/KG OF
MLCAPE WITH LITTLE CIN IN THIS CORRIDOR...THOUGH. THUS...A WAIT
AND SEE IF ANYTHING CAN POP. SHOULD A STORM FIRE...IT WILL
PROBABLY TURN SEVERE QUICKLY.

NEEDLESS TO SAY...THE COMBINATION OF THE LONG PERIOD OF HAVING
THE STRATUS AROUND TODAY AND NOT A LOT OF CONVERGENCE ON THE
FRONT HAVE BEEN DETRIMENTAL TO SEVERE POTENTIAL.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 201 PM CDT SUN JUL 6 2014

MAIN SHORT TERM CONCERNS ARE ON CONVECTIVE EVOLUTION AND SEVERE
POTENTIAL FOR THIS AFTERNOON/EVENING AND AGAIN LATE MONDAY.

CURRENTLY AS OF 19Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED STRONG RIDGING OVER THE WESTERN U.S. WHILE GENERAL WEAK
TROUGHING PRESIDED OVER THE GREAT LAKES. A WEAK SHORTWAVE WAS
EVIDENT OVER CENTRAL MN. ACCOMPANYING THIS SHORTWAVE PER THE RAP AT
800MB WERE 30 KT NORTHWEST WINDS AND 14-15C TEMPERATURES. COMPARE
THIS TO 25-30 KT SOUTHWEST WINDS AND 18-20C TEMPERATURES OVER THE
FORECAST AREA. THAT WARM NOSE COMBINED WITH MORNING STRATUS AND
DEBRIS CLOUDS HAS KEPT CONDITIONS CAPPED THUS FAR. EDGE OF CAP
REFLECTED NICELY TOO BY SOME ELEVATED SHOWERS AND THUNDERSTORMS
GOING ON OVER WEST-CENTRAL WISCONSIN. TEMPERATURES FOR THE MOST PART
HAVE BEEN STUCK IN THE 70S WITH A FEW 80S WHERE CLEARING BRIEFLY
OCCURRED IN SOUTHEAST MN AND WEST CENTRAL WI. DEWPOINTS HAVE BEEN ON
THE RISE...THOUGH...NOW IN THE LOW 70S. BACK IN WESTERN IA...
EVAPOTRANSPORATION PUSHING DEWPOINTS THERE IN THE UPPER 70S.
THINKING THESE HIGHER DEWPOINTS ADVECTING TOWARDS THE AREA IS NOT
HELPING MATTERS TO CLEAR THE STRATUS. THE AFOREMENTIONED
TEMPERATURES AND DEWPOINTS HAVE RESULTED IN MLCAPE VALUES OF 1500-
2010 J/KG WHILE MLCIN SITS 50-100 J/KG WHERE IT CLEARED TO
201-300 J/KG WHERE ITS STILL CLOUDY. MEANWHILE...IN SOUTHWEST
MN... DEWPOINTS HAVE FALLEN OFF INTO MID LOW 50S BEHIND A
TROUGH/DRYLINE THAT STRETCHES FROM NORTHWEST IOWA INTO NORTHWEST
WI.

ANTICIPATING CONVECTION TO FIRE IN THE NEXT 1-2 HOURS ALONG THE
TROUGH/DRYLINE NEAR/WEST OF THE FORECAST AREA AS DAYTIME HEATING
CONTINUES TO GET RID OF THE CIN. CONVECTION SHOULD TAKE ON A
SCATTERED NATURE GIVEN THE CAP IN PLACE. WHERE CONVECTION DOES
FIRE...0-3KM AND 0-6KM SHEAR ARE ON THE ORDER OF 20-25KT... WHICH
SHOULD FAVOR MORE MULTI-CELLULAR ACTIVITY. GIVEN THE AMOUNT OF
CAPE...CANNOT RULE OUT AN INITIAL SUPERCELL...BUT THINKING MORE
INTENSE MULTI-CELLS ARE MORE LIKELY. LARGE HAIL AND DAMAGING WINDS
WILL BE THE MAIN CONCERNS. GENERAL MODEL CONSENSUS OF BOTH
DETERMINISTIC AND HIGH RESOLUTION MODELS SUGGEST MUCH OF THE
CONVECTION SHOULD BE SOUTHEAST OF THE FORECAST AREA BY 01-02Z.
HOWEVER...THERE IS POTENTIAL THAT THE CONVECTION DOESNT EVEN MAKE
IT INTO THE SOUTHEAST END OF THE FORECAST AREA BECAUSE OF THE
MASSIVE AMOUNT OF CIN RIGHT NOW IN PLACE. MANY HRRR RUNS TODAY HAVE
SHOWN THIS.

MUCH OF TONIGHT AND INTO MONDAY MORNING THEN LOOKS DRY AS
UNIDIRECTIONAL NORTHWEST FLOW FROM THE SURFACE TO 500MB BRINGS IN
SOMEWHAT COOLER AND DRIER AIR IN FROM NORTH DAKOTA. THIS IS
REFLECTED WELL IN GOES PRECIPITABLE WATER IMAGERY WHICH SHOWS VALUES
OF 1 INCH OR LESS OVER WESTERN MN COMPARED TO 1.5-1.75 INCHES OVER
THE FORECAST AREA.

HEADING INTO MONDAY AFTERNOON...A LONG WAVE SHORTWAVE TROUGH IS
PROGGED TO DROP INTO THE EASTERN DAKOTAS AND WESTERN MN. INCREASING
850MB MOISTURE TRANSPORT AHEAD OF THE TROUGH...COMBINED WITH 1000-
1500 J/KG OF MLCAPE WITH LITTLE CAPPING AND A SURFACE TROUGH MOVING
THROUGH...SHOULD RESULT IN A DECENT AMOUNT OF CONVECTION ACROSS
MINNESOTA IN THE AFTERNOON HOURS...AS DEPICTED TOO BY DETERMINISTIC
AND HIGH RESOLUTION GUIDANCE. THIS CONVECTION COULD SPREAD INTO THE
NORTHWEST HALF OF THE FORECAST AREA BY LATE IN THE DAY. GIVEN 0-3KM
SHEAR VALUES OF 25-35 KT AND MORE IMPORTANTLY 0-6KM SHEAR VALUES OF
40-55 KT...ORGANIZED SEVERE CONVECTION STILL APPEARS POSSIBLE. COULD
END UP SEEING A MIX OF SUPERCELL AND LINE SEGMENTS...THOUGH THE
SHEAR BEING UNIDIRECTIONAL MAY FAVOR MORE LINE SEGMENTS AND THUS
DAMAGING WINDS. NEED TO WATCH THE LARGE HAIL CONCERN INITIALLY TOO
GIVEN LOWER FREEZING LEVELS...DROPPING FROM NEAR 14000 FT THIS
AFTERNOON TO 12010 FT LATE MONDAY.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 201 PM CDT SUN JUL 6 2014

MAIN HIGHLIGHTS FOR THE LONG TERM PERIOD ARE SEVERE POTENTIAL MONDAY
EVENING FOLLOWED BY COOLER WEATHER FOR MID-WEEK.

MONDAY NIGHT...BOTH THE LONG WAVE SHORTWAVE TROUGH AT 500MB AND THE
ASSOCIATED SURFACE TROUGH ARE PROGGED TO MOVE SOUTHEAST THROUGH THE
REGION. THERE ALSO APPEARS TO BE A POINT IN THE EVENING WHERE WE GET
INTO A LEFT EXIT REGION OF AN UPPER JET STREAK. COMBINE THIS
DYNAMICAL FORCING WITH AN 850MB MOISTURE TRANSPORT PLUME AND
LINGERING INSTABILITY MEANS WE SHOULD BE ABLE TO KEEP SOME SHOWERS
AND THUNDERSTORMS GOING THROUGH THE EVENING. UNTIL INSTABILITY
WANES...EXPECT A SEVERE THREAT TO EXIST...JUST AS THE 06.12Z HIRES
ARW/NMM SUGGEST. MUCH OF THE CONVECTION COULD BE EAST OF THE AREA BY
THE OVERNIGHT HOURS...OR AT LEAST OVER THE SOUTHEAST HALF...SO
PRECIPITATION DIMINISH NORTHWEST TO SOUTHEAST THROUGH THE NIGHT.
PLUS...PRECIPITABLE WATER VALUES TANK AGAIN AFTER BRIEFLY COMING UP
MONDAY AFTERNOON.

ON TUESDAY...MODEL AGREEMENT IS GOOD ON SETTING UP AN UPPER LEVEL
TROUGH FROM NORTHERN ONTARIO SOUTHWARD THROUGH THE WESTERN GREAT
LAKES REGION. COOL AIR ALOFT COMBINED WITH A SHORTWAVE DROPPING
THROUGH THIS TROUGH IN WISCONSIN...DAYTIME HEATING...AS WELL AS
LINGERING LOW LEVEL MOISTURE COULD SPARK SOME DIURNALLY DRIVEN
SHOWERS AND THUNDERSTORMS. BEST CHANCE FOR THIS WILL BE IN WISCONSIN
WITH THE SHORTWAVE DROPPING THROUGH.

DRIER WEATHER LOOKS TO PREVAIL TUESDAY NIGHT THROUGH THURSDAY WITH
THE FORECAST AREA. THIS IS A RESULT OF A DRIER WESTERN CANADIAN HIGH
PRESSURE AREA MOVING THROUGH...AND BEING AROUND THE INFLECTION POINT
BEHIND THE WESTERN GREAT LAKES UPPER TROUGH PUSHING OFF TO THE EAST.
TEMPERATURES ARE LIKELY TO BE A BIT ON THE COOL SIDE WITH 850MB TEMP
ANOMALIES ABOUT 1 STANDARD DEVIATION BELOW NORMAL...OR BETWEEN 9-
13C. LOW PRECIPITABLE WATER AROUND 0.75 INCHES WILL HELP TOO IN
RADIATIVE COOLING AT NIGHT...ALONG WITH MIXING OF DEWPOINTS IN THE
DAY. COULD SEE SOME VALLEY FOG TUESDAY AND WEDNESDAY NIGHTS.

FOR THURSDAY NIGHT INTO THE WEEKEND. WARM ADVECTION BEGINS IN
EARNEST THURSDAY NIGHT AS THE HIGH HEADS OFF TO THE EAST. MODEL
CONSENSUS IS FOR NUMEROUS SHOWERS AND THUNDERSTORMS TO INITIATE WITH
THE MOISTURE RETURN FROM THE UPPER MIDWEST SOUTHWARD INTO THE
CENTRAL PLAINS...PERHAPS CREEPING INTO THE FORECAST AREA EITHER LATE
THURSDAY NIGHT OR DURING THE DAY FRIDAY. STORM CHANCES THEN LOOK TO
CONTINUE THROUGH SATURDAY AS AN UPPER TROUGH DROPS SOUTH FROM
MANITOBA INTO THE WESTERN GREAT LAKES REGION. PERHAPS BY SUNDAY ALL
THE CONVECTIVE POTENTIAL WILL GET SHOVED TO THE SOUTH AS THE UPPER
TROUGH CONTINUES TO DIG SOUTHEASTWARD. HOWEVER...HAVE STILL
MAINTAINED CHANCES OF SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN
PORTIONS OF THE FORECAST AREA. TEMPERATURE WISE...850MB TEMPS
GENERALLY RANGE 16-18C THROUGH SATURDAY...SUPPORTING HIGHS IN THE
80S. THESE SHOULD COOL BACK SOME ON SUNDAY WITH THE TROUGH DROPPING
IN. HUMIDITY WILL BE UP TOO FRIDAY AND SATURDAY WITH THAT RETURN
FLOW...EVAPOTRANSPORATION AND POTENTIAL CONVECTION ADDING MOISTURE
TO THE BOUNDARY LAYER.

&&

.AVIATION...(FOR THE 00Z TAFS...THROUGH 00Z MONDAY EVENING)
ISSUED AT 550 PM CDT SUN JUL 6 2014

SHRA/TS HAVE FIRED ALONG AND AHEAD OF A FRONT/DRY LINE TRACKING EAST
ACROSS EASTERN MN/IA EARLY THIS EVENING...AND SHOULD BE EAST OF KRST
BY 00Z...BUT COULD LINGER FOR AN HOUR OR TWO NEAR KLSE PAST TAF
ISSUANCE. SKIES WILL CLEAR BY MID EVENING...WITH VFR CONDITIONS THEN
EXPECTED THROUGH MONDAY MORNING.

ANOTHER UPPER LEVEL TROUGH/SFC FRONT COMBO WILL SLIDE ACROSS THE
UPPER MISSISSIPPI RIVER VALLEY MONDAY AFTERNOON/EVENING...TRIGGERING
MORE SHRA/TS. THREAT TIME APPEARS TO BE IN THE 20-03Z TIME FRAME AT
THE MOMENT. AMPLE ATMOSPHERIC SUPPORT FOR A STRONG-SEVERE STORM
THREAT.


&&

.HYDROLOGY...
ISSUED AT 331 PM CDT SUN JUL 6 2014

RIVER STAGES ARE FALLING ALONG THE MISSISSIPPI RIVER AND IT
APPEARS THAT ALL OF THEM WILL BE BELOW FLOOD STAGE BY THURSDAY.
THERE IS SOME RAIN FORECAST OVER THE NEXT FEW DAYS...BUT NONE OF
IT LOOKS WIDESPREAD HEAVY ENOUGH TO MAKE A SIGNIFICANT IMPACT ON
THE MISSISSIPPI...OR EVEN TRIBUTARIES FOR THAT MATTER.

&&

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

$$

MESOSCALE...AJ
SHORT TERM..AJ
LONG TERM...AJ
AVIATION....RIECK
HYDROLOGY...AJ


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