000
FXUS63 KARX 141141
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
640 AM CDT FRI JUN 14 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 329 AM CDT FRI JUN 14 2013

MAIN FORECAST FOCUS IS ON POTENTIAL FOR HEAVY RAIN/FLASH FLOODING
LATER TODAY THROUGH SATURDAY.

CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED A HIGHLY AMPLIFIED PATTERN ACROSS NORTH AMERICA...CONSISTING
OF TROUGHING OVER ALBERTA AND IDAHO...RIDGING FROM THE SOUTHERN
PLAINS INTO MANITOBA...AND TROUGHING FROM SOUTHEAST CANADA SOUTHWARD
ALONG THE EAST COAST OF THE U.S.. THE FORECAST AREA LIES ON THE
SUBSIDENT SIDE OF THE RIDGING...RESULTING IN HIGH PRESSURE AT THE
SURFACE WHICH EXISTS OVER WISCONSIN. 00Z SOUNDINGS FROM MPX...GRB
AND DVN DEPICTED A DRY AIRMASS WITH THIS HIGH PRESSURE AREA WITH
PRECIPITABLE WATER VALUES OF 0.7-0.8 INCHES OR 80-90 PERCENT OF
NORMAL. THE DRY AIRMASS HAS HELPED KEEP SKIES MOSTLY CLEAR OVERNIGHT
AND WITH LIGHT WINDS...TEMPERATURES HAVE DROPPED INTO THE UPPER 40S
TO UPPER 50S. MEANWHILE...TO THE WEST UNDER AND WEST OF THE UPPER
RIDGE AXIS...MOISTURE HAS BEEN GRADUALLY ADVECTING NORTHWARD THROUGH
THE PLAINS ON A 30-45 KT 850MB JET PER VWP DATA. GOES DERIVED
PRECIPITABLE WATER SHOWED VALUES OF 1-1.5 INCHES ACROSS MUCH OF THE
PLAINS...HIGHEST ACROSS SOUTH CENTRAL NEBRASKA AND NORTH CENTRAL KS.
THIS MAXIMA WAS ALSO CORRELATED WITH THE REMNANTS OF AN MCS THAT
INITIATED OFF THE FRONT RANGE IN COLORADO YESTERDAY AFTERNOON. ALONG
WITH THE INCREASED MOISTURE...00Z RAOBS SHOWED 850MB TEMPS OF 16-21C
FROM RAPID CITY TO OMAHA AND TOPEKA...QUITE A BIT WARMER COMPARED TO
THE 10-13C AROUND THE FORECAST AREA. ALONG THE GRADIENT OF THIS
TEMPERATURE DIFFERENCE...A NARROW LINE OF SHOWERS AND THUNDERSTORMS
HAS BROKE OUT OVER SOUTHWEST MN INTO WESTERN IA.

OVER THE NEXT 24 HOURS...THE UPPER RIDGE AXIS OVER THE PLAINS IS
PROGGED TO SHIFT EAST OVER THE FORECAST AREA. THIS IS IN RESPONSE TO
THE TROUGH OVER IDAHO AND ALBERTA EJECTING NORTHEAST...AS WELL AS
FORMING A DEEP CLOSED LOW CIRCULATION OVER CENTRAL SASKATCHEWAN.
WHAT THIS MEANS FOR THE FORECAST AREA IS ALL OF THAT WARMER 850MB
AIR AND HIGHER PRECIPITABLE WATER UNDER THE UPPER RIDGE WILL MOVE
TOWARDS US. GIVEN THE WARM ADVECTION PATTERN...EXPECT CONCERN FOR
PRECIPITATION TO INCREASE. IN ADDITION...CONVECTIVELY INDUCED
SHORTWAVES FROM CONVECTION COMING OFF THE ROCKIES AND THE PLAINS
THIS MORNING...AND THOSE THAT FIRE THIS AFTERNOON...WILL ALSO PLAY A
ROLE AS THEY HEAD NORTHEAST AROUND THE UPPER RIDGE.

FOR TODAY...GENERAL CONSENSUS FROM THE MODELS IS FOR INCREASING
310-315K ISENTROPIC LIFT AND 700MB MOISTURE TRANSPORT TO COME ACROSS
THE FORECAST AREA DURING THE AFTERNOON. ANTICIPATING AN
ALTOSTRATUS/ACCAS DECK TO FORM AS A RESULT AND OVERSPREAD MUCH OF
THE AREA. THIS CAN ALREADY BE SEEN ALONG THE DAKOTAS/MN BORDER WHERE
THOSE SHOWERS AND THUNDERSTORMS HAVE BEEN OCCURRING. HAVE
CONTINUED THE MENTION OF SOME LOW PROBABILITIES FOR PRECIPITATION
WEST OF THE MS RIVER EARLY THIS AFTERNOON TO ACCOUNT FOR THIS SHOWER
POTENTIAL.

LATE IN THE AFTERNOON...SOMETHING TO WATCH IS THE 14.00Z NAM
SCENARIO WHICH DEPICTS A LARGER AMOUNT OF CONVECTION OVER SOUTH
CENTRAL MN AND NORTH CENTRAL IA...CLIPPING FAR WESTERN PORTIONS OF
THE FORECAST AREA. THE GFS/ECMWF/REGIONAL CANADIAN ARE VERY
SIMILAR...THOUGH QPF VALUES ARE NOT NEARLY AS HIGH WHICH MAY BE A
RESULT OF MODEL RESOLUTION. THE SITUATION APPEARS TO BE A RESULT OF
INCREASING 700-850MB MOISTURE TRANSPORT...ON THE LEADING EDGE OF THE
HIGHER PRECIPITABLE WATER VALUES OF 1.5-1.8 INCHES PER RAP COMING
INTO WESTERN IA...CAPE OF 1000 J/KG OR SO THAT IS UNCAPPED LIFTED
FROM 725MB...AND A POSSIBLE RIGHT ENTRANCE REGION OF A JET STREAK
TRACKING SOUTHEAST THROUGH WISCONSIN. SHOULD THIS PAN OUT...GIVEN
THE HIGH PRECIPITABLE WATER...THESE STORMS WILL BE HEAVY RAIN
PRODUCERS.

NAM/GFS/ECMWF/REGIONAL CANADIAN MOISTURE TRANSPORT FIELDS FROM
925-700MB ARE ALL IN AGREEMENT THAT THE STREAM SHIFTS NORTHEAST
TONIGHT...FOLLOWING THE UPPER RIDGE AXIS. THUS...THINKING THE
CONVECTION THAT FIRES LATE THIS AFTERNOON SHOULD SLOWLY PROGRESS
EASTWARD THROUGH THE FORECAST AREA. ADDITIONALLY...IT APPEARS THERE
IS A SECOND SURGE OF MOISTURE TRANSPORT COMING UP OUT OF KS INTO
CENTRAL IA OVERNIGHT...LIKELY FIRING MORE CONVECTION ON ITS NOSE
FROM NORTH CENTRAL INTO EASTERN IA. THE ECMWF HAS BEEN EXTREMELY
CONSISTENT RUN TO RUN WITH THIS.

ALTHOUGH INSTABILITY IS ADVECTING TOWARDS US ON THIS MOISTURE
TRANSPORT...THE INSTABILITY IS TALL AND SKINNY. WITH WARM CLOUD
DEPTHS APPROACHING 14 KFT...THINKING HEAVY RAIN WOULD BE THE MAIN
SEVERE WEATHER CONCERN. ADDITIONALLY...THE 2-7KM SHEAR WHICH IS MORE
REPRESENTATIVE OF THE INSTABILITY USED BY THE STORMS...IS LESS THAN
30 KTS. SEE THE HYDROLOGY SECTION BELOW FOR MORE ON THE IMPACTS FROM
THE PRECIPITATION. MAIN THING TO NOTE HERE IS THAT GIVEN THE MOIST
SOILS OVER PORTIONS OF NORTHEAST IA AND SOUTHEAST MN...ANY HEAVY
RAIN MAY CAUSE FLASH FLOODING...ESPECIALLY IN FLOYD AND MITCHELL
COUNTIES IN IA. THEREFORE...HAVE ISSUED FLASH FLOOD WATCHES FOR THE
MOST CONCERNING AREAS.

850MB TEMPERATURES ARE PROGGED TO STAY BETWEEN 10-13C TODAY. WITH
INCREASING CLOUDS...TEMPERATURES SHOULD END UP NEAR OR A LITTLE
BELOW YESTERDAY HIGHS. WARMER NIGHT ON TAP AS HIGHER DEWPOINTS MOVE
IN ACCOMPANYING THE HIGHER PRECIPITABLE WATER.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 329 AM CDT FRI JUN 14 2013

SATURDAY THROUGH MONDAY...
MODELS ARE IN GOOD AGREEMENT FLATTENING THE UPPER RIDGE OVER THE
AREA ON SATURDAY...AGAIN RESULTING FROM THE EJECTING IDAHO TROUGH.
EVENTUALLY...THE CLOSED UPPER LOW THAT FORMED OVER SASKATCHEWAN ON
SATURDAY WILL APPROACH THE AREA...PROGGED TO DROP INTO CENTRAL MN AT
12Z MONDAY AS A SHORTWAVE TROUGH. THIS TROUGH MAY EVEN BEGIN TO
PHASE WITH THE GENERAL TROUGHING OVER SOUTHEAST CANADA AS INDICATED
BY THE 00Z ECMWF.

WITH THE FLOW TURNING ZONAL ON SATURDAY...THE MAIN MOISTURE
TRANSPORT STREAM SUPPORTING CONVECTION TONIGHT SHOULD PUSH OFF TO
THE EAST. THUS...LIKE CLIMATOLOGY FOR NOCTURNAL CONVECTION...
EXPECTING IT TO WEAKEN THROUGH THE MORNING HOURS. HOWEVER...OUTFLOW
BOUNDARIES FROM THE CONVECTION AND WHAT SHOULD BE A COLD FRONT AT
THE SURFACE ARE SUGGESTED TO LAY UP OVER SOUTHERN SECTIONS OVER THE
FORECAST AREA. GROWING INSTABILITY FROM ANY DAYTIME HEATING PLUS A
HUMID AIRMASS CHARACTERIZED BY DEWPOINTS IN THE MID-UPPER
60S...ALONG WITH PRECIPITABLE WATER VALUES OF 1.5-1.8 INCHES...
SHOULD PROMOTE RENEWED CONVECTION. AGAIN...HEAVY RAIN WOULD BE THE
MAIN CONCERN AND THUS THE FLASH FLOOD WATCH GOES THROUGH THE DAY
SATURDAY. OUTFLOWS FROM THIS NEW CONVECTION COMBINED WITH THE COLD
FRONT DROPPING SOUTHEAST SHOULD PUSH MUCH OF THE CONVECTION OUT OF
THE AREA SOMETIME DURING THE EVENING. EXACT TIMING STILL HARD TO PIN
DOWN. LEFT SOME LOW CHANCES IN AFTER MIDNIGHT INTO THE DAY SUNDAY
ACROSS FAR SOUTHERN SECTIONS OF THE AREA WITH THE 14.00Z GFS/ECMWF
SHOWING SOME LIGHT QPF LINGERING. HOWEVER...BELIEVE THESE MIGHT BE
ABLE TO BE REMOVED IN LATER FORECASTS WITH A WEAK RIDGE OF HIGH
PRESSURE IN PLACE. ATTENTION SUNDAY NIGHT AND MONDAY TURNS TO THE
TROUGHING DROPPING INTO MINNESOTA. DPVA AHEAD OF THE TROUGH PLUS A
SURGE OF 850-700MB MOISTURE TRANSPORT MAY BE ENOUGH TO KICK OFF SOME
SHOWER AND THUNDERSTORM ACTIVITY. HOWEVER...THE TROUGH IS COMING
THROUGH AT THE WRONG TIME OF DAY TO GET EXCITED ABOUT IT...AND
MOISTURE IS LACKING WITH PRECIPITABLE WATER VALUES MAYBE AROUND 1
INCH. THEREFORE...HAVE ONLY WENT WITH 20-40 PERCENT CHANCES ACROSS
THE FORECAST AREA. 13.12Z/14.00Z ECMWF EVEN SUGGESTS THE TROUGH AND
ITS ASSOCIATED COLD FRONT COULD COME THROUGH THE AREA MAINLY DRY.

WITH WARMER 850MB TEMPS ON SATURDAY...14-17C...AND MORE SUNSHINE ON
SUNDAY WITH SIMILAR READINGS...EXPECT TEMPERATURES TO RISE EACH DAY.
MOST LOCATIONS SHOULD SEE GOOD MIXING ON SUNDAY...BOOSTING HIGHS
INTO THE LOW TO MID 80S. COOLER READINGS ON TAP FOR MONDAY WITH THE
COLD FRONT COMING THROUGH. GENERALLY FOLLOWED A BLEND OF GUIDANCE
FOR HIGHS AND LOWS.

MONDAY NIGHT THROUGH THURSDAY...
VERY GOOD MODEL AGREEMENT EXISTS AMONGST THE 14.00Z
ECMWF/GFS/CANADIAN AND GFS ENSEMBLES ON THE UPPER LEVEL PATTERN.
MUCH OF THE PERIOD IS DOMINATED BY TROUGHING ALONG THE U.S. WEST
COAST...RIDGING FROM THE NORTHWEST TERRITORIES OF CANADA INTO THE
CENTRAL PLAINS...AND TROUGHING OVER EASTERN CANADA INTO THE GREAT
LAKES. THIS MEANS MOSTLY A NORTHWEST FLOW OF COOL AND DRY AIR FROM
CANADA. THUS...MUCH OF THE FORECAST IS DRY. THERE ARE INDICATIONS OF
A SHORTWAVE DROPPING THROUGH THE WESTERN GREAT LAKES ON
THURSDAY...BRINGING A COLD FRONT INTO THE AREA. HAVE INCLUDED 20
PERCENT CHANCES FOR SHOWERS AND THUNDERSTORMS NORTH OF I-90 FOR THIS
FEATURE. TEMPERATURE WISE...THE COOLEST DAY LOOKS TO BE TUESDAY WITH
HIGH PRESSURE OVERHEAD AND 850MB TEMPS OF 8-10C. AIRMASS
MODIFICATION THANKS TO THE STRONG JUNE SUN SHOULD HELP WARM
TEMPERATURES EACH DAY THEREAFTER.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 640 AM CDT THU JUN 13 2013

HIGH PRESSURE WILL CONTINUE TO MOVE EAST OF THE AREA TODAY...WITH
LOW PRESSURE AND A COLD FRONT MOVING INTO MN/IA TONIGHT. VFR
CONDITIONS THIS MORNING WILL GIVE WAY TO GRADUALLY LOWERING
CONDITIONS THIS AFTERNOON AND TONIGHT AS THE LOW/FRONT MOVE INTO THE
REGION. WITH A WIDE VARIETY OF CONVECTION OUTCOMES AMONG THE
FORECAST MODELS...NOT A LOT OF CONFIDENCE ON THE DETAILS OF SHRA/
TSRA EXPECTED TO SPREAD WEST TO EAST ACROSS THE AREA LATER THIS
AFTERNOON THRU TONIGHT.

RATHER THAN BURY THE KRST/KLSE TAFS IN LONG PERIODS OF TSRA OR IFR
CONDITIONS WHEN CONFIDENCE IS LOWER THAN AVERAGE...JUST CARRIED A
TREND CIGS/VSBYS GRADUALLY LOWERING INTO MVFR TONIGHT. CONTINUED A
PERIOD OF TSRA THIS EVENING WHEN THERE IS SOME MODEL CONSISTENCY FOR
STRONGER FORCING/INCREASED MOISTURE AND INSTABILITY TO BE OVER THE
AREA. SHRA/EMBEDDED TSRA LOOKING TO PERSIST OVERNIGHT BUT WITH THE
LOWER CONFIDENCE LEFT TSRA MENTION OUT OF THE OVERNIGHT HOURS FOR
NOW.

&&

.HYDROLOGY...LATE THIS AFTERNOON THROUGH SATURDAY
ISSUED AT 329 AM CDT FRI JUN 14 2013

VERY WET SOILS ACROSS MOWER AND FILLMORE COUNTIES IN MN ALONG WITH
MUCH OF NORTHEAST IOWA OVER THE PAST WEEK...AND REALLY THE PAST
COUPLE MONTHS...RESULT IN A HUGE CONCERN FOR FLOODING. THAT 1-2
INCHES OF RAINFALL THAT IMPACTED FLOYD COUNTY IA LATE WEDNESDAY...
MOSTLY IN A SHORT TIME PERIOD...CAUSED A LOT OF FLOODING ISSUES.

EXPECTING A BAND OF THUNDERSTORMS TO MOVE INTO MOWER THROUGH FLOYD
COUNTIES LATE THIS AFTERNOON...SLOWLY MOVING EAST THROUGH THE
EVENING. ADDITIONAL THUNDERSTORMS ARE FORECAST AFTER MIDNIGHT AND
THROUGH MUCH OF THE DAY SATURDAY SOUTH OF I-90. WITH PRECIPITABLE
WATER VALUES OF 1.5-1.8 INCHES AND WARM CLOUD DEPTHS OF 3500-4200
METERS ACCOMPANYING THESE THUNDERSTORMS...HEAVY RAIN IS LIKELY. WE
COULD BE LOOKING AT A WIDESPREAD 1-2 INCHES OF RAINFALL SOUTH OF
I-90...HIGHEST ACROSS NORTHEAST IOWA. LOCALLY HEAVIER RAINFALL IS
EASILY POSSIBLE.

GIVEN THE VERY WET SOILS AND POTENTIAL FOR HEAVY RAIN...HAVE ISSUED
A FLASH FLOOD WATCH FOR MOWER AND FILLMORE COUNTIES IN MN AND MUCH
OF NORTHEAST IA EXCEPT ALLAMAKEE. DEPENDING ON HOW CONVECTION
EVOLVES...THE WATCH MAY NEED TO BE EXPANDED EASTWARD...MOST LIKELY
INTO FAR SOUTHWEST WI.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...FLASH FLOOD WATCH FROM THIS AFTERNOON THROUGH SATURDAY EVENING
     FOR MNZ094-095.

IA...FLASH FLOOD WATCH FROM THIS AFTERNOON THROUGH SATURDAY EVENING
     FOR IAZ008>010-018-019-029-030.

&&

$$

SHORT TERM...AJ
LONG TERM....AJ
AVIATION.....RRS
HYDROLOGY....AJ