Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 030345
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1045 PM CDT TUE SEP 2 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 226 PM CDT TUE SEP 2 2014

FAIRLY BENIGN FIRST 12 HOURS OF THIS PERIOD WILL THEN BE FOLLOWED
BY A POTENTIALLY ACTIVE NEXT 24 HOURS.

HIGH PRES CENTERED OVER THE MID MISS RIVER VALLEY WITH ITS NRN
EXTENSION OVER THE UPR MISS RIVER VALLEY WILL SHIFT OFF TO THE E
OVERNIGHT. THIS WILL RESULT IN MAINLY HIGH CLOUD COVERAGE FOR THE
WFO MPX CWFA...THOUGH SOME ISOLD SHWRS/TSTMS MAY DRIFT EWD OVER
NRN MN AND STAY AWAY FROM CENTRAL-SRN MN. WINDS WILL BACK FROM W
TO SW AND S...ALLOWING ANOTHER SURGE OF WARM AND MOIST AIR TO THIS
REGION...BRINGING A BRIEF TASTE OF MID-SUMMER BACK TO THE REGION
FOR WED.

A POTENT TROF WILL MOVE ONSHORE THE PAC NW TNGT...SHIFTING ACRS
THE NRN ROCKIES SLOWLY WED INTO WED NIGHT. THIS UPR TROF WILL HELP
STRENGTHEN AND PUSH A LOW PRES CENTER EWD ACRS THE NRN PLAINS THRU
THE DAKOTAS WED AND WED NIGHT. ATTENDANT FROM THIS LOW PRES CENTER
WILL BE A TRAILING CDFNT OFF TO THE SW. THE MAIN CONCERN HOWEVER
WILL BE A NEWD MOVG WMFNT IN ADVANCE OF THE LOW PRES CENTER.
STRONG WAA MAY AID SOME SHWR/TSTM DEVELOPMENT OVER SWRN MN IN THE
MRNG BUT THIS WMFNT WILL CREATE MUCH WARMER/MOIST AIR TO THE S...
INCLUDING DEWPOINTS HITTING THE LWR 70S. STRONG SFC CONVERGENCE
COUPLED WITH DIFLUENT FLOW ALOFT WITH THE WMFNT SHOULD HELP BREAK
CAPPING AND PROMOTE STORM DEVELOPMENT STARTING IN THE AFTN OVER
CENTRAL MN WHICH SHOULD GRADUALLY TRANSLATE EWD THRU THE REST OF
THE AFTN INTO WED EVE. MODELS INDICATE HEIGHTENED DEEP LAYER SHEAR
WHICH MAY LEAD TO SUPERCELLULAR DEVELOPMENT...AND THIS IS HINTED
AT BY LARGE LOOPING HODOGRAPHS FROM THE GFS AND NAM. COVERAGE OF
THUNDERSTORMS LOOKS TO BE MUCH OF CENTRAL AND SOUTH-CENTRAL MN...
THOUGH THE BEST COVERAGE OF SEVERE WILL BE CENTRAL MN...EITHER
SIDE OF THE I-94 CORRIDOR...INCLUDING ALL OF THE TWIN CITIES
METRO. THE DEEP LIFT OF ANY TSTMS WILL MAKE LARGE HAIL A PRIMARY
HAZARD...PARTICULARLY WITH LOW WBZ HEIGHTS...BUT THE DEEP LAYER
SHEAR WILL ALSO BE CONDUCIVE TO PRODUCING ISOLD TORNADOES AS 0-3KM
HELICITIES ARE IN THE 350-500 M2/S2 RANGE. CONVECTIVE ACTIVITY
WHICH WILL BE STARTED BY THE NWD-MOVING WMFNT MAY BE HIGHLY
DEPENDENT ON HOW MUCH INSOLATION THAT CAN BE RECEIVED BETWEEN THE
ACTIVITY IN SWRN MN AND THE AFTN BREAKING OF THE CAP. CONVECTION
LOOKS TO CONTINUE THRU MUCH OF WED EVE THEN GRADUALLY DISSIPATE
AND SHIFT OFF TO THE E WED NIGHT. AS MENTIONED...THE SURGE OF
WARMER AIR WILL PUSH HIGHS INTO THE LOW- MID 80S...WHICH WHEN
COMBINED WITH DEWPOINTS ARND 70 WILL PUSH HEAT INDEX VALUES INTO
THE MID-UPR 80S. WITH THE CDFNT STILL TO THE W OF THE MPX CWFA
THRU WED NIGHT...THIS WILL MAKE FOR A WARM AND MUGGY WED NIGHT
PERIOD AS LOWS ONLY DROP TO THE UPR 60S TO LWR 70S.

ONE OTHER CONCERN IS HEAVY RAINFALL...PARTICULARLY FOR ERN MN INTO
WRN WI FOR WED AFTN AND EVE. FOR MUCH OF SE-E MN INTO WRN WI...THE
PAST 10 DAYS HAVE SEEN THOSE AREAS RECEIVE 4-9 INCHES OF RAIN...
MAKING FOR A VERY SATURATED GROUND. AN ADDITIONAL 1-2 INCHES...AND
POSSIBLY LOCALLY MORE...CANNOT BE RULED OUT FROM THIS SYSTEM...
ESPECIALLY AS PWATS RANGE 1.50-2.00 INCHES BY WED AFTN AND EVE
OVER ERN MN AND WRN WI. DIFFICULT TO PINPOINT EXACTLY WHERE THE
HEAVY RAIN WILL BE DUE TO THE CONVECTIVE NATURE OF THE PRECIP...
BUT HAVING FLOODING RAINS OVER ERN PORTIONS OF THE WFO MPX CWFA
CANNOT BE RULED OUT. IT WILL ALSO NEED TO BE MONITORED FOR HOW
HEAVY RAIN MAY IMPACT MAIN STEM RIVERS...PARTICULARLY THE CHIPPEWA
RIVER IN WRN WI.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 226 PM CDT TUE SEP 2 2014

OVERALL THE LONG TERM PORTION OF THE FORECAST WILL BE
CHARACTERIZED BY FALL-LIKE WEATHER...WITH SHOWER AND
THUNDERSTORM CHANCES BOOKENDING THE PERIOD ON THURSDAY AND
TUESDAY.

THURSDAY WILL START OFF WITH THE SURFACE LOW CIRCA 1000MB
BISECTING THE FORECAST AREA. NOCTURNAL CONVECTION MAY LINGER A
TAD DURING THE MORNING HOURS...BUT WILL LIKELY SEE A BREAK IN THE
ACTIVITY UNTIL THE PASSING COLD FRONT POTENTIALLY SPARKS
ADDITIONAL SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON. IT
CURRENTLY LOOKS TO BE THE MOST PROBABLE ALONG AND EAST OF THE
INTERSTATE 35 CORRIDOR. HOWEVER...THE STRONGER MID/UPPER FORCING
WILL BE DISPLACED TO THE NORTH...AND RESIDUAL CLOUDS/PRECIP COULD
LIMIT DESTABILIZATION /ESPECIALLY GIVEN THE PROGGED MID LEVEL
CAP/...SO THE THREAT FOR SEVERE STORMS IS MINIMAL.

FROM FRIDAY THROUGH THE WEEKEND...NEARLY ZONAL FLOW BECOMES
ESTABLISHED ACROSS THE NORTH CENTRAL CONUS...WITH A BROAD HIGH
PRESSURE RIDGE PREVAILING AT THE SURFACE. THIS WILL MEAN DRY
WEATHER WITH COOLER THAN NORMAL TEMPERATURES AND LIGHT
WINDS...QUITE FALL-LIKE WEATHER. HIGHS FROM FRIDAY THROUGH SUNDAY
WILL MAX OUT IN THE UPPER 60S TO LOWER 70S RANGE...WHILE LOWS DIP
INTO THE 40S AND LOWER 50S.

ON MONDAY...A TROUGH BEGINS TO DIG OVER THE PACIFIC
NORTHWEST...INDUCING HIGH PLAINS SURFACE CYCLOGENESIS. BOTH 02.12Z
ECMWF AND GFS MODELS INDICATE A WARM FRONT WILL LIFT INTO THE
AREA LATE MONDAY AND TUESDAY...AND FACILITATE FAIRLY DECENT
CHANCES FOR SHOWERS AND THUNDERSTORMS ON MONDAY EVENING AND
TUESDAY. HAVE INCLUDED HIGH CHANCE POPS FOR NOW UNTIL TIMING AND
FUTURE MODEL RUNS CAN PIN DOWN WHEN AND IF HIGHER POPS WOULD BE
JUSTIFIED.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1045 PM CDT TUE SEP 2 2014

LITTLE CHANGE IN THE OVERNIGHT SCENARIO OF ELEVATED INSTABILITY
SPREADING INTO WEST CENTRAL AND SOUTHWEST MN. PRETTY GOOD CHANCES
FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO REACH KRWF
BEFORE DAYBREAK AND THEN SPREAD NORTHEAST PAST KAXN AND KSTC
DURING THE MORNING. THERE IS A SMALL CHANCE THAT THIS ACTIVITY MAY
BRUSH THE TWIN CITIES AND ADJOINING AREAS OF WEST CENTRAL WI
DURING THE MID MORNING HOURS. LATEST MODEL DATA CONTINUES TO SHOW
CONCENTRATED CONVECTION DEVELOPING BY WEDNESDAY EVENING JUST TO
THE NORTH OF A LINE FROM KAXN THROUGH KSTC TO KRNH. THIS PUSHES
ESE DURING THE LATE EVENING HOURS. THEREFORE...INCLUDED PROB30
GROUPS FOR THUNDER AT ALL BUT KRWF WEDNESDAY EVENING. DUE TO THE
STRONG INFLOW OF LOW LEVEL MOISTURE ON WEDNESDAY...CONCERN IS
INCREASING THAT LOW MVFR CEILINGS MAY DEVELOP WEDNESDAY
NIGHT/EARLY THURSDAY MORNING. THIS IS AT OR BEYOND THE END OF THE
TAF WITH THE EXCEPTION OF KMSP WHICH GOES THROUGH 12Z. THIS WILL
NEED TO BE TACKLED WITH THE NEXT SET OF TAFS. IN ADDITION...MVFR
VISIBILITIES COULD OCCUR AS WELL. SOUTHERLY WINDS OVERNIGHT 5 TO
10 KNOTS INCREASING TO 10 TO 15 WITH GUSTS TO AROUND 20 KNOTS ON
WEDNESDAY.

KMSP...CONFIDENCE HIGH ON VFR CONDITIONS OVERNIGHT AND WEDNESDAY
MORNING WITH CHANCES INCREASING WEDNESDAY AFTERNOON AND NIGHT FOR
MVFR OR LOWER CONDITIONS. A FEW SHOWERS ARE POSSIBLE WEDNESDAY
MORNING WITH THUNDERSTORMS POSSIBLE WEDNESDAY EVENING...ALTHOUGH
CONFIDENCE IS HIGHER FOR THE STORMS TO THE NORTH OF THE AIRFIELD.

/OUTLOOK FOR KMSP/

THU...MVFR/IFR CIGS/VSBYS POSSIBLE EARLY THEN SCT TSRA IN THE
AFTN. WINDS S 10-15 KTS BCMG W.
FRI...VFR. WINDS NW 10 KTS.
SAT...VFR. WINDS W 4-8 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

SHORT TERM...JPC
LONG TERM...LS
AVIATION...RAH






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