Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KMPX 022007
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
307 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 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1258 PM CDT TUE SEP 2 2014

RATHER BENIGN START TO THE 02/18Z TAFS WITH LOTS OF SUNSHINE AND
ONLY MINIMAL CLOUD COVER. THAT BEING SAID...EARLIER RUNS OF
HRRR/HOPWRF LOCAL MODELS INDICATED SOME WEAK MIDLVL PERTURBATIONS
ON THE BACKSIDE OF DEPARTING HIGH PRES ALONG WITH SOME KINKS IN
THE WNW-ESE FLOW ALOFT. THIS COULD BE ENOUGH TO SPARK SOME ISOLD
SHWR/TSTM DEVELOPMENT LATER THIS AFTN INTO THE EARLY EVE...BUT
CHANCES AND COVERAGE ARE TOO LOW FOR INCLUSION SO HAVE OMITTED IT
ATTM BUT WILL CONTINUE TO MONITOR.

GOING THROUGH TNGT AND INTO WED...A WMFNT WILL SLOWLY LIFT N OVER
THE CENTRAL PLAINS ON INTO THE UPR MISS RIVER VALLEY. SOME ISOLD
TO SCTRD -SHRA LOOK TO DEVELOP OVERNIGHT OVER MAINLY SWRN MN...
BUT THEN THE BULK OF THE ACTION WILL TRANSITION TO CENTRAL MN BY
LATE DAY WED...LIKELY PAST THE TIME PERIOD OF THIS 18Z TAF.
NEVERTHELESS...THERE ARE SOME INDICATIONS THAT THE PRECIP MAY
OCCUR FASTER THAN WHAT IS BEING ADVERTISED SO IF ANYTHING... THE
TIMING OF THE PRECIP MAY NEED TO BE ADJUSTED EARLIER. AS FOR TSTM
POTENTIAL...TSTM PARAMETERS ARE FAIRLY WEAK SO HAVE OMITTED TSTM
MENTION ATTM.

KMSP...FAIRLY HIGH CONFIDENCE IN VFR CONDS THROUGH THE OVERNIGHT
HRS. LOW CHCS OF ISOLD SHWR/TSTM THIS AFTN...BUT AM GROWING MORE
CONFIDENT THAT PRECIP SHOULD EVADE MSP. GOING THRU TMRW...CHCS DO
INCRS OF SEEING SHWRS/TSTMS IN AND AROUND MSP...ESPECIALLY LATE
AFTN INTO THE EARLY EVE. AM NOT THINKING TSTMS WOULD IMPACT MSP BY
00Z SO HAVE OMITTED IT ATTM...BUT THERE IS STILL SOME POTENTIAL
THAT FLIGHT CONDITION REDUCING PRECIP COULD IMPACT MSP PRIOR TO
00Z TMRW EVE.

/OUTLOOK FOR KMSP/
WED...VFR. CHC MVFR/TSRA. WINDS S 10-15 KTS.
THU...VFR. CHC MVFR/TSRA LATE. WINDS S 10-15 KTS BCMG W LATE.
FRI...VFR. WINDS NW 10 KNOTS.


&&

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

$$

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





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.