Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 021736
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1236 PM CDT SUN AUG 2 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT SUN AUG 2 2015

TODAY AND TONIGHT...SFC ANALYSIS DEPICTS A SFC LOW OVER ERN SD THIS
MRNG WITH A WMFNT EXTENDING SEWD AND A CDFNT EXTENDING SWWD FROM
THIS CENTER. ISOLD CONVECTION OVERNIGHT DUE TO CONVERGENCE INVOF THE
WMFNT AND A LOCALIZED MIDLVL JET EVIDENT ON WV IMAGERY HAS SHIFTED
OFF TO THE E AND WEAKENED...RESULTING IN A MAINLY DRY START TO THE
DAY. KMPX RADAR SHOWS A FEW STRONG STORMS WITHIN MOSTLY WEAK
ECHOES DRIVING SEWD FROM NERN ND AND NRN MN. ASIDE FROM THE
STRONGER STORMS...MUCH OF THIS IS NOT REACHING THE GROUND WITHIN
THE WFO MPX CWFA. HOWEVER...AS THE DAY PROGRESSES...DEEP MIXING
WILL STILL PROMOTE 30-40 KT OF BULK SHEAR HIGHLIGHTED OVER FAR ERN
MN INTO WRN WI THIS AFTN AND EVE. BEST INSTABILITY AND FORCING
ALOFT WILL BE WELL SE OF THE CWFA...BUT STILL BEING IN THE WARM
SECTOR OF THIS SYSTEM WILL ALLOW FOR SOME SBCAPE TO DEVELOP WHICH
WILL MAKE FOR SOME ISOLD- SCTD TSTM DEVELOPMENT LATER TDA. HAVE
MAINTAINED SLGT-LOW CHC POPS IN ERN PORTIONS OF THE CWFA TO
ACCOUNT FOR THIS. AS THE CDFNT SWEEPS SEWD ACRS THE REGION
TDA...THIS WILL BRING AN END TO ANY AND ALL PRECIP BY THIS EVE.
COOLER/DRIER HIGH PRES WILL THEN BEGIN TO MAKE INROADS TO THE
REGION TNGT...STARTING A DRYING OUT PERIOD FOR THE REGION GOING
INTO THE FIRST HALF OF THE WEEK.

TEMPERATURES WILL STILL RUN WARM IN ADVANCE OF THE CDFNT TDA. HIGHS
WILL GENERALLY RANGE 80-90 DEGREES NORTH-TO-SOUTH ACRS THE CWFA TDA.
WITH LATE AFTN TIMING OF THE COLD FROPA...THIS WILL START CAA THAT
WILL BE FELT FOR TNGT. LOWS TNGT INTO EARLY MON MRNG WILL FALL TO
THE 50S ACRS THE CWFA...WHICH WILL BE ABOUT 10 DEGREES COOLER THAN
LOWS EXPERIENCED THIS MRNG.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 400 AM CDT SUN AUG 2 2015

THE MAIN FEATURE OF NOTE IN THE LONG TERM PERIOD CONTINUES TO BE
THE LARGE UPPER LOW OVER HUDSON BAY. BY TOMORROW MORNING...THIS
FEATURE WILL BEGIN SAGGING SOUTH TOWARD THE UPPER GREAT LAKES
REGION. THE LONGWAVE TROUGH ASSOCIATED WITH THE LOW WILL BE IN
PLACE INTO AT LEAST WEDNESDAY...MEANING MONDAY AND TUESDAY WE WILL
REMAIN IN RELATIVELY COOL NORTHWEST FLOW...WITH LITTLE CLOUD COVER
OWING TO THE DRY AIR MASS COMING IN FROM CANADA. HIGH TEMPERATURES
WILL GENERALLY BE IN THE MID TO UPPER 70S ALL WEEK...SLIGHTLY
COOLER THAN NORMAL FOR THIS TIME OF YEAR.

IT LOOKS LIKE WE HAVE ONE DECENT CHANCE OF PRECIPITATION IN THE
LONG TERM PERIOD...AND THAT COMES ON WEDNESDAY INTO WEDNESDAY
NIGHT. THE AFOREMENTIONED UPPER LOW WILL BEGIN DRIFTING VERY
SLOWLY EAST BY WEDNESDAY AS A SHORTWAVE TROUGH ADVANCES EAST OVER
THE ALONG THE LONGWAVE RIDGE OVER THE WESTERN CONUS. AT THIS
TIME...THIS FEATURE LOOKS TO HAVE THE INGREDIENTS FOR A DECENT
RAINFALL MAKER. AS THE TROUGH PUSHED INTO MN...A CYCLONICALLY
CURVED JET STREAK AROUND THE LONG WAVE TROUGH TO OUR NORTHEAST
WILL PLACE THE UPPER MIDWEST IN A FAVORABLE AREA OF UPPER LEVEL
DIVERGENCE. IN ADDITION...STRONG THETA-E ADVECTION IS FORECAST
WEDNESDAY- WEDNESDAY NIGHT AS LOW LEVEL WINDS TURN SOUTHERLY ON
THE LEADING EDGE OF THE WAVE...AND WE MAKE A GULF MOISTURE
CONNECTION WITH PRECIPITABLE WATER VALUES INCREASING TO GREATER
THAN 1.5 INCHES. AT THE SURFACE...A FRONTAL BOUNDARY WILL LIFT
NORTH INTO THE UPPER MIDWEST WITH INCREASING SURFACE DEW POINTS AS
WELL. BEST LI VALUES BECOME NEGATIVE FOR MOST OF SOUTHERN MN BY
WEDNESDAY AFTERNOON...SO THERE IS SOME INSTABILITY TO WORK WITH AS
WELL. BEING 4 DAYS AWAY HOWEVER...CONFIDENCE IN THE PLACEMENT OF
POTENTIAL RAINFALL IS NOT HIGH...ESPECIALLY GIVEN THE VARIOUS
SOLUTIONS OFFERED BY THE DETERMINISTIC GUIDANCE...AND THE FACT
THAT THE HUDSON BAY UPPER LOW COULD WREAK HAVOC ON THE ENTIRE
UPPER AIR PATTERN. SO...DECIDED TO STICK WITH THE ALLBLEND
GUIDANCE FOR THIS PERIOD WHICH FOR NOW SUGGESTS CHANCE POPS.

SLIGHT CHANCE POPS LITTER THE FORECAST LATE IN THE WEEK AS A WEAK
FRONTAL BOUNDARY PUSHES INTO WESTERN MN...BUT AT THIS TIME THERE
IS LITTLE AGREEMENT IN SEEING ORGANIZED PRECIPITATION DURING THAT
PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1236 PM CDT SUN AUG 2 2015

A COLD FRONT IS MOVING ACROSS THE TWIN CITIES AT TAF ISSUANCE AND WILL
BE EAST AND SOUTH OF KEAU BY LATE THIS AFTERNOON. CONVECTION THIS
MORNING HAS YIELDED A SMALL BKN BAND OF MVFR CEILINGS...WHICH WILL
MOVE PAST KRNH AND KMSP BY 20Z. ADDITIONAL SHRA/TSRA DEVELOPMENT
IS LIKELY EAST OF THE FRONT THIS AFTERNOON WITH KEAU HAVING THE
BEST CHANCE. USED A 2 HOUR WINDOW FROM 20Z-22Z TO CAPTURE THE
SHRA/TSRA CHANCES. NW WINDS ARE INCREASING IN THE WAKE OF THE
FRONT WITH A FAIRLY STRONG RISE/FALL PRESSURE COUPLET ACROSS MN
AND WI. NAM/RAP PROFILE DATA SUGGESTS 15-18 KNOT WINDS THIS
AFTERNOON WITH TOP OF THE CHANNEL AROUND 28 KNOTS. HENCE...WIND
SPEEDS/GUSTS PUSHED UP A BIT IN THIS TAF CYCLE.

KMSP...BKN OF NEAR MVFR CEILINGS (035) WILL SKIM THE AIRFIELD
EARLY IN THE TAF PERIOD. SCT-BKN 045-050 FOR THE REST OF THE
AFTERNOON. RAISED SUSTAINED WINDS TO 18 KNOTS FOR THE MID TO LATE
AFTERNOON PERIOD ALONG WITH GUSTS TO 27 KNOTS.

/OUTLOOK FOR KMSP/
TUE...VFR. WIND NW 5-10 KTS.
WED...VFR. CHC MVFR SHRA/TSRA. WIND E 5-10 KTS.
THU...VFR. CHC MVFR SHRA/TSRA. WIND E 10 KTS.

&&

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

$$

SHORT TERM...JPC
LONG TERM...SPD
AVIATION...RAH



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