Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 050927
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
427 AM CDT SAT SEP 5 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 420 AM CDT SAT SEP 5 2015

HOT AND HUMID WEATHER WILL BE THE MAIN STORY TODAY...WITH A HEAT
ADVISORY FOR HENNEPIN/RAMSEY COUNTIES WHERE EFFECTS OF
URBANIZATION WILL ADD SOME IMPACT TO THE HOT WEATHER THAT WILL
OBVIOUSLY BE ACROSS THE ENTIRE REGION TODAY. ONE CONCERN IS TEMPS
THIS PAST NIGHT HAVE NOT COOLED DOWN VERY MUCH...AND THE EFFECTS
OF HEAT ARE MORE LIKELY TO BE FELT IF IT DOES NOT COOL DOWN VERY
MUCH AT NIGHT. MAIN CONCERN OF COURSE IS DURING THE AFTERNOON AND
EARLY EVENING. INCOMING CLOUDS AND A FEW STORMS WILL MOVE THROUGH
THE METRO THE NEXT FEW HOURS. RESIDUAL CLOUDINESS WILL GRADUALLY
THIN OUT AND THERE SHOULD BE PLENTY OF SUN THIS AFTERNOON.

NEXT SHORT WAVE TO AFFECT THE AREA WILL ARRIVE LATER THIS
AFTERNOON AND MOSTLY AFFECT WEST CENTRAL INTO CENTRAL MN. THERE
IS SOME POTENTIAL MOST OF THIS WILL REMAIN WEST OF MN...BUT
CERTAINLY THERE IS A BETTER CHANCE OF IT SPREADING OR DEVELOPING
INTO WESTERN AND CENTRAL MN BY LATE AFTERNOON. INSTABILITY IS SUCH
THAT IT WILL NOT TAKE MUCH TO SET OFF A FEW STORMS. MORE
IMPRESSIVE WAVE ARRIVES TONIGHT...AND THIS IS WHEN HEAVY RAIN
COULD BE A THREAT TO MUCH OF OUR AREA. PRECIPITABLE WATER VALUES
MAY EXCEED 2 INCHES ACCORDING TO A COUPLE MODELS.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 420 AM CDT SAT SEP 5 2015

SUNDAY-MONDAY...SUN WILL START OUT WITH A NEGATIVELY-TILTED TROF
AXIS OVER THE NRN ROCKIES EXTENDING SSEWD FROM A CUTOFF LOW OVER
SRN ALBERTA PROVINCE WITH PRONOUNCED SW-NE UPR LVL FLOW OVER THE
NRN PLAINS INTO THE UPR MISS RIVER VALLEY. AT THE SFC...A LARGE
SFC LOW WILL BE CENTERED OVER THE DAKOTAS WITH A SWD-SAGGING
CDFNT. THE UPR LOW IS EXPECTED TO SWING A POIGNANT TROF AXIS
NEWD...HELPING KICK THE SFC LOW AND ASSOCIATED CDFNT ALSO TO THE E
AND NE. IN ADVANCE OF THIS FNT...LINGERING/ONGOING SHWRS AND TSTMS
IN THE MRNG LOOK TO DIMINISH AND SHIFT OFF TO THE E...ALLOWING FOR
SOME MIDDAY INSOLATION TO HELP HEIGHTEN AFTN INSTABILITY WHICH
WILL ALREADY BE OF CONCERN DUE TO PWATS LIKELY IN EXCESS OF 1.75
INCHES. SCATTERED TO NUMEROUS SHWRS/TSTMS ARE EXPECTED TO RE-
DEVELOP DURG THE AFTN AND EVE HRS ON SUN AND THE CONCERN IS FOR
STRONG TO SEVERE TSTMS TO DEVELOP DUE TO MLCAPES ARND 2500 J/KG
AND BULK SHEAR ARND 30 KT. THOUGH UPR LVL SUPPORT MAY NOT ENTIRELY
PHASE SFC FEATURES TO CREATE IDEAL SUPERCELLULAR TRAITS FOR
TSTMS...THE INSTABILITY IN PLACE AND STEEPER LAPSE RATES LOOK TO
BE CONDUCIVE TO THE CREATION OF MULTICELLULAR STORMS CAPABLE OF
LARGE HAIL AND/OR DAMAGING WINDS SUN AFTN AND EVE IN ADVANCE OF
THE CDFNT. THE UPR LOW WILL ROTATE ITSELF INTO SASKATCHEWAN
PROVINCE SUN EVE...QUICKLY DRAGGING THE SFC LOW INTO S-CENTRAL
CANADA IN THE PROCESS. HIGH PRES STEADILY MOVING IN BEHIND THE
CDFNT SUN NIGHT INTO MON MRNG WILL PUSH THE CDFNT INTO THE GRT
LKS...ALLOWING FOR A DRYING OUT PERIOD ON MON WITH A MUCH
COOLER/DRIER AIRMASS ORIGINATING FROM THE ROCKIES TO SETTLE INTO
THE UPR MISS RIVER VALLEY REGION. THE DIFFERENCE WILL CERTAINLY BE
FELT IN TERMS OF TEMPERATURES AND HUMIDITY LEVELS ON EITHER SIDE
OF THE FRONT...MEANING FROM SUNDAY TO MONDAY. HIGHS ON SUN HITTING
THE MID 80S /WITH HEAT INDEX VALUES INTO THE LWR 90S/ WILL DROP TO
THE MID- UPR 70S WITH MUCH LOWER HUMIDITY LEVELS.

TUESDAY-FRIDAY...THE COOLING TREND WILL CONTINUE THROUGH THE
UPCOMING POST-LABOR DAY WEEK AS UPR LVL FLOW REMAINS PROGRESSIVELY
E-W...NOT ALLOWING ANY SLY WARM AIR SURGES TO REACH THE UPR MISS
RIVER VALLEY. IN FACT...MODELS INDICATE A FEW WEAK SYSTEMS WILL
ENABLE COOLER CANADIAN AIR TO DROP INTO THE REGION IN SMALL
PIECES...MAKING FOR HIGH TEMPERATURES ONLY INTO THE 60S BY THE END
OF THE WEEK. AS FOR ANY POTENTIAL PRECIPITATION...THE BEST CHANCES
LOOK TO BE MON NIGHT INTO TUE...OWING TO THE WESTERN PARTS OF THE
WEEKEND CDFNT LIFTING SLIGHTLY N TO BRING ISOLD/SCTD SHOWERS...AND
THEN WED NIGHT INTO THU...AS A CLIPPER-TYPE LOW PRES CENTER DRIFTS
THROUGH THE REGION ORIGINATING FROM WRN CANADA. NEITHER SYSTEM
LOOKS TO BRING ANY SIGNIFICANT AMT OF RAIN NOR STRONG/SEVERE
TSTMS...JUST PASSING SHWRS WITH POSSIBLY ISOLD TSTMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1045 PM CDT FRI SEP 4 2015

SHRA/TSRA ARE FADING LATE THIS EVENING ACROSS EASTERN MN AND
CONFIDENCE ON NEW DEVELOPMENT IN WESTERN MN AFTER MIDNIGHT IS
WANING. HENCE...CONCERN IS CHANGING FROM ADDITIONAL SHRA/TSRA TO
ONE OF MVFR OR LOWER CEILINGS/VSBYS IN STRATUS AND FOG DUE TO THE
VERY MOIST LEVEL CONDITIONS. NOT TOTALLY SOLD ON THIS IDEA AS WELL
AS USUALLY ONE DOMINATES OVER THE OTHER. WITH SOME WIND TONIGHT
ACROSS THE MN TAF SITES...VSBY ISSUES DURING THE LATE NIGHT HOURS
MAY DOMINATE OVER CEILINGS. AN EXCEPTION IS KEAU WHERE LIGHT
WINDS WILL PREVAIL WITH LESS THAN MVFR CEILINGS AND VSBYS
DEVELOPING. THE NEXT SHRA/TSRA CHANCES RETURN TO KAXN SATURDAY
EVENING. SOUTHERLY WINDS WILL BE ON THE INCREASE SATURDAY
AFTERNOON WITH 12-18 KNOTS GUSTING TO 20-25 KNOTS.

KMSP...THE AIRFIELD MAY ESCAPE WITH ONLY A NARROW BAND OF LIGHT
SHOWERS PASSING THROUGH IN THE 06Z-07Z PERIOD.
THEREAFTER...THINKING HAS CHANGED TO A DRY FORECAST. SOME MVFR
VSBY EXPECTED TOWARDS DAYBREAK ALONG WITH A SMALL CHANCE FOR AN
MVFR CEILING. THE MOST SIGNIFICANT WIND REMAINS SATURDAY AFTERNOON
WITH SOUTH WINDS 15 KNOTS GUSTING 22 KNOTS.

/OUTLOOK FOR KMSP/
SUN...VFR WITH MVFR/TSRA LIKELY AT TIMES. WIND SW AT 15G20KT.
MON...MVFR/TSRA POSSIBLE EARLY. THEN VFR. WIND NE AT 5-10KT.
TUE...VFR. WIND NNW AT 10KT.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...HEAT ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS EVENING
     FOR MNZ060-062.

WI...NONE.
&&

$$

SHORT TERM...TDK
LONG TERM...JPC
AVIATION...RAH


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