Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 291957
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
257 PM CDT FRI AUG 29 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 256 PM CDT FRI AUG 29 2014

TWO AREAS OF CONVECTION ACROSS THE UPPER MIDWEST AND CENTRAL
PLAINS WILL LIKELY CONGEAL INTO A LINE OR BROKEN LINE ACROSS
EC/SC MN BY LATE THIS AFTN/EARLY EVENING. THIS IS BASED ON THE
CURRENT SFC TROUGH ACROSS CENTRAL MN AND THE UPPER LOW ACROSS
WESTERN IOWA SLOWLY MOVING E/NE ACROSS THE UPPER MIDWEST/WESTERN
GREAT LAKES REGION BY LATE TONIGHT. THE UPPER LOW ACROSS WESTERN
IOWA HAS A FAIRLY STRONG JET STREAK MOVING NORTHWARD WHICH HAS
ENHANCED AN AREA OF UPPER LEVEL DIVERGENCE IN SW MN SINCE 1 PM
/HINT INCREASING CONVECTION/. HIGHER INSTABILITY ACROSS WESTERN
WI...AS SUNSHINE OCCURRED...HAS ALSO ALLOWED FOR SCATTERED TSRA TO
DEVELOP ACROSS THIS AREA. WX/POPS REFLECT THE CURRENT TREND OF THE
HRRR/HOPWRF AS NUMEROUS SHRA/TSRA ARE EXPECTED TO DEVELOP ACROSS
EC MN IN THE NEXT FEW HRS. AS THE UPPER LOW FINALLY SHEARS OUT AND
MOVE TO THE NE...THE AREA OF SHRA/TSRA SHOULD MOVE INTO WC WI BY
MID/LATE EVENING. A PERIOD OF HEAVY RAINFALL IS LIKELY IN EC/SC MN
DURING THE LATE AFTN/EARLY EVENING BEFORE TAPERING OFF AFT SUNSET.
ELSEWHERE...LIMITED INSTABILITY WILL LIKELY HOLD OFF ON WIDESPREAD
SHRA/TSRA...WITH ONLY ISOLD COVERAGE AT BEST THRU SUNSET. SFC
WINDS BEHIND THE SFC TROUGH ARE FAIRLY WEAK WHICH MAY ALLOW FOR
FOG/LOW CLDS TO FORM OVERNIGHT WHERE THE RAINFALL ENDED. SATURDAY
WILL BE THE DRIEST FOR THE WEEKEND AS WEAK HIGH PRESSURE SETTLES
ACROSS THE REGION.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 256 PM CDT FRI AUG 29 2014

SATURDAY NIGHT THROUGH SUNDAY NIGHT...SFC HIGH PRES WITH NARROW
RIDGING ALOFT WILL CROSS OVER THE REGION IN TANDEM SAT NIGHT...
ALLOWING FOR A FAIRLY BENIGN 12-HOUR PERIOD WITH MOCLR SKIES AHEAD
OF WHAT MAY BE A FAIRLY ACTIVE LATE SUNDAY THRU SUNDAY NIGHT
PERIOD.

A VERY BROAD LONGWAVE TROUGH OVER THE NRN PACIFIC WILL MOVE
ONSHORE THE WRN CONUS SAT AND IT IS THIS TROUGH THAT WILL WORK
WITH A DEVELOPING AREA OF LOW PRES OFF THE NRN ROCKIES. A POTENT
AXIS OFF THE LONGWAVE TROUGH WILL SWING OVER THE ROCKIES SUN WHILE
THE MAIN TROUGH CENTERS ITSELF OVER CENTRAL CANADA. THIS TROUGH
WILL GRAB THE DEVELOPING LOW PRES CENTER OVER THE NRN ROCKIES AND
SHOVE IT NEWD FROM NRN WYOMING ACRS THE DAKOTAS INTO NRN MN BY SUN
EVE...DRAGGING A CDFNT INTO CENTRAL-SRN MN. A WMFNT ASSOCIATED
WITH THIS SYSTEM WILL RAPIDLY SHIFT NWD DURG THE DAY ON
SUN...ALLOWING A STRONG SURGE OF BOTH WARMER AIR /MID-80S FOR
HIGHS/ AND LOW-MID LVL MOISTURE INTO THE REGION...HELPING INCRS
PWATS /TO OVER 1.25 INCHES/ AND INSTABILITY PARAMETERS /MUCAPES
OVER 2500 J/KG/. EVEN ANY ONGOING MORNING CONVECTION WILL LIFT OFF
TO THE N...MAKING THE MORNING INTO EARLY AFTN POTENTIALLY DEVOID
OF PRECIP...SETTING THE STAGE FOR LATER IN THE DAY. STRONG HEIGHT
FALLS COMBINED WITH HEIGHTENED DEEP LAYER SHEAR WILL ALLOW FOR
ELEVATED CONVECTION TO QUICKLY BECOME SFC-BASED IN THE MID-TO-LATE
AFTN HOURS. BEST TIMING FOR THE POTENTIAL FOR SEVERE WX LOOKS TO
BE 21Z-00Z IN WRN MN...THEN TRANSITIONING INTO ERN MN INTO WRN WI
00Z-06Z. THE CURRENT THINKING IS SEVERAL CLUSTERS OF STORMS WILL
BECOME QUITE ORGANIZED... POSSIBLY EVEN SHOWING CHARACTERISTICS OF
A MCS OR QLCS WHEN LATE DAY AND EVENING JETTING INCRS. THIS EVENT
LOOKS TO FEATURE THE HAZARDS OF LARGE HAIL AND DAMAGING
WINDS...NOT SO MUCH TORNADIC CHARACTERISTICS. THE CDFNT LOOKS TO
CLEAR MN AND MUCH OF WRN WI BY DAYBREAK MON MRNG...BRINGING THIS
EVENT TO A CLOSE WHILE FAIRLY ZONAL FLOW SETS UP ALOFT.

MONDAY-THURSDAY...A WEAK QUASI-STNRY FRONT WILL DEVELOP S OF THE
AREA BY MID-WEEK... GIVING MORE OF A FOCUS FOR ORGANIZED
SHOWERS/TSTMS WED INTO THU...AS OPPOSED TO MON-TUE WHICH WILL BE
MORE OF THE ISOLD POP-UP VARIETY WITH LITTLE STRENGTH. IMPROVED
COVERAGE FOR STORMS IS EXPECTED WED-THU WITH THE ADDITION OF THE
FRONT AND SEVERAL WEAK SHORTWAVE BUCKLES WITHIN THE PREVAILING
ZONAL FLOW...BUT MAINLY SHOWERS WITH POSSIBLY A FEW TSTMS. TEMPS
COOL DOWN ON THE BACKSIDE OF THE DEPARTING CDFNT MON...WITH HIGHS
BACK INTO THE MID-70S BEFORE WARMING BACK INTO THE LOWER 80S BY
LATE WEEK AS WARMER AIR SURGES N WITH THE DEVELOPMENT OF THE
LINGERING SFC BOUNDARY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1153 AM CDT FRI AUG 29 2014

TWO AREAS OF CONVECTION ACROSS THE PLAINS AND UPPER MIDWEST WILL
LEAD TO OCCASIONAL SHRA/TSRA FOR MOST OF MPX TAF AREA THRU THE
AFTN WITH THE EXCEPTION OF KAXN WHERE THE SFC TROUGH HAS MOVED
THRU AS OF 17Z. AN UPPER LOW WHICH IS CURRENTLY NEAR KOMA WILL
LIKELY HOLD THE SFC TROUGH ACROSS CENTRAL MN THIS AFTN AS THE
UPPER LOW MOVES NE ACROSS NC IA/SE MN. THIS WILL LEAD TO THE
CONTINUATION OF SHRA/TSRA FROM KRWF TO KSTC...EASTWARD TOWARD EC
MN/WC WI THRU THE AFTN. TIMING OF HEAVIER TSRA WILL BE PROBLEMATIC
SO WILL CONTINUE WITH TEMPO PERIOD FOR MOST AREAS WITH 2SM +TSRA.
ALTHOUGH VSBYS WILL BE REDUCED TO LESS THAN 1SM AT TIMES...IT
SHOULD BE VERY SHORT AND LAST 5 TO 10 MINS. MORE MODERATE
SHRA/TSRA WILL MEAN PERIODS OF 2-3SM WITH A PREDOMINATE 4-6SM IN
LIGHTER ACTIVITY. MOST OF THE SHRA/TSRA SHOULD MOVE OFF INTO WC WI
BY 23-01Z...WITH IFR/LIFR CIGS/VSBYS DEVELOPING IN THE WAKE OF
THIS SYSTEM. WINDS WILL BE FROM THE S/SW AHEAD OF THE SFC
TROUGH...WITH A WEAK WEST/NW FLOW BEHIND IT THRU THIS EVENING. A
MORE NW/NNW IS EXPECTED BY SATURDAY MORNING ARND 5-10 KTS.

KMSP...

TWO AREAS OF CONVECTION WILL LEAD TO A CONTINUED TREND OF SHRA AND
EMBEDDED TSRA THRU THE AFTN. NOT UNTIL THE SFC TROUGH MOVES EAST
OF THE AREA ALONG WITH THE UPPER LOW...WILL CHC/S OF SHRA/TSRA
DIMINISH. TIMING OF THE HEAVIER TSRA REMAINS QUESTIONABLE...SO
WILL CONTINUE WITH A TEMPO OF 2SM +TSRA DURING THE AFTN. A BRIEF
PERIOD OF VSBYS LESS THAN 1SM IS LIKELY...BUT SHOULD ONLY LAST 5
TO 10 MINS. MOST OF THE STEADIER SHRA SHOULD MOVE OUT OF MSP
TERMINAL AREA BY 1-3Z WITH IFR/LIFR CIGS/VSBYS DEVELOPING
OVERNIGHT. VFR CONDS ARE NOT EXPECTED UNTIL AFT 18Z ON SATURDAY.
WINDS WILL BE GENERALLY FROM THE SW THIS AFTN ARND 5-10 KTS...THEN
WEAKEN AND VEER WEST TO NORTHWEST OVERNIGHT.

/OUTLOOK FOR KMSP/

SAT AFTN...VFR. WIND NNE AT 5-10 KTS.
SUN...VFR WITH MVFR/TSRA LATE. WINDS SSE AT 10-20 KTS.
MON...MVFR/TSRA ENDING EARLY. VFR BY AFTN WINDS W 10-15KTS.

&&

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

$$

SHORT TERM...JLT
LONG TERM...JPC
AVIATION...JLT





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