Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 302308
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
608 PM CDT SAT AUG 30 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 242 PM CDT SAT AUG 30 2014

WEAK CONVERGENCE ZONE ALONG WITH MLCAPES ARND 500 J/KG HAD
GENERATED A FEW SHRA ACROSS SOUTHERN MN TODAY. BOUNDARY LAYER
MOISTURE REMAINS ROBUST...SO CLDS HAVE BEEN SLOW TO ERODE DURING
THE TYPICAL DIURNAL AFTN TIME FRAME. AS WINDS REMAIN WEAK AND
CYCLONIC CONTINUES DURING THE LATE AFTN/EARLY EVENING...THESE LOW
CLDS MAY HOLD ON UNTIL LATER TONIGHT. ONCE WINDS SHIFT TO THE
SOUTHEAST AHEAD OF A DEEPENING AREA OF LOW PRESSURE ACROSS SD
LATER TONIGHT...ANY LOW CLDS SHOULD QUICKLY MOVE OUT OR DISSIPATE.
SOME FOG MAY DEVELOP ACROSS WC WI AS THIS AREA WILL BE LAST TO SEE
BOUNDARY LAYER MOISTURE RETREAT ALONG WITH WEAK MIXING IN THE
BOUNDARY LAYER.

A STRONG JET STREAM MOVING INTO THE PACIFIC NW TODAY WILL SET THE
STAGE FOR A VERY ACTIVE SUNDAY AFTN/EVENING ACROSS THE UPPER
MIDWEST. BOTH AMPLE MOISTURE AND INCREASING SHEAR VALUES...ALONG A
DEEPENING AREA OF LOW PRESSURE ACROSS THE NORTHERN PLAINS...SHOULD
LEAD TO WIDESPREAD THUNDERSTORMS DEVELOPMENT BY THE LATE AFTN
AHEAD OF A COLD FRONT. THERE REMAINS SOME DIFFERENCES IN THE
MODELS IN TERMS OF STRENGTH OF THE LLJ ALONG WITH THE UPPER LEVEL
JET CORE TO CONCLUDE WIDESPREAD SEVERE WX ACROSS THE UPPER
MIDWEST. THE UPPER JET CORE...WHICH IS EXPECTED TO BECOME A JET
COUPLET FROM THE NORTHERN AND SOUTHERN JET STREAMS...SHOULD LEAD
TO STRONG UPPER LEVEL DIFFLUENCE BY SUNDAY EVENING. AGAIN...MODELS
HAVE SOME DIFFERENCES IN THIS JET COUPLET WHICH LEADS TO
DIFFERENCES IN TIMING AND PLACEMENT OF THE HIGHER QPF AMTS. IN
ADDITION...RESIDUAL CLD CVR FROM DECAYING MORNING TSRA COULD LIMIT
FULL AFTN ISOLATION. THE BEST AREA FOR BOTH JET STRUCTURE/HIGHER
INSTABILITY AND SHEAR VALUES REMAIN ACROSS IOWA. FAR SC/SW MN
COULD ALSO BE IN THIS AREA OF HIGHER SVR WX POTENTIAL. LATER
SHIFTS WILL NEED MONITOR STRENGTH OF THIS JET ALONG WITH TSRA
DEVELOPMENT TOWARD MORNING.

IN ADDITION TO THE SVR WX THREAT...PWATS VALUES RISE INTO THE 1.5"
RANGE. IF ANY TSRA BEGIN TO TRAIN OR BACK BUILD...FLASH FLOODING
IS POSSIBLE...ESPECIALLY ONCE THE LLJ INCREASES DURING THE EVENING
HRS.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 242 PM CDT SAT AUG 30 2014

POTENT CDFNT WILL HAVE SHIFTED THROUGH MUCH OF THE MPX CWFA BY
DAYBREAK MON MRNG...WITH IT PROGRESSING JUST BARELY INTO WRN WI
AND SERN MN. SOME LINGERING SHWRS/TSTMS WILL LIKELY BE ONGOING IN
FAR ERN PORTIONS OF THE CWFA AT THE START OF THIS PERIOD BUT
STRENGTH WILL BE FAIRLY WEAK...MEANING THAT ANY SEVERE POTENTIAL
WILL HAVE BEEN TAPPED BY THIS POINT. SUPPORTING THIS FACT IS THAT
THE UPPER LEVEL TROF AXIS WILL BE E OF THE CWFA AND THE FRONT WILL
BE RATHER STRETCHED OUT BETWEEN THE MAIN LOW PRES CENTER OVER WRN
ONTARIO PROVINCE AND A SECONDARY LOW PRES CENTER OVER KS. HIGH
PRES WILL THEN NUDGE IN FROM THE CENTRAL PLAINS WHILE FLOW ALOFT
IS MAINLY ZONAL WNW-ESE. A FEW BUCKLES IN THE FLOW WITHIN A
PERSISTENTLY DEEP MOIST ATMOS MAY PRODUCE ISOLD SHWRS FROM TIME TO
TIME LATE MON THRU MUCH OF WED. THIS AREA OF HIGH PRES WILL SHIFT
E INTO THE MID-MISS RIVER VALLEY THEN OHIO VALLEY BY WED MRNG...
ALLOWING FOR A WARMER AND MORE MOIST SLY RETURN FLOW TO DEVELOP BY
MIDDAY WED.

THE ADDITIONAL MOISTURE WILL PRECEDE THE ARRIVAL OF A SLOW-MOVING
LOW PRES CENTER FROM THE NRN ROCKIES WED NIGHT. THIS LOW WILL
STALL OUT OVER THE NRN PLAINS...HELPING SET UP A SFC FRONTAL
BOUNDARY EXTENDING FROM WRN MN ACRS THE ROCKIES. THIS BOUNDARY
WILL ACT AS A LOW-LEVEL CONFLUENT ZONE AND AID IN PRECIPITATION
DEVELOPMENT THU THROUGH SAT. NOT LOOKING FOR A LOT IN THE WAY OF
QPF NOR STORM STRENGTH...BUT FINDING SOLID DRY TIME WILL BE
DIFFICULT DUE TO SCATTERED SHOWERS FOR MUCH OF THE LATTER PORTION
OF THE WEEK. CANNOT SAY ANY DAY WILL BE A WASHOUT ATTM...BUT ALSO
HARD TO PINPOINT ONE TIMEFRAME OVER ANOTHER FOR BEST TIMING OF
PRECIPITATION.

TEMPERATURES LOOK TO GO ON A SLOW WARMING TREND THRU THE
WORKWEEK...CLIMBING THROUGH THE MID-UPR 70S INTO THE LWR 80S BY
FRI. HOWEVER...THERE WILL BE PLENTY OF CLOUD/RAIN COMPLICATIONS
WHICH ON SMALL SCALES MAY CREATE SOME VARIETY WITH MAX/MIN TEMPS.
BY SAT... THIS LOW PRES COMPLEX WILL SHIFT S AND E OF THE MPX
CWFA...ALLOWING FOR A COOLING OF TEMPERATURES FOR NEXT WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 557 PM CDT SAT AUG 30 2014

MVFR CIGS REMAIN AT SEVERAL LOCATIONS THIS EVENING. EXPECT THEY
WILL BREAK OUT IN AN HOUR OR TWO. WILL LIKELY SEE SOME CLOUD REMAIN
FOR A TIME INTO THE NIGH...WITH BEST SHOT OF MVFR REMAINING
LONGEST INTO KEAU. EVENING SHRA ALONG WEAKENING TROUGH OVER
WESTERN METRO...SHOULD WEAKEN FURTHER THROUGH 03Z. WILL MENTION
VCSH AT KMSP UNTIL THEN.  CONFIDENCE NOT HIGH ON OVERALL
STRATUS/FOG DEVELOPMENT AGAIN OVERNIGHT. IF IT WAS GOING TO
OCCUR...LOOKS BEST INTO THE WEST CENTRAL WI. WILL MAINTAIN LIFR
FCST AT KEAU FOR NOW. THEN MODELS SUGGEST SOME FORM OF CONVECTION
MOVING INTO WESTERN MN MAINLY AFTER 10Z. WILL MENTION SOME VCSH AT
KAXN FOR NOW. INCREASING THUNDER THREAT TO THE WEST SUNDAY
AFTERNOON AND THEN INTO EASTERN MN BY 00Z MON. LIGHT WINDS WILL
BECOME MORE SOUTHEAST AND THEN SOUTH AND INCREASE/GUSTY THROUGH
17Z-18Z SUNDAY AS PRESSURE GRADIENT INCREASES AHEAD OF COLD FRONT.

KMSP...
SHOWERS WEST OF THE FIELD ARE EXPECTED TO WEAKEN THROUGH 03Z. WILL
HOLD ONTO VCSH FOR NOW. OUTFLOW BOUNDARY MAY AFFECT THE AREA AND
SWITCH WINDS BRIEFLY MORE WEST/SOUTHWEST. OVERALL WILL HOLD ONTO
SOME CLOUDS OVERNIGHT...BUT SHOULD REMAIN VFR UNTIL LATE SUNDAY
AFTERNOON S THUNDER THREAT ARRIVES. LOOKS BEST AFTER 23Z SUNDAY.
EXPECT WINDS TO INCREASE/BECOME GUSTY AND MORE SE-S DIRECTION INTO
SUNDAY AHEAD OF THE FRONT.

/OUTLOOK FOR KMSP/
SUN EVENING...MVFR/IFR CIGS IN +TSRA LIKELY. WNDS SSE AT 10-20
KTS. MON...MVFR/TSRA ENDING EARLY. VFR BY AFTN WINDS W 10-15 KTS.
TUE...VFR. WINDS WSW 10 KTS.

&&

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

$$

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






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