Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 201259
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
759 AM CDT SAT SEP 20 2014

.UPDATE...
ISSUED AT 732 AM CDT SAT SEP 20 2014

UPDATED TO INCLUDE 12Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 239 AM CDT SAT SEP 20 2014

CURRENT SFC ANALYSIS SHOWS A WMFNT PUSHING INTO SWRN WI WITH ITS
ASSOCIATED TRAILING CDFNT OVER CENTRAL-SWRN MN. WITHIN THIS WARM
SECTOR...BANDS OF RAIN/TSTMS BROKE OUT OVER FAR SRN MN INTO NRN
IA...NOW MOVING INTO FAR SERN MN/SWRN WI/NE IA. THIS LINE WILL
CONTINUE TO PUSH OFF TO THE E AS THE CDFNT SHIFTS ACRS CENTRAL-SRN
MN. THERE WILL NOT BE MUCH OF AN AIRMASS CHANGE WITH THIS FNT...SO
LOWS WILL ONLY DROP TO THE UPR 50S TO MID 60S THIS MRNG. THE CDFNT
WILL ACT TO TEMPORARILY STABILIZE THE ATMOS IN CONJUNCTION WITH A
LONGWAVE TROUGH AXIS ALOFT ALSO SHIFTING TO THE E. HOWEVER...THE
FOCUS WILL THEN TURN TO A SHORTWAVE DISTURBANCE WHICH SHOWS UP
NICELY ON WV IMAGERY THIS MRNG DRIVING SEWD OVER CENTRAL ALBERTA
PROVINCE ON ITS WAY TO NRN MN AND WRN WI BY THIS EVE. A COMPACT
SFC LOW PRES REFLECTION WILL ALSO BE ASSOCIATED WITH THIS UPR LVL
DISTURBANCE...ARRIVING WITHIN A STILL FAIRLY DEEP MOISTURE COLUMN
DUE TO THE CDFNT FOR THIS MORNING FAILING TO REMOVE MUCH OF THE
AMBIENT MOISTURE. MODELS STILL DEPICT AN 80-100 KT UPR LVL JET MAX
MOVING INTO WRN MN BY MIDDAY...HELPING ENHANCE LIFT OVER NRN AND
CENTRAL PORTION OF THE STATE IN ITS EXIT REGION. THE ACCELERATING
STRONG DYNAMICS...ALONG WITH MORE FAVORABLE LAPSE RATES DUE TO
COOLING AIR ARRIVING ALOFT...SHOULD OVERCOME ANY MOISTURE
DEFICIENCIES TO PROMOTE LINEAR TSTM DEVELOPMENT STARTING IN NRN MN
THEN SHIFTING SWD INTO CENTRAL-SRN MN LATER TODAY. STILL SOME
MINOR TIMING ISSUES...BUT THE BULK OF ANY PRECIP ACTIVITY OVER MN
WILL OCCUR IN THE AFTN HOURS FROM W TO E COINCIDENT WITH THE
MOVING JET STREAK ALOFT. THE SEVERE WX NATURE WILL BE LARGE
HAIL...GIVEN PROLONGED ENOUGH UPDRAFTS...AND DAMAGING WINDS...
GIVEN THE EXPECTED MCS DEVELOPMENT OF THE TSTMS. AS THE POTENT
SHORTWAVE ALOFT DRIVES INTO WRN MN...IT WILL SHIFT THE EXPECTED
LINE OF TSTMS ACRS THE CWFA BY THE MID-EVE HOURS...ALLOWING FOR A
GRADUAL CLEARING FROM W TO E THIS EVENING THRU TONIGHT. THERE MAY
BE SOME LINGERING SHWRS AFTER MIDNIGHT IN FAR ERN PORTIONS OF THE
WFO MPX CWFA BUT THE BULK OF THE CWFA SHOULD BE DRY BY THEN.
RESIDUAL MILD/MOIST AIR WILL KEEP TEMPS ABOVE NORMAL THRU TDA WITH
HIGHS HITTING THE LOW-MID 70S GENERALLY. AS THE AFTN-EVE COMPACT
LOW PRES SYSTEM BLAZES THRU THE AREA THIS EVE...THIS WILL BE A
MORE EFFECTIVE STARTER OF CAA AS COOLER/DRIER CANADIAN HIGH
PRESSURE DROPS INTO THE REGION AND FLOW ALOFT IS DECIDEDLY NW.
THIS COMBINATION OF CLEARING SKIES AND CAA WILL FORCE LOW TEMPS
TNGT INTO THE UPR 40S AND LWR 50S.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 239 AM CDT SAT SEP 20 2014

SUNDAY MARKS THE BEGINNING OF A MOSTLY DRY AND WARM PATTERN THAT
WILL TAKE US THROUGH NEXT WEEK.

EASTERN MN AND WESTERN WI WILL STILL BE UNDER THE INFLUENCE OF
SHORT WAVE ENERGY ON THE BACKSIDE OF THE SYNOPTIC-SCALE TROUGH
THAT SHOULD BE CENTERED OVER LAKE MICHIGAN BY 12Z SUNDAY. THERE IS
GOOD MODEL CONSENSUS ON THE TIMING AND LOCATION OF THE LONG WAVE
PATTERN. THIS LIKELY MEANS WESTERN WI AND POSSIBLY EASTERN MN WILL
HANG ONTO CLOUD COVER AND LIGHT RAIN SHOWERS BETWEEN 12-18Z
SUNDAY. THE WESTERN FORECAST AREA WILL REMAIN DRY AND EVEN AREAS
IN WEST CENTRAL WI COULD SEE IMPROVEMENT DURING THE AFTERNOON.
HIGH AMPLITUDE TROUGH-RIDGE PATTERN SETS UP MON/TUE IN AREAS TO
OUR WEST. IT WILL CONTINUE TO BE WELL ABOVE NORMAL IN THE WESTERN
CONUS SUNDAY AND MONDAY. THE RIDGE SLIDES EAST ACROSS THE NORTHERN
PLAINS AND UPPER MISSISSIPPI RIVER VALLEY ON TUESDAY. THE LOW
LEVEL JET INCREASES OUT OF THE SOUTHWEST AND WARMER AIR WILL FIND
ITS WAY INTO MN/WI. THE UPPER TROUGH THAT`S FORECAST TO ARRIVE
HERE ON WEDNESDAY IS CURRENTLY JUST KIND OF HANGING OUT OFF THE
COAST OF CALIFORNIA THIS MORNING...CUT OFF FROM THE MAIN JET
CURRENTLY OVERHEAD. THIS LOW GETS KICKED OUT OF THE WEST COAST IN
A COUPLE DAYS AND HEADS THIS WAY AS A MUCH STRONGER TROUGH
ADVANCES ACROSS THE NORTHEAST PACIFIC. WE HAVE CHANCE POPS IN THE
FORECAST TUE-WED...BUT NO REAL STRONG FEELING FOR EXACT TIMING OR
AMOUNTS AT THIS POINT. THESE CUTOFF LOWS ARE ALMOST ALWAYS SLOWER
THAN WHAT THE NUMERICAL GUIDANCE SUGGESTS...BUT AT LEAST THERE IS
A STRONG WAVE IN THE PACIFIC TO DO THE MOVING. OTHERWISE...NEXT
WEEK WILL FEATURE MUCH ABOVE NORMAL TEMPS WITH PLENTY OF MIDDLE
TO UPPER 70S TO GO AROUND. WOULDN`T BE SURPRISED TO SEE SOME SITES
HIT 80 AT SOME POINT LATE NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 732 AM CDT SAT SEP 20 2014

ASIDE FROM PATCHY LOW CEILINGS DROPPING S AS SHOWN ON IR FOG
SATELLITE IMAGERY PRODUCT...AFFECTING PARTS OF CENTRAL MN AND WRN
WI...SKIES ARE MOSTLY CLEAR. ANY LOW CEILINGS WILL BURN OFF BY
14Z-15Z. THE FOCUS THEN TURNS TO THE INCOMING UPPER LEVEL
SHORTWAVE RACING IN FROM CENTRAL ALBERTA INTO WRN MN FOR THIS
AFTN. BANDS OF SHWRS/TSTMS ARE EXPECTED TO FORM IN NWRN MN AND
DRIVE ESEWD ACRS MN INTO WI LATE THIS AFTN INTO THE EARLY EVE HRS.
HAVE TRIED TO TIME THE PRECIP INTO EACH TAF SITE FROM W TO E...
BUT DIFFERENT SHORT-TERM MODELS DEPICT SLIGHT DIFFERENCES IN
TIMING SO HAVE USED A 3-4 HR WINDOW FOR THE SITES AS OPPOSED TO A
2-HR WINDOW. STRONG WIND GUSTS MAY ACCOMPANY THE CONVECTION.
TSTMS LIKELY TO EXIT ALL TAF SITES BY 01Z-02Z BUT ERN MN AND WRN
WI MAY BE SUSCEPTIBLE TO COLD POOL -SHRA IN THE WAKE OF THE TSTMS
FOR A FEW HRS...WITH ALL PRECIP EXPECTED TO END BY 06Z.

KMSP...VFR THRU THIS AFTN...THEN CHCS INCRS FOR MVFR-TO-IFR CONDS
THIS AFTN INTO THIS EVE WITH TSTMS LIKELY TO PUSH THROUGH THE
AREA. MAIN REDUCTION EXPECTED TO BE DUE TO VSBY IN HVY RAIN... BUT
CIGS LOWER THAN ADVERTISED ARE POSSIBLE. -SHRA TO CONTINUE INTO
THE EVE HRS...THEN CONDS REMAIN VFR OVERNIGHT THRU MIDDAY SUNDAY.

/OUTLOOK FOR KMSP/
SUN...VFR. WINDS NW 10-15 KTS.
MON...VFR. WINDS W 5-10 KTS.
TUE...VFR. WINDS SE 5-10 KTS.

&&

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

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...CLF
AVIATION...JPC






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