Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 121720
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1220 PM CDT FRI SEP 12 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 319 AM CDT FRI SEP 12 2014

TWO ISSUES FOR TODAY/TONIGHT...

FIRST...HOW MUCH...IF ANY RAINFALL IS EXPECTED BASED ON CAA AND LOW
LEVELS MOISTURE LIMITED. THE SECOND CONCERN IS WHETHER SKIES CLEAR
AND CALM WINDS DEVELOP FOR THE POTENTIAL OF WIDESPREAD FROST.

MAIN MID & UPPER LEVEL FORCING FOR THE POTENTIAL OF WIDESPREAD
RAINFALL IS EXPECTED TO REMAIN IN IOWA AND SOUTHERN WI TODAY/THIS
EVENING. THIS IS BASED ON THE UPPER JET CORE AND ASSOCIATED RIGHT
ENTRANCE REGION. ONLY THE FAR SOUTHERN PART OF MN AND PARTS OF WC
WI...SOUTH OF I-94 WILL SEE ANY TYPE OF DEEP MOISTURE TO CONSIDER
HIGHER THAN SLIGHT CHC. HOWEVER...THE COMBINATION OF STEEP LOW LEVEL
LAPSE RATES AND MOISTURE AT MID LEVELS...ISOLATED SHOWERS MAY
DEVELOP ANYWHERE IN MPX CWA. BUT COVERAGE WILL BE LOW.

THE UPPER LEVEL SYSTEM THAT CONTINUES THE CHC/S OF RAINFALL TODAY
SOUTH OF THE MN/IA BORDER...WILL QUICKLY MOVE OFF TO THE EAST BY
THIS EVENING. CLOUDS SHOULD QUICKLY MOVE OUT BY MIDNIGHT...SETTING
THE STAGE FOR FROST. THE CONCERNS FOR WIDESPREAD FROST ARE RETURN
FLOW IN WC MN AFTER MIDNIGHT...AND RESIDUAL CLOUD COVER IN WC WI.
WILL CONTINUE TO ADVERTISE PATCHY TO AREAS OF FROST IN THE WX
GRIDS...BUT HOLD OFF ON AN ADVISORY THIS MORNING. LATER SHIFTS CAN
RE-EVALUATE THE WINDS AND CLOUD COVER.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 319 AM CDT FRI SEP 12 2014

THE SURFACE RIDGE OF HIGH PRESSURE THAT IS SPONSORING COOL
TEMPERATURES AND THE THREAT FOR AN EARLY FROST WILL SLIP
SOUTHEAST OF THE AREA ON SATURDAY...AS THE MID/UPPER TROUGH OVER
SOUTHERN SASKATCHEWAN/MANITOBA SAGS INTO THE NORTH CENTRAL CONUS.
THIS WILL BRING MULTIPLE CHANCES FOR RAIN SHOWERS BETWEEN LATE
SUNDAY AND MONDAY. THE FIRST WILL OCCUR OVER WEST CENTRAL WI ON
SUNDAY AFTERNOON AS MID LEVEL FORCING INTERACTS WITH THE TAIL OF
THE NORTHWESTERN ONTARIO SURFACE TROUGH. THE SECOND /AND MORE
PROBABLE/ WINDOW WILL BE ON SUNDAY NIGHT INTO MONDAY AS A
CENTRAL PLAINS SURFACE TROUGH NOSES INTO NORTHERN IOWA AND
COMBINES WITH A DECENT POCKET OF 700-600MB FRONTOGENESIS/OMEGA
SETTING UP FROM SOUTHERN MN TOWARD WEST CENTRAL WI. THE ONE CAVEAT
IS THAT MODEL AGREEMENT IS POOR WITH RESPECT TO HOW FAR NORTH THE
TROUGH AND PRECIPITATION WILL EXIST. FOR RIGHT NOW WILL TAILOR
POPS TOWARD THE CONSENSUS SOLUTION...WHICH KEEPS THE PRECIP
FARTHER SOUTH THAN THE 12.00Z NAM AND NORTH OF THE 12.00Z ECMWF
AND GEM SOLUTIONS /THAT KEEP THE BULK OF THE PRECIPITATION TO THE
SOUTH IN IOWA/.

AFTER MONDAY...THE REMAINDER OF THE LONG TERM FORECAST IS
DRY...WITH MUCH OF IT DOMINATED BY ANOTHER SURFACE RIDGE AND MID
LEVELS FEATURING TROUGHING NEAR HUDSON BAY AND RIDGING OVER THE
WEST. TEMPERATURES WILL REMAIN ON THE COOL SIDE OF CLIMATOLOGICAL
NORMALS THROUGH THE UPCOMING WEEK...WITH HIGHS IN THE 60S AND LOWS
MOSTLY FROM THE LOWER 40S TO LOWER 50S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1219 PM CDT FRI SEP 12 2014

DEFORMATION PRECIP THAT MOVED ACROSS SRN MN THIS MORNING NOW EAST OF
THE MPX TERMINALS...BUT COLD POOL ALOFT IS ALLOWING FOR SCATTERED
SHOWERS TO DEVELOP. COVERAGE WILL NOT BE ALL THAT IMPRESSIVE...SO
ADDED VCSH TO ALL TERMINALS THROUGH 00Z...AS THAT SHOULD ADEQUATELY
COVER THE THREAT. WE HAVE A LARGE TEMP/DEWP SPREAD SO CIGS WILL
REMAIN VFR...WITH RAINFALL INTENSITY ALSO WEAK ENOUGH TO KEEP VSBYS
MAINLY VFR AS WELL. WILL SEE SKIES CLEAR OUT OVERNIGHT...WITH SW
WINDS SLOWLY OVERTAKING THE AREA FROM WEST TO EAST TONIGHT THROUGH
SAT MORNING.

KMSP...SHOWERS ARE BEGINNING TO DEVELOP ACROSS THE AREA...MAY SEE A
BRIEF RAIN SHOWER AT THE FIELD...BUT WILL BE OF MINIMAL IMPACT. NOT
MUCH HAPPENING OTHERWISE WITH THIS TAF...WITH HIGH CONFIDENCE IN VFR
CONDS PREVAILING...WITH WINDS BY THIS TIME SAT TURNING TO THE SSW.

/OUTLOOK FOR KMSP/

SUN...VFR. WINDS SW 10 KTS.
MON...VFR. WINDS NW 10 KTS.
TUE...VFR. WINDS SW 5 KTS.

&&

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

$$

SHORT TERM...JLT
LONG TERM...LS
AVIATION...MPG





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