Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 222359
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
659 PM CDT FRI MAY 22 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 220 PM CDT FRI MAY 22 2015

THE SHORT TERM PERIOD STARTS OUT BENIGN...THEN SHOWER AND
THUNDERSTORM CHANCES INCREASE ON SATURDAY.

NEARLY A PICTURE-PERFECT DAY OUT THERE...WITH SUNNY SKIES...MILD
TEMPERATURES...LOW DEWPOINTS...AND LIGHT WINDS. NOT MUCH IN THE WAY
OF CHANGE IS EXPECTED FOR TONIGHT...WITH THE EXCEPTION OF INCREASING
CLOUDS STREAMING IN AHEAD OF AN ADVANCING MID LEVEL TROUGH OVER THE
FOUR CORNERS REGION. LOW LEVEL WARM/MOISTURE ADVECTION WILL ENSUE
LOCALLY AHEAD OF THIS FEATURE ON SATURDAY. THE RESULT WILL LIKELY
BE VIRGA INITIALLY...ALTHOUGH LIFT/MOISTURE WILL BE SLIGHTLY MORE
PLENTIFUL ACROSS SOUTHWEST/WEST CENTRAL MN...SO HAVE INCLUDED
20-30 POPS THERE. GIVEN THE INCREASE IN CLOUD COVER AND SLIGHT
REDUCTION IN 925-850MB TEMPS...EXPECT SATURDAY HIGH TEMPS TO BE
SLIGHTLY COOLER THAN OBSERVED FRIDAY. ANTICIPATE HIGHS RANGING
FROM THE MID/UPPER 60S IN WEST CENTRAL MN...TO AROUND 70 DEGREES
IN EAST CENTRAL MN AND WEST CENTRAL WI.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 220 PM CDT FRI MAY 22 2015

MAIN CONCERN IN THE EXTENDED REVOLVES AROUND PRECIP CHANCES...AS
ARGUMENTS FOR INCLUDING THUNDERSTORM CHANCES IN PARTS OF THE AREA
EXIST FOR JUST ABOUT EVERY PERIOD FROM SATURDAY NIGHT THROUGH FRIDAY.

DURING THE EXTENDED...THE ONE UPPER AIR FEATURE THAT WILL BE WITH US
THROUGH AT LEAST THE NEXT WEEK IS THE BLOCKING HIGH OVER WRN
CANADA...WHICH BOTH THE ECMWF/GFS KEEP IN PLACE. THIS WILL CONTINUE
TO LEAD TO A PRONOUNCED SPLIT IN THE FLOW ACROSS NOAM. THE MAIN
THING THAT CHANGES WITH THE UPPER AIR PATTERN IS THIS WEEKEND
PROGRESSES IS AN UPPER RIDGE WILL BUILD ACROSS THE SE CONUS WHICH
WILL PUSH THE SRN STREAM BACK OUR DIRECTION...HENCE PRECIPITATION
CHANCES RETURNING. THIS WEEKEND...THE TROUGH CURRENTLY ACROSS THE
ROCKIES WILL LIFT NORTH ACROSS THE PLAINS...WITH SW TO S UPPER FLOW
PREVAILING ACROSS THE UPPER MS RIVER VALLEY. AS WE GO THROUGH NEXT
WEEK...THE LOSS OF THE WRN TROUGH WILL ALLOW THE FLOW TO BECOME MORE
ZONAL...BUT WE WILL FIND OURSELVES IN SAID ZONAL FLOW WHILE A FRONT
MEANDERS AROUND THE NRN CONUS...HENCE THE ENDLESS CHANCES FOR
THUNDERSTORMS.

FOR THE WEEKEND...THE GFS/NAM HAVE COME AROUND TO WHAT THE ECMWF HAS
BEEN SHOWING FOR DAYS THROUGH SUNDAY...BUT SIGNIFICANT DIFFERENCES
ARE STILL SHOWING UP SUNDAY NIGHT ON. DURING THE WEEKEND...ALL
GUIDANCE SHOWS THE TROUGH CURRENTLY ACROSS THE 4 CORNERS REGION
FILLING AS IT SLOWLY LIFTS TOWARD NW ONTARIO BY TUESDAY. THE MAIN
DIFFERENCE CONTINUES TO BE ONE OF STRENGTH OF THE WAVE. THE GFS/NAM
MAINTAIN A CLOSED LOW MUCH LONGER THAN THE ECMWF AND THEREFORE A
MUCH STRONGER SYSTEM COME MONDAY. BOTH THE GFS/NAM SHOW A SFC LOW
OVER THE DAKOTAS DEEPENING ON MONDAY TO UNDER 1000 MB AS A COLD
FRONT SURGES ACROSS MN/WI. CIPS SEVERE WEATHER ANALOGS WOULD SUPPORT
A GOOD DEAL OF SEVERE WEATHER ACROSS THE AREA ON MONDAY IF THE 22.12
GFS SCENARIO PLAYED OUT. THE ECMWF ON THE OTHER HAND HAS A MORE OPEN
WAVE MOVING ACROSS THE REGION SUNDAY NIGHT...WITH THE DEEPENING SFC
LOW OVER THE DAKOTAS ON MONDAY IN THE GFS/NAM REPLACED BY A RATHER
INNOCUOUS LOW MOVING ACROSS WRN WI SUNDAY NIGHT WHILE MONDAY WOULD
FEATURE SCATTERED THUNDERSTORMS AS THE UPPER COLD POOL MOVES
OVERHEAD. FOR POP GRIDS THIS WEEKEND...CHANGES MADE WERE TO SLOW
DOWN ARRIVAL OF HIGH POPS SATURDAY NIGHT...WHILE ALLOWING
CATEGORICAL POPS TO MOVE JUST TO AROUND SE MN AS THE LLJ GOES FROM
CENTRAL IA TOWARD SRN WI SATURDAY NIGHT. SUNDAY AFTERNOON/EVENING
STILL FEATURES THE HIGHEST POPS AS THE THETA-E ADVECTION INCREASES
IN RESPONSE TO A WARM FRONT MOVING NORTH ACROSS IOWA...WITH MONDAY
FEATURING AREA WIDE LIKELY POPS. FROM THE SEVERE WEATHER
POTENTIAL...ACTIVITY SUNDAY/SUNDAY EVENING WILL BE ELEVATED...SO
WOULD ONLY OFFER A HAIL THREAT...THOUGH DEEP LAYER SHEAR AND MUCAPE
BOTH LOOK LOW ENOUGH TO LIMIT THAT POTENTIAL. MONDAY HAS THE
POTENTIAL FOR SEVERE WEATHER...IF...AND THATS A BIG IF...THE GFS/NAM
FORECAST WERE TO VERIFY. AS FOR A PREFERRED SOLUTION FOR THIS
WEEKEND IT IS THE ECMWF. THIS WHOLE WEEK WE HAVE SIMPLY BEEN
WATCHING THE GFS/NAM START OFF ONE DIRECTION...ONLY TO SLOWLY WORK
TOWARD THE ECMWF WITH TIME /SEE THE MAINLY DRY SATURDAY THE GFS/NAM
ARE NOW SHOWING...BUT THE ECMWF HAS BEEN SHOWING FOR DAYS/.

FOR THE REST OF NEXT WEEK...UNCERTAINTY IS THE NAME OF THE GAME AS
WE GET INTO A MORE ZONAL PATTERN. TIMING OF SUBTLE WAVES WITHIN THE
FLOW WILL DETERMINE THUNDERSTORM POTENTIAL...AND THIS FAR
OUT...THERE IS A GOOD AMOUNT OF MODEL SPREAD FOR WHEN EACH
INDIVIDUAL WAVE MOVES THROUGH. ONE ADVANTAGE THESE WAVE WILL HAVE IS
THAT WE NEVER LOOK TO DRIVE THE FRONTAL BOUNDARY VERY FAR SOUTH OF
MN/WI...SO THERE WILL BE AMPLE MOISTURE FOR THEM TO WORK WITH. THE
RESULT OF THIS PATTERN IN THE GRIDS WAS FOR SLIGHT CHANCE/CHANCE
POPS TO LITTER THE FORECAST FROM TUESDAY THROUGH FRIDAY. FOR WHAT IS
WORTH...THE 22.12 GUIDANCE WOULD HAVE US MAINLY DRY TUE/WED...WITH
THUNDERSTORM CHANCES INCREASING AGAIN THU/FRI AS THE NEXT FRONTAL
BOUNDARY MOVES INTO THE REGION.

WHAT THIS PATTERN MEANS FOR TEMPERATURES IS THAT IT WILL BE
MILD...WITH RIGHT AT OR SLIGHTLY ABOVE NORMAL HIGHS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 658 PM CDT FRI MAY 22 2015

MAINTAINED VFR CONDITIONS THROUGH THE TAF PERIOD. CEILINGS
GRADUALLY LOWERING OVERNIGHT WITH BKN-OVC050-060 ON
SATURDAY...ESPECIALLY FROM THE AFTERNOON ONWARD. GUIDANCE
CONTINUES TO SLOW THE ONSET OF RAIN WITH ONLY KAXN AND KRWF
HAVING A MENTION OF VCSH IN THE AFTERNOON. LIGHT AND VARIABLE
WINDS OVERNIGHT BECOMING SOUTH 6-10 KNOTS BY LATE SATURDAY MORNING.

KMSP...VFR THROUGH THE PERIOD WITH BKN-OVC050-060 DEVELOPING BY
AFTERNOON. KEPT THE MENTION OF SHRA OUT OF THIS TAF. ANY ORGANIZED
SHRA DOES NOT LOOK LIKELY UNTIL LATE SATURDAY NIGHT.

/OUTLOOK FOR KMSP/
SUN...VFR. SCT SHRA/TSRA WITH MVFR OR LOWER CONDITIONS.
      WINDS SE 10 KTS.
MON...VFR. SCT SHRA/TSRA WITH MVFR OR LOWER CONDITIONS.
      WINDS S 10 KTS.
TUE...VFR. CHC SHRA/-TSRA. WINDS SW 10 KTS.

&&

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

$$

SHORT TERM...LS
LONG TERM...MPG
AVIATION...RAH



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