Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 271047
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
547 AM CDT SAT SEP 27 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 404 AM CDT SAT SEP 27 2014

UPPER LOW CENTERED NEAR DES MOINES THIS MORNING WILL BE MAIN
HEADACHE IN THE SHORT TERM. THIS LOW IS STILL WELL DETACHED FROM
THE MAIN FLOW...WHICH IS STILL WELL NORTH OF THE INTERNATIONAL
BORDER IN CANADA EAST OF THE ROCKIES. THIS WAVE WILL BE TAKING THE
SCENIC ROUTE ACROSS THE PLAINS...COMING UP INTO SRN MN THIS
AFTERNOON...BEFORE HEADING BACK TO THE SOUTHEAST TONIGHT INTO
SUNDAY. PERSISTENT MOIST SRLY FLOW HAS ALLOWED FOR PLENTY OF ACCAS
TO DEVELOP FROM IOWA UP INTO MN...WITH A COUPLE OF THUNDERSTORMS
PERSISTING THROUGH THE NIGHT UNDER THE CENTER OF THE LOW SOUTH OF
I-80 IN CENTRAL IA. REGIONAL RADAR IMAGERY THE PAST COUPLE OF HOURS
HAS SHOWED LIGHT ISOLATED RETURNS PULSING UP AND DOWN FROM NRN IA
INTO SRN MN. WE EXPECT THIS TREND OF ISOLATED SHOWERS TO CONTINUE
THROUGH THE DAY AS THE UPPER LOW SLOWLY LIFTS NORTH. PRECIP CHANCES
BY THE AFTERNOON WILL BE AIDED BY THE DEVELOPMENT OF 500-1500 J/KG
OF MLCAPE THAT THE NAM SHOWS DEVELOPING FROM SOUTH CENTRAL MN UP
INTO THE ST. CROIX VALLEY. THE CAMS ARE RELATIVELY QUIET WITH THE
DEVELOPMENT OF ANY SHOWERS OUTSIDE OF THE HRRR...BUT THE
GFS/ECMWF/GEM/SREF ALL SHOW SOME LIGHT QPF DEVELOPING UNDER THE
UPPER LOW WITHIN THE INSTABILITY PLUME...SO MAINTAINED THE SLIGHT
CHANCE POPS WE HAD GOING. THE VAST MAJORITY OF PEOPLE WILL GO
THROUGH THE DAY DRY...BUT FEEL THERE IS ENOUGH SUPPORT /ESPECIALLY
WITH WHAT WE HAVE SEEN IN IOWA OVERNIGHT/ TO CONTINUE THE ISOLATED
SHOWER MENTION. ONLY CHANGE MADE TO THESE POPS WAS TO PULL THEM OUT
OF THE NRN CWA...AS THESE SHOWERS LOOK TO REMAIN CLOSE TO THE UPPER
LOW.

VERY LITTLE CHANGE IN THE AIRMASS HAS HAPPENED OVERNIGHT...SO EXPECT
VERY SIMILAR CONDITIONS IN TERMS OF TEMPS/DEWPS/WINDS TO WHAT WAS
SEEN FRIDAY. AGAIN...BUFR SOUNDINGS SHOW MOST LOCATIONS MIXING UP TO
BETWEEN 850-825 MB. MIXING TO 825MB WORKED WELL FOR HIGHS
YESTERDAY...SO THE MAGIC BLEND USED FOR HIGHS TODAY WAS TO USE 2
PARTS MIX DOWN TEMPS TO 825MB...WITH 1 PART HIGHS FROM YESTERDAY.
THIS YIELDED HIGHS IN THE 80S FOR JUST ABOUT EVERYONE...ENJOY!

QUIET WEATHER IS EXPECTED FOR TONIGHT...WITH ONLY CLOUD COVER
EXPECTED TO BE A CONTINUATION OF SCT CLOUDS IN THE 5K TO 7K FT
RANGE. WE WILL SEE A COLD FRONT ENTER NW MN TONIGHT...BUT ALL PRECIP
ASSOCIATED WITH IT IS LOOKING TO BE POST FRONTAL. WILL BE A FEW
DEGREES COOLER SATURDAY NIGHT THOUGH...AS WINDS LOOK TO BE WEAKER
WITH A LITTLE LESS CLOUD COVER AS WELL...BUT LOWS WILL STILL BE A
GOOD 10 DEGREES ABOVE NORMAL.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 404 AM CDT SAT SEP 27 2014

THE LONG TERM REMAINS AN ACTIVE PERIOD WITH MUCH BETTER AGREEMENT
WITH THE INDIVIDUAL FEATURES ON THE 27.00Z GFS/ECMWF RUNS ACROSS
THE UPPER MISSISSIPPI VALLEY. BETWEEN THE TWO...THE GFS HAS SHOWN
THE BEST CONSISTENCY OVER THE PAST FOUR NIGHTS WITH THE PROJECTED
UPPER AIR PATTERN FOR THE WEEK AHEAD.

A WEAK UPPER LOW WILL BE CENTERED OVER SOUTHERN MN SUNDAY MORNING
WITH THIS FEATURE DRIFTING SOUTHEAST DURING THE DAY. A DRY
FORECAST REMAINS IN PLACE WITH A FEW SHOWERS POSSIBLY DEVELOPING
OUTSIDE OF OUR NW CWA SUNDAY AFTERNOON AS A COLD FRONT APPROACHES
FROM THE NORTH. SUNDAY WILL BE ANOTHER WARM DAY WITH HIGHS IN THE
UPPER 70S TO LOWER 80S. AS IN THE SHORT TERM...MIX-DOWN FROM 825MB
WAS THE FOUNDATION FOR THE HIGH TEMPERATURE FORECAST.

A COLD FRONT WILL DRIFT SOUTHWARD ACROSS THE CWA SUNDAY NIGHT AND
EARLY MONDAY. THE FORCING AND DEEP LAYER MOISTURE REMAINS BEST
WELL TO OUR NORTHEAST WITH JUST SMALL POPS INDICATED ACROSS
CENTRAL MN AND ADJOINING PORTIONS OF WEST CENTRAL WI. HIGHS ON
MONDAY WILL BE MUCH COOLER ACROSS THE NORTHERN HALF OF THE FA WITH
HIGHS FROM 60 TO 70 FORECAST. HIGHS WILL BE IN THE LOWER TO MIDDLE
70S FOR SOUTHERN MN.

THE FIRST IN A SERIES OF SHORT WAVES WILL MOVE INTO THE CENTRAL PLAINS
ON TUESDAY AND THEN LIFT NORTHEAST ACROSS THE UPPER MISSISSIPPI
VALLEY TUESDAY NIGHT AND WEDNESDAY. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS WILL ACCOMPANY THIS FEATURE WITH RAINFALL AMOUNTS
FROM A QUARTER TO HALF INCH POSSIBLE.

ONE BIG CHANCE WITH THE 27.00Z RUNS WAS WITH THE ECMWF BACKING
DOWN FROM PHASING ENERGY STREAMS TO OUR WEST FROM WEDNESDAY INTO
THURSDAY. THIS IS NOW PROJECTED TO BE OVER AND TO THE EAST OF US
FROM THURSDAY INTO FRIDAY...WHICH IS SIMILAR TO PREVIOUS RUNS OF
THE GFS. THIS PATTERN WILL LIKELY RESULT IN WIDESPREAD RAIN
AMOUNTS NEAR AN INCH FROM SOUTH CENTRAL MN THROUGH THE SOUTH METRO
AND ACROSS WEST CENTRAL WI WEDNESDAY NIGHT AND THURSDAY. BLENDED
POPS WERE RAISED TO ACHIEVE THE LIKELY STATUS.

YET ANOTHER SHORT WAVE AND COLDER AIR WILL FOLLOW ON FRIDAY.
SHOWER CHANCES REMAIN ACROSS THE REGION WITH HIGHS ONLY REACHING
THE MIDDLE 50S TO AROUND 60. IF THE TIMING HOLDS...HIGH PRESSURE
WILL BE OVER THE FA ON SATURDAY WITH MORNING LOWS IN THE 30S TO
LOWER 40S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 538 AM CDT SAT SEP 27 2014

SHRA/TSRA CONTINUE TO LIFT NORTH ACROSS IOWA AND WILL MOVE INTO MN
THIS MORNING. HRRR SHOWS ISO SHOWERS WORKING UP INTO THE TWIN
CITIES...BUT STILL APPEARS COVERAGE WILL BE PRETTY SPARSE AT
BEST...SO HAVE MAINTAINED DRY TAFS. SIMILAR DIURNAL INCREASE IS
EXPECTED WITH WINDS TODAY GIVEN SIMILAR PRESSURE GRADIENT TO
FRIDAY...BUT TONIGHT WE WILL LOSE THAT GRADIENT...WHICH MEANS WE
WILL HAVE TO START THINKING ABOUT FOG AGAIN. WITH HIGHS EXPECTED
TO GET INTO THE 80S...WILL TAKE QUITE A BIT OF WORK THROUGH
RADIATIONAL COOLING TO GET FOG FORMATION...BUT WI TERMINALS MAY
HAVE ISSUES...AS THEY WILL SEE AN INCREASE IN MOISTURE TODAY AND
WILL BE CLOSER TO THE SFC RIDGE...WHICH WILL BE PROTRUDING WEST
FROM THE GREAT LAKES. BESIDE THE WARM STARTING POINT
TONIGHT...THESE CLOUDS BETWEEN 5K AND 7K FT WILL LIKELY STILL BE
AROUND TONIGHT...ADDING ANOTHER LAYER OF UNCERTAINTY ON FOG
POTENTIAL. FOR NOW...HAVE SOME MVFR VIS RESTRICTION AT EAU/RNH.

KMSP...CAN NOT COMPLETELY RULE OUT A STRAY SHOWER THIS
AFTERNOON...BUT COVERAGE AND CONFIDENCE ARE BOTH STILL PLENTY LOW
ENOUGH TO KEEP THE TAF DRY. MAY ALSO HAVE TO WATCH FOR SOME VSBY
RESTRICTIONS SATURDAY MORNING...BUT GIVEN HOW WARM WE ARE EXPECTED
TO GET TODAY...WILL BE TOUGH TO GET VIS RESTRICTIONS GOING.

/OUTLOOK FOR KMSP/
SUN...VFR. WINDS S 10KTS.
MON...VFR. WINDS NE 5 KTS.
TUE...VFR. CHANCE MVFR/SHRA OVERNIGHT. WINDS SE 10 KTS.

&&

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

$$

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






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