Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 302034
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
334 PM CDT TUE SEP 30 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 311 PM CDT TUE SEP 30 2014

HIGH PRESSURE WAS CENTERED OVER SOUTHERN ONTARIO EARLY THIS MORNING
WITH AN EXTENSIVE AREA OF STRATUS COVERING THE MUCH OF THE GREAT
LAKES AND THE UPPER MISSISSIPPI VALLEY REGION. THE HIGH WILL DRIFT
SLOWLY EAST TODAY AS A VIGOROUS LOW PRESSURE SYSTEM LIFTS THROUGH
THE NORTHERN PLAINS. THE SURFACE PRESSURE GRADIENT WILL BE
INCREASING THIS MORNING WITH WINDS BECOMING MORE SOUTHEAST WITH
TIME. THIS WILL AID IN SHREDDING OF THE STRATUS DURING THE MORNING.
HOWEVER...AS THE LOW CLOUDS GO...MID/HIGH LEVEL CLOUDINESS WILL BE
ON THE INCREASE FROM THE WEST ENDING UP IN A MOSTLY CLOUDY TO CLOUDY
DAY.

A BAND OF SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE LOW PRESSURE
SYSTEM TO OUR WEST WILL DRIVE INTO WEST CENTRAL AND SOUTHWEST MN BY
EARLY THIS AFTERNOON. THE VARIOUS CAMS ARE IN REALLY GOOD AGREEMENT
WITH THE TIMING AND LOCATION...WITH THE ACTIVITY SPREADING INTO
EASTERN MN BY THIS EVENING AND ACROSS WESTERN WI TONIGHT. AT THIS
POINT...THE TWIN CITIES SHOULD REMAIN DRY UNTIL SUNSET. THE ONE
ASPECT NOTED WITH THIS SYSTEM IS THAT DUE TO THE SHORT WAVE LIFTING
ALMOST DUE NORTH THROUGH THE NORTHERN PLAINS...THERE IS A CONTINUED
SLOWING TO THE EASTWARD PROGRESSION OF THE SHOWERS AND THUNDERSTORMS
TONIGHT. THIS MAY RESULT IN THE RAIN NOT REACHING LADYSMITH AND EAU
CLAIRE UNTIL LATE IN THE NIGHT/DAYBREAK WEDNESDAY. RAIN AMOUNTS
THROUGH TONIGHT WILL BE GREATEST OVER SOUTH CENTRAL MN WITH AMOUNTS
UP TO A HALF INCH. NO SEVERE WEATHER IS EXPECTED IN OUR FA
WITH THE STORMS.

HIGH TEMPERATURES WILL REMAIN A LITTLE BELOW NORMAL TODAY IN MOST
AREAS. THE EXCEPTION IS IN THE MN RIVER VALLEY WHERE MIDDLE TO UPPER
60S ARE FORECAST NEAR THE LOW LEVEL THERMAL RIDGE. THERE WILL BE
QUITE THE CONTRAST IN LOW TEMPERATURES TONIGHT FROM WEST TO EAST DUE
TO THE WET/DRY SCENARIO. LOWS FROM NEAR 60 IN SOUTHWEST MN TO THE
LOWER 40S NEAR LADYSMITH.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 311 PM CDT TUE SEP 30 2014

THE PHASING OF THE NORTHERN AND SOUTHERN JET STREAMS WILL BE
CRITICAL IN TERMS OF HOW WIDESPREAD THE PRECIPITATION BECOMES
WEDNESDAY NIGHT THRU FRIDAY MORNING...ESPECIALLY ACROSS WESTERN
AND SOUTHWEST MN.

SEVERAL STRONG SHRTWV/S MOVING INTO THE PACIFIC NW ALONG WITH A
POWERFUL 100-120 KT JET WILL CRAVE OUT A SIGNIFICANT STORM SYSTEM
BY THE END OF THE WEEK ACROSS THE GREAT LAKES REGION. DEPENDING
UPON HOW THE PHASING OF THE SOUTHERN AND NORTHERN JET AND
CONVECTION ACROSS IOWA WEDNESDAY NIGHT...WILL DETERMINE WHETHER
WESTERN MN REMAINS DRY OR BECOMES MUCH WETTER. UPPER LEVEL JET
STRUCTURE REMAINS FAVORABLE FOR A WIDESPREAD RAINFALL EVENT ACROSS
IOWA WEDNESDAY NIGHT...AND TAKING THIS AREA NORTHEAST ACROSS THE
EASTERN 1/4 OF MPX CWA. ALTHOUGH TIME DETAILS REMAIN UNCLEAR...THE
BULK OF THE WET WEATHER WILL OCCUR THURSDAY AFTN/EVENING ACROSS
THE EASTERN 1/4 OF MPX CWA. AS FAR WEST THIS AREA OF PRECIPITATION
EXPANDS IS DEPENDENT ON THE LOCATION OF THE SFC LOW AND HOW MUCH
MOISTURE ADVECTION IS HELD TO THE SE ACROSS EASTERN IA/NORTHERN
IL. THERE HAS BEEN SOME SLOWING OF THE OVERALL PATTERN ONCE THIS
SYSTEM TAKES SHAPE THURSDAY NIGHT. BUT...INCONSISTENCIES AND THE
FACT THE SFC LOW REMAINS MOSTLY SE OF MPX CWA...WILL LEAN TOWARD
ONLY CHC POPS IN THE WEST...WITH LIKELY/CATEGORICAL IN THE FAR
EAST. PRECIPITABLE WATER VALUES DUE INCREASE ENOUGH FOR HEAVY
RAINFALL...ESPECIALLY IF TSRA CAN DEVELOP ABOVE THE BOUNDARY
LAYER. BUT THE BEST CHC/S OF WIDESPREAD ONE INCH RAINFALL TOTALS
WILL BE S/SE OF OUR REGION.

ONCE THIS SYSTEM BEGINS TO ORGANIZE AND DEEPEN ACROSS THE NORTHERN
GREAT LAKES...STRONG WEST/NW WINDS WILL DEVELOP...LEADING TO WIND
CHILL VALUES IN THE 20S/30S FOR FRIDAY EVENING.

PAST FRIDAY...THE OVERALL PATTERN REMAINS FAVORABLE FOR
ISOLD/SCATTERED SHRA AS THE MEAN FLOW BECOMES NW AND EMBEDDED
SHRTWV/S RIDE SE ALONG THIS NW FLOW PATTERN. TIMING AND HOW
WIDESPREAD THIS ACTIVITY BECOMES REMAINS UNCLEAR. THE CLEAR PART
OF THE EXTENDED PERIOD WILL BE COOLER THAN NORMAL FOR EARLY
OCTOBER. ONE OF THE MAIN FACTORS OF THIS COOLER THAN NORMAL
PATTERN IS THE DEVELOPMENT OF THE NEGATIVE /-AO/ ARCTIC OSCILLATION
WHERE THE MEDIUM RANGE MODELS HAVE BEEN ADVERTISING. IF THIS
BECOMES DOMINATE...THE FIRST/SECOND WEEK OF OCTOBER WILL BE
UNSEASONABLY COOL. IN ADDITION TO THE -AO...THE MEAN UPPER PATTERN
IS FORECASTING A STRONG UPPER RIDGE DEVELOPING ACROSS GREENLAND
WHICH LEADS TO A BLOCKING PATTERN AND THE CONTINUATION OF THE NW
FLOW ALOFT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1245 PM CDT TUE SEP 30 2014

VFR FOR MOST LOCATIONS THIS AFTERNOON...BUT CLOUDS SHOULD RETURN
LATER TONIGHT AS A SYSTEM BRING PERIODS OF RAIN...AND POSSIBLY A
THUNDERSTORM...BUT CONFIDENCE IN THUNDER IS TOO LOW TO INCLUDE
MENTION IN THE TAF. MODEL GUIDANCE SHOWS ABUNDANT LOW LEVEL
MOISTURE...SO ANTICIPATE A RETURN OF IFR AND PERHAPS LIFR
CIGS...ALONG WITH LOWER VISBYS. CONDITIONS SHOULD GRADUALLY
IMPROVE BY LATE MORNING...ESPECIALLY IN THE WESTERN SITES.

KMSP...
AT THIS TIME IT APPEARS THAT THE FIRST ROUND OF PRECIP WILL SPLIT
MSP THIS EVENING...SO ONLY HAVE VCSH. LATER TONIGHT PRECIP SHOULD
LIFT UP FROM THE SOUTH SOUTHWEST. LOW CEILINGS WILL BE THE MAIN
RESTRICTION...BUT COULD SEE REDUCED VSBYS WITH THE RAIN/DRIZZLE.
CONDITIONS WILL SLOWLY IMPROVE ON WEDNESDAY.

/OUTLOOK FOR KMSP/
THU...IFR EARLY BECOMING MVFR WITH -SHRA. WINDS SSE AT 10G15KTS.
THR NIGHT...INCREASING WINDS AFTER MIDNIGHT. NW AT 20G25KTS.
FRI...MVFR WITH -SHRA POSSIBLE. WINDS WNW AT 20G30KTS.
SAT...VFR. WINDS NW AT 20G30KTS.

&&

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

$$

SHORT TERM...JRB
LONG TERM...JLT
AVIATION...JRB



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