Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 010027
AFDMPX

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

.UPDATE...
ISSUED AT 717 PM CDT TUE SEP 30 2014

UPDATED TO INCLUDE 00Z AVIATION DISCUSSION BELOW.

&&

.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 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 717 PM CDT TUE SEP 30 2014

DEEP LOW PRES CENTER OVER THE DAKOTAS WILL CONTINUE TO MOVE NWD
INTO CENTRAL CANADA THRU TMRW. IN ADVANCE OF THIS LOW...A WEAK SFC
CDFNT WILL APPROACH WITH SCT SHWRS/ISOLD TSTMS ALONG IT. VERY WEAK
SUPPORT FOR THIS BAND OF PRECIP EARLY ON IN THE TAF PERIOD WILL
MEAN THAT LITTLE TO NO PRECIP CAN BE EXPECTED AT THE TAF SITES
THRU THE EARLY MRNG HOURS. HOWEVER...CONDITIONS ARE AGAIN GOOD FOR
LOW STRATUS DEVELOPMENT OVERNIGHT THRU MUCH OF THE DAY TMRW.
ANOTHER ROUND OF RAIN LOOKS TO DEVELOP AROUND DAYBREAK AND SHORTLY
THEREAFTER...LASTING INTO THE EARLY AFTN HRS. THIS SECOND ROUND OF
PRECIP LOOKS HEAVIER SO HAVE INDICATED SOME VSBY RESTRICTION DUE
TO THE HEAVIER AND STEADIER EXPECTED PRECIP...WHILE ALSO SLIGHTLY
RAISING CEILINGS. ONCE THE PRECIP ENDS...THE LOW CEILINGS WILL BE
DIFFICULT TO ERODE SO WOULD NOT BE SURPRISED IF TAF SITES REMAINED
NO BETTER THAN MVFR THRU LATE AFTN AND POSSIBLY THRU 00Z TMRW EVE.
BREEZY SE WINDS THIS EVE WILL SETTLE DOWN TO CLOSE TO 10 KT...THEN
BECOME BREEZY AGAIN TMRW AFTN.

KMSP...CONDS TO GRADUALLY DETERIORATE THIS EVE THRU OVERNIGHT AS
MVFR CIGS DEVELOP THEN DROP TO IFR LOW STRATUS CEILINGS. NOT
LOOKING FOR FOG WITH WINDS BEING ELEVATED. MAIN BATCH OF RAIN
LOOKS TO HOLD OFF UNTIL AROUND DAYBREAK TMRW...POSSIBLY IMPACTING
THE MRNG RUSH WITH MVFR VSBY...AND POSSIBLY LOWER THAN WHAT IS
CURRENTLY ADVERTISED. RAIN TO LINGER THRU MIDDAY BUT EVEN AFTER
ENDING...IFR CONDS LIKELY TO REMAIN IN PLACE THRU LATE DAY BEFORE
EVENING IMPROVEMENT.

/OUTLOOK FOR KMSP/
FRI...MAINLY MVFR WITH CHC -SHRA. WINDS WNW 20G30 KTS.
SAT...VFR. WINDS NW 10-15 KTS.
SUN...VFR. SLGT CHC -SHRA. WINDS NW 10 KTS.

&&

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

$$

UPDATE...JPC
SHORT TERM...JRB
LONG TERM...JLT
AVIATION...JPC





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