Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 011657
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1157 AM CDT WED OCT 1 2014

.UPDATE...FOR 18Z AVIATION DISCUSSION BELOW

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 343 AM CDT WED OCT 1 2014

SURFACE ANALYSIS THIS MORNING SHOWS A COMPACT 995 MB LOW NEAR RUGBY
/ND/ WITH A TRAILING SFC COLD/OCCLUDED FRONT DOWN THROUGH THE
CENTRAL DAKOTAS THAT EVENTUALLY WORKS INTO THE ERN TX PANHANDLE. TO
THE EAST...HIGH PRESSURE CONTINUES TO SLIDE ACROSS ONTARIO...BUT DRY
SE WINDS EMANATING FROM IT HAVE REALLY IMPEDED THE DEVELOPMENT OF
PRECIP ACROSS THE MPX CWA...TO THIS POINT ANYWAYS. ALOFT...THE
FEATURE OF INTEREST SHOWS UP NICELY ON WATER VAPOR IMAGERY MOVING
INTO WRN KS...AND THIS WAVE WILL BE OVER SRN MN BY THE AFTERNOON.

SE WINDS EMANATING FROM THE GREAT LAKES HIGH HAS HELD SFC DEWPS IN
THE 40S ACROSS ERN MN/WRN WI THROUGH THE NIGHT...WHICH COMBINED WITH
THE INITIAL SHORT WAVE AND ITS FORCING GOING DUE NORTH THROUGH THE
DAKOTAS AND INTO SRN CANADA...BYPASSING THE MPX AREA TO THE
NW...RESULTED IN THE MPX CWA REMAINING MAINLY DRY THROUGH THE NIGHT.
HOWEVER...AS THE KS WAVE APPROACHES...CONTINUED HEIGHT FALLS OUT
AHEAD OF THE WAVE WILL ALLOW PRECIP TO BLOSSOM ACROSS THE ERN HALF
OF THE MPX AREA WITHIN THE ZONE OF GREATEST ASCENT WITHIN THE
LLJ...WHICH WILL BE WORKING UP THROUGH WRN WI. HI-RES REFLECTIVITY
FORECASTS CERTAINLY BEAR THE LOOK OF A LIMITED THUNDERSTORM ACTIVITY
FORECAST...SO HAVE CONTINUE TO HOLD A THUNDER MENTION THROUGH THE
DAY AT ISOLATED. GOOD MODEL AGREEMENT IN TERMS OF QPF WITH A GOOD
HALF TO ONE RAIN OF RAIN FALLING TODAY ALONG/EAST OF THE I-35
CORRIDOR. AS A RESULT...USED A PRETTY MUCH EVEN MODEL BLEND FOR
QPF...WHICH RESULTED IN THE DESIRED HALF TO ONE INCH AMOUNTS.  OF
COURSE WITH THIS AMOUNT OF RAIN FALLING INTO AN AIRMASS WITH DEWPS
CURRENTLY IN THE 40S...IT WILL NOT WARM UP MUCH TODAY...SO COOLED
HIGHS ACROSS ERN MN/WRN WI...KEEPING THEM MAINLY IN THE 50S.

OUT IN WRN MN...DID INTRODUCE SOME LOW CHANCE POPS OUT THERE THIS
AFTERNOON. THIS IS IN RESPONSE TO THE THREAT FOR SEEING ISO-SCT
SHOWERS/STORM DEVELOPING ALONG THE COLD FRONT...WHICH WILL BE
ENTERING WRN MN DURING PEAK HEATING. MOST GUIDANCE POINTS TO SOME
BREAKS DEVELOPING BY THE AFTERNOON OUT WEST...WHICH WILL ALLOW
TEMPERATURES TO WARM INTO THE 70S. THE NAM SHOWS 500-1000 J/KG OF
MLCAPE WORKING EAST WITH THE FRONT TODAY...SO FELT SOME 20/30 POPS
WERE WARRANTED OUT WEST WITH THE HRRR SHOWING A LINE OF SHOWERS
DEVELOPING ALONG THE FRONT BY THE AFTERNOON AND THE 01.00 ECMWF
SHOWING A NARROW BAND OF LIGHT QPF OUT IN WRN MN ALONG THE BOUNDARY
AS WELL.

FOR TONIGHT...DRIED OUT THE ENTIRE CWA AFTER 6Z AS THE KS WAVE WILL
BE WELL OFF INTO NRN MN BY THEN...WITH ANY ACTIVITY ALONG THE FRONT
LOSING INTEREST WITH THE LOSS OF DAYTIME HEATING. BY 12Z THU...THIS
BOUNDARY WILL BE NEAR THE MN/WI BORDER. WINDS WILL BE CALM/LIGHT
ALONG AND AHEAD OF THE BOUNDARY...SO WE WILL LIKELY HAVE TO WATCH
FOR THE DEVELOPMENT OF LOW STRATUS AND FOG ACROSS ERN MN/WRN WI
WEDNESDAY NIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 343 AM CDT WED OCT 1 2014

THE MOST ACTIVE PERIOD IN THE 7-DAY FORECAST IS THE THU-FRI
TIME FRAME WITH A DEEP TROUGH DROPPING SOUTH OUT OF BRITISH
COLUMBIA AND ALBERTA THAT IS EXPECTED TO PHASE WITH THE TROUGH
CURRENTLY OVER MT/ID/NV BY FRIDAY AFTERNOON. WE DELAYED THE ONSET
OF PRECIP ON THURSDAY TO INCLUDE A MORE DEFINED BREAK IN THE
PRECIP BETWEEN THE SYSTEM CURRENTLY IN PLACE ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY AND THE ONE EXPECTED LATE THIS WEEK. THIS
ENTIRE SYSTEM HAS SLOWED OVER THE PAST COUPLE DAYS AND THERE HAS
ALSO BEEN AN EASTWARD TREND IN MOST OF THE GUIDANCE. THE 10.00Z
NAM WAS THE FARTHEST WEST AND THUS WETTEST SOLUTION FOR THE
FORECAST AREA...BUT EVEN THE 10.06Z GUIDANCE HAS SHIFTED EAST -
ALTHOUGH THE NAM STILL HAS REALLY GOOD FGEN AND HEAVY BANDED
PRECIP IN WESTERN WI AND FAR EASTERN MN FRIDAY MORNING. THERE WAS
ALSO AN EASTWARD SHIFT WITH 10.00Z ECMWF. THE GFS SORT OF SPLITS
THE DIFFERENCE BETWEEN THE NAM AND ECMWF. THE UNCERTAINTY WITH THE
PRECIP LOCALLY IS DUE TO THE DEVELOPING DRY SLOT WITH MOST OF THE
PRECIP POTENTIALLY SLIDING EAST. EVEN IF MOST OF THE PRECIP
SLIDES EAST THURSDAY NIGHT AND FRIDAY MORNING...THE POTENT UPPER
WAVE SHOULD PRODUCE LIGHT TO MODERATE SHOWERS ACROSS THE FORECAST
AREA ON FRIDAY. THIS WILL BE COINCIDENT WITH STRONG COLD ADVECTION
AND STRONG WINDS DURING THE DAY.

FRIDAY LOOKS QUITE BLUSTERY AND WE ARE NOW THINKING MANY LOCATIONS
MIGHT NOT EVEN HIT 50 FOR A HIGH. THE GUSTY WINDS...CLOUDS AND
LIGHT RAIN WILL MAKE THE UPPER 40S FEEL EVEN COOLER. SPEAKING OF
THE WIND...WE WILL LIKELY BE WITHIN 5-10 MPH OF WIND ADVISORY
CONDITIONS ACROSS WESTERN MN. THE PRESSURE GRADIENT WILL TIGHTEN
AS THE SURFACE LOW DEEPENS OVER THE GREAT LAKES AND A HIGH BUILDS
IN THE NORTHERN PLAINS. THE SPEED OF THE MSLP PRESSURE FALLS IS
NOT WELL AGREED UPON AMONGST THE NAM/GFS/ECMWF. THE CIPS ANALOGS
FOR FRIDAY ARE NOT VERY CONVINCING FOR WIND ADVISORY...BUT STILL
SHOW PLENTY OF WIND AND ALSO MATCH MANY OCTOBER DAYS WHERE MN/WI
STAYED IN THE 40S FOR HIGHS. NONETHELESS...WE HAVE SUSTAINED 25-30
MPH WITH GUSTS TO 40 MPH IN THE FORECAST FOR MN SIMPLY BASED ON
THE NAM AND GFS FORECAST SOUNDINGS SHOWING REALLY GOOD MIXING WITH
THE COLD ADVECTION AND 40-50KTS AT 850MB BY 00Z SATURDAY.

FOR THE MOST PART WE THINK THE COMING WEEKEND WILL BE DRY...BUT
STILL QUITE COOL. THERE HAS BEEN SOME RUNS SHOWING SHORTWAVE
ENERGY DROPPING DOWN FROM CANADA ALONG THE BACKSIDE OF LONGWAVE
TROUGH WHICH ESTABLISHES ITSELF OVER UPPER MISS...GREAT LAKES AND
NORTHEAST US EARLY NEXT WEEK...HOWEVER...A VAST MAJORITY OF THE
PRECIP SHOULD REMAIN ATTACHED TO THE CORE OF THE TROUGH WHERE
THERE IS MUCH BETTER LIFT. THE GFS AND ECMWF DIVERGE NEXT WEEK
WITH THE GFS KEEPING THE TROUGH ANCHORED AND THE ECMWF BEING MUCH
MORE PROGRESSIVE IN BUILDING HEIGHTS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1158 AM CDT WED OCT 1 2014

THE TROUGH OVER NORTH DAKOTA THAT HAS FACILITATED A SOLID AREA OF  RAIN
SHOWERS OVER CENTRAL/EASTERN MN AND WESTERN WI ALONG WITH LIFR/IFR
CONDITIONS WILL LIFT NORTH ACROSS MANITOBA DURING THE TAF PERIOD.
PERIODIC WAVES OF SHORTWAVE ENERGY AND WEAK SURFACE TROUGHING WILL
MAINTAIN REDUCTIONS TO FLYING CONDITIONS THROUGH THE PERIOD. IN
THE WAKE OF THE SHOWERS THIS AFTERNOON...THE CONCERN WILL SHIFT TO
THE POTENTIAL FOR FOG DEVELOPMENT AND STRATUS THROUGH THE
OVERNIGHT HOURS. THE CIGS LOOK TO BE THE WORST FOR WEST CENTRAL WI
SITES...WHERE LIFR AND EVEN VLIFR CONDITIONS ARE EXPECTED TO
DEVELOP OVERNIGHT. CONDITIONS WILL BE SLIGHTLY LESS IMPACTFUL WITH
WESTWARD PROGRESSION TOWARD KAXN/KSTC/KRWF.

THE NEXT SLUG OF MOISTURE AND ROBUST LIFT ARRIVE ON THURSDAY
AFTERNOON AND EVENING...PRIMARILY AFFECTING KMSP/KRNH/KEAU...WITH
KSTC AND KRWF ON THE WESTERN FRINGES.

SOUTH-SOUTHEAST WINDS GRADUALLY VEER TONIGHT...WITH NORTHWEST
WINDS EXPECTED FOR THURSDAY. SPEEDS GENERALLY AROUND OR UNDER 6
KTS THROUGH THE PERIOD.

KMSP...
CIGS ARE ADMITTEDLY TRICKY FOR THIS AFTERNOON/EVE. EXPECT THE AREA OF
RAIN TO EXIT THE AIRPORT BY 20Z. THERE WILL BE THE POTENTIAL FOR
SCT BREAKS IN THE SUB-1000FT DECK THIS AFTERNOON...BUT OVERALL
CIGS SHOULD REMAIN BELOW 1700 FT THROUGH 22Z. WILL THEN HAVE A
WINDOW OF TIME UNTIL 02Z WHEN CIGS COULD IMPROVE TO OVC020...BUT
THEN SHOULD DROP BACK TO AROUND 1500FT AROUND/AFTER SUNSET AND
REMAIN IFR OVERNIGHT. FOG IS EXPECTED TO DEVELOP OVERNIGHT...WITH
POCKETS OF 1/2SM VSBYS NEAR THE AIRPORT. NOT CONFIDENT IF KMSP
WILL GO THAT LOW DIRECTLY AT THE SITE...SO WILL STICK WITH 1SM
PREVAILING FOR NOW.

/OUTLOOK FOR KMSP/

FRI...MAINLY MVFR WITH CHC -SHRA. WINDS WNW 20G30 KTS.
SAT...VFR. WINDS NW 10-15 KTS.
SUN...VFR. WINDS NW 10 KTS.

&&

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

$$


SHORT TERM...MPG
LONG TERM...CLF
AVIATION...LS





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