Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 011112
AFDMPX

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

.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 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 543 AM CDT WED OCT 1 2014

RAIN IS QUICKLY OVERSPREADING ERN MN/WRN WI THIS MORNING...A
SCENARIO THAT HAS BEEN HANDLED WELL BE THE LAST FEW RUNS OF THE
HRRR. AS A RESULT...FOLLOWED THE HRRR PRETTY CLOSE FOR TIMING THE
AREA OF RAIN CURRENTLY HEADING OUR DIRECTION IN IOWA.
OVERNIGHT...WE SAW IFR/MVFR CIGS EXPAND ACROSS WRN MN OUT AHEAD A
OF A COLD FRONT THAT WAS ONLY ABOUT TO ABERDEEN AT 12Z. THE RAP
HAS HAD A GOOD HANDEL ON BOTH THE FRONT AND BACK EDGES OF THIS
CLOUD SHIELD...SO FOLLOWED ITS IDEA FOR TIMING IMPROVEMENTS BACK
TO VFR FROM WEST TO EAST THIS AFTERNOON. ABOUT THE ONLY BIT OF
UNCERTAINTY WITH TAFS TODAY IS CIGS MAY COME IN A BIT LOWER /USED
THE SCT IFR GROUPS FOR THAT POSSIBILITY/ AND WE MAY BE A BIT TOO
AGGRESSIVE WITH VFR IMPROVEMENT THIS AFTERNOON. THIS
AFTERNOON...THE DAKOTAS FRONT WILL BE MOVING INTO WRN MN...WITH
THE HRRR SHOWING SCT SHOWERS DEVELOPING ALONG THE FRONT...SO ADDED
A VCSH TO AXN/RWF FOR THAT. LATE TONIGHT...IS LOOKING LIKELY THAT
ERN MN AND WRN WI WILL BE DEALING WITH LOW STRATUS AND FOG AS THE
FRONT GETS HUNG UP ALONG THE MN/WI BORDER. THERE WILL BE LGT AND
VRB WINDS AND PLENTIFUL LOW LEVEL MOISTURE ALONG AND EAST OF THE
BOUNDARY. AS A RESULT...KEPT THE TAFS FOR RNH/EAU CLOSE TO WHAT
THE LAMP HAS.

KMSP...
ASSUMING THE HRRR IS CORRECT...AND I SEE NO REASON WHY IT WOULD BE
SIGNIFICANTLY OFF THE MARK...LOOKS GOOD TO SEE SEVERAL HOURS OF
-RA THIS MORNING INTO THE AFTERNOON. SOME UNCERTAINTY AS TO
WHETHER OR NOT CIGS WILL GO SUB 1K...BUT CONFIDENCE IS HIGH THE
CIGS WILL DIP UNDER 018 AS THE MAIN RAIN SHIELD ARRIVES. FOR
TONIGHT...THE SREF MVFR CIG/VIS PROBABILITIES HAVE MSP ON THE WRN
EDGE OF THE BETTER PROBABILITIES FOR LOW CIGS AND FG/BR...BUT WITH
WINDS LOOKING LIGHT WITH THE BOUNDARY HUNG UP NEAR THE TWIN
CITIES...LOOKS MORE LIKELY THAN NOT THAT WE WILL BE DEALING WITH
SOME PRETTY LOW CONDS THU MORNING.

/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...MPG






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