Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 250517
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1217 AM CDT SAT JUL 25 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 327 PM CDT FRI JUL 24 2015

COLD FRONT NOW MOVING ACROSS WRN MN AT ABOUT A 20 MPH CLIP BUT HAS
BEEN ACCELERATING AS THE INFLUENCE OF A REMNANT OUTFLOW BOUNDARY
FROM THIS MORNINGS MCS CONTINUES TO DIMINISH. THOUGH WE HAVE SEEN
DEWPOINTS INCREASE INTO THE LOW 70S AHEAD OF THE BOUNDARY WITH
SBCAPES OF 2K-3K J/KG ON THE 19Z SPC MESOANALYSIS...STILL NOT
ANTICIPATING ANY ADDITIONAL TSRA DEVELOPMENT IN THE MPX CWA FOR A
COUPLE OF REASONS. 1) WE REMAIN IN A GENERAL ZONE OF SUBSIDENCE IN
THE WAKE OF THIS MORNINGS SYSTEM WITH ANY ADDITIONAL UPPER ENERGY
PASSING TO THE NORTH OF OUR AREA ACROSS THE LAKE SUPERIOR REGION. 2)
WINDS HAVE NOW VEERED CONSIDERABLY OUT AHEAD OF THE FRONT...GREATLY
REDUCING THE AMOUNT OF CONVERGENCE ALONG THE BOUNDARY. EXPECT THE
GREATEST THUNDERSTORM AND SEVERE THREAT TODAY TO BE UP ALONG LAKE
SUPERIOR FROM NRN WI INTO WRN UPPER MICHIGAN. STILL THE FRONT WILL
BE CROSSING INTO WI JUST PAST PEAK HEATING...SO LEFT A SMALL AREA OF
AN ISO TSRA MENTION IN WRN WI LATE THIS AFTERNOON.

TONIGHT...HIGH PRESSURE PUSHES IN FROM THE NRN HIGH PLAINS. AS A
RESULT...AIRMASS COMING IN WITH IT IS NOT REALLY MUCH COOLER THAN
WHAT WE HAVE NOW...WITH DEWPOINT ONLY FALLING BACK INTO THE LOW/MID
60S. NOT TOO CONCERNED ABOUT FOG TONIGHT EITHER THANKS TO
TEMPERATURES THAT HAVE WARMED INTO THE 80S. PROBABLY WILL NOT HAVE
ENOUGH DARKNESS /AND THEREFOR HOURS OF COOLING/ TO GET MUCH IN THE
WAY OF RADIATIONAL FOG GOING TONIGHT.

SATURDAY IS STILL LOOKING LIKE A BEAUTIFUL SUMMER DAY...WITH MAINLY
SUNNY SKIES AND HIGHS IN THE MID/UPPER 80S. FRONT THAT IS WORKING
THROUGH THE AREA NOW WILL STALL OUT DOWN AROUND I-80...WHICH WILL
KEEP ANY DIURNALLY DRIVEN ACTIVITY TO OUR SOUTH DURING THE DAYLIGHT
HOURS SATURDAY.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 327 PM CDT FRI JUL 24 2015

THE MAIN CONCERN FOR THE LONG TERM REVOLVES AROUND CONVECTIVE
PLACEMENT AND TIMING...WHICH WILL LIKELY REMAIN UNCERTAIN TO SOME
DEGREE FOR THE NEXT SEVERAL MODEL CYCLES. THE HIGHEST CONFIDENCE
IS ACTUALLY LATE TUESDAY AND TUESDAY NIGHT WITH A STRONG COLD
FRONT.

THUNDERSTORMS MAY BE ONGOING SATURDAY AFTERNOON ACROSS THE
DAKOTAS IN RESPONSE TO A MID LEVEL DISTURBANCE ROUNDING THE
BUILDING RIDGE TO THE SOUTH. THE NAM/GFS/CANADIAN ARE ALL IN
FAIRLY GOOD AGREEMENT WITH THIS FEATURE ALTHOUGH THERE IS SOME
CONVECTIVE FEEDBACK EVIDENT...PARTICULARLY ON THE NAM. UP UNTIL
TODAY/S 12Z RUN...THE ECMWF ALSO BROUGHT THIS FEATURE ACROSS WITH
A GOOD SHOT AT THUNDERSTORM ACTIVITY SATURDAY NIGHT AND SUNDAY.
HOWEVER...THE NEW RUN WEAKENS THIS MID LEVEL FEATURE AS IT HEADS
INTO MN...AND ALSO LEAVES THE MAIN WARM FRONT SOUTHWEST ACROSS THE
CENTRAL PLAINS AND MID MO VALLEY AS THE NAM/GFS/CANADIAN ALSO DO.
THIS RESULTS IN VERY LITTLE ACTIVITY ACROSS THE CWA AND INCREASES
UNCERTAINTY QUITE A BIT DURING THIS TIME FRAME. WAS THINKING OF
RAISING POPS INTO THE LIKELY RANGE FOR PORTIONS OF THE AREA...BUT
AFTER SEEING THE COMPLETELY DRY ECMWF AND KNOWING ITS BETTER TRACK
RECORD WITH THESE COMPLEXES THIS SUMMER...LEFT POPS IN THE CHC
RANGE...BASICALLY AS THE MIDNIGHT SHIFT HAD THEM. THE MORE LIKELY
SCENARIO SEEMS TO BE LEANING TO CONVECTIVE DEVELOPMENT ON THE
WARM FRONT TO THE SOUTHWEST ACROSS NE/IA/MO SATURDAY AND SATURDAY
NIGHT.

THE WARM FRONT TO THE SOUTH WASHES OUT SOME SUNDAY LEAVING ALMOST
NOTHING FOR STORMS TO FOCUS ON. IF THE MID LEVEL WAVE DOES
DIMINISH...SUNDAY WILL LIKELY REMAIN DRY.

A SHARP TROUGH WILL DIVE DOWN INTO THE PACIFIC NORTHWEST SUNDAY
NIGHT AND MONDAY...INDUCING CYCLOGENESIS OVER THE NORTHERN HIGH
PLAINS. THE UPPER RIDGE WILL ALSO BUILD OVER THE MISSISSIPPI
VALLEY INTO TUESDAY. THIS WILL FINALLY BRING A SURFACE WARM FRONT
NORTH MONDAY NIGHT/TUESDAY MORNING WITH A BETTER SHOT AT
THUNDERSTORMS BEFORE CAPPING AND HOT AIR ARRIVES LATE TUESDAY
MORNING AND AFTERNOON. THICKNESSES CLIMB INTO THE MID 580S DM AND
850 MB TEMPS RISE INTO THE MID 20S C. SLU CIPS ANALOG GUIDANCE
INDICATES A 50-70 PERCENT CHANCE FOR HIGHS ABOVE 90 AND A 30 TO 50
PERCENT CHANCE FOR HEAT INDICES EXCEEDING 105. SO IT LOOKS RATHER
WARM...BUT THE QUESTION IS HOW MORNING CONVECTION WILL IMPACT THE
WARM FRONT AND HOW QUICKLY STORMS WILL FIRE ON THE COLD FRONT
DURING THE AFTERNOON. DID RAISE TEMPS A FEW DEGREES...BUT NOT AS
MUCH AS WHAT MAY EVENTUALLY BE NEEDED.

THE CIPS ANALOG ALSO INDICATES GOOD POTENTIAL FOR SEVERE WEATHER
WITH THIS FRONT TUESDAY EVENING. HEIGHT FALLS SHOULD OVERSPREAD
THE WARM SECTOR LATE...AND THE FRONT SHOULD ERODE THE LOW LEVEL
CAPPING SOME. EXPECTING A BROKEN LINE OF THUNDERSTORMS
INITIALLY LATE AFTERNOON...FILLING IN SOME DURING THE EVENING
EAST OF I-35. ALL MODES OF SEVERE WEATHER WILL BE POSSIBLE.

COOLER AND DRIER AIR WILL FOLLOW THE FRONT FOR THE MIDDLE OF THE
WEEK WITH ANOTHER FRONT DROPPING SOUTH ABOUT FRIDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1215 AM CDT SAT JUL 25 2015

MAIN AVIATION CONCERN IS THE POTENTIAL OF FOG THIS
MORNING...ESPECIALLY IN WESTERN AND CENTRAL MN AS BOUNDARY LAYER
WINDS WILL BE VERY LIGHT AND MOISTURE NEAR THE SFC WILL BE HIGH
FROM EARLIER RAINFALL. DEBATED ON HOW LOW TO DECREASE THE
VSBY...BUT KEPT MVFR VSBY BASED ON LOW CONFIDENCE ON HOW
WIDESPREAD THE FOG GETS OVERNIGHT AND HIGH LEVEL CLOUDINESS MOVES IN
FROM THE WEST TOWARD SUNRISE. OTHERWISE...VFR CONDS WILL PREVAIL
BY MID MORNING WITH WINDS BECOMING E/SE ARND 5-10 KTS.

KMSP...

SOME BR/FG IS POSSIBLE TOWARD 10-12Z BUT CONFIDENCE REMAINS LOW SO
KEPT CONDS AT 6SM BR FROM 9-1230Z. OTHERWISE...VFR CONDS WILL
PREVAIL WITH AN EAST WIND SATURDAY MORNING...BECOMING MORE SE BY
THE AFTN...BUT UNDER 10 KTS.

/OUTLOOK FOR KMSP/

SUN...MAINLY VFR. CHC MVFR/IFR IN SHRA/TSRA. WINDS SE 5-10 KTS.
MON...VFR. WINDS SE 5-10 KTS.
TUE...MAINLY VFR. CHC MVFR/IFR IN SHRA/TSRA. WINDS S 10-15 KTS.

&&

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

$$

SHORT TERM...MPG
LONG TERM...BORGHOFF
AVIATION...JLT


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