Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 252026
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
326 PM CDT TUE AUG 25 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 325 PM CDT TUE AUG 25 2015

DRY CONDITIONS WILL PREVAIL THROUGH THE PERIOD AS A SURFACE HIGH
REMAINS ENTRENCHED OVER THE UPPER MIDWEST AND NORTHERN PLAINS.  LOW
CLOUDS OVER WESTERN WISCONSIN SHOULD CONTINUE TO ERODE VERY
SLOWLY...AND MOSTLY CLEAR SKIES ARE EXPECTED ACROSS OUR ENTIRE
REGION FROM LATE TONIGHT THROUGH WEDNESDAY.  THE PRESSURE GRADIENT
WILL RELAX TONIGHT AS WELL...LEADING TO LIGHT WINDS ACROSS THE AREA.
THEREFORE...RADIATIONAL COOLING SHOULD BE EFFICIENT TONIGHT...AND
SOME PATCHY FOG IS CERTAINLY POSSIBLE AROUND SUNRISE ON WEDNESDAY
FROM THE MISSISSIPPI RIVER VALLEY THROUGH PARTS OF WEST CENTRAL
WISCONSIN.  LOWS WILL BE COOL FOR THIS TIME OF YEAR...RANGING FROM
THE LOW TO MID 40S IN RURAL AREAS TO LOWER 50S IN THE TWIN CITIES.

SMOKE ORIGINATING FROM THE FIRES IN THE PACIFIC NORTHWEST HAS MOVED
OVER THE DAKOTAS TODAY...AND CURRENT AIR QUALITY AND SMOKE
DISPERSION MODELS SHOW A CONTINUED PUSH EASTWARD TONIGHT THROUGH
WEDNESDAY. AS A RESULT...SOME UPPER LEVEL SMOKE CANNOT BE RULED OUT
OVER OUR AREA...ESPECIALLY ON WEDNESDAY OVER WESTERN AND CENTRAL MN.
THE SMOKE IS NOT EXPECTED TO IMPACT AIR QUALITY AT THIS TIME.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 325 PM CDT TUE AUG 25 2015

TWO MAIN FEATURES IN THE LONG TERM WILL BE A MONSOON WAVE COMING
ACROSS THE REGION THURSDAY NIGHT/FRIDAY...FOLLOWED BY A SIGNIFICANT
SHIFT IN THE UPPER AIR PATTERN NEXT WEEK.

THE WAVE COMING THURSDAY NIGHT CAN BE FOUND ON WATER VAPOR THIS
AFTERNOON IN ARIZONA ROUNDING THE WEST SIDE OF THE SUB-TROPICAL
CENTERED OVER NM/CO. THIS WAVE WILL SLOWLY ROUND THE RIDGE OVER THE
NEXT COUPLE OF DAYS...EVENTUALLY HEADING ACROSS IA THURSDAY NIGHT
INTO FRIDAY. GFS/GEM/ECMWF WERE IN PRETTY GOOD AGREEMENT WITH THIS
SYSTEM...TAKING ITS SFC WAVE ACROSS NEB TOWARD NE MISSOURI. FAVORED
A FORECAST TO THIS BLEND...WITH THE NAM IGNORED FOR THIS FORECAST
PACKAGE. THE 12Z NAM DISPLAYED A SIMILAR ISSUE IT HAS HAD A FEW
OTHER TIMES THIS SUMMER...WITH A LACK OF QPF GENERATED IN THE
CONVECTIVE SCHEME RESULTING IN UNREALISTIC AMOUNTS OF STABLE QPF
GETTING GENERATED...WITH SAID QPF ALSO ENDING UP TOO FAR NORTH FROM
WHERE IT WILL ACTUALLY END UP. THIS IS A MONSOON WAVE...SO PWATS
WILL BE HIGH...WITH THE GFS SHOWING VALUES EXCEEDING 1.8 INCHES DOWN
ACROSS IOWA. FOLLOWING THE PREFERRED MODEL BLEND...EXPECT A HEALTHY
BURST OF RAIN DOWN ALONG THE I-80 CORRIDOR...LIKELY IN THE 2-3 INCH
RANGE. QPF WILL BE TRAILING OFF QUICKLY AS YOU HEAD NORTH. CURRENT
GRIDS HAVE 1-1.5 INCHES OF QPF ALONG THE I-90 CORRIDOR...WITH
AMOUNTS UNDER A HALF INCH BY THE TIME YOU GET TO THE TWIN CITIES.

FOR POPS...DID EXPAND LIKELIES ACROSS THE SOUTH FROM THU NIGHT INTO
FRIDAY AND BROUGHT IN A PERIOD OF CATEGORICAL POPS ALONG THE I-90
CORRIDOR THU NIGHT AS WELL. IN ADDITION...INSTABILITY LOOKS
LIMITED...SO THIS LOOKS TO BE A SYSTEM THAT PRODUCES MAINLY RAIN
WITH THE OCCASIONAL RUMBLE OF THUNDER...SO LIMITED THUNDER MENTION
TO A SLIGHT CHANCE FOR THE DURATION OF THE EVENT. ALSO CONTINUED TO
NUDGE HIGHS DOWN IN THE SOUTHEAST ON FRIDAY...THOUGH WE MAY STILL BE
SEVERAL DEGREES TOO WARM...IS VERY PLAUSIBLE THAT RAIN/CLOUDS MAKE
IT DIFFICULT FOR AREAS AROUND SE MN TO GET OUT OF THE LOW 60S ON
FRIDAY.

THIS WEEKEND...AS THIS SYSTEM MOVES TOWARD THE GREAT LAKES...OUR
SIGNIFICANT PATTERN SHIFT BEGINS TO TAKE SHAPE. THE ECMWF/GFS ARE IN
GOOD AGREEMENT ON THEIR H5 PATTERNS THIS WEEKEND INTO NEXT
WEEK...WITH THE MAIN LONGWAVE TROUGHS/RIDGES SWAPPING POSITIONS FROM
THEIR CURRENT LOCATION. RIGHT NOW WE HAVE A RIDGE OVER THE ROCKIES
WITH A DEEP TROUGH NORTH OF THE GREAT LAKES. FAST FORWARD A WEEK AND
WE WILL BE LOOKING AT A TROUGH DIGGING INTO THE PAC NW WITH AN UPPER
RIDGE BUILDING INTO THE GREAT LAKES. THIS WILL SEND OUR TEMPERATURES
BACK INTO THE 80S FOR NEXT WEEK WITH SOME 90S NOT OUT OF THE
QUESTION EITHER TOWARD THE END OF THE WEEK AS WE BEGIN SEPTEMBER.
THERE IS A SMALL CHANCE FOR THUNDERSTORMS ON TUESDAY AS A COLD FRONT
WORKS INTO THE AREA. HOWEVER...THIS FRONT WILL BE WASHING OUT OVER
MN AS IT ENCOUNTERS THE RIDGE...SO THIS PART OF THE FORECAST IS
BOUND TO CHANGE...LIKELY TOWARD THE DRIER DIRECTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1225 PM CDT TUE AUG 25 2015

NW WIND GUSTS OF 18-20 KTS WILL PERSIST ACROSS EASTERN MN AND
WESTERN WI THIS AFTERNOON. THE WINDS WILL DIMINISH QUICKLY THIS
EVENING AS A RIDGE OF HIGH PRESSURE MOVES IN FROM THE EASTERN
DAKOTAS. LIGHT AND VARIABLE WINDS FOR THE OVERNIGHT HOURS AS WELL
AS WEDNESDAY MORNING.

THE MVFR CEILINGS AFFECTING KEAU WILL LIFT AND SCT BY THIS EVENING
AS A VERTICALLY STACKED LOW PRESSURE SYSTEM OVER THE UPPER LAKES
BEGINS MOVING NORTHEAST. AT THIS POINT...IT LOOKS AS THOUGH KRNH
WILL BE ON THE EDGE OF SCT-BKN VFR CLOUDINESS THIS AFTERNOON WHILE
MAINLY SKC PREVAILS TO THE WEST FOR THE MN TAF SITES.

KMSP...

/OUTLOOK FOR KMSP/
THU...VFR. WIND S AT 10-15 KTS.
FRI...VFR. CHC SHRA/TSRA WITH MVFR POSSIBLE. WINDS SE 5-10 KTS.
SAT...VFR. WINDS E 5-10 KTS.


&&

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

$$

SHORT TERM...ADL
LONG TERM...MPG
AVIATION...RAH


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