Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 252326
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
626 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 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 614 PM CDT TUE AUG 25 2015

VFR CONDS EXPECTED AT ALL SITES WITH CLEARING SKIES AS HIGH PRES
MOVES ATOP THE AREA. ONLY POSSIBLE EXCEPTION IS KEAU WHERE SUNRISE
IFR MIFG IS POSSIBLE DUE TO LIGHT NWLY WINDS AND AN OTHERWISE
FAVORABLE SETUP FOR PRE-DAWN FOG. OTHERWISE...NWLY WINDS THIS EVE
WILL GENERALLY GO LGT/VRBL FOR MUCH OF THE PERIOD BEFORE PICKING
UP FROM THE SE TMRW AFTN.

KMSP...NO SIGNIFICANT WX IMPACTS EXPECTED.

/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...JPC


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