Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 081820
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
120 PM CDT TUE JUL 8 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 332 AM CDT TUE JUL 8 2014

CYCLONIC FLOW WILL PREVAIL OVER THE AREA TODAY IN THE BASE OF THE
TROUGH PIVOTING OVER ONTARIO. THIS WILL GENERATE A FAIR AMOUNT OF
CUMULUS CLOUD DEVELOPMENT BY MID MORNING...ESPECIALLY FROM CENTRAL
MN INTO WEST CENTRAL WI. MID LEVEL TEMPERATURES AND LAPSE RATES
INDICATE THE POTENTIAL FOR SCATTERED DIURNALLY DRIVEN SHOWERS TODAY
AS WELL...PARTICULARLY OVER WEST CENTRAL WI...BUT ALSO ACROSS WEST
CENTRAL MN.

GIVEN THE ANTICIPATED CLOUD COVER AND COLD AIR ADVECTION
TODAY...TEMPERATURES WILL BE ON THE COOL SIDE OF NORMAL AND BE
ACCOMPANIED BY BREEZY NORTHWEST WINDS. HIGHS WILL GENERALLY RANGE AROUND
5 DEGREES BELOW NORMAL...AND TOP OUT IN THE LOW/MID 70S. CLOUDS
SCATTER OUT TONIGHT AND TEMPERATURES WILL COOL INTO THE 50S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 332 AM CDT TUE JUL 8 2014

DRY AND COOL WEATHER WILL GIVE WAY TO WARMER TEMPERATURES AND
INCREASING HUMIDITY TOWARD THE END OF THE WEEK WITH RETURNING
CHANCES FOR SHOWERS AND THUNDERSTORMS. THE BEST CHANCE FOR RAIN WILL
BE THURSDAY NIGHT AND AGAIN OVER THE WEEKEND.

WEDNESDAY...AT THE START OF THE PERIOD WEDNESDAY HIGH PRESSURE
SHOULD BE ACROSS THE MISSISSIPPI RIVER VALLEY WITH LIGHT WINDS AND
CLEAR SKIES EXPECTED AT THE START OF THE DAY. CLOUDS WILL INCREASE
DURING THE AFTERNOON AS RELATIVELY COOL AIR ALOFT...H850 TEMPS
HOOVER AROUND 10C...TOGETHER WITH MID SUMMER DIABATIC SURFACE
HEATING PROMOTE DEEP BOUNDARY LAYER MIXING. HOWEVER...500MB HEIGHT
RISES TOGETHER WITH THE ANTICYCLONIC CURVATURE LEAD TO LARGE SCALE
SUBSIDENCE. THIS SUBSIDENCE IS EVIDENT BY THE STOUT INVERSION WITHIN
THE 650-700MB LAYER SHOWN IN BOTH THE GFS AND NAM BUFR
SOUNDINGS...AND SHOULD HOLD OFF ANY PRECIP WITH THE FAIR WEATHER
CUMULUS THAT DO MANAGE TO DEVELOP WEDNESDAY AFTERNOON. IF THE
FORECAST MODELS OVERDO THE BOUNDARY LAYER MOISTURE...AS IS OFTEN THE
CASE...THEN THE CONFIDENCE IN A DRY WEDNESDAY FORECAST INCREASES.

BY THURSDAY A SHORTWAVE CURRENTLY LOCATED ACROSS NORTHERN CALIFORNIA
WILL TRAVERSE THE RIDGE ACROSS THE MOUNTAINS AND BE THE FOCUS FOR
SHOWERS AND THUNDERSTORMS THURSDAY NIGHT. BASED ON THE TIMING OF THE
UPPER LEVEL WAVE AND LOW LEVEL THETA_E ADVECTION FEEL THAT THE
PRECIP WILL MOVE OUT QUICKER THAN PREVIOUSLY FORECAST...SO HAVE
SPLIT THE PRECIP GRIDS INTO 3HR BLOCKS TO CONVEY THIS QUICKER
TIMING. DIRECTIONAL SHEAR WILL BE FAVORABLE FOR ELEVATED SEVERE
STORMS...BUT WITHOUT AN ELEVATED MIXED LAYER THE CAPE PROFILE ENDS UP
BEING LONG AND SKINNY...SO ONLY ANTICIPATING A MARGINAL THREAT FOR
SEVERE WEATHER AT THIS TIME.

LOOKING AHEAD...THE GFS AND GEM 08.00 BRING ANOTHER SHORTWAVE ACROSS
THE HIGH PLAINS AND INTO THE UPPER MIDWEST OVER THE WEEKEND. THIS
WOULD BRING ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS.
HOWEVER...THE ECMWF IS VIRTUALLY NONEXISTENT WITH THIS FEATURE...SO
DID NOT STRAY FROM A BLENDED APPROACH TO THE PRECIP CHANCES OVER THE
WEEKEND. IF THE GFS/GEM VERIFY SHOULD SEE A GOOD CHANCE FOR SEVERE
WEATHER SATURDAY AFTERNOON AND EVENING...BUT AT THIS TIME CONFIDENCE
IS TOO LOW TO DO ANYTHING MORE THAN SPECULATE. COOLER AIR WILL
OVERSPREAD THE REGION EARLY NEXT WEEK...SO DROPPED MONDAYS TEMPS A
DEGREE COOLER THAN GUIDANCE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1259 PM CDT TUE JUL 8 2014

NO MAJOR AVIATION WEATHER CONCERNS OVER THE NEXT 24-26 HOURS.
SCATTERED TO BROKEN CUMULUS CLOUDS WILL DISSIPATE AROUND
SUNSET...AS WILL THE WINDS. NO PRECIP IS EXPECTED AND WE HAVE HIGH
CONFIDENCE IN VFR AND LITTLE VARIATION IN WIND DIRECTION. SHOWERS
WILL GRAZE THE KEAU AIRPORT THIS AIRPORT THIS AFTERNOON...BUT
SHOULD ONLY LAST A COUPLE HOURS.

KMSP...

NO MAJOR AVIATION WEATHER CONCERNS...BUT WE SHOULD KEEP THE BROKEN
CUMULUS CLOUDS UNTIL WE BEGIN TO LOSE OUT HEATING LATE THIS
AFTERNOON. THEY WILL QUICKLY CLEAR IN THE EARLY EVENING.

/OUTLOOK FOR KMSP/

WED...VFR. W-NW WIND LESS THAN 5 KT.
THU...VFR. MVFR POSSIBLE IN SHRA/TS LATE. SSE WIND 10 TO 15 KT.
FRI...MVFR CONDITIONS POSSIBLE WITH A CHANCE OF SHRA/TSRA. SOUTH
WIND 5 TO 10 KT.

&&

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

$$

SHORT TERM...LS
LONG TERM...JRB
AVIATION...CLF






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