Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 081122
AFDMPX

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

.UPDATE...FOR 12Z AVIATION DISCUSSION BELOW

&&

.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 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 622 AM CDT TUE JUL 8 2014

CYCLONIC FLOW WILL INSTIGATE CUMULUS CLOUD DEVELOPMENT BY LATE
MORNING...ALONG WITH DIURNALLY DRIVEN SHOWERS. COVERAGE SHOULD BE
WIDELY SCATTERED IN NATURE...WITH THE HIGHEST CONCENTRATION
EXPECTED OVER WEST CENTRAL WI IN CLOSER PROXIMITY TO THE MAIN
MID/UPPER SHORTWAVE TROUGH. HAVE THEREFORE INCLUDED VCSH MENTIONS
AT KEAU AND KRNH FOR THIS AFTERNOON...AND LEFT THE REMAINDER OF
THE TAF SITES DRY FOR NOW GIVEN THAT COVERAGE/PROBABILITY OF A
SHOWER AT OTHER SITES IS LOW. NORTHWEST WINDS WILL INCREASE TO
SUSTAINED SPEEDS AROUND OR JUST ABOVE 15 KTS...WITH GUSTS TO
AROUND OR SLIGHTLY HIGHER THAN 25 KTS. CLOUDS CLEAR OUT BY
NIGHTFALL AND WINDS DECREASE TO AOB 5 KTS.

KMSP...
WED...VFR. W 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.

/OUTLOOK FOR KMSP/
CUMULUS CLOUDS /CIRCA 5KFT/ WILL DEVELOP BETWEEN 15Z AND 18Z...AND
PERSIST UNTIL AROUND 00Z. A FEW SHOWERS MAY SKIRT THE
NORTHERN/EASTERN FRINGES OF KSMP...BUT COVERAGE/PROBABILITY IS TOO
LOW TO WARRANT A VCSH AT THIS POINT. NORTHWEST WINDS WILL INCREASE
TO SUSTAINED 15-17KTS WITH GUSTS TO 26 KTS FROM 15Z TO 01Z...THEN
DECREASE BELOW 5KTS OVERNIGHT.

&&

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

$$


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






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