Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 011732
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
ISSUED BY NATIONAL WEATHER SERVICE DULUTH MN
1232 PM CDT TUE SEP 1 2015

***18Z TAFS AVIATION DISCUSSION ISSUED AT 1230 PM AT BOTTOM***

.UPDATE...
ISSUED AT 1002 AM CDT TUE SEP 1 2015

UPDATED THE CLOUDS AND TEMPS TO REFLECT CURRENT TRANDS AND OBS.
WEAK FRONT SLOWLY MOVING ACROSS FORECAST AREA WITH RADAR
INDICATING SOME RETURNS. THE SHOWERS HAVE NOT HIT ANY OB SITES
YET. WILL INTRODUCE AN ISOLATED THUNDERSTORMS IN FAR WESTERN AREAS
FOR LATE THIS AFTERNONN AS CAPES APPROACH 1000 AND WITH DEW POINTS
IN THE 60S WITH FRONTAL SURFACE MOVING THROUGH REGION. REST OF
FCST UNCHANGED.


&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 323 AM CDT TUE SEP 1 2015

CONDITIONS TODAY WILL BE SOMEWHAT SIMILAR TO MONDAY...STARTING OFF
WITH A BIT LESS STRATUS BUT SLIGHTLY LOWER VISIBILITIES DUE TO FOG.
EARLY MORNING SURFACE ANALYSIS SHOWS A WEAK COLD FRONT STRETCHING
FROM WEST CENTRAL MN INTO THE ARROWHEAD REGION. LACK OF MOISTURE AND
FORCING HAVE TRANSLATED TO MERELY AN INCREASE IN MID/HIGH CLOUDS
OVERNIGHT. EXPECT THIS TO BE THE CASE THROUGH THE DAY...WITH
TEMPERATURES MODERATING INTO THE LOW/MID 80S AGAIN AND SOMEWHAT
STICKY CONDITIONS AHEAD OF THE FRONT GIVEN DEWPOINTS IN THE UPPER
60S TO LOWER 70S. WINDS WILL LACK THE GUSTINESS THAT MONDAY
BROUGHT...WITH THE DECAYING FRONT NEARBY.

TONIGHT BRINGS AN INCREASE IN LLVL MOISTURE CONVERGENCE OVER
SOUTHERN MN ON THE NOSE OF THE LLJ...AND A POCKET OF PV ADVECTION
FROM SOUTHERN MN INTO WEST CENTRAL WI. HAVE INCLUDED 20-30 POPS
AFTER DARK WHEN THESE TRIGGERS ARE FORECAST TO KICK IN. LOWS TONIGHT
SHOULD REMAIN MILD...RANGING FROM THE MID 60S TO LOWER 70S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 323 AM CDT TUE SEP 1 2015

A FEW SHORTWAVES EMBEDDED IN SOUTHWEST FLOW ARE THE CAUSE FOR SLIGHT
CHANCES OF PRECIPITATION. THE TIMING AND PLACEMENT OF THESE WAVES
ARE STILL UNCERTAIN BECAUSE THEY ARE DRIVEN PRIMARILY FROM UPSTREAM
CONVECTION. A BETTER CHANCE FOR WIDESPREAD PRECIPITATION IS EXPECTED
ALTER THIS WEEKEND AS HEIGHT FALLS FROM AN UPPER LEVEL WAVE
CURRENTLY LOCATED OFF THE BRITISH COLUMBIA COAST OVERSPREAD THE
REGION.

DETERMINISTIC NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT THAT A
SHORTWAVE WILL MOVE ACROSS THE REGION LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING. HOWEVER...FORECAST SOUNDINGS SHOW A WARM LAYER
NEAR 800MB THAT WILL ACT TO INHIBIT CONVECTION...SO ONLY HAVE A
SLIGHT CHANCE OF POPS DURING THIS TIMEFRAME. MID LEVEL SATURATION
JUST ABOVE THIS CAPPING INVERSION SHOULD HOLD OFF HIGH
TEMPERATURES...SO LOWERED THEM A COUPLE DEGREES ON WEDNESDAY.

ONCE THIS WAVE MOVES THROUGH THURSDAY AND MOST OF FRIDAY WILL BE
DRY...ESPECIALLY EAST OF I-35. ANOTHER PV ANOMALY...THAT SEEMS TO
ORIGINATE FROM CONVECTION ON THE HIGH PLAINS OF TEXAS...WILL LIFT
NORTHWARD TOWARD THE DAKOTAS. THIS FEATURE IS THE PRIMARY DRIVER
BEHIND FRIDAY POPS. ON SATURDAY THE REMNANTS OF TROPICAL DEPRESSION
14_3 WILL BRING CHANCES FOR SHOWERS AND THUNDERSTORMS ONCE AGAIN
ACROSS PRIMARILY THE WESTERN HALF OF THE FORECAST AREA. LOOKING
AHEAD...THE NORTHERN STREAM UPPER LEVEL WAVE HAS SLOWED SOMEWHAT AND
TAKEN A MORE NORTHERLY TRACK...SO HAVE TRIED TO DELAY POPS ACROSS
THE EAST. AS OF NOW THE BEST CHANCE FOR PRECIPITATION IS LATE IN THE
WEEKEND AND EARLY NEXT WEEK...BUT IF THE RIDGING HOLDS ACROSS THE
EASTERN CONUS THIS TOO MAY BE PUSHED BACK IN TIME. THE MOISTURE IS
STILL IN PLACE...SO LOCATIONS THAT SEE STORMS WILL ALSO HAVE THE
POTENTIAL FOR HEAVY RAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1230 PM CDT TUE SEP 1 2015

MAINLY VFR CONDITIONS AT ALL TAF SITES THIS AFTERNOON AND EVENING.
HOWEVER...THERE COULD BE SOME SCATTERED THUNDERSTORM DEVELOPMENT
AFTER 06Z AT SOME SITES DUE TO THE ABUNDANT MOISTURE...SOME
INSTABLITY...AND A WEAK FRONT MOVING ACROSS THE FORECAST AREA.
THERE ALSO COULD BE MVFR CONDITIONS WITH POSSIBLE IFR CONDITIONS
WITH EARLY MORNING FOG. ALL TAF SITES WILL IMPROVE TO VFR BY MID-
MORNING WEDNESDAY.

KMSP...

/OUTLOOK FOR KMSP/

&&

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

$$

UPDATE...STEWART(DLH)
SHORT TERM...LS
LONG TERM...JRB
AVIATION...99


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