Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 210853
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
353 AM CDT TUE OCT 21 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 319 AM CDT TUE OCT 21 2014

TODAY-TONIGHT...VERY QUIET PERIOD IN THE FORECAST. SFC ANALYSIS
SHOWS AN ELONGATED N-S ORIENTED AREA OF HIGH PRES ATOP THE AREA
WHICH WILL SHIFT OFF TO THE E DURING THE DAY TODAY...THEN STALL OUT
OVER THE GREAT LAKES TONIGHT. ALOFT...A RIDGE OF HIGH PRES
STRADDLING THE BORDER OF MN AND WESTERN DAKOTAS THIS MORNING WILL
SLOWLY SLIDE E ACROSS MN AND WI DURING THE DAY TODAY...ALSO
EXPECTED TO STALL OUT TONIGHT OVER THE WESTERN GREAT LAKES
SOUTHWARD THROUGH THE MID MISSISSIPPI RIVER VALLEY. THIS DEEP
RIDGING COMBINATION WILL KEEP SKIES MOSTLY CLEAR FOR THE PERIOD
THROUGH TONIGHT...ASIDE FROM SOME WRAPAROUND MOISTURE FROM A
DEPARTING UPPER LEVEL LOW PRES CENTER OVER THE EASTERN GREAT
LAKES...BRINGING STRATOCU DOWN OVER MAINLY EASTERN AND NORTHERN
WI...POSSIBLY AS FAR W AS BARRON/RUSK/CHIPPEWA COUNTIES IN WESTERN
WI. THIS CLOUD COVER MAY LINGER FOR MUCH OF THE DAY IN THE FAR
EASTERN PORTION OF THE MPX CWFA WHILE FAIR WEATHER CU CLOUDS
DEVELOP OVER EASTERN INTO CENTRAL MN. COLD AIR ADVECTION IN
ADVANCE OF THE INCOMING RIDGE WILL KEEP HIGHS IN THE LOW-MID 50S
FOR WESTERN WI. IN CONTRAST TO THIS...MODEST WARM AIR ADVECTION
WILL OCCUR FOR CENTRAL-WESTERN MN ON THE BACKSIDE OF THE UPPER
RIDGE WHERE HIGHS WILL RANGE THROUGH THE 60S...AND POSSIBLY TO
NEAR 70 ALONG THE SD BORDER. FOR TONIGHT...THE BEST RADIATIONAL
COOLING CONDITIONS WILL BE OVER WESTERN WI WHERE LOWS WILL DROP TO
NEAR THE FREEZING MARK. THE SPREAD IN LOWS TO CENTRAL-WESTERN MN
WILL BE QUITE LARGE AS WARMER RETURN FLOW WILL HAVE MUCH MORE
INFLUENCE OUT WEST. LOWS TONIGHT IN WESTERN MN WILL ONLY DROP TO
THE MID-UPPER 40S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 319 AM CDT TUE OCT 21 2014

EARLY MORNING WATER VAPOR IMAGERY SHOWED A PROMINENT CIRCULATION
MOVING EAST ACROSS NORTHERN CALIFORNIA INTO NEVADA. THIS
CIRCULATION IS IN ASSOCIATION WITH AN UPPER LEVEL SHORTWAVE THAT
IS THE MAIN CONCERN FOR THE LONG TERM FORECAST PERIOD. THIS WAVE
IS EXPECTED TO MOVE ENE ACROSS THE WESTERN CONUS AND PRODUCE RAIN
ACROSS THE FA FROM WEDNESDAY THROUGH THURSDAY THAT WILL MOVE WEST
TO EAST ACROSS THE AREA. THERE REMAIN MODEL DIFFERENCES IN TIMING
AND AMOUNTS EXPECTED THAT STILL NEED TO BE SORTED OUT. THE GFS
MOVES THE ENERGY THROUGH THE FASTEST...WHILE THE NAM IS SEVERAL
HOURS SLOWER WITH THE EXPANSION OF ISENTROPIC ASCENT AND
SATURATION ACROSS THE FA. RAINFALL AMOUNTS GENERALLY LOOK TO BE
LESS THAN 0.5".  OVERALL...FORECASTER CONFIDENCE IS BELOW AVERAGE
AT THIS TIME DUE TO THESE DIFFERENCES.

ONCE THIS SYSTEM PASSES...UPPER LEVEL RIDGING WILL ENSUE ACROSS
THE UPPER MIDWEST. LITTLE CHANGE WAS MADE TO THE FORECAST BEYOND
FRIDAY...AS WARM AND DRY CONDITIONS STILL LOOK LIKE A GOOD BET.
WENT WARMER THAN BLENDED GUIDANCE ON FRIDAY AND SUNDAY AS
TEMPERATURES WARM UNDER THE RIDGE. ECMWF AND GFS STILL INDICATE
CYCLOGENESIS ON THE LEE OF THE ROCKIES TOWARD THE END OF THE
WEEKEND WITH SPATIAL AND TEMPORAL DIFFERENCES IN THE EVOLUTION OF
THE SYSTEM. THIS SYSTEM GIVES US OUR NEXT OPPORTUNITY AT
PRECIP...MOST LIKELY AT THE VERY END OF THE WEEKEND INTO EARLY
NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1049 PM CDT MON OCT 20 2014

SURFACE RIDGING ACROSS MN WILL WORK EAST TO THE WESTERN GREAT
LAKES DURING THE TAF PERIOD. A TIGHTENING PRESSURE GRADIENT ON
THE WESTERN SIDE OF THE RIDGE WILL LEAD TO SE WINDS AT 15G25KTS
FOR KAXN AND KRWF FROM LATE TUESDAY MORNING AND AFTERNOON. THE
EASTERN TAF SITES WILL SEE SE WINDS ON TUESDAY FROM 8-12 KNOTS.
A CONCERN REMAINS ON WHETHER OR NOT THE WESTERN EDGE OF THE VFR
CEILINGS NEAR KEAU WILL BECOME MVFR OVERNIGHT AS THE LIGHT
NORTHEAST WINDS BECOME EAST SOUTHEAST. CONFIDENCE IS NOT HIGH ON
THE MVFR AS EACH SUBSEQUENT UPDATE TO THE LAMP PROBABILITIES
CONTINUE TO BACK AWAY ON THE CEILINGS IN THE 12Z-15Z TIME FRAME.

KMSP...VFR THROUGH THE PERIOD. LIGHT NE WINDS BECOMING EASTERLY BY
MORNING AND SE 10 KTS DURING THE MORNING.

/OUTLOOK FOR KMSP/

WED...VFR. WINDS SSE AT 15G20KTS.
WED NGT...VFR WITH MVFR/SHRA POSSIBLE. WINDS S AT 10KTS.
THU...VFR WITH MVFR/SHRA POSSIBLE. WINDS SSW AT 8KTS.
FRI...VFR. WINDS SSW 5KTS.


&&

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

$$

SHORT TERM...JPC
LONG TERM...SPD
AVIATION...RAH






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