Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 240926
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
426 AM CDT FRI OCT 24 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 314 AM CDT FRI OCT 24 2014

MAIN CONCERN TODAY IS DENSE FOG AND THE POSSIBILITY OF HOLDING
DOWN TEMPS IN THE SE CWA DUE TO ANOTHER SHRTWV AND ASSOCIATED
MOISTURE MOVING ACROSS THE AREA.

FIRST...S/SW BOUNDARY LAYER WINDS BEGAN TO INCREASE SHORTLY BEFORE
MIDNIGHT WHICH LED TO MOST OF THE MOISTURE/FOG FORMATION IN EC/SE
MN TO HALT. THESE WINDS WILL ALSO KEEP THE BULK OF THE LOWER
CLDS/FOG ACROSS WC WI THIS MORNING AND THEREFORE...THE DENSE FOG
ADV HAS BEEN DROPPED IN MN /WITH THE EXCEPTION OF GOODHUE CTY/.
EVEN IN WC WI...THE DENSE FOG HAS BEEN LIMITED TO THE HIGHER
TERRAIN OR ALONG THE RIVER VALLEYS. MOST OF THE OBS WERE NOTING
LOW CIGS...BUT VSBYS WERE AOA 1SM. THE SW/S WINDS IN THE BOUNDARY
LAYER WILL ALSO LEAD TO MORE MOISTURE SURGING N/NE ACROSS SC/SE/EC
MN BY MID/LATE MORNING...AND ACROSS MOST OF WC WI DURING THE AFTN.
THIS WILL KEEP TEMPS FROM RISING TOO MUCH...WITH 60S A BETTER
SCENARIO. ELSEWHERE...UPPER 60S/LOWER 70S REMAIN REASONABLE WITH
NEAR 80 IN THE TYPICAL AREAS OF WC MN WITH A SLIGHTLY STRONGER
DOWNSLOPE WIND COMPONENT ALONG THE BUFFALO RIDGE.

THERE REMAINS SOME UNCERTAINTY WITH -SHRA/SPRINKLES IN SE/SC MN
DURING THE MID/LATE AFTN HRS. ALTHOUGH MOISTURE WILL BE LIMITED TO
THE FIRST 10K...WAA IN THIS LAYER MAY ALLOW FOR SOME ISOLD SHRA TO
DEVELOP. WILL KEEP CONDS DRY AT THIS TIME...BUT SOMETHING TO LOOK
AT FOR LATER THIS MORNING.

NO CHGS OVERNIGHT WITH SKIES RAPIDLY CLEARING FROM THE WEST AS A
POTENT STORM SYSTEM SWEEPS ACROSS SOUTH CENTRAL CANADA.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 314 AM CDT FRI OCT 24 2014

THE LONG TERM PERIOD STARTS AND ENDS CALMLY. IT/S THE MIDDLE
PORTION THAT IS UNSETTLED DUE TO A POTENT INCOMING LONGWAVE TROUGH
FROM THE WEST COAST THAT WILL SHIFT INTO THE CENTRAL
CONUS...BRINGING A STORM SYSTEM WITH IT.

SATURDAY WILL START WITH A LARGE RIDGE THAT WILL ENCOMPASS MUCH OF
THE LOWER 48 STATES...ORIGINATING FROM THE SOUTHERN PLAINS. THIS
RIDGE WILL HOLD ITS OWN...SHIFTING SLOWLY EWD THRU SUNDAY AND
ALLOWING ITS AXIS TO MOVE ACRS THE MISSISSIPPI RIVER DURG THE DAY
ON SUNDAY. IT WILL BREAK DOWN SOMEWHAT...BUT NOT TO THE DEGREE
PREVIOUSLY DEPICTED ON MODELS SO THE COOLING ASSOCIATED WITH
TDA/S CDFNT WILL NOT BE AS STRONG. THERE WILL BE VERY LITTLE CLOUD
COVER ON SATURDAY FOLLOWED BY MAINLY HIGH CLOUDS ON SUNDAY WITH
HIGHS BOTH DAYS IN THE LOW-MID 60S. THE RIDGE WILL ALSO HELP SLOW
THE PROGRESSION OF THE AFOREMENTIONED STORM SYSTEM EXPECTED TO
MOVE ACROSS THE REGION EARLY NEXT WEEK.

GETTING INTO THE DETAILS...A LONGWAVE TROUGH WILL MOVE ONSHORE THE
PAC NW DURG THE DAY ON SUN WHILE A WEAK AREA OF LOW PRES DEVELOPS
IN THE LEE OF THE ROCKIES. A STRONGER LOW PRES CENTER WILL MOVE
EWD IN ADVANCE OF THE TROUGH JUST N OF THE CANADIAN BORDER. THE
TROUGH WILL SHOVE THE CANADIAN /NRN STREAM/ LOW EWD WHILE PICKING
UP THE ROCKIES /SRN STREAM/ LOW. THE ROCKIES LOW AGAIN LOOKS
WEAKER IN CONSECUTIVE MODEL RUNS...MAKING THE CANADIAN LOW THE
MAIN FEATURE BUT STILL WITH SFC FRONTS DROPPING INTO THE CENTRAL
CONUS FROM IT. THE CONGLOMERATION OF THESE LOW PRES CENTERS WILL
SHIFT ACRS MN/WI MON THRU TUE MRNG. IN ADDITION...THE UPR LVL
TROUGH BECOMES MORE COMPACT AND SLIGHTLY NEGATIVELY TILTED BY
DAYBREAK TUE...ALLOWING FOR SLIGHTLY ENHANCED LIFT FOR BETTER
PRECIP GENERATION. PROBLEM IS...THERE ARE STILL MODEL-TO-MODEL
DISAGREEMENTS IN THE INTENSITY OF THIS SYSTEM DUE TO THE
DIFFICULTY OF HANDLING THE PHASING...OR RATHER NON-PHASING... OF
THE NRN AND SRN STREAMS UPSTREAM FROM THE MPX CWFA. THIS MAKES
TIMING AND COVERAGE OF PRECIP A BIT PROBLEMATIC. CONFIDENCE IS
HIGHER THAT THE PRECIP WILL BE DELAYED SO HAVE REMOVED POPS FROM
SUNDAY BUT MAINTAINED POPS NO HIGHER THAN CHC RANGE SUN NIGHT THRU
TUE. WITHIN THAT RANGE...BEST TIMING FOR PRECIP LOOKS TO BE MON
NIGHT...ESP OVER ERN MN INTO WRN WI...AS THE UPR TROF DEEPENS AND
SHIFTS THE SRN STREAM LOW THRU THE AREA.

THE UPR TROUGH AND ITS ASSOCIATED LOW PRES CENTERS THEN SHIFT THRU
THE REGION BY TUE EVENING...FOLLOWED BY PREVAILING ZONAL /SLIGHTLY
WNW-ESE/ FLOW ALOFT AND A NON-DESCRIPT SFC PRES PATTERN. THIS WILL
RESULT IN GENERALLY PRECIP-FREE WX CONDS WITH PTLY CLOUDY SKIES
FOR THE MIDDLE OF NEXT WEEK. IT WILL ALSO RESULT IN NOTICEABLY
COOLER CONDS FOR THE LAST WEEK OF OCTOBER. HIGHS WILL DROP TO THE
UPR 40S TO LWR 50S FOR THE MIDDLE OF NEXT WEEK WHILE LOWS DROP TO
30S FOR THE MIDDLE OF NEXT WEEK...AND POSSIBLY THE 20S BY THE END
OF NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1046 PM CDT THU OCT 23 2014

CONFIDENCE IS INCREASING THAT LOW MVFR/IFR CEILINGS ACROSS WESTERN
WI AND FAR SE MN WILL BACK INTO EAST CENTRAL MN...INCLUDING THE
TWIN CITIES...OVERNIGHT. VISIBILITIES WILL SLOWLY DETERIORATE
UNDER THE STRATUS DURING THE NIGHT. AREAS OF EASTERN MN WHERE IT
IS CLEAR RIGHT NOW HAVE A BETTER CHANCE OF LIFR/VLIFR CEILINGS AND
VISIBILITIES DEVELOPING BETWEEN 06Z AND 08Z. DEW POINTS ARE LOWER
FOR THE WESTERN MN TERMINALS...RESULTING IN A LARGER TEMP/DEW
POINT SPREADS. THERE IS A ALSO INCREASING HIGH CLOUDS IN THE WEST
THAT WILL HELP KEEP TEMPERATURES FROM FALLING. HENCE...VFR
CONDITIONS STILL EXPECTED FOR KRWF..KSTC AND KAXN. CEILINGS AND
VISIBILITIES IMPROVING BY LATE MORNING ACROSS EASTERN MN AND EARLY
IN THE AFTERNOON ACROSS WESTERN WI. LIGHT SE WINDS OVERNIGHT
GRADUALLY VEERING SW ON FRIDAY WITH SPEEDS IN THE AFTERNOON 8-10
KNOTS.

KMSP...LOW MVFR/IFR CEILINGS CONTINUE DRIFTING NW TOWARDS THE
AIRFIELD WITH BKN-OVC010 EXPECTED BY 07Z. CEILINGS WILL PERSIST
THROUGH MUCH OF THE MORNING BEFORE THE LOW LEVEL FLOW TURNS SW AND
PUSHES THINGS OFF TO THE EAST.

/OUTLOOK FOR KMSP/

SAT...VFR. WINDS W-NW AT 10-15KTS.
SUN...CHC MVFR/-SHRA LATE SUNDAY NIGHT. WINDS BECOMING SE AT
08-14KTS IN AFTERNOON.
MON...CHC MVFR/-SHRA WINDS E-NE AT 08-13KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR MNZ078.

WI...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR WIZ014>016-
     023>028.

&&

$$

SHORT TERM...JLT
LONG TERM...JPC
AVIATION...RAH






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