Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 180910
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
410 AM CDT THU SEP 18 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 405 AM CDT THU SEP 18 2014

A COOLER AIR MASS MOVED SW ACROSS MN OVERNIGHT. THE LEADING EDGE
OF THIS COOLER AIR MASS HAD SOME LOWER CLDS...ALONG WITH GUSTY
NE WINDS. ALTHOUGH RETURN FLOW WILL COMMENCE LATER TODAY...SOME
RESIDUAL LOW CLDS/FOG MAY DEVELOP AND PERSIST ACROSS PORTIONS OF
MN/WI BEFORE NOON. NOT TOO MANY CHGS OVERNIGHT AS THE MAIN FORCING
REMAINS NORTH OF MPX CWA THRU 12Z FRIDAY. MOISTURE LEVELS DUE
INCREASE TODAY/TONIGHT IN RESPONSE TO INCREASING SE/S WINDS. THE
BEST CHC OF SHRA/TSRA WILL OCCUR IN CENTRAL MN...WITH THE BULK OF
THE HEAVIER ACTIVITY IN NORTHERN MN BEFORE DAYBREAK FRIDAY. EVEN
SOME OF THE CAMS REFLECTIVITY PATTERN HOLDS THE BULK OF THE
CONVECTION NORTH OF MPX CWA. TEMPS MAY BE A FEW DEGREES COOLER
THAN ON WEDNESDAY...BUT STILL RISING INTO THE 70S IN MN...WITH
LOWER TO MID 60S IN WC WI.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 405 AM CDT THU SEP 18 2014

FRIDAY THROUGH SATURDAY...THE MAIN FOCUS FOR THE EXTENDED PORTION
OF THE FORECAST REMAINS IN THIS 36-HR PERIOD. AN APPROACHING UPR
LEVEL RIDGE FROM THE NRN PLAINS WILL FLATTEN AS IT ENTERS THE UPR
MISS RIVER VALLEY REGION. RIGHT ON THE HEELS OF THIS DISSIPATING
RIDGE IS A DIGGING SHORTWAVE TROUGH. THIS TROUGH WILL AID IN THE
LIFTING OF A SFC WMFNT OVER THE DAKOTAS AND MN/WI...WHILE A PAIR
OF LOW PRES CENTERS /ONE OVER SRN MANITOBA PROVINCE AND ANOTHER
COMING OFF THE LEE OF THE ROCKIES/ SHIFT EWD IN TANDEM. A CDFNT
TRAILING SWWD FROM THE NRN LOW WILL SLOWLY APPROACH FROM THE W
DURG THE DAY ON FRI AND GRADUALLY CROSS THE REGION FRI NIGHT INTO
SAT MRNG. A DEEP PLUME OF MOISTURE FROM THE GOMEX ON THE BACKSIDE
OF THE DEPARTING HIGH WILL THRUST HIGHER DEWPOINT AIR INTO THE
REGION...HELPING BUILD INSTABILITY IN ADVANCE OF THE CDFNT FOR FRI
AFTN AND EVE. WHILE SOME SCATTERED SHWRS AND POSSIBLY A FEW TSTMS
ARE POSSIBLE DURG THE DAY ON FRI WITH THE WMFNT...THE BULK OF THE
PRECIP ACTIVITY WILL OCCUR FRI NIGHT IN THE WARM SECTOR OF THIS
SYSTEM. CAPPING ALOFT WILL DISSIPATE BY THE EVE HRS BUT THERE MAY
BE SOME INVERSION AT/NEAR THE SFC WHICH MAY INHIBIT MORE
WIDESPREAD CONVECTION. NEVERTHELESS...MUCAPES APPROACH THE
1500-2000 J/KG RANGE...0-6KM BULK SHEAR REACH 40-45 KT AND MIDLVL
LAPSE RATES BECOME DECENT ENOUGH FOR STRONG STORM STRENGTH
/APPROXIMATELY 7.0-8.0 C/KM/. THIS WILL ALLOW FOR NOT ONLY DECENT
COVERAGE OF TSTMS...ESP IN ERN MN INTO WRN WI...BUT ALSO FOR THE
SMALL POSSIBILITY THAT SHOULD STORMS GROW DEEP ENOUGH WITH THE
APPROACHING UPR LVL SHORTWAVE TROUGH...SOME STORMS COULD BE STRONG
TO SEVERE WITH LARGE HAIL OR DAMAGING WINDS. SPC SWODY2 MAINTAINS
A 5 PERCENT SEVERE TSTM RISK OVER CENTRAL AND SRN PORTIONS OF THE
CWFA FOR FRI NIGHT WHICH IS CERTAINLY REASONABLE. AS THE CDFNT
PUSHES THROUGH THE REGION FRI NIGHT INTO SAT MRNG...COVERAGE OF
PRECIP WILL DIMINISH AS PRECIP ENDS FROM W TO E. ONLY SOME
LINGERING SHWRS ARE EXPECTED FOR THE FIRST HALF OF SATURDAY. AS
FOR TEMPERATURES...A NOTICEABLE WARMING TREND WILL TAKE PLACE WITH
THE LIFTING OF THE WMFNT ACRS THE AREA FRI AND AHEAD OF CAA THAT
IS NOT EXPECTED TO TRULY KICK IN UNTIL AFTER MAX TEMPS HAVE BEEN
REACHED ON SATURDAY. HIGHS WILL HIT THE MID-UPR 70S BOTH DAYS
WHILE DEWPOINTS CLIMB TO THE CLIMB TO THE LOW-MID 60S...PRODUCING
HEAT INDEX VALUES INTO THE LOW-MID 80S.

SUNDAY THROUGH WEDNESDAY...THE WARMUP AND PRECIP ACTIVITY FEATURED
IN THE FRI-SAT PERIOD WILL NOT BE PRESENT FOR THE REMAINDER OF THE
LONG-TERM FCST PERIOD AS CANADIAN HIGH PRES FOLLOWS THE CDFNT SAT
NIGHT. THIS COOLER AND DRIER HIGH PRES AIRMASS WILL THEN REMAIN
OVER THE AREA THROUGH THE MIDDLE OF NEXT WEEK...KEEPING THE AREA
DEVOID OF PRECIPITATION AND TEMPERATURES CLOSE TO NORMAL VALUES.
HIGHS WILL STRUGGLE TO HIT THE 70-DEGREE MARK...LIKELY REMAINING
IN THE MID-UPR 60S...WITH LOWS IN THE 40S TO ARND 50.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1054 PM CDT WED SEP 17 2014

IFR CEILINGS ARE RACING WESTWARD ACROSS CENTRAL MN LATE THIS
EVENING WITH KSTC AND KAXN BEING IMPACTED BEFORE THE 06Z TAFS.
BOTH OF THESE SITES MAY NOT STAY IFR ALL NIGHT LONG DUE TO THE LOW
LEVEL FLOW BECOMING MORE SE. THIS WILL LIFT THE LOW CEILINGS TO
THE NW LATE IN THE NIGHT. KEAU AND KRNH WILL LIKELY SEE MVFR OR
LOWER BR/FG DEVELOP AFTER 06Z WITH IFR CEILINGS DEVELOPING AFTER
09Z. THESE SITES ARE MORE PRONE TO A LONGER DURATION OF MVFR OR
LOWER CEILINGS THROUGH THE MORNING ON THURSDAY AS ADDITIONAL
CEILINGS DEVELOP OVER SOUTHERN WI LATE IN THE NIGHT AND ADVECT
NORTHWEST THURSDAY MORNING. KMSP IS ON THE EDGE AND SHOULD ONLY
SEE SCT LOW MVFR CLOUDS AND 5-6SM BR. KRWF IS STILL EXPECTED TO
DEVELOP A LOW MVFR CEILING LATE IN THE NIGHT. LIGHT NE TO E WINDS
EARLY IN THE PERIOD BECOMING SE LATE IN THE NIGHT WITH SPEEDS
INCREASING TO 10-15 KNOTS THURSDAY MORNING. SOME GUSTS TO 20 KNOTS
ACROSS WESTERN MN IN THE AFTERNOON.

KMSP...FIRST SURGE OF LOW MVFR/IFR CEILINGS TO STAY WELL NORTH OF
THE AIRFIELD. HOWEVER...LATE IN THE NIGHT AND THURSDAY MORNING
THERE REMAINS A SMALL CHANCE OF BKN008-010 COMING AT THE AIRPORT
FROM THE SE. THE BULK OF THESE LOW CEILINGS ARE EXPECTED TO BE
EAST OF THE AIRFIELD IN CENTRAL WI.

/OUTLOOK FOR KMSP/
FRI...VFR. CHC SHRA/TSRA BEFORE 9 PM. MORE NUMEROUS AFT 9 PM WITH
MVFR/IFR CIGS/VSBYS. WINDS S-SW 15-25 KT.
SAT...VFR. MORNING -SHRA POSSIBLY MVFR CIGS. WINDS NW 10-15 KT.
SUN...VFR. WINDS NW 10-15 KTS.

&&

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

$$

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







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