Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 281131
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
631 AM CDT TUE OCT 28 2014

.UPDATE...
ISSUED AT 621 AM CDT TUE OCT 28 2014

UPDATED TO INCLUDE 12Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 245 AM CDT TUE OCT 28 2014

TODAY-TONIGHT...SFC ANALYSIS THIS MRNG PUTS A NOW-PHASED LOW PRES
CENTER OVER THE CENTRAL GREAT LAKES WITH CDFNT XTDNG SWWD THRU THE
OH RIVER VALLEY...MID-MISS RIVER VALLEY TO THE DEEP SOUTH. IN
ADDITION...A TRAILING SFC TROUGH XTNDS WNW ALONG THE INTERNATIONAL
BORDER OF MI/MN. ALOFT...A LARGE CUTOFF LOW IS ROTATING EWD OVER
NRN MN. THESE FEATURES ARE XPCTD TO SHIFT EWD TDA...BUT THE ISSUE
IS THE TRAILING SFC TROF. THIS TROF WILL SWING SEWD AROUND THE
DEEPENING SFC LOW...AND WILL AID IN MAINTAINING NOT ONLY EXTENSIVE
CLOUD COVER OVER MN/WI BUT ALSO SCATTERED TO NUMEROUS RAIN SHOWERS
OVER NRN MN...N OF THE WFO MPX CWFA. ONCE THIS TROF BEGINS TO
ROTATE AROUND THE DEPARTING LOW...COLD POOLING ALOFT COMBINED WITH
WEAK LIFT MAY BE ABLE TO SPREAD SOME OF THESE SHOWERS SWD INTO
CENTRAL MN AND WRN WI. NOT LOOKING FOR MUCH IN THE WAY OF
COVERAGE...ONLY ISOLD TO SCATTERED...AND ANY SHOWERS WILL PRODUCE
LIGHT PRECIP. NEVERTHELESS...THE WRAPAROUND FLOW WITH WEAK
INSTABILITY WILL WARRANT INCLUDING -RA MENTION FOR TDA INTO TNGT.
ANY AND ALL PRECIP WILL SHIFT OFF TO THE E THIS EVE WITH STEADILY
CLEARING OVERNIGHT INTO EARLY TUE MRNG AS THE STACKED LOW PRES
SYSTEM DRIVES INTO ERN CANADA AND SFC HIGH PRES ARRIVES FROM THE
E.

AS FOR TEMPERATURES...CAA WILL COMMENCE IN FULL FORCE BY LATER TDA
INTO TNGT AS PRONOUNCED NW FLOW ALOFT WILL BRING IN COLDER
CANADIAN AIR TO THE AREA. VERY SMALL DIURNAL RANGE FROM THIS
MRNG/S LOWS TO THIS AFTN/S HIGHS ARE EXPECTED...WITH HIGHS THIS
AFTN ONLY HITTING THE MID-UPR 40S...AND POSSIBLY EVEN REMAINING IN
THE LWR 40S IN NWRN PORTIONS OF THE CWFA. WITH SKIES CLEARING OUT
AND DEEP NW FLOW IN PLACE FROM THE SFC ON UP...TEMPERATURES TNGT
ARE EXPECTED TO DROP INTO THE UPR 20S IN WRN MN TO THE MID 30S IN
ERN MN AND WRN WI.

THE OTHER CONCERN FOR TDA IS STRONG WINDS DUE TO A TIGHTENING PRES
GRADIENT BEHIND THE DEPARTING LOW PRES SYSTEM AND INCOMING HIGH
PRES. WIND SPEEDS ARE EXPECTED TO INCRS TO THE 15-25 MPH RANGE
WITH GUSTS HITTING 30-40 MPH. THESE SPEEDS LOOK TO FALL JUST
SHORT OF WIND ADVY CRITERIA...BUT WILL STILL CERTAINLY MAKE FOR
BREEZY CONDS.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 245 AM CDT TUE OCT 28 2014

MAIN THEME FOR THE EXTENDED PERIOD...
THE PROGRESSIVE PATTERN WILL REMAIN IN PLACE ACROSS NORTH AMERICA
WITH A HIGHLY AMPLIFIED TROUGH/RIDGE/TROUGH FROM WEST TO EAST BY
FRIDAY/SATURDAY. THE MAIN FORECAST CONCERN IS WHETHER THE
PROGRESSIVE PATTERN CONTINUES...OR A BLOCKING PATTERN STARTS.

AS TODAYS SYSTEM DEPARTS...ANOTHER AND MORE POTENT SHRTWV WILL
RIDE SSE ACROSS CANADA AND INTO THE GREAT LAKES BY FRIDAY MORNING.
A STRONG JET STREAM WILL DEVELOP ACROSS THE PLAINS...AND CONTINUE
TO DIG THIS SHRTWV FURTHER TO THE S/SE ACROSS THE DEEP SE CONUS BY
THE WEEKEND. WITH THE TROUGH IN THE WESTERN CONUS REFORMING AND
DIGGING FURTHER ACROSS CALIFORNIA...THIS WILL AMPLIFY THE UPPER
RIDGE IN THE CENTRAL CONUS FOR THE UPCOMING WEEKEND.

ALTHOUGH THE UPPER MIDWEST SHOULD REMAIN DRY THRU SUNDAY...A WEAK
SHRTWV WITH LIMITED MOISTURE AND JET ENERGY WILL BRUSH THE REGION
LATE WEDNESDAY/EARLY THURSDAY. MODELS HAVE BEEN TRENDING FOR A
STRONGER SHRTWV THEN IN THEIR PREVIOUS RUNS. THE DRIER AIR MASS
IN PLACE SHOULD PRECLUDE ANYTHING SIGNIFICANT IN TERMS OF
MEASURABLE PRECIPITATION. A FEW HUNDREDTHS IS NOT OUT OF THE
QUESTION...BUT MORE THAN LIKELY VIRGA OR SPRINKLES WILL DEVELOP.

THE COLDEST PERIOD WILL BE THURSDAY NIGHT THRU SATURDAY MORNING AS
BOTH THICKNESS VALUES BOTTOM OUT AND CAA SLOWLY LESSENS. HIGHS
NEAR 40 FRIDAY WILL REBOUND INTO THE 50S BY SUNDAY WHICH IS ABV
NORMAL FOR EARLY NOVEMBER.

NOT OVERLY CONFIDENT ON HOW THE UPPER RIDGE BEGINS TO BREAK DOWN
LATE IN THE WEEKEND AND A MORE SW FLOW DEVELOPS ALOFT. STILL
CONCERN WITH THE STRONG TROUGH/STORM SYSTEM AFFECTING THE EAST
COAST THIS WEEKEND AND HOW IT HOLDS BACK OR EVEN BLOCKS THE UPPER
RIDGE FROM MOVING TO FAR EAST. WILL CONTINUE TO LEAN TOWARD THE
PROGRESSIVE PATTERN IN THE MODELS...BUT CONFIDENCE STILL REMAINS
LOW...ESPECIALLY IN TERMS OF AN UNSETTLED WETTER PATTERN FOR THE
UPPER MIDWEST BY MONDAY/TUESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 621 AM CDT TUE OCT 28 2014

LOW CLOUDS...A FUNCTION OF WRAPAROUND MOISTURE FROM A DEPARTING
UPPER LEVEL LOW PRESSURE AREA AND SUBSIDENCE IN ITS WAKE...WILL
MAKE FOR MVFR CEILINGS FOR MUCH OF THE DAY BEFORE LIFTING BY THIS
EVENING. VFR CONDS THEN EXPECTED TO PREVAIL OVERNIGHT THRU TMRW.
NO PRECIP XPCTD FOR MN SITES...AND CHCS TOO LOW FOR INCLUSION ATTM
FOR WI SITES...SO HAVE RUN WITH A DRY FCST THERE. THAT SAID...A
FEW ISOLD -SHRA CANNOT BE RULED OUT. STRONG NWLY WINDS WILL BE THE
OTHER MAIN STORY...WITH SPEEDS REACHING UPWARDS OF 20G30KT.

KMSP...VFR AT INITIALIZATION...BUT SATELLITE SHOWS MVFR CEILINGS
MOVING IN FROM THE NW SO IT APPEARS TO BE A MATTER OF TIME BEFORE
MVFR CIGS ARE REACHED AT MSP. NOT XPCTG CIGS TO DROP BELOW 2 KFT.
CONDS IMPROVE LATE THIS AFTN...WITH VFR CONDS XPCTD OVERNIGHT
INTO TUESDAY DESPITE CONTINUED BKN/OVC SKIES.

/OUTLOOK FOR KMSP/
THU...VFR. WINDS VARIABLE 5 KTS.
FRI...VFR. WINDS N 5-10 KTS.
SAT...VFR. WINDS SE 10-15 KTS.

&&

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

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...JLT
AVIATION...JPC






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