Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 262215
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
415 PM CST FRI DEC 26 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 258 PM CST FRI DEC 26 2014

SFC ANALYSIS PUTS A DEVELOPING LOW PRES CENTER
NEAR KANSAS CITY WITH ITS KICKER UPPER LEVEL TROUGH JUST COMING
ACROSS THE ROCKIES IN WRN NE/WRN KS/ERN CO. A RESIDUAL SFC FRONTAL
BOUNDARY FROM CENTRAL WI SNAKING SWWD INTO CENTRAL KS WILL MAKE FOR
A PATH ALONG WHICH THE LOW PRES CENTER WILL TRAVEL...WHILE THE UPR
LVL TROF SWINGS ACRS THE CENTRAL PLAINS INTO THE GREAT LAKES REGION
THRU MIDDAY TMRW. THIS TROF WILL BECOME NEGATIVELY TILTED AS THE LOW
PRES CENTER DEEPENS...ALLOWING ADDITIONAL MOISTURE FROM THE S AND E
OF THE CENTER TO BE WRAPPED AROUND IT WHILE DRAGGING DOWN COLDER
CANADIAN AIR ON ITS BACKSIDE. THIS COMBINATION WILL BE AN EFFICIENT
SETUP TO ALLOW FOR MEASURABLE...AND LIKELY PLOWABLE...SNOWFALL TO
FALL OVER SRN-ERN MN INTO WRN WI TNGT THRU TMRW MRNG. MODEL QPFS ARE
GENERALLY IN THE 0.20-0.30 RANGE WHILE SNOW RATIOS HAVE HOVERED IN
THE 11/1 TO 15/1 AREA...SO THIS WOULD TRANSLATE TO A GOOD 2-5 INCH
SWATH FOR PORTIONS OF THE WFO MPX CWFA SOUTH OF A LINE FROM
KRWF-KMIC-KRPD. THERE IS POTENTIAL FOR A 4-6 INCH SWATH OF SNOW FROM
ROUGHLY KMKT-KRGK-KRCX...BUT AT LEAST THE MODEL RUNS TDA HAVE COME
IN LOWER THAN THE EARLY MRNG MODELS WHICH DEPICTED SNOWFALL AMOUNTS
AS HIGH AS 7-10 INCHES. THEREFORE...WITH SOLID ADVISORY AMOUNTS
FORECAST...AM OPTING TO STICK WITH THE WINTER WEATHER ADVISORY FOR
SNOW AS ISSUED. AFTER ANY LINGERING AREAS OF FLURRIES/-FZDZ THIS
AFTN...MODELS INDICATE THE MORE SOLID BATCHES OF SNOW TO DEVELOP IN
SWRN MN BETWEEN 00Z-03Z THIS EVE THEN STEADILY PICK UP GOING EWD
OVERNIGHT WITH THE HEAVIEST SNOW EXPECTED LATE THIS EVENING THRU THE
EARLY MRNG HRS SAT. SNOWFALL LOOKS TO TAPER OFF LATE MRNG INTO EARLY
AFTN SAT AS DRIER AIR MOVES IN AHEAD OF A COLDER HIGH PRES AIRMASS
EXPECTED TO MAKE A NOTICEABLE DROP IN TEMPERATURES GOING INTO NEXT
WEEK. THIS COLD AIR ADVECTION WILL BE FELT IN PART TNGT...ESP IN WRN
MN...WHERE LOWS WILL DROP TO THE MID TEENS TO ARND 20...WHILE LOWS
DROP TO THE LOW-MID 20S IN ERN MN INTO WRN WI. THESE TEMPERATURES
WILL BE QUITE EFFICIENT FOR ACCUMULATING SNOW...AND THE MAIN REASON
THE SNOWFALL AMOUNTS DO NOT LOOK TO BE HIGHER IS BECAUSE OF THE
RELATIVELY QUICK SPEED AND COMPACT NATURE OF THIS LOW PRES CENTER
MOVING THROUGH THE REGION. HIGHS ON SAT WILL THEN ONLY RANGE FROM
THE UPR TEENS TO MID 20S...MARKING THE TREND TO COLDER TEMPERATURES
GOING INTO NEXT WEEK.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 258 PM CST FRI DEC 26 2014

THERE LONG TERM IS FAIRLY QUIET COMPARED TO THE SHORT TERM WITH
THE EXCEPTION OF A COUPLE NOTABLE FEATURES IN THE COMING DAYS.
AFTER SATURDAY...THE ONLY RESPECTABLE CHANCE OF SNOW COMES ON
MONDAY WITH A SECOND SURGE OF COLDER AIR THAT WILL BE MUCH COLDER
THAN THE COLD FROM ON SATURDAY. THIS WILL LIKELY BE THE COLDEST
AIR SINCE LAST FEBRUARY. ALTHOUGH WE DID HAVE ONE DAY /DECEMBER
1ST/ WITH SUB ZERO LOWS AND SINGLE DIGIT HIGHS.

THE MONDAY SYSTEM IS FAR FROM CERTAIN AT THIS POINT...WITH THE
ECMWF/GFS LARGELY BEING DRY AND THE NAM/SREF BEING THE MOST
AGGRESSIVE WITH DEVELOPING A WEAK WAVE ALONG THE SURGING ARCTIC
BOUNDARY AND SPREADING SNOW ACROSS AT LEAST THE SOUTHERN AND
WESTERN PORTIONS OF THE FORECAST AREA. THE 26.12Z GEM IS SLOWER
WITH THE ONSET OF SNOW...BUT ALSO DEVELOPS A WEAK WAVE ALONG THE
BOUNDARY AND DROPS SNOW IN IOWA WITH ABOUT 0.10-0.20"...GOOD ENOUGH
FOR RESPECTABLE ACCUMULATION GIVEN THE LIKELY HIGH SNOW RATIO. IF
YOU`RE A FAN OF SNOW...THE 26.15Z SREF IS THE SOLUTION FOR YOU. IT
DEVELOPS A DECENT MID LEVEL CIRCULATION AND THE RESPONSE IS 6-12
HOURS OF GOOD MID LEVEL FGEN. THE SREF PROPS FOR SNOWFALL >4"
/30-50% IN SOUTHERN MN/ IN 12 HOURS IS HIGHER ON MONDAY THAN IT IS
FOR THE SYSTEM TONIGHT. WE`LL SEE HOW THIS SIGNAL CHANGES WITH
TIME...AND IF WE START TO SEE SOME RUN-TO-RUN CONSISTENCY OR SOME
OF THE OTHER MODELING SYSTEMS JUMP ON BOARD WITH THE SREF. AT THIS
POINT...THE FORECAST DOESN`T REFLECT THE POTENTIAL FOR
ACCUMULATING SNOW. REGARDLESS OF WHETHER OR NOT THERE IS SNOW ON
MONDAY OR IF THE ARCTIC BOUNDARY SIMPLY COMES THROUGH WITH
STRATUS OR FLURRIES...THE AIR MASS TO FOLLOW IS COLD. THERE IS
GOOD AGREEMENT ON -18C TO -22C AT 850MB ACROSS THE FORECAST AREA.
WITH SNOW ON THE GROUND...THAT TYPE OF AIR MASS CAN YIELD SUB ZERO
HIGHS...BUT AT THE VERY LEAST...A FEW DAYS OF BELOW ZERO LOWS ARE
LIKELY IF SKIES ARE CLEAR.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1142 AM CST FRI DEC 26 2014

ALL SITES EXPECTED TO LINGER IN THE LOWER-END MVFR RANGE FOR
CEILINGS THRU THIS AFTN THEN DROP INTO IFR RANGE THIS EVENING THRU
OVERNIGHT. BEST CHCS FOR -SN WILL BE ALONG AND EAST OF A KRWF-KMSP
LINE...SO THOSE TWO SITES PLUS THE TWO WI SITES ARE EXPCTED TO SEE
-SN DEVELOP SHORTLY AFTER 00Z...STARTING OUT WITH MVFR VSBY BUT
THEN DROPPING INTO IFR RANGE SHORTLY THEREAFTER FOR GENERALLY 4-6
HOURS. CONDS IMPROVE BEYOND 12Z TMRW MRNG. HAVE ONLY GONE DOWN TO
1SM FOR VSBY BUT GOING DOWN TO 1/2SM OR LOWER...ESP FOR KMSP-KRNH-
KEAU...CERTAINLY CANNOT BE RULED OUT. SAME AS HAVING CEILINGS /OR
VV/ DROPPING TO 500FT OR LOWER AT TIMES. WINDS WILL REMAIN
GENERALLY NLY THROUGHOUT THIS TAF SET...THEN BECOME MORE WNW BY
MIDDAY TMRW.

KMSP...CEILINGS TO REMAIN SUB-1700FT FOR THE START OF THE 26/18Z
TAF...BUT THERE IS A WINDOW OF TIME CEILINGS MAY NUDGE ABOVE THAT
LEVEL TO CLOSE TO 2 KFT. HOWEVER...AS -SN MOVES IN THIS EVENING...
CEILINGS DROP BACK DOWN AND MAY WELL HIT IFR LEVELS BY MIDNIGHT.
LITTLE TRICKY TO SEE HOW LONG THE IFR-VSBY -SN WILL LAST BUT HAVE
OPTED TO KEEP THE 6-HOURS-WORTH OF IFR CONDS ATTM. CONDS IMPROVE
AROUND DAYBREAK WITH MID-UPR RANGE MVFR CEILINGS VERY POSSIBLE SAT
AFTN.

/OUTLOOK FOR KMSP/
SUN...VFR...CHC MVFR CIGS. WINDS S 5 KTS...BCMG E.
MON...VFR. WINDS N 10 KTS.
TUE...VFR. WINDS NW 5-10 KTS.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 9 AM CST
     SATURDAY FOR MNZ053-060>063-065>070-073>078-082>085-091>093.

WI...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON CST
     SATURDAY FOR WIZ014>016-023>028.

&&

$$

SHORT TERM...JPC
LONG TERM...CLF
AVIATION...JPC






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