Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 270457
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1057 PM CST FRI DEC 26 2014

.UPDATE...
ISSUED AT 1051 PM CST FRI DEC 26 2014

UPDATED TO INCLUDE 06Z AVIATION DISCUSSION BELOW.

&&

.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 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1051 PM CST FRI DEC 26 2014

-SN HAS OVERSPREAD MUCH OF THE WFO MPX COVERAGE AREA...INCLUDING
CEILINGS FROM LOWER-END MVFR INTO BARELY IFR RANGE WITH VSBYS AS
LOW AS 1SM IN SOME OF THE HEAVIER SNOW BANDS. THE SNOWFALL WILL
CONTINUE TO FILL IN FROM THE SW OVERNIGHT...AFFECTING ALL BUT KAXN
AND POSSIBLY NOT KSTC...OR AT LEAST NOT AS BAD AT KSTC AS THE
REMAINING TAF SITES. ALL SITES /BUT KAXN/ WILL EXPERIENCE FLIGHT
CATEGORY REDUCTIONS AT TIMES TO IFR DURING THE FIRST HALF OF THIS
TAF PERIOD. HAVE DROPPED CONDS TO AS LOW AS 1SM...BUT GOING LESS
THAN THAT FOR VSBY CERTAINLY CANNOT BE RULED OUT. SAME WITH
CEILINGS...SEEING IFR CONDS WILL BE LIKELY WITH CEILINGS INTO LIFR
NOT UNREASONABLE. CONDS WILL IMPROVE FROM DAYBREAK ON THRU LATE
MRNG AS THE -SN PULLS OUT. VFR CONDS ARE EXPECTED BY LATE SAT
AFTN INTO EARLY SAT EVE.

KMSP...CONDS HAVE IMPROVED AT KMSP...EVEN TO VFR AT TIMES...AFTER
THE INITIAL BAND OF SNOW DEVELOPED OVER THE S/E TWIN CITIES
METRO AT THE START OF THE 27/00Z TAF. MORE WIDESPREAD SNOW IS
EXPECTED DURING THE THE EARLY MRNG HRS. CONDS IMPROVE AROUND
DAYBREAK. VSBY MAY WELL DROP BELOW 1SM FOR A TIME...BUT RATES OF 1
IN/HR ARE NOT EXPECTED BUT WILL CONTINUE TO MONITOR FOR ANY
POTENTIAL OF AN AIRPORT WEATHER WARNING AS THE EVENT UNFOLDS.
AFTER DAYBREAK...CEILINGS WILL INCRS TO MVFR LEVELS AND LIKELY GO
TO VFR SAT AFTN-EVE.

/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 UNTIL 9 AM CST SATURDAY FOR MNZ053-
     060>063-065>070-073>078-082>085-091>093.

WI...WINTER WEATHER ADVISORY UNTIL NOON CST SATURDAY FOR WIZ014>016-
     023>028.

&&

$$

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





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