Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 260936
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
436 AM EST FRI DEC 26 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 433 AM EST FRI DEC 26 2014

CONCERNS FOCUS ON LIGHT PCPN TODAY ALONG SFC TROUGH MOVING SLOWLY
EASTWARD ACROSS THE AREA...THEN THE POTENTIAL FOR MODERATE SNOW LATE
TONIGHT INTO SATURDAY OVER CENTRAL AND ERN UPPER MI AS WAVE FROM SW
CONUS EJECTS NE ALONG SFC TROUGH.

WATER VAPOR IMAGERY SHOWS A WEAK SHORTWAVE LIFTING NE THROUGH SRN MN
INTO UPPER MI. MODELS INDICATE WEAK TO MODERATE Q-VECT CONV AND
800-750 MB FGEN FORCING ASSOC WITH THIS SHORTWAVE WILL SUPPORT A
BAND OF LIGHT SNOW OVER MAINLY THE NW PORTION OF THE CWA THIS
MORNING WITH THE BAND MOVING SLOWLY EAST INTO NCNTRL AND ERN UPPER
MI THIS AFTERNOON. MODEL AVERAGED QPF OF .06-.08 INCH ALONG WITH A
12/1 SLR COULD YIELD HALF AN INCH TO ONE INCH OF SNOW OVER FAR WRN
UPPER MI TODAY WITH ONLY A DUSTING OF SNOW EXPECTED ELSEWHERE ACROSS
THE NRN TIER. WEAK UPSLOPE SRLY FLOW AND SHALLOW MOISTURE BLO DGZ
COULD YIELD SOME PATCHY DZ/FZDZ OVER THE SE CWA. LAKE ENHANCEMENT
FOR WRN COUNTIES WILL LIKELY BE MINIMAL LATE TODAY IN DEVELOPING NW
FLOW DUE TO MARGINAL 8H TEMPS OF -8 TO -9C AND FAIRLY SHALLOW
MOISTURE.

TONIGHT...A SHORTWAVE EJECTING FROM A TROF OVER THE SRN ROCKIES IS
FCST TO STREAK NE INTO THE GREAT LAKES. MODERATE Q-VECT CONV AND
INCREASING 285-290K ISENTROPIC ASCENT ASSOC WITH THE SHORTWAVE ALONG
WITH A DEEPENING MOISTURE PROFILE AND GOOD UPWARD MOTION THROUGH DGZ
COULD LEAD TO A WIDESPREAD 1-1.5 INCHES LATE TONIGHT ACROSS MUCH OF
THE CWA ESPECIALLY THE CENTRAL. WITH MODELS SUGGESTING 285-290K
ISENTROPIC ASCENT AND GOOD DENDRITIC SNOW GROWTH CONTINUING INTO SAT
AFTERNOON OVER MUCH OF THE ERN HALF OF THE CWA...WOULD NOT BE
SURPRISED TO SEE SOME ERN HALF COUNTIES REACH ADVISORY CRITERIA WITH
TOTAL SNOWFALL LATE TONIGHT INTO SATURDAY APPROACHING FOUR INCHES AT
SOME LOCATIONS. SINCE MUCH OF THE SNOW WILL FALL SATURDAY (THIRD FCST
PD) WILL HOLD OFF ON ISSUING ADVISORY FOR NOW BUT WILL CONTINUE TO
MENTION POTENTIAL FOR MODERATE SNOW ACCUMULATION IN HWO.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 447 PM EST THU DEC 25 2014

AFTER AN EXTENDED PERIOD OF MOSTLY ABOVE NORMAL TEMPS OVER THE LAST
2 WEEKS OR SO...A PATTERN CHANGE BACK TO A STRONG NE PACIFIC/WRN
NAMERICA RIDGE AND CNTRL/ERN NAMERICA TROF CONFIGURATION WILL OCCUR
DURING THE LONG TERM. THIS WILL BRING A RETURN OF A BLO NORMAL TEMP
REGIME TO THE UPPER LAKES...BEGINNING EARLY NEXT WEEK AND LASTING
THRU THE WEEK. AS FOR PCPN...THERE IS ONE SYSTEM EJECTING FROM THE
TROF CURRENTLY OVER THE ROCKIES THAT WARRANTS SOME WATCHING FOR FRI
NIGHT/SAT. OTHERWISE...WITH INCREASINGLY COLDER AIR AND NW FLOW
BECOMING DOMINANT...PCPN POTENTIAL WILL SHIFT MOSTLY TO THE LAKE
EFFECT SNOW BELTS NEAR LAKE SUPERIOR NEXT WEEK.

BEGINNING FRI NIGHT/SAT...A SHORTWAVE EJECTING FROM THE TROF
CURENTLY OVER THE ROCKIES IS FCST TO STREAK NE INTO THE GREAT LAKES.
AS THE SHORTWAVE LIFTS NE...IT WILL ENCOUNTER CONFLUENT FLOW BTWN
THE SRN BRANCH SUPPORTING THE ROCKIES TROF AND NRN BRANCH FLOW
ACROSS SRN CANADA. THIS WILL EVENTUALLY RESULT IN SHEARING/WEAKENING
OF THE SHORTWAVE. ON THE OTHER HAND...ENERGY IN THE WRN TROF LOOKS
QUITE VIGOROUS RIGHT NOW...AND OVERALL TREND FROM THE GEM/ECMWF/GFS
IS FOR THE SHORTWAVE TO WEAKEN LESS QUICKLY AS IT STREAKS NE.
DPROG/DT MODEL QPFS COMPARING 12Z DEC 24 AND 00Z DEC 25 ECMWF AND
00Z AND 12Z DEC 25 GEM ARE QUITE STRIKING IN THE INCREASE IN
QPF...AND THERE IS ALSO A SLIGHT NW TREND NOTED AS WELL. THE GFS/NAM
SHOW A SIMILAR TREND...THOUGH NOT AS DRAMATIC AS THE ECMWF/GEM.
GIVEN SIMILAR MULTI-MODEL TRENDS...WILL BEGIN EDGING POPS AND SNOW
ACCUMULATIONS UP FOR LATE FRI NIGHT/SAT. WILL TREND QPF TOWARD THE
00Z/12Z ECMWF WHICH ARE VERY SIMILAR AND PROBABLY REPRESENT A GOOD
COMPROMISE BTWN THE DRIER GFS AND THE VERY WET GEM WHICH GENERATES
OVER 0.75 INCHES OF PCPN ACROSS THE SE FCST AREA. 24HR PCPN ENDING
AT 00Z/28 DEC ON THE ECMWF RANGES FROM AROUND 0.15 FAR W TO
0.35-0.45 INCH ACROSS THE SCNTRL AND E. NAM/GFS FCST SOUNDINGS SHOW
FAIRLY VIGOROUS UPWARD MOTION THRU THE DGZ...SO SNOW RATIOS MAY END
UP AROUND 15/1 OR SO...SUGGESTING A GOOD POTENTIAL FOR ADVY LEVEL
SNOW ACCUMULATIONS FOR THE SCNTRL AND E FCST AREA LATE FRI NIGHT/SAT
IF THE HEAVIER QPF UTILIZED IN THIS FCST VERIFIES. THE ARRIVAL OF
DEEP LAYER QVECTOR DIVERGENCE IN THE WAKE OF THE DEPARTING SHORTWAVE
LATER IN THE DAY WILL CAUSE THE SYNOPTIC SCALE SNOW TO DIMINISH W-E.
ARRIVAL OF 850MB TEMPS AS LOW AS -12C TOWARD 00Z SUN IN THE WNW FLOW
IN THE WAKE OF THE DEPARTING SHORTWAVE WILL BRING A RETURN OF LIGHT
LES FOR SAT EVENING.

SAT NIGHT...LARGER SCALE DNVA/DEEP LAYER QVECTOR DIVERGENCE WILL
DOMINATE MOST OF SAT NIGHT...SUGGESTING LIGHT LES. HOWEVER...MEDIUM
RANGE MODELS DO SHOW SOME INCREASE IN MOISTURE DEPTH AND SOME
SHARPENING OF LAKE INDUCED SFC TROF DURING THE NIGHT. THIS SETUP
COULD SUPPORT SOME INCREASE IN LAKE EFFECT OVERNIGHT SAT NIGHT...
ESPECIALLY ALONG LAKE INDUCED TROF AND WHERE THE LOW-LEVEL NW FLOW
IS MOST FAVORABLE. GFS FCST SOUNDINGS INDICATE FAVORABLE UPWARD
MOTION WITHIN A FAIRLY DEEP DGZ AS WELL. IF SO...MIGHT BE ABLE TO
FLUFF UP A FEW INCHES OF SNOW WHERE LES IS MOST PERSISTENT AND WHERE
UPSLOPING IS STRONGEST.

WITH DECREASING MOISTURE DEPTH AND INCREASINGLY ANTICYCLONIC LARGER
SCALE LOW-LEVEL FLOW...LES ON SUN WILL BE LIGHT FOR AREAS FAVORED BY
NW FLOW.

MON/TUE...INCREASINGLY COLDER AIR FLOWS INTO THE UPPER LAKES WITH
850MB TEMPS FALLING TO -20 TO -24C DURING THAT TIME...RESULTING IN
SFC TEMPS FALLING TO BLO NORMAL VALUES FOR LATE DEC. WITH SUCH COLD
AIR...EXPECT NMRS SNOW SHOWERS IN THE SNOW BELTS FAVORED BY NW
WINDS. GFS FCST SOUNDINGS SHOW INVERSIONS BASED BLO 5KFT...SO LES
WILL OVERALL BE ON THE LIGHT SIDE...MOSTLY SUB ADVY. SINCE THE DGZ
WILL DOMINATE THE CONVECTIVE LAYER...MIGHT BE ABLE TO FLUFF UP SOME
ADVY LEVEL ACCUMULATIONS WHERE LOW-LEVEL CONVERGENCE FOCUSES HEAVIER
SNOW SHOWERS. A COUPLE OF WEAK SHORTWAVES ARE FCST TO SWING THRU THE
UPPER LAKES...ONE MON AND THE OTHER TUE. IT LOOKS LIKE THE ONE ON
TUE MAY HAVE SOME IMPACT ON MOISTURE DEPTH/INVERSION HEIGHTS...SO
LES MAY PERK UP FOR A SHORT TIME ON TUE.

LOW-LEVEL WINDS WILL BACK TO THE WSW ON NEW YEARS EVE IN RESPONSE TO
A STRONG SHORTWAVE DIVING SE THRU NRN MANITOBA AND ASSOCIATED DEEP
SFC LOW PRES SETTLING OVER HUDSON BAY. AS A RESULT...LES SHOULD
SHIFT TO AFFECT MAINLY THE KEWEENAW PENINSULA. TIGHTENING PRES
GRADIENT WILL RESULT IN INCREASING SFC WINDS...ESPECIALLY OVER THE
EXPOSED KEWEENAW. BLSN MAY BECOME AN ISSUE THERE ON NEW YEARS EVE.

NEXT ARCTIC COLD FRONT SHOULD THEN SWEEP ACROSS THE AREA ON NEW
YEARS DAY...ENHANCING LES AND PROBABLY BRINGING AT LEAST A LITTLE
-SN TO THE REMAINDER OF THE AREA.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1204 AM EST FRI DEC 26 2014

OVERNIGHT...A COUPLE WEAK DISTURBANCES WILL SHIFT NORTHEAST THROUGH
UPPER MICHIGAN. THE FIRST WAVE WILL LARGELY AFFECT CENTRAL UPPER
MICHIGAN AND HAVE SHOWN A PERIOD OF MVFR VISIBILITIES AS THE SNOW
MOVES THROUGH KSAW. AS THE SECOND WAVE ARRIVES OVERNIGHT...THE
BETTER SNOWFALL WILL SHIFT TO THE NORTHWEST AND AFFECT KCMX/KIWD.
EXPECT VISIBILITIES TO LARGELY STAY MVFR...BUT DID BRING KIWD DOWN
TO IFR FOR A PERIOD LATE TONIGHT INTO FRIDAY AS WINDS SHIFT TO THE
NORTH AND LAKE ENHANCEMENT INCREASES THE SNOWFALL INTENSITY.
CONDITIONS WILL STAY MVFR AT KCMX THROUGH THE PERIOD AND WILL GO TO
IFR AT KSAW IN THE EVENING AS UPSLOPE NORTH WINDS BRING IN A LOWER
CIG FROM LAKE SUPERIOR MOISTURE.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 433 AM EST FRI DEC 26 2014

A TROUGH HANGING OVER THE AREA TODAY WILL KEEP THE PRES GRADIENT
WEAK AS WINDS REMAIN GENERALLY BLO 20 KT THROUGH TONIGHT. A LOW
MOVING NORTHEAST ALONG THE TROUGH ON SATURDAY WILL INCREASE THE
NORTH AND EVENTUALLY NORTHWEST WINDS ON SATURDAY AFTERNOON AND
SATURDAY NIGHT...WITH GUSTS UP TO 30KTS OVER THE EASTERN LAKE. THE
REST OF THE PERIOD WILL EXPERIENCE NORTHWEST TO NORTHERLY WINDS
UNDER 25KTS AS A STRONG HIGH BUILDS INTO THE NORTHERN/CENTRAL PLAINS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...VOSS
LONG TERM...ROLFSON
AVIATION...07
MARINE...VOSS





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