Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 220939
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
439 AM EST MON DEC 22 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 425 AM EST MON DEC 22 2014

12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SW FLOW ALOFT OVER
THE WRN GREAT LKS TO THE E OF A DEEPENING UPR TROF IN THE CENTRAL
CONUS CAUSED BY SHRTWVS DIGGING SEWD IN NW FLOW ALOFT E OF UPR RDG
ALONG THE W COAST. SHRTWV RESPONSIBLE FOR THE SN ON SUN EVNG IS
LIFTING NEWD THRU NW ONTARIO. AS THE ACCOMPANYING STRONGER DYNAMIC
FORCING SHIFTS TO THE NE...IR STLT IMAGERY SHOWS WARMING CLD TOP
TEMPS AS THE COMMA TAIL MSTR BAND SHIFTS TO THE E. ALTHOUGH RADAR
SHOWS THE HEAVIER PCPN IS FOLLOWING OFF TO THE NE...SOME PATCHY
ECHOES REMAIN OVER MUCH OF THE CWA. COMPOSITE RADAR INDICATES
GENERALLY LIGHT MIXED PCPN STRETCHES OFF TO THE SW THRU MUCH OF THE
NW HALF OF WI...WHERE MODELS SHOW AN AXIS OF WEAKER DEEP LYR QVECTOR
CNVGC. SFC OBS INDICATE LOWER SFC DEWPTS OVER NRN LOWER MI...UPWIND
OF THE E HALF OF THE CWA.

MAIN FCST CONCERNS TODAY FOCUS ON DIMINISHING PCPN TRENDS. FOCUS FOR
TNGT SHIFTS TO TIMING THE ARRIVAL OF ANOTHER AREA OF SN/MIXED PCPN
AS ANOTHER SHRTWV LIFTS NEWD OUT OF DEEPENING UPR TROF THAT CAUSES A
CLOSED H5 LO TO DEVELOP IN THE CENTRAL PLAINS.

TODAY...EXPECT SOME GENERALLY LGT SN/MIXED WITH RA TO IMPACT MAINLY
THE W HALF OF THE CWA THRU THIS MRNG AWAY FM THE DRIER NEAR SFC AIR
ADVECTING INTO THE ERN ZNS AND UNDER LINGERING BUT SLOWLY FADING
DEEP LYR QVECTOR CNVGC AS SHRTWV RDG APRCHS FM THE SW. DURING THE
AFTN...ARRIVAL OF DRIER AIR ALOFT FM THE S WITHIN THE NVA SHOULD END
ANY LINGERNING LARGE SCALE PCPN. BUT CONCERNED SOME SN GRAINS/
FREEZING DZ/DZ WL LINGER OVER MAINLY THE CENTRAL CWA WITH UPSLOPE SE
FLOW OFF LK MI. THIS POTENTIAL WL BE LIMITED BY ADVECTION OF LOWER
H95-9 SPECIFIC HUMIDITY NOW OVER NRN LOWER MI...ESPECIALLY OVER THE
E HALF AND BY LATE AFTN EVEN OVER THE CENTRAL. EXPECT TEMPS TO TOP
OUT ABOVE FREEZING EVERYWHERE...SO ANY FREEZING DZ SHOULD END BY
NOON OR SO.

TNGT...AS AREA OF SGNFT DEEP LYR QVECTOR CNVGC/DEEP ISENTROPIC
ASCENT/UPR DVGC IN ADVANCE OF SHRTWV LIFTING NE TOWARD THE GREAT LKS
OVERSPREADS THE AREA...EXPECT PCPN TO DEVELOP OVER THE SCENTRAL BY
MIDNGT AND THEN SPREAD TO OVER ALL THE KEWEENAW BY 12Z TUE. PER NCEP
PREFERENCE...TENDED TOWARD THE 00Z NAM FOR FCST DETAILS. THIS MODEL
GENERATES ABOUT 0.25 INCH OF TOTAL QPF AT MENOMINEE BY 12Z TUE.
PTYPE IS A CONCERN. WHILE THE NAM FCST SDNG FOR MENOMINEE INDICATES
MAINLY RA FOR THAT LOCATION...MODEL SDNGS/H100-85 THKNS INDICATE
AREAS AWAY FM LK MI WL SEE MAINLY SN THRU 12Z TUE. ARRIVAL OF LLVL
DRY AIR TODAY THAT WL ENHANCE NEAR SFC EVAPORATIVE COOLING AND
BACKING NEAR SFC FLOW TOWARD THE ENE THAT WL CUTOFF THE ARRIVAL OF
WARMER AIR APPEAR TO BE THE REASON THE LLVL TEMPS TREND COLD ENUF
FOR MAINLY SN EXCEPT NEAR LK MI. SN/WATER RATIOS WL BE LIMITED BY
RELATIVELY HI/THIN DGZ...SO AN INCH OR TWO OF SN WL LIKELY
ACCUMULATE BY SUNRISE OVER MUCH OF THE SE HALF OF THE CWA TO THE NW
OF THE RA/SN LINE.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 438 AM EST MON DEC 22 2014

...WIDESPREAD MODERATE SNOW ON TUESDAY...

ONE PRIMARY CHANCE FOR ACCUMULATING SNOW OVER ALL OF CWA IN THE LONG
TERM ON TUESDAY BUT CANNOT RULE OUT MORE SNOW CHIRSTMAS EVE FOR
EASTERN CWA AS THE ON AGAIN OFF AGAIN LOW PRESSURE SYSTEM IS STILL
AROUND IN LATEST MODELS. ANOTHER SYSTEM MAY IMPACT REGION WITH SWATH
OF SNOW FRIDAY INTO SATURDAY...BUT LACK OF CONTINUITY FM THE MODELS
LIMITS CONFIDENCE IN THAT PART OF FORECAST ATTM.

EVOLVING LOW PRESSURE SYSTEM MOVING OUT OF THE PLAINS TUESDAY INTO
WEDNESDAY APPEARS MORE LIKE RECENT RUNS OF ECMWF. QUESTION IS HOW
FAR EAST THE MID-LEVEL AND SFC LOWS REACH ON TUESDAY AS THAT IMPACTS
DRY SLOT AND PRECIP INTENSITY...ESPECIALLY OVER THE SOUTHERN PART OF
CWA. BLEND OF NAM/SREF SUPPORTED BY NCEP AND LOOKED LIKE 12Z ECMWF.
PRIMARY SHORTWAVE AND SFC LOW MOVE TO EASTERN IOWA BY 12Z TUESDAY
AND LIFT ACROSS EASTERN WISCONSIN ON TUESDAY AFTN. CIRCULATION AROUND
SFC-H85 LOWS PULLS H7 MIXING RATIOS OVER 3G/KG NORTH OF THE LOWS OVER
MAJORITY OF UPR MICHIGAN. PER GARCIA METHOD WITH NO PTYPE
CONSIDERATIONS THAT WOULD FAVOR 3 INCHES OF SNOW IN 6 HRS. BLEND OF
FAVORED QPFS POINT TO 0.30-0.50 INCH OF LIQUID EQUIVALENT OVER MOST
CWA...WITH HIGHER AMOUNTS OVER 0.50 INCH OVER FAR WEST AND SCNTRL.
TROUBLE IS 00Z ECMWF TRENDED EAST WITH SFC LOW AND HAS DRY SLOT INTO
SCNTRL...REALLY CUTTING ITS PRECIP THERE.

PTYPE ALSO AN ISSUE...UNFORTUNATELY. SOUNDINGS FM NAM KEEP BLYR
COOL...WITH ONLY SURE CHANGE TO RAIN AT MNM WITH ENE FLOW OFF BAY OF
GREEN BAY. ENE WINDS WOULD LEAD TO COOLING TO PERSIST AT KESC AND
KISQ. GFS SIMILAR WHILE GEM-REGIONAL IS MUCH WARMER/WESTWARD WITH
1000-850MB THICKNESSES OVER 1305M. SINCE WINDS ARE BACKING AND OFF
LAND IN LOW-LAYERS WILL FAVOR COOLER IDEA OFFERED BY NAM/GFS IN THE
MORNING BUT WILL BRING MORE GEM IDEA IN THE AFTN AS SFC LOW EDGES
CLOSER TO THE AREA FM THE SOUTH. RESULT WILL BE RAIN/SNOW MIX OVER
SCNTRL UPR MICHIGAN ALONG BAY OF GREEN BAY...WITH SNOW ELSEWHERE
INTO EARLY AFTN...THEN GO FOR A MIX OF RAIN AND SNOW OVER MOST OF
THE EAST HALF CWA BY MID AFTN. NAM SOUNDINGS SHOW THE SNOW MAY LAST
THROUGH THE DAY OVER MOST OF THE WEST HALF OF CWA AND EVEN FOLLOWING
GEM THICKNESSES QPF THAT OCCURS THERE IN THE MORNING WOULD STAY ALL
SNOW. OVERALL...WILL LEAN TOWARD MOST SNOW OVER WEST HALF. SOUNDINGS
MAINTAIN LOOK OF ELEVATED NARROW DGZ AND TEMPS WARMER THAN -8C
BLO...SO LOW SLR/S...PROBABLY AROUND 10:1. BY LATE TUESDAY
AFTN...EXPECT TOTAL SNOWFALL OVER 4 INCHES OVER MOST OF THE WEST
HALF OF THE CWA...MAYBE PUSHING TOWARD 6 INCHES OVER INTERIOR WEST.
CLOSER TO LK SUPERIOR OVR NCNTRL WHERE ENE WINDS PROVIDE FLOW OF
LAKE MODIFIED WARMING...EXPECT SNOW TOTALS TO BE HELD DOWN. CONTINUED
TO INCREASE POPS TO CATEGORICAL. IT WILL SNOW. ONLY THING THAT
TEMPERS CONFIDENCE ON ISSUING 3RD PERIOD ADVY IS INCONSISTENCIES IN
WHERE THE HIGHER QPF IS ON MODELS. WILL OPT FOR A SPECIAL WEATHER
STATEMENT AND LET DAYSHIFT GET SOME MORE DATA BEFORE MAKING FINAL
CALL ON HEADLINE.

BULK OF PRECIP WILL BE DONE BY WEDNESDAY EVENING. 00Z NAM WAS QUITE
EMPHATIC WITH DEFORMATION ZONE OF LINGERING SNOW OVER THE WEST CWA
BUT WAS NOT SUPPORTED IN ITS INTENSITY BY ANY OTHER GUIDANCE. 06Z
NAM IS NOT AS BULLISH. THOUGH SOME LGT SNOW COULD CONTINUE AS AN
AREA OF MID LEVEL FGEN/DEFORMATION WILL BE REINFORCED BY WEAK TROWAL.
EVEN THIS AREA OF SNOW SHOULD DIMINISH TO LGT SNOW/FLURRIES LATE ON
TUESDAY NIGHT. FARTHER EAST...SOUNDINGS SIGNAL POSSIBLE DRIZZLE OR
FREEZING DRIZZLE AND FOG AS MID-LEVEL DRYING LEAVES MOIST LOW-LEVELS
WITH TEMPS MAINLY WARMER THAN -7C. CARRIED SLIGHT CHANCE POPS FOR
RAIN/SNOW...BUT THIS MAY NEED TO BE CONVERTED TO DZ/FOG WITH LATER
FORECASTS.

MODELS CONTINUE TO HAVE FUN WITH THE CHRISTMAS EVE SYSTEM AFFECTING
THE GREAT LAKES. AFTER BACKING AWAY COMPLETELY 24 HR AGO...MOST OF
THE MODELS CAME BACK TO SHOWING A STRONG LOW LIFTING NORTHWARD OVER
THE CNTRL GREAT LAKES WITH THE RUNS ON SUNDAY. THAT IS WHERE WE
REMAIN FOR MOST PART NOW...WITH ALL BUT THE GEM-GLOBAL AND PARALLEL
GFS INDICATING THIS SYSTEM MISSES UPR MICHIGAN. KEPT SMALL CHANCES
IN OVER FAR EAST...VCNTY OF LUCE COUNTY...BUT OTHERWISE KEPT THE CWA
VOID OF ANY POPS FM THE SYSTEM. HAVE SOME SMALL CHANCE POPS OVER THE
WEST HALF ON CHRISTMAS EVE DAY...BUT THIS IS GENERALLY DUE TO SOME
SIMBLANCE OF THE LINGERING DEFORMATION AREA FM THE TUESDAY SYSTEM
THAT WILL ONLY BE SLOWLY UNRAVELING OVER THE EAST PART OF CWA ON
WEDNESDAY.

INTO CHRISTMAS AND BEYOND...RAN WITH CONSENSUS. COULD SEE SOME LGT
LK EFFECT FOR WNW-NW FLOW AREAS ON CHRISTMAS THOUGH H85 TEMPS NEAR
-10C ARE ONLY MARGINAL FOR PURE LES. WOULD NEED SOME ADDITIONAL
LARGE SCALE SUPPORT TO RESULT IN BETTER CHANCES OF LES VIA LAKE
ENHANCEMENT. AS LONG AS THE CNTRL GREAT LAKES LOW DOES NOT COME ANY
FARTHER WEST...WILL NOT BE VERY WINDY EITHER. HIGHS ON CHRISTMAS TOP
OUT ABOVE NORMAL...WITH LOW TO MID 30S EXPECTED. AS ALLUDED TO
EARLIER...ANOTHER CLIPPER TYPE SYSTEM COULD SPREAD SOME LGT SNOW TO
THE AREA ON FRIDAY. UNCERTAINTY AND CONSISTENCY IN THAT IDEA BOTH
ARE HIGH...SO CHANCE POPS UNTIL IT GETS MORE REFINED. AT THE MOST
COULD SEE MODERATE SNOW AMOUNTS. IDEA OF COLDER WEATHER WITH LK
EFFECT STILL ON TRACK FOR THE WEEKEND. MOISTURE IS A QUESTION THOUGH
SO EVEN THOUGH H85 TEMPS FALL DOWN BLO -15C ON SUNDAY...EVEN
MODERATE LK EFFECT SNOW IS NOT A DONE DEAL YET. COOLER TEMPS WILL BE
NOTICABLE THOUGH AFTER THE RATHER MILD CHRISTMAS WEEK.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1236 AM EST MON DEC 22 2014

LIGHT/MODERATE SNOW CONTINUES ACROSS THE AREA UNDER A SOUTH FLOW OF
MOIST LLVL AIR WITH CONDITIONS RANGING FROM LIFR/VLIFR AT KCMX TO
MVFR AT KIWD. EXPECT IMPROVING CONDITIONS AT KCMX AND KSAW TO HIGH
END IFR LATE TONIGHT AND THEN TO MVFR LATE MON MORNING AS DRIER AIR
MOVES IN FM THE SOUTH. CONDITIONS WILL REMAIN MVFR THROUGH THE PD AT
KIWD AS DOWNSLOPE SOUTH WINDS SHOULD LIMIT LOWER CIGS AND VSBY
RESTRICTIONS.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 425 AM EST MON DEC 22 2014

SSE WINDS UP TO 25-30 KTS OVER MAINLY THE E HALF OF LK SUPERIOR WILL
PERSIST THRU TODAY BUT THEN BACK TO THE E TONIGHT AND THEN THE NE ON
TUE AS A LO PRES SYSTEM MOVES NE FROM THE CENTRAL PLAINS TO OVER
LAKE MICHIGAN BY LATE IN THE DAY ON TUE. SINCE THIS LO WILL SLOWLY
WEAKEN AS IT MOVES TO THE NE...THE NE WINDS WILL FALL UNDER 20 KTS
ON TUE NIGHT. SINCE THE LATEST GUIDANCE INDICATES THE NEXT DEEPER LO
WILL TRACK N FARTHER TO THE E ON WED...A WEAKER PRES GRADIENT/N WIND
UNDER 20 KTS WILL DOMINATE ON WED. YET ANOTHER LO PRES MAY MOVE NE
FROM THE CENTRAL PLAINS LATE IN THE WEEK. AT THIS TIME...WINDS UNDER
25 KTS ARE EXPECTED.
&&

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

$$

SHORT TERM...KC
LONG TERM...JLA
AVIATION...VOSS
MARINE...KC







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