Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 211212
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
712 AM EST SUN DEC 21 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 434 AM EST SUN DEC 21 2014

00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW A RELATIVELY WEAK
W-E FLOW ALOFT EXTENDING FROM THE NRN PLAINS INTO THE NW GREAT LKS.
THERE IS EXTENSIVE LO CLD COVER OVER THE UPR MIDWEST/NW GREAT LKS
CONSISTENT WITH THE MOIST AIR LLVL AIR ADVECTED TO THE N BY THE S
WIND BTWN SFC HI PRES IN THE CNDN MARITIMES AND LOWER PRES IN THE
NRN PLAINS. LOCAL 00Z RAOBS SHOW THIS MSTR EXTENDS UP TO H85 TO AS
HI AS H7. ALTHOUGH THERE IS A WEAK SHRTWV PASSING OVER UPR MI EARLY
THIS MRNG...MID LVL DRYNESS SHOWN ON THE RAOBS ABOVE THE LOWER LVL
MSTR AND ABSENCE OF DYNAMIC FORCING HAS PREVENTED ANY PCPN. THERE IS
ANOTHER MORE VIGOROUS SHRTWV/SHARPER DPVA AND DEEP LYR QVECTOR CNVGC
MOVING INTO FAR NW MN...BUT RATHER DRY MID LVL AIR TO THE W AS WELL
IS LIMITING THE ACCOMPANYING PCPN TO SOME LIGHT SN OVER NCENTRAL MN.

MAIN FCST CONCERNS IN THE SHORT TERM FOCUS ON THE POTENTIAL FOR SOME
FREEZING DZ TODAY AS THE STEADY S LLVL FLOW ADVECTS SOMEWHAT HIER
DEWPTS INTO THE UPR LKS. FOCUS FOR LATER TDAY/TNGT SHIFTS TO THE CHC
FOR STEADY SN AS SHRTWV/QVECTOR CNVGC NOW IN NW MN DRIFTS TOWARD UPR
MI.

TODAY...MODELS SHOW H95-9 S WINDS INCRSG THRU THE DAY AND UP TO 30
KTS BY 00Z MON. AS THESE STRONGER WINDS TAP THE HIER NEAR SFC
SPECIFIC HUMIDITY...MOST OF THE MODELS GENERATE SOME SPOTTY LIGHT
PCPN OVER MAINLY THE SCENTRAL THIS MRNG INTO THE AFTN. SINCE THE
DEPTH OF THE LLVL MOIST LYR DOES NOT REACH THE DGZ...WL MAINTAIN THE
MENTION OF SOME FREEZING DZ OVER THE SCENTRAL WHERE THE LLVL SSE
FLOW UPSLOPES AND WHERE THE LLVLS ARE LIKELY TO BE SUFFICIENTLY
MOIST TO SUPPORT SOME DZ. BUT AS THE SHRTWV NOW MOVING THRU NW MN
MOVES ENE INTO NW ONTARIO AND TAIL OF DEEP LYR QVECTOR CNVGC/DEEPER
MSTR ARRIVE W-E THIS AFTN...EXPECT SOME LIGHT SN TO PUSH INTO THE
AREA. BUT OVERALL DRYNESS OF THE MID LVLS SHOULD LIMIT THE INTENSITY
OF THIS PCPN. THE PCPN OVER THE SCENTRAL AND E MAY REMAIN IN THE
FORM OF FREEZING DZ/DZ/FLURRIES WELL INTO THE AFTN AS THE STRONGER
FORCING/DEEPER MOISTENING REMAIN TO THE W. HI TEMPS TODAY WL BE
ABOVE NORMAL AND IN THE 30S.

TNGT...AS THE SHRTWV IN ONTARIO CONTINUES TO THE NE AND AWAY FM UPR
MI...THE BULK OF THE DEEP LYR FORCING IS FCST TO LIFT TO THE NE. SO
AFTER A PERIOD OF LIKELY POPS MAINLY OVER THE W AND CENTRAL IN THE
EVNG...EXPECT DIMINISHING POPS OVERNGT. BULK OF THE SHORTER RANGE
MODELS INDICATE THE HEAVIER PCPN WL BE OVER THE CENTRAL CWA...WHERE
UPSLOPE SSE FLOW OFF LK MI WL COINCIDE WITH THE SHARPER DEEP LYR
QVECTOR DVGC. MAIN CONCERN REMAINS HOW MUCH DRY MID LVL DRY AIR IN
PLACE WL LIMIT PCPN TOTALS. BUT EXPECTED QPF UP TO 0.15 INCH IN THIS
AREA WL SUPPORT UP TO 2 INCHES OF SN. WITH OVC SKIES AND A STEADY S
WIND...THERE WL BE LTL DIURNAL DROP IN TEMP AND WELL ABV NORMAL LOWS.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 434 AM EST SUN DEC 21 2014

COMPLICATED FORECAST STILL IN FULL SWING. DIFFERENCES ABOUND IN THE
MODELS...BOTH WITH THE INITIAL WEAKENING CLOSED LOW/SFC LOW DRIFTING
OUT OF THE NORTHERN PLAINS MONDAY AFTN THROUGH TUESDAY...THEN AGAIN
WITH SOUTHERN STREAM SFC LOW LIFTING NORTHWARD OVER THE GREAT LAKES
WEDNESDAY INTO CHRISTMAS DAY. SOME BREAKING NEWS THERE IN TERMS OF
MODEL TRENDS FOR SURE.

SHORTWAVE TROUGH WILL BE HEADING OVER THE NORTHERN PLAINS ON MONDAY
MORNING. SNOW THAT DEVELOPS LATER TODAY OVER UPPER LAKES WELL AHEAD
OF THIS SYSTEM DRIVEN BY LEAD SHORTWAVE/H85-H5 Q-VECTOR CONVERGENCE
AND H85-H7 MOISTURE TRANSPORT SHOULD BE IN PROCESS OF LIFTING OUT OF
UPR MICHIGAN ON MONDAY MORNING. SOUNDINGS SHOW RISK OF FZDZ IN WAKE
OF DEPARTING LGT SNOW ON MONDAY MORNING WITH DRY LAYER H85-H6 BUT
MOIST UPSLOPE SSE FLOW OFF LK MICHIGAN BLO H85. BY MONDAY AFTN OR
MON EVENING...SOUNDINGS MOISTEN MID-LEVELS IN RESPONSE TO SHORTWAVE
AND SFC LOW MOVING OVER THE NORTHERN PLAINS. SLOWER TREND SHOWS UP
IN THE LAST TWO RUNS OF THE ECMWF WITH THIS SYSTEM INTO TUESDAY AND
THAT PUTS THE ECMWF AT ODDS WITH THE GFS/NAM IDEAS WITH REGARD TO
SPEED OF SYSTEM AND LOCATION OF HEAVIER QPF. MAIN ISSUE IS GFS/NAM
SHOWING FARTHER NORTH H85-H7 LOW CENTER/DRY SLOT COMPARED TO FARTHER
SW ECMWF. GEM-REGIONAL SIMILAR TO ECMWF BUT NOT AS FAR NORTH WITH
HEAVIER QPF ON TUESDAY. USED A GENERAL CONSENSUS...BUT ULTIMATELY
WEIGHTED QPF INTO TUESDAY MORE TOWARD SLOWER/WETTER ECMWF/CANADIAN.
BASED ON 1000-850MB THICKNESS AND NAM SOUNDINGS...APPEARS THAT PTYPE
FOR AT LEAST TUESDAY MORNING SHOULD BE MAINLY SNOW JUST INLAND FM LK
MICHIGAN AND OVER REST OF CWA. BY AFTN THOUGH...NEAR SFC LAYER WARMS
ENOUGH TO RESULT IN MIX OF RAIN AND SNOW OVER MOST CWA...WITH MAINLY
RAIN EXPECTED OVER EAST HALF. A NARROW AND ELEVATED DGZ AROUND 600MB
WITH TEMPS WARMER THAN -10C BLO POINTS TO LOW SLR/S. EVEN SO...SEEMS
THAT INTERIOR SECTIONS OF CNTRL UPR MICHIGAN NEAR THE WI BORDER AND
MAYBE INTO THE INTERIOR SOUTH CNTRL...JUST INLAND FM KESC AND KMNM
COULD END UP WITH THE NEAR ADVY SNOW AMOUNTS MONDAY NIGHT INTO
TUESDAY MORNING. NEED 3 INCHES OF WET SLOPPY SNOW /SLR/S LESS THAN
20:1/ IN 12 HRS TO MEET ADVISORY CRITERIA. WILL BE SOMETHING TO
WATCH...BUT BASED ON CURRENT SPREAD OF SOLUTIONS...WILL PROBABLY
WILL NOT HAVE THIS PINNED DOWN UNTIL WITHIN 12-24 HR OF THE ARRIVAL
OF STEADIER SNOW.

EVENTUALLY AS TUESDAY WEARS ON REMNANT OF UPR/SFC LOWS SLIDE ACROSS
UPR MICHIGAN AND DRY SLOT WILL BECOME BIGGER FACTOR. ATTN BY LATE
TUESDAY INTO TUESDAY NIGHT WILL BE TO THE SOUTH AS STRONGER SHORTWAVE
IN SOUTHERN STREAM WILL BE POISED TO LIFT NORTH OVER THE TENNESSEE
AND OHIO VALLEYS. FOR BETTER OR WORSE...THIS PART OF THE FORECAST
HAS BECOME EVEN MORE MUDDLED THAN THE LAST COUPLE DAYS.

THE UPSHOT OF THE TRENDS FM THE 00Z GFS AND PARALLEL GFS/UKMET AND
ECMWF IS THAT THE STRONG SFC LOW THAT WAS FORECAST TO IMPACT THE
REGION IS NOT FORMING UNTIL IT IS WELL TO THE EAST OF HERE. THIS
ESSENTIALLY TURNS THIS SYSTEM INTO A NON-EVENT FOR THE UPPER GREAT
LAKES AS H85-H3 DPVA STAYS OVER LOWER LAKES AND PRIME SURGE OF STRONG
MOISTURE ADVECTION AND ASSOCIATED HEAVIER QPF ALSO STAYS MORE OVER
LOWER GREAT LAKES. NOT SAYING THAT IS EXACTLY WHAT WILL HAPPEN BUT IT
IS WHAT MAJORITY OF MODELS NOW SHOW. UPPER GREAT LAKES WOULD BE
AFFECTED BY A MOISTURE STARVED NORTHERN STREAM SHORTWAVE AND WEAK
TROUGH. NOT COLD AT ALL WITH H85 TEMPS AS THIS CROSSES LATE WEDNESDAY
INTO CHRISTMAS WARMER THAN -8C...SO IMPACT FM THAT SYSTEM WOULD BE
MINIMAL. OBVIOUSLY...THIS IS A FAR CRY FM BLOCKBUSTER STORM MODELS
HAD BEEN ADVERTISING AT LEAST FOR MAJORITY OF RUNS IN RECENT DAYS.
CURRENTLY THE ONLY MODEL THAT SHOWS THE STRONG STORM IS THE 00Z
CANADIAN WHICH HAS MAINTAINED CONTINUITY AS IT PEGS A 970MB LOW AT
00Z ON THURSDAY OVER NORTHERN LOWER MICHIGAN HEADING NORTH TOWARD
JAMES BAY ON THURSDAY. CONCERNED THAT TREND THAT GFS STARTED ON
SATURDAY HAS NOW BEEN LATCHED ON TO BY ECMWF WHICH HAD BEEN VERY
CONSISTENT UP TO THIS RUN. VERY STRIKING TO SEE THE NCEP FAVORED
UKMET SOLUTION CHANGE FROM A 968MB LOW OVER LK HURON AT 00Z THURSDAY
TO A 1004MB RIDGE WITH LATEST RUN VALID AT THE SAME TIME. WHOLE
FORECAST SITUATION IS HIGHLY CHANGEABLE...AND CANNOT RULE OUT THAT
MODELS WILL TREND BACK TO THE STRONG STORM. SHORTWAVE AND JET ENERGY
THAT ALL THIS EMERGES OUT OF IS JUST ENTERING PACIFIC NORTHWEST THIS
MORNING SO IT WILL NOW BE SAMPLED WELL FM HERE ON OUT. WE WILL SEE IF
THIS AFFECTS FOLLOWING MODEL SOLUTIONS. LIKELY IT WILL...BUT TO WHAT
DEGREE IS THE QUESTION.

GIVEN THE BIG CHANGES...LEANED HEAVILY ON CONSENSUS OF MODELS FOR
WEDNESDAY AND BEYOND. STILL APPEARS TO TURN COLDER BY NEXT WEEKEND
BEHIND THIS SYSTEM WITH DECENT SHOT OF LAKE EFFECT SNOW SHOWERS FOR
AREAS FAVORED BY NW WINDS.
&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 708 AM EST SUN DEC 21 2014

AS AN INCRSG LLVL S WIND DRAWS MOISTER LLVL AIR INTO THE UPPER LKS
AND AN APRCHG DISTURBANCE CAUSES SN TO DEVELOP OVER THE AREA...
EXPECT CONDITIONS AT CMX AND SAW TO DETERIORATE TO IFR. SAW WL SEE
THE FASTER DETERIORATION AND STRONGER WINDS BECAUSE OF THE UPSLOPE
WIND COMPONENT AT THAT MORE EXPOSED SITE. SINCE THE S WIND PRESENTS
A DOWNSLOPE COMPONENT AT IWD AND EVEN THOUGH SOME IFR CONDITIONS MAY
BE OBSVD THERE FROM TIME TO TIME AFTER THE SN ARRIVES THIS AFTN...
SUSPECT PREDOMINANT CONDITIONS AT THAT LOCATION WL REMAIN MVFR.
AFTER THE EXIT OF THE HEAVIER SN LATE TNGT...CONDITIONS ARE LIKELY
TO IMPROVE TO LO END MVFR AT CMX AND SAW.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 434 AM EST SUN DEC 21 2014

S-SE WINDS INCREASE THIS AFTN AND SHOULD REMAIN UP TO 30 KTS OVER
MAINLY THE EAST HALF OF LK SUPERIOR TONIGHT THROUGH MONDAY AS A LOW
PRESSURE SYSTEM MOVES FM THE NORTHERN PLAINS TO THE WESTERN GREAT
LAKES. AS THE LOW LIFTS OVER THE AREA ON TUESDAY...WINDS WILL SETTLE
DOWN BLO 20 KTS. NEXT CHANCE FOR STRONGER WINDS DEVELOPS LATE
WEDNESDAY INTO THURSDAY AS LOW PRESSURE SYSTEM DEEPENS EAST OF LK
SUPERIOR. WNW-NW WINDS OF 30 KTS WITH A FEW GALE GUSTS TO 35 KTS
FAIRLY CERTAIN...BUT CONFIDENCE IN SYSTEM PRODUCING STRONGER GALES
ON THURSDAY IS NOT AS HIGH AS THE LAST COUPLE DAYS AS THE TREND IS
NOW FOR A WEAKER SYSTEM.
&&

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

$$

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






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