Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 201154
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
654 AM EST SAT DEC 20 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 434 AM EST SAT DEC 20 2014

WV LOOP AND 00Z RAOBS SHOW A LARGE SCALE ZONAL FLOW...BUT THERE IS
EMBEDDED AMPLIFICATION. TROUGHING WAS AS CLOSE BY AS NORTHERN PLAINS
AND MINNESOTA THIS MORNING. PRIMARY PV ANAMOLIES/SHORTWAVES WITHIN
TROUGH WERE OVER FAR NORTHWEST ONTARIO AND OVER WESTERN IOWA. WEAK
SFC TROUGH NOTED OVER WESTERN MINNESOTA TOO...WHILE SFC RIDGING
EXTENDING OUT OF QUEBEC WAS STILL MAIN FEATURE OVER GREAT LAKES. THE
ONTARIO WAVE AND WEAK WARM AIR ADVECTION AHEAD OF THE MINNESOTA
TROUGH AND UPSLOPE LOW-LEVEL FLOW IS SUPPORTING LGT WINTRY MIX OF
SNOW AND FREEZING DRIZZLE OVER NORTHERN MINNESOTA THIS MORNING. ONLY
AFFECT FM ONTARIO SHORTWAVE OVER UPR MICHIGAN IS BATCH OF MID CLOUDS
OVER WEST HALF OF CWA. NO PRECIP THROUGH. ONLY WEATHER OF NOTE IN
THE CWA THIS MORNING IS PATCHY DENSE FOG OVER CNTRL CWA...VCNTY OF
IMT TO SAW.

ONTARIO WAVE MOVES LITTLE EASTWARD TODAY AS ANOTHER SHORTWAVE
CURRENTLY OVER MT TRIES TO CATCH UP WITH IT. THUS...SFC TROUGH AND
WARM AIR ADVECTION STAY MAINLY OVER MN. RAP SHOWS WEAK LIFT TRYING
TO IMPACT KEWEENAW THIS MORNING INTO EARLY AFTN...BUT IT LOOKS MUCH
DRIER THAN IT IS UPSTREAM OVER MN WHERE PRECIP IN OCCURRING THIS
MORNING...SO NOT EXPECTING ANY PRECIP OUT OF THIS FOR OUR AREA. LOW
CLOUDS OVER NW WI AND WEST UPR MICHIGAN GRADUALLY EASE
EASTWARD...BUT A FEW SPOTS IN EAST HALF OF CWA MAY STAY CLEAR OF THE
LOW CLOUDS ALL DAY. TOUGH TO SAY EXACTLY WHERE THOUGH AS THERE ARE
DIFFERENT AREAS OF CLOUDS AFFECTING THE AREA AND MODELS FORECASTING
OF THEM IS ONLY FAIR. FOR TEMPS...WENT AT OR 1-2 DEGREES ABOVE
FRIDAY READINGS AS 925MB TEMPS WARM SLIGHTLY COMPARED TO FRIDAY.
WHERE SUNSHINE CAN PERSIST INTO THE AFTN...TEMPS COULD BUMP INTO THE
MID 30S. BEST SHOT AT THAT WOULD BE EAST CENTRAL CWA...VCTY OF
MUNISING AND GRAND MARAIS. FARTHER WEST...CLOUDS WILL HOLD TEMPS
DOWN OVER INTERIOR WEST TO UPR 20S. INTO THIS EVENING...EXPECT LOW
CLOUDS /HIGHER 925MB-850MB RH/ TO BE OVER WEST HALF OF CWA AND ALSO
THE FAR EAST CWA. EVENTUALLY THOUGH...CLOUDS SHOULD FILL IN OVER ALL
CWA. UNTIL THAT OCCURS...TEMPS FOR INTERIOR CNTRL CWA OR AT LEAST
PORTIONS OF THESE AREAS MAY DROP OFF QUICKLY. CLOSEST MODEL TO
INCICATE THAT WAS BIAS CORRECTED NAM MOS. TWEAKED DOWN EVEN FURTHER
THOUGH /LOW TEENS/ SEEING HOW MUCH TEMPS FELL EARLY THIS MORNING
WHERE SKIES WERE CLEAR. ALSO WILL ADD FOG TO THOSE AREAS SINCE THESE
TEMPS WILL BE WELL BELOW THE EXPECTED AFTN DWPNTS. WHERE CLOUDS STAY
IN ALL NIGHT...MIN TEMPS LIKELY STAY ABOVE 20 DEGREES.

SOUNDINGS FM NAM AND GFS INDICATE INCREASING SUB 950MB MOISTURE
LATE TONIGHT FM THE SOUTH AND WITH UPSLOPE SOUTH FLOW OVER CNTRL
CWA COULD SEE PATCHY FREEZING DRIZZLE IMT TO NEGAUNEE. NOT MUCH UVM
SHOWN ON THE SOUNDINGS THOUGH...SO LEFT IT OUT OF GRIDS ATTM.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 434 AM EST SAT DEC 20 2014

MAIN FOCUS FOR THE LONGER TERM REMAINS THE POTENTIAL FOR SOME SN OR
MIXED PCPN IN THE MON INTO XMAS PERIOD ASSOCIATED WITH A DEEPENING
UPR TROF IN THE CENTRAL CONUS AS A SERIES OF SHRTWVS RIDING OVER A
MEAN RDG ALONG THE W COAST DIG INTO THE PLAINS. THE STRONGEST OF
THESE DISTURBANCE IS NOW OVER THE NE PACIFIC OCEAN. ALTHOUGH THE
MODELS ARE COMING INTO BETTER AGREEMENT ON WARMER LLVL TEMPS IN THE
TUE/WED TIME AND ON THE DEVELOPMENT OF A LO PRES IN THE LO/MID MS
RIVER VALLEY THAT WL TRACK SOMEWHERE NEAR THE CENTRAL GREAT LKS ON
WED AND INTO CANADA ON XMAS DAY...THERE ARE STILL SOME SIGNIFICANT
DIFFERENCES ON THE DETAILS OF HOW THE INTERACTION/PHASING BTWN THESE
SEPARATE DISTURBANCES THAT ARE STILL OVER THE DATA POOR PACIFIC WL
IMPACT THE SFC LO TRACK AND UPR MI.

SUN/SUN NIGHT...AS LLVL S WIND BTWN DEPARTING HI PRES IN SE CANADA
AND FALLING MSLP TO THE W ADVECT MOISTER LLVL AIR INTO THE CWA...
OPTED TO INCLUCE SOME FREEZING DZ OVER THE SCENTRAL IN THE MRNG
WHERE LLVL WIND WL UPSLOPE OFF LK MI. THEN OPERATIONAL MODELS SHOW A
SHRTWV MOVING E FM THE NRN PLAINS ACROSS THE NW GREAT LKS AND INTO
NW ONTARIO BY 12Z MON... BRINGING A PERIOD OF DEEP LYR QVECTOR CNVGC
ASSOCIATED WITH SOME DPVA AND ISENTROPIC ASCENT BEST DEPICTED ON THE
285-290K SFCS /ABOUT H85-75/ IN THE STRONGER SSW FLOW BTWN HI PRES
OVER THE CNDN MARITIMES AND LO PRES IN THE NRN PLAINS. ARRIVAL OF
THE DEEPER MSTR SHOULD END THE FREEZING DZ. THE BULK OF THE GUIDANCE
INDICATES THE ACCOMPANYING SN WL BEGIN OVER THE SCENTRAL SUN AFTN
AND THEN OVERSPREAD THE REST OF THE FA THRU SUN NGT. THE NAM SHOWS
THE HIEST QPF UP TO 0.25-0.30 INCH OVER THE SCENTRAL...WHERE THE
NEAR SFC SSE FLOW WL UPSLOPE OFF LK MI AND H85 MSTR CNVGC IS A BIT
SHARPER. THE GFS ON THE OTHER HAND SHIFTS THE HIER QPF TO OVER THE
NW CWA LATE AT NGT. GIVEN THE GREATER CONSISTENCY OF THE NAM WITH
PREVIOUS FCST GUIDANCE...TENDED TOWARD THAT MODEL SCENARIO. WL BUMP
POPS UP TO LIKELY OVER THE SCENTRAL CENTERED ARND SUN EVNG WHEN THE
FORCING WL BE GREATEST. THERE COULD BE A FEW INCHES OF SN ACCUM IN
THIS AREA AS WELL. SSW FLOW UP THE LENGTH OF LK MI MAY SUPPORT SOME
HIER POPS OVER THE E...BUT MARGINAL CHILL OF THE AIRMASS FOR LK
ENHANCEMENT WITH H85 TEMPS RISING TO -5C BY 00Z MON SHOULD LIMIT THE
POTENTIAL FOR A SGNFT IMPACT. TEMPS WL REMAIN ABOVE NORMAL...
ESPECIALLY ON SUN NGT WITH CLD COVER AND A STEADY S WIND GREATLY
LIMITING THE DIURNAL TEMP FALL.

MON...FOLLOWING THE EXIT OF THE SHRTWV INTO NW ONTARIO ON MON AND
THE ARRIVAL OF SOME MID LVL DRYING ASSOCIATED WITH A SHRTWV RDG AXIS
ROTATING NEWD THRU THE NW GREAT LKS TO THE E OF THE DEEPENING UPR
TROF IN THE PLAINS...EXPECT DIMINISHED POPS. BUT PERSISTENT WAA IN
THE DEEP S FLOW BTWN LO PRES SLIDING SEWD THRU THE NRN PLAINS AND HI
PRES OVER THE CNDN MARITIMES WL CAUSE LOTS OF CLDS AND CONTINUED LO
CHC POPS. AS THE LLVLS WARM INTO THE 30S ESPECIALLY NEAR THE WARMING
INFLUENCE OF THE GREAT LKS...LIGHT PCPN MAY INCLUDE A MIX OF RA AND
SN.

MON NGT/TUE...THE 00Z GFS REMAINS CONSISTENT ON SHOWING A CLOSED H5
LO WITHIN THE DEEPENING CENTRAL CONUS TROF/DEEPER SFC LO PRES MOVING
INTO THE UPR LKS DURING THIS TIME ALONG WITH HIER H85 TEMPS UP TO
ARND 0C. THE 12Z/00Z ECMWF MODELS ON THE OTHER HAND HOLD THE CLOSED
H5 LO/SFC LO FARTHER TO THE SW...WITH A SLOWER ARRIVAL OF DEEPER
MSTR AND LOWER H85 TEMPS. BOTH MODELS SHOW DISTURBANCES DIGGING SEWD
TO THE E OF THE UPR RDG ACROSS THE W DEEPENING THE PLAINS TROF.
SINCE THIS GREATER FORCING INTO THE SRN PLAINS SHOULD TEND TO HOLD
THE CLOSED LO THE SW...WL TEND TOWARD THE 12Z ECMWF SCENARIO. THIS
MODEL SHOWS DEEPER MSTR ARRIVING LATE MON NGT AND PERSISTING THRU
TUE AS THE WEAKER SHRTWV LIFTS NEWD AWAY FM CLOSED LO TO THE SW.
ALTHOUGH THE 00Z ECMWF H85 TEMPS ARE LOWER THAN FCST BY THE GFS...
THE FCST H100-85 THKNS IS ONLY A BIT LOWER THAN THE GFS FCST. A LOOK
AT THE 00Z ECMWF FCST SDNGS SHOW A TREND TOWARD A WARMER NEAR SFC
LYR THAT WOULD SUPPORT MORE RA...AS SHOWN BY RECENT GFS RUNS. SO
TENDED TO RAISE FCST TEMPS AND INCLUDE A GREATER AREA OF AT LEAST A
MIX WITH RA. THE FCST SDNGS FM NEITHER MODEL SHOW AN ELEVATED WARM
LYR...SO THE PCPN SHOULD BE RA OR SN. ADDED A MENTION OF SOME FOG
DURING THE MON NIGHT/TUE TIME TO REFLECT THE RA/HIER TEMPS AND
DEWPTS OVER A MELTING SN PACK AT MANY LOCATIONS THAT UPSLOPE OFF LK
MI IN THE EXPECTED LLVL SE FLOW. THIS MIXED PCPN WL TEND TO DIMINISH
ON TUE NGT AS SOME UPR DRYING FOLLOWS THE SHRTWV EXITING NNEWD INTO
ONTARIO.

WED/THU...THE LONGER RANGE MODELS ARE BEGINNING TO COME INTO BETTER
AGREEMENT ON SHOWING A SECOND LO DVLPG IN THE LOWER TO MID MS RIVER
VALLEY ON TUE AT THE SRN END OF THE DEEPING CENTRAL CONUS TROF AND
THEN MOVING NNE INTO THE CENTRAL GREAT LKS ON WED AND THEN INTO ERN
ONTARIO ON XMAS DAY WHILE DEEPENING SIGNIFICANTLY AS THE UPR TROF
TAKES ON A MORE NEGATIVE TILT. NOT SURPRISINGLY...THE EXACT TRACK OF
THE SFC LO...WHICH WL MAKE A SGNFT DIFFERNCE ON PTYPE/PCPN TOTALS
OVER UPR MI...IS STILL UNCERTAIN. THE 00Z GFS INDICATES A FARTHER W
TRACK ACROSS THE ERN U.P. THAN THE 00Z ECMWF/UKMET RUNS...BUT THE
GFS INDICATES THE PCPN WOULD BE HEAVY SN OVER THE W HALF OF UPR MI.
THE FARTHER E ECMWF MODEL GENERATES MUCH LIGHT PCPN OVER THE E.
CONSIDERING THE SGNFT DIFFERNCES THAT REMAIN...RELIED ON THE MODEL
CONSENSUS FOR THE FCST DETAILS. THIS CONSENSUS SUPPORTS HIER POPS
OVER THE E WITH A CHANGE IN PTYPE FM MIXED RA/SN TO MAINLY SN AS THE
INCREASING N BACKING NW WINDS ADVECT COLDER AIR INTO THE CWA.
IN THE WAKE OF THE DEEPENING LO MOVING INTO ONTARIO ON XMAS DAY...
THE PRES GRADIENT IS PROGGED TO TIGTHEN SGNFTLY AND H925 WINDS
INCREASE TO NEAR 45 KTS. NW WIND GUSTS MAY AT LEAST APRCH ADVY
CRITERIA...ESPECIALLY AT EXPOSED LOCATIONS NEAR LK SUP.
&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 652 AM EST SAT DEC 20 2014

LOW CLOUD FCST THE MAIN ISSUE THROUGH TONIGHT. CURRENTLY MVFR CIGS
REMAIN OVER KIWD AND ARE JUST TO WEST OF KCMX. EXPECT BKN-OVC CIGS
TO PERSIST AT BOTH TAFS TODAY AND TONIGHT. PRIMARY ISSUE WILL BE
WHETHER CIGS STAY BLO 020 OR JUST ABOVE AS THIS AFFECTS ALTERNATE
FLIGHT PLANNING. MEANWHILE...AT KSAW...STILL SOME FOG ISSUES VERY
EARLY ON AS LOW CLOUDS ARE JUST TO THE WEST AND MID CLOUDS HAVE
THINNED SOME IN THE LAST COUPLE HOURS. FOG IS SHALLOW THOUGH AND NOT
WIDESPREAD...SO DO NOT IT EXPECT IT TO LAST TOO LONG. THIS WILL BE
ESPECIALLY TRUE AFTER BKN-OVC MVFR STRATUS DECK SPREADS OVER CNTRL
UPR MICHIGAN THIS MORNING. WILL COVER THE FOG WITH TEMPO WHICH WORKED
WELL EARLIER TONIGHT AT KSAW. MVFR CLOUDS SHOULD PERSIST INTO TONIGHT
THOUGH LIKE THE WESTERN TAF SITES...MAIN QUESTION WILL REVOLVE
AROUND WHETHER PREVAILING CIGS END UP ABOVE OR BELOW 020.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 434 AM EST SAT DEC 20 2014

EXPECT S WINDS UNDER 20 KTS ASSOCIATED WITH HI PRES DRIFTING E THRU
SE CANADA TO PERSIST INTO SUN. THE S WINDS WILL INCREASE UP TO 25
KTS OVER AT LEAST THE E HALF OF THE LAKE ON SUN INTO MON AS A LO
PRES TRACKS E THRU THE NORTHERN PLAINS AND THE PRES GRADIENT
TIGHTENS OVER THE UPPER LAKES. AS ANOTHER LO PRES DEVELOPS TO THE S
ON TUE...THE FLOW WILL TEND TO BACK TOWARD THE NW. THE LATEST TRENDS
INDICATE THIS LO WILL DEEPEN SIGNFICANTLY AS IT MOVES TO THE NNE
THRU THE CENTRAL GREAT LAKES ON WED AND INTO SE ONTARIO ON XMAS DAY.
THE POTENTIAL FOR A N VEERING NW GALE EVENT FROM LATE ON WED THRU
XMAS DAY NOW LOOKS GREATER.
&&

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

$$

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







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