Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 201958
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
258 PM EST SAT DEC 20 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 257 PM EST SAT DEC 20 2014

THE THEME OF THIS SHORT TERM PERIOD WILL BE STEADY S WINDS...WITH
INCREASED MOISTURE PUSHING INTO THE UPPER GREAT LAKES REGION.

TAKING A LOOK AT THE LATEST WV IMAGERY...MOISTURE WAS SET UP FROM W
ONTARIO THROUGH MUCH OF THE UPPER GREAT LAKES...ASSOCIATED WITH THE
500MB TROUGH EXTENDING ACROSS THE AREA. MOISTURE STUCK UNDER THE
500MB RIDGE OVER MANITOBA THROUGH E ND/SD AND FAR W MN IS KEEPING
CEILINGS AROUND 1KFT OR LOWER WITH VIS DOWN AOB 5SM.

PW VALUES AT A LOW OF AROUND 0.3IN THIS MORNING WILL SLOWLY INCREASE
THROUGH THE DAY SUNDAY...TO AN AVERAGE OF AROUND 0.4IN. NOT
EXPECTING MUCH IMPROVEMENT TO THE MID TO OCCASIONAL CLOUDS CURRENTLY
PUSHING INTO THE CWA THROUGH THE PERIOD. ALTHOUGH...A FEW POCKETS
OF TEMPORARY CLEARING COULD DEVELOP OVER THE E HALF OF UPPER MI.

THE MAIN 500MB TROUGH EXTENDING ACROSS THE REGION WILL SHIFT
SLIGHTLY N THROUGH THE MORNING HOURS SUNDAY...IN ADVANCE OF THE NEXT
TROUGH NEARING FROM THE E DAKOTAS AND W MN. CAN/T RULE OUT PATCHY
FREEZING DRIZZLE OVER THE S CENTRAL CWA EARLY SUNDAY MORNING...SO
FEW CHANGES WERE MADE TO THE ONGOING PRECIP FCST. ALSO KEPT HIGH
CHANCE POPS GOING FOR THE S CENTRAL CWA BY LATE SUNDAY AFTERNOON AS
THIS NEXT TROUGH NEARS.

BREEZY S WINDS WILL BEGIN SUNDAY AFTERNOON. THIS WILL BE AS THE
PRESSURE GRADIENT INCREASES ACROSS THE REGION...IN BETWEEN EXITING
HIGH PRESSURE STRETCHING FROM EASTERN QUEBEC THROUGH THE MID
ATLANTIC STATES...AND THE SFC LOW NEARING FROM S
SASKATCHEWAN/ALBERTA/E MT.

.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 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 129 PM EST SAT DEC 20 2014

MVFR CEILINGS AND VIS SHOULD BE THE RULE THROUGH THE PERIOD. LIGHT S
WINDS WILL BE ON THE INCREASE DURING THE DAY SUNDAY...BUT REMAIN
AROUND 10KTS OR LESS THROUGH 18Z. THIS WILL BE IN RESPONSE TO THE
LARGE AREA OF HIGH PRESSURE TO OUR E CONTINUING TO EXIT TO E QUEBEC
AND THE NEW ENGLAND STATES. ON SUNDAY THE NEXT LOW PRESSURE SYSTEM
WILL BE NEARING FROM ALBERTA/SASKATCHEWAN/MONTANA.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 257 PM EST SAT DEC 20 2014

THE LARGE HIGH OVER QUEBEC WITH A RIDGE EXTENDING THROUGH THE LOWER
GREAT LAKES WILL SLOWLY EXIT TO THE ATLANTIC THROUGH MONDAY. LOOK
FOR A LOW OVER THE N PAINS SUNDAY NIGHT WILL PUSH ACROSS MINNESOTA
MONDAY NIGHT...AND THE UPPER GREAT LAKES TUESDAY. IN THE
MEANTIME...A DEEPENING LOW OVER TEXAS MONDAY NIGHT WILL SWING ACROSS
KENTUCKY AND INDIANA TUESDAY NIGHT...BEFORE SHIFTING TO LOWER
MICHIGAN WEDNESDAY AND WEDNESDAY NIGHT...AND EXITING TO AROUND JAMES
BAY THURSDAY. EXPECT OUR STEADY S WINDS TO INCREASE UP TO 25KTS OVER
MAINLY E LAKE SUPERIOR SUNDAY INTO MONDAY AS A RESPONSE TO THE
TIGHTENING PRESSURE GRADIENT. N-NW GALES OF 35-45KTS WILL BE
POSSIBLE /STRONGEST OVER THE E HALF OF LAKE SUPERIOR/ LATE WEDNESDAY
NIGHT THROUGH THURSDAY EVENING. A GALE WATCH WILL LIKELY BE NEEDED
WHEN WE GET CLOSER TO OUR 60HR /2.5DAY/ ISSUANCE PERIOD.
&&

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

$$

SHORT TERM...KF
LONG TERM...KC
AVIATION...KF
MARINE...KF






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