Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 180233
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
1033 PM EDT WED SEP 17 2014

.UPDATE...
ISSUED AT 1032 PM EDT WED SEP 17 2014

UPDATED FORECAST TO INCLUDE KEWEENAW COUNTY IN FROST ADVY OVERNIGHT.
THE KEWEENAW PENINSULA HAS HAD CLEAR SKIES MOST OF THE EVENING. IN
FACT...THE KEWEENAW HAS REALLY BEEN THE ONLY AREA TO SEE MAINLY
CLEAR SKIES SO FAR TONIGHT. ALTHOUGH COPPER HARBOR IS THE ONLY AVBL
OB IN KEWEENAW COUNTY...OBSERVATIONS JUST ACROSS THE COUNTY LINE IN
NRN HOUGHTON COUNTY SHOW TEMPS ALREADY DOWN INTO THE MID 30S.
THUS...A FROST ADVY IS WARRANTED FOR KEWEENAW COUNTY OVERNIGHT.

ELSEWHERE...CLOUDS HAVE HELD TOUGH THIS EVENING...AND GIVEN ANOTHER
BATCH OF CLOUDS DROPPING SSW ACROSS THE LAKE...CLEARING WILL LIKELY
BE A SLOW PROCESS IN MANY AREAS DURING THE NIGHT. BASED ON SATELLITE
TRENDS...IT APPEARS CLEARING WILL REALLY GET UNDERWAY AFTER THIS
LAST AREA OF CLOUDS/LOW-LEVEL MOISTURE PASSES ACROSS THE AREA.
CLOUDS WILL PROBABLY END UP LINGERING LONGEST TO THE SW AND W OF
MARQUETTE AS THERE MAY BE A LITTLE LAKE COMPONENT TO THE CLOUD
COVER. IN THE END...EVEN IF THERE ARE ONLY 2-3 HRS OF MOSTLY CLEAR
SKIES...TEMPS SHOULD HAVE NO PROBLEM FALLING TO OR BLO FREEZING
INLAND FROM LAKE SUPERIOR...SO FROST/FREEZE HEADLINES APPEAR ON
TRACK.
&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 320 PM EDT WED SEP 17 2014

THE PASSAGE OF THE SAGGING COLD FRONT EARLY THIS AFTERNOON HAS
RESULTED IN LOW CLOUDS...SOME FOG...AND SIGNIFICANT COOLING ALONG
THE LAKE SUPERIOR SHORELINES. PLENTY OF CLEARING IS JUST UPSTREAM
OVER CENTRAL LAKE SUPERIOR...THANKS TO THE LARGE AREA OF HIGH
PRESSURE SET UP ACROSS MUCH OF MANITOBA. LOOK FOR THE SFC LOW TO
DRIFT SE ACROSS LAKE SUPERIOR OVERNIGHT.

PW VALUES AROUND 30 PERCENT OF NORMAL /0.2IN/ OVER LAKE WINNIPEG
THIS AFTERNOON WILL BE ABLE TO SLIDE ACROSS THE W HALF OF UPPER MI
OVERNIGHT. FEW CHANGES WERE MADE TO THE EXPECTED TEMPS
OVERNIGHT...BOTTOMING OUT IN THE UPPER 20S TO MID 30S...EXCEPT NEAR
40F ALONG THE GREAT LAKES SHORELINES. ONGOING FROST/FREEZE HEADLINES
STILL LOOK GOOD FOR ALL AREAS BUT KEWEENAW COUNTY. THERE IS A VERY
SMALL CHANCE FOR FOG THE TYPICAL LOCATION OF E GOGEBIC AND MUCH OF
IRON COUNTY OVERNIGHT WITH VIS FALLING TO MVFR CATEGORY. LOOKS LIKE
THIS COULD BE A POSSIBILITY...BUT WILL NOT INCLUDE IT AT THIS TIME
DUE TO THE LOWER PROBABILITY WITH THE SIGNIFICANTLY DRY AIR MOVING
IN AND LIMITED IMPACT IF IT WERE TO OCCUR.

LOOKING AHEAD INTO THURSDAY...THE SFC HIGH SLOWLY EXITING TO THE E
/ALONG THE ONTARIO AND QUEBEC BORDER BY 00Z FRIDAY/...WHILE THE
500MB RIDGE BUILDS IN ALOFT. LIGHT WINDS AROUND 10KTS OR LESS WILL
BE THE RULE. HOWEVER...DESPITE SOME WAA AT 850MB WITH 850MB TEMPS
RISING TO A CWA AVERAGED 5C...HIGH TEMPS IN THE 50S STILL LOOK
REASONABLE. THIS IS APPROX 10F BELOW THE SEASONAL AVERAGE FOR THIS
TIME OF YEAR.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 406 PM EDT WED SEP 17 2014

MAIN FCST CONCERN IN THE MEDIUM RANGE PERIOD IS FOCUSED ON POPS FOR
FRI THRU SAT AS A SERIES OF SHRTWVS EMBEDDED IN A ZONAL FLOW ON THE
NRN FLANK OF AN UPR RDG OVER THE SCENTRAL CONUS INTERACT WITH AN
INCRSGLY MOIST SW FLOW ON THE NW FLANK OF HI PRES SHIFTING INTO THE
MID ATLANTIC STATES.

THU NGT...THE COMBINATION OF A STRENGTHENING SW FLOW...WITH H925
WINDS INCRSG UP TO 35-45 KTS BY 12Z FRI ON THE SRN FLANK OF SHARP
PRES FALLS OVER NW ONTARIO...BTWN HI PRES MOVING THRU NEW ENGLAND
AND A COLD FNT ASSOCIATED WITH SFC LO PRES OVER HUDSON BAY AS WELL
AS INCRSG PWAT UP TO NEAR 1 INCH OVER THE W/INCRSG HIER CLDS OVER
SHARPENING DEEP ISENTROPIC ASCENT WL GREATLY RESTRICT THE DIURNAL
TEMP FALL. EXPECT THE WARMEST MIN TEMPS OVER THE NW HALF IN THE
DOWNSLOPE AREAS NEAR LK SUP AND WHERE THE H925 WINDS WL BE STRONGER.
OVER THE INTERIOR E AND SCENTRAL...TEMPS MAY FALL MORE QUICKLY IN
THE EVNG WHEN SKIES WL BE MOCLR AND SFC WINDS STILL RATHER WEAK
UNDER RADIATION/WAD INVRN. BUT STRONGER SW FLOW DVLPG LATE SHOULD
MITIGATE A FURTHER TEMP DROP.

FRI/FRI NGT...ALTHOUGH THE MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD
AGREEMENT SHOWING SHRTWVS STREAMING THRU THE GREAT LKS WITHIN A W-E
FLOW ALF AND INTERACTING WITH THE LLVL SW FLOW THAT IS FCST TO LIFT
PWAT UP TO ARND 1.5 INCH FRI NGT/SAT MRNG...THERE REMAIN SOME
DISCREPANCIES ON THE DETAILS OF THE FCST. DESPITE THE INCRS IN
ABSOLUTE MSTR AND OVERALL INSTABILITY THAT IS FCST TO DROP THE SSI
AS LO AS -3C TO -4C AND INCRS THE POTENTIAL FOR ELEVATED TS LATE
FRI/FRI NGT WITH APRCH OF WARM FNT...BULK OF THE MODEL FCST SDNGS
SHOW AN INVRN BTWN H75-85 AND MID LVL DRYING AT TIMES THRU FRI NGT
THAT WOULD TEND TO LIMIT CONVECTION. MODEL CONSENSUS SUGGESTS THE
BEST CHC FOR SHOWERS WL BE OVER THE NCENTRAL FRI AFTN AND THE E HALF
FRI EVNG...WHEN ISENTROPIC ASCENT/ H925-7 MSTR TRANSPORT AND
CNVGC/DEEP LYR QVECTOR CNVGC WL BE SHARPER IN THOSE AREAS. BUT THERE
ARE ENUF MODEL DIFFERENCES IN TIMING OF SHRTWVS TRACKING THRU THE
AREA AS WELL AS IMPACT OF LINGERING LLVL DRY AIR ON FRI TO CAST
DOUBT ON THIS CONSENSUS. AS FOR TEMPS...INCRSG CLD COVER WL HOLD
DOWN SFC HI TEMPS ON FRI DESPITE INFLUX OF WARMER AIR. EXPECT
RELATIVELY SMALL TEMP FALL ON FRI NGT WITH STRONG SW FLOW/HIER PWAT.

AS A STRONGER SHRTWV APRCHS SAT AND ASSOCIATED SFC LO PRES/COLD FNT
SWING THRU THE UPR LKS...THERE MAY BE A BETTER CHANCE OF SHOWERS/TS
AGAIN WITH THE DYNAMIC FORCING IN SYNC WITH DAYTIME HEATING AND FCST
SDNGS SHOWING A WEAKENING OF THE MID LVL INVRN. LOOKS LIKE THE BEST
CHC FOR THIS CONVECTION WOULD BE OVER THE E HALF...ESPECIALLY IF THE
FASTER MODELS VERIFY AND SHOW SFC FNT SWEEPING THRU THE W TOO EARLY
IN THE DAY. DEPENDING ON HOW QUICKLY THE SFC COLD FNT PASSES ON
SAT...SOME PLACES MAINLY OVER THE SCENTRL MAY SEE TEMPS RISE INTO
THE 70S AS H85 TEMPS ARE FCST TO PEAK AS HI AS 17C.

SAT NGT INTO SUN NGT...ALTHOUGH THE DETAILS REMAIN SKETCHY...
ADDITIONAL SHRTWVS/REINFORCING COLD FROPA DROPPING INTO THE GREAT
LKS THAT ARE FCST TO DEEPEN AN UPR TROF AND CAUSE A W SLOWLY VEERING
N CYC FLOW OVER THE AREA INDICATE THERE WL BE A GOOD DEAL OF CLD
COVER...PERIODS OF SHOWERS AND COOLER WX AS H85 TEMPS DROP FM AS HI
AS 15C ON SAT AFTN TO AS LO AS -2C ON SUN NGT. AS H85 TEMPS FALL...
THERE MAY BE A LK ENHANCED COMPONENT OF THE CLDS/SHOWERS SUN AND SUN
NGT WITH WSHFT TO THE N. BUT CHILLY LK WATERS...WITH BUOYS SHOWING
OPEN WATER TEMPS IN THE MID 40S...MIGHT MITIGATE THIS POTENTIAL.

EXTENDED...WITH HI PRES AND MUCH DRIER AIR MOVING INTO THE GREAT LKS
EARLY NEXT WEEK...EXPECT DRY WX TO PREVAIL. MON IS LIKELY TO BE
RATHER COOL...BUT RETURN SW FLOW ON THE NW FLANK OF THE HI SHIFTING
TOWARD THE LOWER LKS WL BRING A WARMING TREND THRU WED.
&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 736 PM EDT WED SEP 17 2014

LOW-LEVEL MOISTURE/CLOUDS BEHIND COLD FRONT THAT PASSED EARLIER
TODAY WILL CONTINUE TO BE AN ISSUE TONIGHT AT KSAW. WITH SOME
MOISTURE OFF LAKE SUPERIOR AND NORTHERLY UPSLOPE FLOW...EXPECT LOW
CLOUDS TO PERSIST UNTIL LATE TONIGHT WHEN WINDS VEER MORE EASTERLY
OFF LAND. INITIAL IFR CIGS...POSSIBLY LIFR...SHOULD LIFT TO LOW MVFR
MID TO LATE EVENING BEFORE SCATTERING OUT LATE TONIGHT. VFR
CONDITIONS WILL THEN BE THE RULE AT KSAW ON THU UNDER DRY AIR MASS.
AT KCMX...VFR CONDITIONS SHOULD PREVAIL TONIGHT...THOUGH CAN`T RULE
OUT OCNL MVFR CIGS GIVEN CLOUDS STILL UPSTREAM. BETTER CHC OF A
PERIOD OF MVFR CIGS SHOULD DEVELOP TOWARD DAYBREAK AS WINDS VEER
MORE EASTERLY AND UPSLOPE OFF THE WARMER WATER OF KEWEENAW BAY. VFR
CONDITIONS WILL THEN PREVAIL LATE MORNING THRU AFTN AT KCMX. AT
KIWD...OCNL MVFR CIGS ARE STILL POSSIBLE FOR THE NEXT FEW HRS...BUT
EXPECT VFR CONDITIONS TO PREVAIL THRU THE REMAINDER OF THE FCST
PERIOD AS WINDS VEER TO A DOWNSLOPE E TO SE DIRECTION.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 406 PM EDT WED SEP 17 2014

ENE WINDS ON THE SOUTHERN FLANK OF HI PRES MOVING SEWARD THRU NW
ONTARIO AS HI AS 20-25 KTS THIS EVENING WILL TEND TO DIMINISH
TONIGHT EXCEPT OVER THE FAR W...WHERE FUNNELING OF THE FLOW MIGHT
MAINTAIN STRONGER WINDS UP TO 20 KTS. AS THE HI SHIFTS TOWARD NEW
ENGLAND TOMORROW...THE WINDS WL VEER TO THE S AND THEN INCREASE THRU
THE DAY ON FRI AS THE PRES GRADIENT SHARPENS BETWEEN THE DEPARTING
HI AND A COLD FRONT MOVING THRU SCENTRAL CANADA/NORTHERN PLAINS. SSW
WINDS COULD REACH 30 KTS...BUT HI STABILITY OVER THE UNUSUALLY
CHILLY LAKE WATERS WILL LIMIT THE POTENTIAL FOR ANY GALES DESPITE
THE STRENGTH OF THE EXPECTED WINDS NOT FAR ABOVE THE WATER. WINDS
WILL THEN DIMINISH TO AROUND 20 KTS AND GRADUALLY VEER TO THE W-NW
FOLLOWING A COLD FRONTAL PASSAGE ON SAT BEFORE VEERING FURTHER TO
THE N AND INCREASING UP TO 25 KTS ON SUN/MON FOLLOWING THE PASSAGE
OF A REINFORCING COLD FRONT.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
  FROST ADVISORY UNTIL 10 AM EDT /9 AM CDT/ THURSDAY FOR MIZ001-
     003-005>007-012>014-085.

  FREEZE WARNING UNTIL 10 AM EDT /9 AM CDT/ THURSDAY FOR MIZ002-
     004-009>011-084.

LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

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






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