Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 301733
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
133 PM EDT TUE SEP 30 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 535 AM EDT TUE SEP 30 2014

WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A POTENT SHORTWAVE LIFTING
N THRU WRN NEBRASKA. IMMEDIATELY DOWNSTREAM IS A SHARP RIDGE
EXTENDING FROM MO THRU MN INTO MANITOBA AND NRN ONTARIO. SHORTWAVE
THAT PRODUCED SHOWERS HERE YESTERDAY IS NOW OVER LWR MI AND SRN
ONTARIO. IN THE WAKE OF THAT SHORTWAVE...ABUNDANT LOW-LEVEL MOISTURE
HAS BEEN TRAPPED UNDER A STRENGTHENING INVERSION...RESULTING IN OVC
SKIES OVERNIGHT ACROSS UPPER MI WITH ONE EXCEPTION. DRIER AIR AND
CLEAR SKIES HAVE ADVANCED S ACROSS CNTRL LAKE SUPERIOR TO THE TIP OF
THE KEWEENAW PENINSULA. AT THE SFC...HIGH PRES WAS CENTERED OVER NRN
ONTARIO.

GIVEN THE STRENGTHENING INVERSION AND LOWER SUN ANGLE AT THIS TIME
OF YEAR...IT WILL LIKELY TAKE A WHILE TO CLEAR OUT THE LOW CLOUDS
ACROSS THE AREA TODAY. ALTHOUGH CLEARING HAS ADVANCED S TO THE TIP
OF THE KEWEENAW OVERNIGHT...VEERING LOW-LEVEL WINDS TO AN EASTERLY
DIRECTION RESULTING FROM THE SFC HIGH SHIFTING EASTWARD WILL SLOW
AND STALL THE SOUTHWARD ADVANCE OF DRIER AIR. SATELLITE IMAGERY
ALREADY SHOWS THIS OCCURRING. GIVEN WHERE THE CLEARING LINE IS
UPSTREAM TO THE E OF LAKE SUPERIOR...HAVE SOME CONCERN THAT A GOOD
PORTION OF THE AREA WILL NOT SEE MUCH CLEARING TODAY. FOR NOW...FCST
WILL SHOW CLOUDS DOMINATING THIS MORNING AND THEN GRADUAL CLEARING
IN THE AFTN. IT MAY END UP BEING THAT DOWNSLOPE AREAS WILL BE THE
FIRST TO SEE INCREASING SUNSHINE THIS AFTN WITH CLEARING THEN SLOWLY
EXPANDING FROM THERE. AS FOR TEMPS...LOWERED TEMPS A BIT FROM
INHERITED FCST TO REFLECT THE MORE PESSIMISTIC CLEARING TREND. TEMPS
MAY STRUGGLE TO REACH 50F OVER THE NCNTRL WHERE CLOUDS ARE LIKELY TO
LINGER LONGEST. OTHERWISE...50S WIL BE THE RULE TODAY.

IF SKIES DO CLEAR THIS AFTN/EVENING...CLOUDS WILL BE ON THE INCREASE
AGAIN TONIGHT DUE TO CLOUDS SPREADING E FROM THE POTENT SHORTWAVE
LIFTING THRU THE DAKOTAS BUT MORE SO DUE TO A RETURN OF LOWER CLOUDS
LIFTING BACK INTO THE AREA FROM THE SE. ALTHOUGH POTENT SHORTWAVE
WILL BE TAKING A TRACK WELL W OF HERE...RIBBON OF FAIRLY STRONG
MOISTURE TRANSPORT INTO THE UPPER MISSISSIPPI VALLEY MAY SPREAD SCT
SHRA AS FAR E AS FAR WRN LAKE SUPERIOR LATE TONIGHT.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 433 AM EDT TUE SEP 30 2014

ATTENTION IN THE LONG TERM WILL BE ON THE UPPER TROUGH THAT WILL
MOVE FROM THE INTERMOUNTAIN WEST AT 12Z WED INTO THE CWA AT 00Z SAT
WHILE DEEPENING AND BECOMING NEGATIVELY TILTED...AS IS GENERALLY
AGREED ON BY NWP. THE UPPER TROUGH THEN LOOKS TO CLOSE OFF INTO A
LOW AS IT MOVES THROUGH THE REGION FRI NIGHT...BUT MODEL
DISAGREEMENT INCREASES SIGNIFICANTLY AT THIS POINT WITH THE STRENGTH
AND TRACK OF THE SYSTEM. GENERAL MODEL AGREEMENT DOES INCREASE SUN
NIGHT INTO MON WITH MODELS SHOWING A DEEP TROUGH OVER THE ERN CONUS.
ONE THING THAT CAN BE SAID WITH CERTAINTY IS THAT THE PATTERN WILL
BE MORE ACTIVE THAN LAST WEEK.

SHOWERS /POSSIBLY WITH SOME THUNDER/ IS STILL EXPECTED TO VERY
GRADUALLY MOVE W TO E ACROSS THE CWA WED THROUGH THU DUE TO
WAA/ISENTROPIC ASCENT AHEAD OF A SFC TROUGH/COLD FRONT. MAIN ISSUE
TO POINT OUT FROM A CONFIDENCE STANDPOINT IS THAT SHORTWAVE ENERGY
WILL PROBABLY EJECT FROM THE UPPER TROUGH TO THE W /AS SHOWN BY
NWP/...BUT THE MODELS DO NO AGREE ON THE STRENGTH/TIMING/TRACK OF
ANY ENERGY AND ASSOCIATED SFC CYCLOGENESIS. THERE WILL PROBABLY BE
PERIODS OF HEAVIER PRECIP AND/OR GREATER PRECIP COVERAGE...BUT
ACCURATELY TIMING THOSE OUT IS NOT POSSIBLE AT THIS TIME. HIGH TEMPS
IN THE 60S LOOK TO MAKE A RETURN ON WED AND THU DUE TO THE WAA AND
RESULTING WARM AIRMASS /850MB TEMPS OF 10-13C/.

AS PREVIOUSLY MENTIONED...THE UPPER TROUGH TEARS INTO THE AREA THU
NIGHT AND FRI...BRINGING A MUCH COLDER AIRMASS WITH IT. AT LEAST
PORTIONS OF THE CWA SHOULD SEE 850MB TEMPS BELOW 0C BY THE END OF
THE DAY FRI. GIVEN THE STRENGTH OF THE TROUGH AND MAGNITUDE OF
RESULTING HEIGHT FALLS AS IT MOVES IN...PERIODS OF PRECIP DOES LOOK
LIKE A GOOD BET THU NIGHT INTO FRI...ALTHOUGH AMOUNTS WILL BE
DEPENDENT ON THE HIGHLY UNCERTAIN SFC LOW LEVEL FEATURES. SOME
MODELS /MAINLY THE GFS AND NAM/ SHOW A DEEPER SFC LOW TRANSITING THE
CWA THU NIGHT INTO FRI /AS THE GFS HAS SHOWN VARIOUS ITERATIONS OF
FOR THE LAST SEVERAL RUNS/. IF THIS DOES OCCUR...GALES WOULD LIKELY
OCCUR ACROSS PORTIONS OF THE GREAT LAKES...ALONG WITH MORE
SUBSTANTIAL RAINFALL AMOUNTS. WHILE THIS IS NOT OUT OF THE
QUESTION...THERE IS JUST TOO MUCH UNCERTAINTY AT THIS POINT TO ADD
THIS SCENARIO TO THE FORECAST. PRECIP FRI NIGHT INTO SAT IS A BIT
MORE CERTAIN SINCE IT WILL BE LESS DUE TO A SYNOPTIC SYSTEM AND MORE
TO SUB ZERO 850MB TEMPS AND WNW-NW LOW LEVEL WINDS LEADING TO LAKE
EFFECT PRECIP NEAR LAKE SUPERIOR. IN FACT...DEPENDING ON EXACTLY HOW
COLD THE AIRMASS IS...SNOW IS CERTAINLY NOT OUT OF THE PICTURE FRI
NIGHT INTO SAT NIGHT...BUT ACCUMULATING SNOW IS UNLIKELY /ESPECIALLY
SIGNIFICANT ACCUMULATIONS/. DID ADD SNOW CHANCES TO THE FORECAST
OVER HIGHER TERRAIN OF WRN UPPER MI FRI NIGHT INTO EARLY SAT AND FOR
PORTIONS OF NWRN AND NERN UPPER MI SAT NIGHT. HIGH TEMPS BY SATURDAY
LOOK TO BE IN THE UPPER 40S TO LOW 50S....WITH LOW TEMPS SAT NIGHT
FROM THE UPPER 20S TO MID 30S.

GOING COMPLETELY WITH MODEL CONSENSUS IDEA SUN AND MON GIVEN
UNCERTAINTY.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 132 PM EDT TUE SEP 30 2014

DAYTIME HEATING/MIXING WL ALLOW LO CLDS AT SAW AND IWD TO BREAK UP
THIS AFTN WITH A PERIOD OF VFR CONDITIONS INTO AT LEAST THIS EVNG.
ALTHOUGH CMX MAY SEE SOME SC/LOWER CIGS EARLY THIS AFTN ON THE NRN
FRINGE OF SLOWLY DISSIPATING MAIN LO CLD AREA TO THE S...EXPECT VFR
CONDITIONS TO PREDOMINATE THERE INTO AT LEAST THIS EVNG. ONCE HI
PRES IN ONTARIO SHIFTS FARTHER TO THE E TNGT AND A LO PRES TROF
APRCHS FM THE W...THE LLVL WINDS WL SHIFT TO A MORE S DIRECTION. IN
THE PRESENCE OF NOCTURNAL COOLING AND THE RETURN OF MOISTER LLVL
AIR...EXPECT LO CLDS/IFR CONDITIONS TO DVLP AT SAW. DOWNSLOPE NATURE
OF THIS LLVL FLOW MAKES THE FCST AN ESPECIALLY TRICKY ONE FOR CMX
AND IWD...SO INCLUDED JUST A SCT DECK FOR NOW. ANY LO CLDS THAT DVLP
TNGT SHOULD DISSIPATE ON WED AT CMX/IWD WITH DAYTIME HEATING...BUT
THESE CLDS WL BE MORE RESILIENT AT SAW EVEN IF THE CIG HGT DOES LIFT
ABV 1K FT INTO THE MVFR RANGE BY NOON.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 535 AM EDT TUE SEP 30 2014

WITH HIGH PRES JUST N OF LAKE SUPERIOR...WINDS WILL DIMINISH TO
UNDER 20KT THIS MORNING. WINDS OVER FAR WRN LAKE SUPERIOR MAY
INCREASE INTO THE 15-25KT RANGE FOR A TIME THIS AFTN/EVENING AS THE
HIGH BEGINS TO MOVE E. WINDS SHOULD OTHERWISE REMAIN UNDER 20KT
THROUGH AT LEAST THU MORNING...THOUGH THERE MAY BE A SLIGHT UPTICK
IN S TO SE WINDS OVER ERN LAKE SUPERIOR WED AS PRES GRADIENT
TIGHTENS BTWN THE DEPARTING HIGH AND A COLD FRONT APPROACHING FROM
THE W. THAT COLD FRONT WILL REACH LAKE SUPERIOR THU...AND THEN A
WAVE OF LOW PRES WILL DEVELOP ALONG THE FRONT OVER THE UPPER GREAT
LAKES. DEPENDING ON WHERE THE LOW ORGANIZES AND HOW QUICKLY IT
STRENGTHENS AS IT MOVES N THRU NRN ONTARIO...THERE WILL BE THE
POTENTIAL FOR A PERIOD OF NW GALES OVER LAKE SUPERIOR AT SOME POINT
FRI AND/OR SAT.
&&

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

$$

SHORT TERM...ROLFSON
LONG TERM...TITUS
AVIATION...KC
MARINE...ROLFSON



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