Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 301953
AFDMQT

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

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 311 PM EDT TUE SEP 30 2014

12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW A SHARP UPR RDG
EXTENDING FM THE MID MS RIVER VALLEY N INTO NW ONTARIO...SUPPORTING
SFC HI PRES JUST N OF LK SUP. ALTHOUGH THE MID TROP IS QUITE DRY...
WITH 12Z H5 DEWPT DEPRESSIONS AS HI AS 45C AT MPX AND QUAD CITIES...
LINGERING LLVL MSTR TO THE S OF THE HI CENTER AND BLO SHARP
SUBSIDENCE INVRN ARND H9-925 CAUSED QUITE A BIT OF LO CLD TO PERSIST
OVER THE UPR LKS THRU THE MRNG. DAYTIME HEATING THAT HAS CAUSED THE
LCL TO RISE THRU THE SLOWLY SINKING INVRN BASE PER FCST SDNGS IS
RESULTING IN STEADY BREAKUP OF THE LO CLD EARLY THIS AFTN. THE LO
CLDS HAVE BEEN MOST RESILIENT OVER THE CENTRAL...WHERE LLVL NE WIND
IS UPSLOPING. LOOKING UPSTREAM...A VIGOROUS NEGATIVELY TILTED SHRTWV
IS LIFTING NNEWD THRU THE NRN PLAINS. DESPITE THE MID LVL DRY AIR IN
PLACE...SOME SHOWERS/TS IN THE RATHER NARROW WARM CONVEYOR BELT
ASSOCIATED WITH THIS DISTURBANCE ARE MOVING INTO SW MN.

MAIN FCST CONCERNS IN THE SHORT TERM ARE FOCUSED ON CLD TRENDS. FCST
CONCERNS ON WED SHIFT TO THE POTENTIAL FOR SOME SHOWERS IN THE
INCRSG SLY FLOW/ISENTROPIC ASCENT TO THE E OF SHRTWV MOVING THRU THE
NRN PLAINS INTO SCENTRAL CANADA.

TNGT...ALTHOUGH THE LO CLDS WL CONTINUE TO DISSIPATE INTO THE EVNG
WITH THE IMPACTS OF DAYTIME HEATING/MIXING...NOCTURNAL COOLING AND
VEERING WINDS TO THE S THAT WL BRING A RETURN OF MOISTER H95-9 AIR
SHOULD RESULT IN MORE LO CLDS. NOT OUT OF THE QUESTION THERE COULD
BE SOME DRIZZLE OVER THE CENTRAL WHERE EXPECTED SSE WIND WL UPSLOPE
OFF LK MI. THE ONE EXCEPTION WL BE OVER THE W...WHERE THE S WIND WL
DOWNSLOPE AND PREVENT/LIMIT THE REFORMATION OF THE LO CLDS. OTRW...
SOME MID/HI CLDS ON THE ERN FLANK OF THE WARM CONVEYOR BELT MSTR
RIBBON MOVING E THRU WL INVADE THE W OVERNGT. THE COMBINATION OF
LINGERING LO CLDS AND/OR INCRSG SLY FLOW WITH H925 WINDS INCRSG UP
TO 20-30 KTS BY 12Z WED WL LIMIT THE DIURNAL TEMP FALL. BUT TEMPS
SHOULD STILL FALL INTO THE 30S AT SOME OF THE INTERIOR COLD SPOTS
THAT SEE MOCLR SKIES FOR A TIME.

WED...ALTHOUGH THE PASSAGE OF SHRTWV/ACCOMPANYING DPVA AND DEEP LYR
QVECTOR CNVGC WELL TO THE W THRU MANITOBA WL LIMIT THE PCPN
POTENTIAL OVER UPR MI...RATHER NARROW WARM CONVEYOR BELT MSTR RIBBON
AND AREA OF H85-5 QVECTOR CNVGC/UPR DVGC AND BAND OF H85-7 FGEN IN
RRQ OF 80KT H3 JET MAX LIFTING NNEWD THRU NW ONTARIO WL BRING THE
THREAT OF SHOWERS TO THE W IN THE AFTN. CONSIDERING THE STRONG
DYNAMIC SUPPORT AND APPRECIABLE DEEP MOISTENING THAT IS FCST TO
RAISE PWAT NEAR 1.5 INCHES /UP TO 200 PCT OF NORMAL/ BY 00Z THU...HI
LIKELY POPS SEEM APPROPRIATE OVER THE FAR W. ALTHOUGH THE MID LVLS
OVER THE E WL REMAIN DRY...FCST SDNGS INDICATE LO CLDS WL PERSIST
MOST OF THE DAY IN THAT AREA AND LIMIT THE DAYTIME TEMP RECOVERY.
BUT WITH STRENGTHENING SLY FLOW BRINGING A RETURN OF H85 TEMPS AS HI
AS 12-13C...MAX TEMPS WL RISE ABV NORMAL...ESPECIALLY IN THE
DOWNSLOPE AREAS NEAR LK SUP.

.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 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 353 PM EDT TUE SEP 30 2014

HIGH PRESSURE OF OVER N ONTARIO WILL MOVE E TO THE CANADIAN
MARITIMES BY WEDNESDAY EVENING. MEANWHILE...LOW PRESSURE OVER
WESTERN NE WILL LIFT ACROSS S MANITOBA WEDNESDAY MORNING...AND
TO HUDSON BAY THURSDAY MORNING. A TROUGH ASSOCIATED WITH THE LOW
WILL MOVE E...REACHING LAKE SUPERIOR ON THURSDAY. A LOW WILL FORM
ALONG THIS TROUGH OVER THE UPPER MS VALLEY THURSDAY EVENING AND THEN
DEEPEN AS IT LIFTS INTO N ONTARIO FRIDAY...AND TO HUDSON BAY FRIDAY
NIGHT. IN ITS WAKE...HIGH PRESSURE OVER THE W PLAINS FRIDAY
AFTERNOON WILL SETTLE OVER THE LOWER MS VALLEY SATURDAY INTO
SUNDAY...AS A TROUGH EXTENDING FROM THE HUDSON BAY LOW LINGERS OVER
N ONTARIO. A PERIOD OF NEAR GALES OUT OF THE W-NW WILL BE POSSIBLE
FROM LATE FRIDAY AFTERNOON THROUGH THE DAY SATURDAY.
&&

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

$$

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






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