Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 302345
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
745 PM EDT TUE JUN 30 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 321 PM EDT TUE JUN 30 2015

12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW A NW FLOW ALF INTO
THE GRT LKS BTWN UPR TROF OVER ERN NAMERICA AND RDG OVER THE
ROCKIES. SHRTWV EMBEDDED WITHIN THIS TROF IS OVER ERN LK SUP
AND MOVING SLOWLY TO THE E. ACCOMPANYING AREA OF DEEPER MSTR AND
LARGE SCALE FORCING IS CAUSING SOME LINGERING SHOWERS OVER THE ERN
CWA. ALTHOUGH DNVA/SUBSIDENCE HAS ENDED THE LARGER SCALE PCPN OVER
THE W AND CENTRAL CWA...LINGERING NEAR SFC MSTR ASSOCIATED WITH
INFLUX OF LLVL COOL AIR/INVRN SHOWN ON THE 12Z INL RAOB AND UPSLOPE
N FLOW OFF LK SUP TO THE S OF SFC HI PRES OVER NW ONTARIO HAS
MAINTAINED QUITE A BIT OF LO CLDS OVER MUCH OF THE CWA. BUT THE AIR
JUST TO THE NW OF LK SUP IS QUITE A BIT DRIER WITH SFC T/TD
DEPRESSIONS AT LEAST CLOSE TO 20F FM THUNDER BAY ONTARIO INTO THE MN
ARROWHEAD. THE ADVECTION OF THIS DRIER AIR IS TENDING TO BREAK UP
THE LO CLDS OVER THAT PART OF LK SUP. CLOSER TO THE SFC HI PRES...
THE 12Z PWAT WAS AS LO AS 0.35 INCH AT YPL OR ABOUT 50 PCT OF NORMAL.

MAIN FCST CONCERNS IN THE SHORT TERM ARE LO CLD TRENDS INTO TNGT AND
TEMPS.

LATE TODAY/TNGT...AS SHRTWV OVER ERN LK SUP EDGES OFF TO THE E LATE
THIS AFTN AND DEEP LYR QVECTOR DVGC/MID LVL DRYING OVERSRPEADS
THE ERN CWA...EXPECT LINGERING SHOWERS OVER THE E TO END BY 00Z.
LINGERING DRIZZLE OVER MAINLY THE HIER TERRAIN NEAR LK SUP SHOULD
ALSO TEND TO DIMINISH THIS AFTN WITH SOME LLVL DRY ADVECTION/IMPACT
OF DAYTIME HEATING...WHICH WL ALSO TEND TO BREAK UP THE LO CLDS
ESPECIALLY OVER THE W WHERE THE LLVL FLOW WL TEND TO BECOME MORE
ACYC CLOSER TO CORE OF INCOMING DRIER AIR. AS THE SFC HI BUILDS OVER
THE W HALF OVERNGT...SKIES WL TURN MOCLR AND ALLOW TEMPS TO FALL OFF
INTO THE 40S. A MORE PERSISTENT CYC N FLOW OVER THE E SHOULD CAUSE
CLDS TO LINGER LONGER THERE AND LIMIT THE DIURNAL TEMP FALL.

WED...AS THE SFC HI PRES EXPANDS SLOWLY OVER THE UPR LKS AND THE
LLVL FLOW TURNS MORE ACYC...EXPECT LINGERING LO CLDS OVER THE E TO
MIX OUT IN THE PRESENCE OF DAYTIME HEATING. UNDER MOSUNNY SKIES OVER
THE W/SCENTRAL...MAX TEMPS SHOULD REACH THE LO 70S WITH H85 TEMPS
FCST NEAR 10C. PERSISTENT LLVL NW FLOW OFF THE CHILLY LK SUP WATERS
AND SOME LINGERING MRNG CLDS WL KEEP THE NEARSHORE AREAS OVER THE E
MUCH COOLER.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 253 PM EDT TUE JUN 30 2015

IMPACT ASSESSMENT...PUT MAIN FOCUS ON FRI AND SAT WITH MANY OUTDOOR
ACTIVITIES AND POSSIBILITIES OF SHOWERS AND GENERAL THUNDER.
ADDITIONALLY...AN UPPER TROUGH AND SFC COLD FRONT MAY BRING SOME
STRONGER STORMS EARLY NEXT WEEK...BUT CONFIDENCE IS LOW AT THIS TIME.

WITH THE FORECAST DRY FOR WED NIGHT AND THU...PUT MAIN FOCUS ON
HIGHER IMPACT FRI-SAT TIME FRAME. A SHORTWAVE MOVING ACROSS ONTARIO
IS EXPECTED TO BRING A WEAK COLD FRONT INTO THE U.P. WHERE IT WILL
STALL OUT THROUGH SAT. THE 12/30 GFS AND 12Z/30 GLOBAL-GEM BOTH
BRING SCATTERED SHOWERS AND THUNDERSTORMS INTO THE U.P. FROM LATE
THU NIGHT INTO FRI NIGHT...WITH SOME POTENTIAL FOR STRONGER STORMS
AS CAPE MAY EXCEED 1000J/KG WITH 0-6KM BULK SHEAR OF 20-30KTS.
HOWEVER...THE 00Z/30 ECMWF AND 12Z/30 NAM ONLY SOME QPF OVER THE NRN
CWA DURING THIS TIME. LOCATION/COVERAGE/STRENGTH OF CONVECTION WILL
BE DEPENDENT ON FRONT TIMING AND SHORTWAVE TIMING/LOCATION. WITH
EXACT DETAILS STILL UNCERTAIN...WILL SHOW SLIGHT CHANCE TO LOW
CHANCE POPS..HIGHEST OVER THE N. HIGHS ON THU WILL BE N THE 70S.

CONFIDENCE IS INCREASING IN DIURNAL SHOWERS ON SAT AS THE FRONT SITS
OVER OR NEAR THE CWA. THE GFS SHOWERS UP TO AROUND 0.2 INCHES OF QPF
OVER INLAND AREAS WHILE THE ECMWF ONLY HAS 0.04 INCHES. THE GFS
SHOULD HANDLE QPF AMOUNTS BETTER IN THIS SITUATION...SO MODEL TO
MODEL AGREEMENT IS ACTUALLY FAIRLY GOOD IN THE OVERALL IDEA. LOOKS
LIKE SHOWERS AND THUNDERSTORMS FIRE UP IN THE EARLY AFTERNOON AND
CONTINUE INTO THE EARLY EVENING AS LOSS OF DAYTIME HEATING WILL LEAD
TO THE QUICK DEMISE OF THE CONVECTION LATER IN THE EVENING. THINK
MAINLY INLAND AREAS WILL SEE PRECIP AS LAKE BREEZES MOVE WELL INLAND
WITH WEAK ATMOSPHERIC FLOW. IN FACT...THE GFS BUFFER SOUNDING SHOWS
WINDS BELOW 25KTS THROUGHOUT THE CONVECTIVE LAYER...MEANING VERY
LITTLE WIND SHEAR. THEREFORE...SEVERE STORMS ARE NOT EXPECTED. TEMPS
WILL BE A COUPLE DEGREES WARMER THAN FRI WITH HIGHS IN THE 70S TO
AROUND 80. THE WEAK FLOW WILL ALSO HELP LIMIT WAVE ACTION ON THE
GREAT LAKES...BUT THE WATER TEMPS WILL STILL BE VERY COLD (IN THE
LOW 40S) WHICH IS THE PRIMARY HAZARD TO SWIMMERS.

QUITE A BIT MORE UNCERTAIN LOOKING AT NEXT WEEK AS MODELS SHOW
WIDELY VARYING MID-UPPER LEVEL PATTERN FOR MON AND TUE. THE ECMWF
HAS A DEEP TROUGH MOVING OVER THE REGION WHILE THE GFS HAS ZONAL
FLOW. THERE IS BETTER AGREEMENT THAT A SFC TROUGH/COLD FRONT WILL
MOVE THROUGH SOMETIME SUN NIGHT INTO TUE...WITH THE ECMWF BEING
FASTER THAN THE GFS. DEPENDING ON TIMING...SEVERE WEATHER COULD
OCCUR IF THE FRONT MOVES THROUGH DURING PEAK HEATING. WILL JUST RUN
WITH A CONSENSUS BLEND.
&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 743 PM EDT TUE JUN 30 2015

AS HIGH PRES AND LOW-LEVEL DRY AIR CONTINUE TO WORK SLOWLY INTO THE
UPPER GREAT LAKES...VFR CONDITIONS WILL PREVAIL AT KIWD/KCMX THRU
THIS FCST PERIOD. ALTHOUGH THE BACK EDGE OF THE CLOUD DECK HAS
SHIFTED E AND IS CLOSE TO KSAW...LOW-LEVEL WINDS ARE EXPECTED TO
VEER SOME TONIGHT. THIS MAY HALT THE SLOW EASTWARD PROGRESSION OF
CLEARING OR EVEN CAUSE THE CLOUDS TO BEGIN SHIFTING BACK TO THE
W...RESULTING IN MVFR CIGS LINGERING THRU THE NIGHT. FOR NOW...EXPECT
CLOUDS TO SCATTER OUT AT KSAW TOWARD DAYBREAK. IF CLOUDS DO LINGER
LONGER...THEY WILL CLEAR OUT BY MID MORNING AS LOW-LEVEL WINDS BACK.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 321 PM EDT TUE JUN 30 2015

EXPECT LIGHT WINDS BELOW 20 KNOTS THROUGH THE FORECAST PERIOD.
LINGERING PATCHY FOG OVER THE E HALF OF THE LAKE TONIGHT WILL
DISSIPATE ON WED WITH THE ARRIVAL OF DRIER AIR ASSOCIATED WITH HI
PRES BUILDING OVER THE UPPER LAKES.
&&

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

$$

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


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