Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 210813
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
413 AM EDT THU AUG 21 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 410 AM EDT THU AUG 21 2014

AT THE PRESENT...THE CWA SITS BETWEEN A WEAK 500MB LOW JUST E OF THE
U.P. AND A 500MB RIDGE AXIS JUST W OF LAKE SUPERIOR. AT THE
SFC...THERE IS A 1002MB LOW OVER ERN SD...WITH A SFC WARM FRONT
EXTENDING ACROSS SRN MN AND SRN WI. THE 850MB PORTION OF THE WARM
FRONT /BASED ON MODEL ANALYSIS AND SATELLITE DATA/ LOOKS TO BE FROM
NWRN MN TO NCENTRAL WI TO SRN LOWER MI. FOG AND LOW CLOUDS COVER
MUCH OF THE CWA /INCLUDING A MARINE DENSE FOG ADVISORY FOR CENTRAL
AND ERN LAKE SUPERIOR INTO THIS MORNING/. EXPECT THE FOG TO
DISSIPATE OVER LAND THIS MORNING WITH DAYTIME HEATING. OVER LAKE
SUPERIOR...EXPECT FOG TO THIN SOME THIS MORNING...BUT WILL CONTINUE
THROUGH THE SHORT TERM PERIOD.

A GENEROUS CLUSTER OF CONVECTION HAS DEVELOPED ALONG THE WARM FRONT
OVER THE SWRN QUARTER OF MN AND INTO SRN WI/NRN IL. THESE
THUNDERSTORMS ARE DECAYING AS THEY MOVE N OF THE WARM FRONT SINCE
MLCAPES ARE MINIMAL N OF THE FRONT. THE FORECAST FOR TODAY AND
TONIGHT IS FAIRLY DIFFICULT GIVEN THE AMOUNT OF CONVECTIVELY INDUCED
UNCERTAINTY THERE IS. WHAT CAN BE SAID IS THAT WHILE THE SFC WARM
FRONT WILL STAY WELL S OF THE CWA...THE 850MB PORTION OF THE WARM
FRONT WILL MOVE NE TODAY...APPROACHING IRONWOOD AROUND 18Z AND
MOVING PAST THE SW THIRD TO HALF OF THE CWA BY 00Z FRI BEFORE
STALLING OUT/WASHING OUT IN A N-S ORIENTATION OVER THE CENTRAL CWA
SHORTLY THEREAFTER. MODELS ARE IN GOOD GENERAL AGREEMENT THAT
MLCAPES INCREASE TO 350-900J/KG OVER THE WRN U.P. AND ALONG THE WI
BORDER LATE THIS AFTERNOON INTO THIS EVENING ALONG AND BEHIND THE
850MB WARM FRONT. SEVERE WEATHER IS NOT EXPECTED GIVEN THE MARGINAL
INSTABILITY AND 0-6KM BULK SHEAR AROUND 30KTS...BUT SOME STRONGER
STORMS ARE POSSIBLE OVER FAR WRN UPPER MI. ALSO...MODELS AGREE THAT AN
UPPER JET WILL NOSE INTO THE AREA THIS EVENING...PROVIDING
ADDITIONAL FORCING FOR ASCENT. MODELS BASICALLY SPLIT INTO TWO CAMPS
ON PRECIPITATION...THE HIGHER RES MODELS (NAM/REG GEM) SHOW A LOT OF
CONVECTION WELL S OF THE CWA WHILE ONLY MINIMAL QPF IS SHOWN OVER
FARTHER N. THIS SCENARIO HAPPENS MORE OFTEN THAN NOT...BUT WITH THE
850MB WARM FRONT MOVING IN...SUFFICIENT INSTABILITY FOR
CONVECTION...UPPER JET FORCING OVER THE AREA AND LARGER SCALE MODELS
KEEPING PRECIP N DID NOT WANT TO GO TOO LOW WITH POPS. OVERALL...DID
NOT MAKE ANY HUGE CHANGES TO THE PREVIOUS FORECAST GIVEN THE
UNCERTAINTY WITH THE CONVECTION AND LACKING SUFFICIENT REASONING TO
MAKE SIGNIFICANT CHANGES. THINK BEST CHANCES FOR PRECIP WILL BE OVER
THE WRN U.P. AND ALONG THE WI BORDER.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 345 AM EDT THU AUG 21 2014

NAM SHOWS A 500 MB RIDGE OVER THE GULF COAST WITH A CLOSED 500 MB
LOW OVER THE DESERT SW AND A TROUGH IN THE WESTERN U.S. 12Z FRI. THE
RIDGE BUILDS INTO THE UPPER GREAT LAKES 12Z SAT WITH A SHORTWAVE
EJECTED OUT OF THE DESERT SW INTO THE NORTHERN PLAINS. THE TROUGH IN
THE WESTERN U.S. MOVES INTO THE NORTHERN ROCKIES AND NORTHERN PLAINS
12Z SUN.

DIFFICULT FORECAST COMING UP AS THERE IS REALLY NOTHING TO PIN DOWN
ON HERE AS THINGS ARE VERY SUBTLE. BIG BUST POTENTIAL FOR
TEMPERATURES EXIST DEPENDING ON HOW MUCH OR HOW LITTLE CLOUD COVER
THERE IS AND THIS ALL HINGES ON HOW MUCH OR HOW LITTLE CONVECTION
OCCURS. I WENT MORE TOWARDS A DRIER SOLUTION WITH MORE SUNSHINE AND
WENT MORE WITH SLIGHT CHANCE POPS FOR ALMOST EVERY PERIOD AND WARMER
AND HUMID CONDITIONS FOR THIS FORECAST PERIOD. THINKING IS MAJORITY
OF CONVECTION WILL STAY TO THE SOUTH AND WEST OF AREA WITH LEFTOVER
STUFF COMING THROUGH AND THERE COULD BE SOME LAKE BREEZE CONVECTION
IN THE AFTERNOON AND EARLY EVENING AS WELL WHICH WOULD JUSTIFY AT
LEAST SLIGHT CHANCE POPS IN FOR MOST AREAS.

IN THE EXTENDED...ECMWF AND GFS SHOW A 500 MB RIDGE OVER THE UPPER
GREAT LAKES 12Z SUN WITH A TROUGH ACROSS THE WESTERN HALF OF THE
U.S. THE RIDGE GETS PUSHED FURTHER TO THE EAST BY THE TROUGH 12Z MON
WITH A SFC FRONT MOVING THROUGH THE U.P. BY 12Z TUE...THE RIDGE IS
PUSHED OVER TO THE ERN U.S. WITH TROUGHING INTO THE UPPER GREAT
LAKES LAGGING BACK INTO THE ROCKIES. THIS TROUGH REMAINS OVER THE
UPPER GREAT LAKES INTO WED. ABOVE NORMAL TEMPERATURES WILL SLOWLY
COOL BACK TOWARDS NORMAL BY THE END OF THIS FORECAST PERIOD AND IT
WILL REMAIN UNSETTLED WITH CHANCES OR SLIGHT CHANCES FOR RAIN.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 125 AM EDT THU AUG 21 2014

AN UPPER LEVEL LOW SPINNING NORTH OF LAKE HURON WILL SLOWLY MOVE
EAST LATE TONIGHT INTO THURSDAY. ABUNDANT LOW LEVEL MOISTURE
ROTATING AROUND THE LOW SHOULD PRODUCE LIFR TO VLIFR CONDITIONS
OVERNIGHT AT THE TAF SITES.

EXPECT SLOW IMPROVEMENT OF CONDITIONS TO MVFR BY LATE MORNING AND TO
VFR BY EARLY THU AFTERNOON WITH COMBINATION OF DIURNAL HEATING AND
LOW CONTINUING TO MOVE EAST OF THE REGION. BROUGHT -RA AND MVFR CIGS
INTO KIWD BY 22Z AND INTO KCMX AT 03Z THU. BROUGHT CIGS BACK DOWN TO
MVFR AT KSAW BY LATE THU EVENING IN UPSLOPE SE FLOW.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 410 AM EDT THU AUG 21 2014

OVERALL...RELATIVELY WEAK PRESSURE GRADIENTS WILL KEEP WINDS BELOW
20 KNOTS THROUGH THIS WEEKEND. THE STRONGEST WINDS WILL OCCUR OVER
THE WESTERN THIRD OF LAKE SUPERIOR ON TODAY AND THIS EVENING WHEN
NORTHEAST WINDS WILL FOCUS ALONG THE WESTERN SHORELINE. IN
ADDITION...PATCHY TO AREAS OF FOG WILL OCCUR OVER PORTIONS OF LAKE
SUPERIOR THROUGH THE UPCOMING WEEKEND. THE DENSE FOG ADVISORY FOR
CENTRAL AND EASTERN LAKE SUPERIOR WAS EXTENDED INTO THIS MORNING AS
SHIP OBS CONTINUE TO SHOW DENSE FOG. THIS MAY NEED TO BE EXTENDED
FURTHER DEPENDING ON THE EVOLUTION AND OBSERVATIONS THIS MORNING.
ADDITIONAL MOISTURE WILL SURGE NORTH THIS AFTERNOON AND REMAIN
THROUGH SUNDAY...PRODUCING ADDITIONAL OPPORTUNITIES FOR FOG OVER
LAKE SUPERIOR.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
  DENSE FOG ADVISORY UNTIL 11 AM EDT THIS MORNING FOR LSZ243-244-
     249>251-264-266-267.

LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...TITUS
LONG TERM...07
AVIATION...TITUS
MARINE...TITUS






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