Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 291929
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
329 PM EDT FRI AUG 29 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 501 AM EDT FRI AUG 29 2014

AN UPPER TROUGH OVER THE CENTRAL UNITED STATES WILL BE THE MAIN
CONTROLLING FACTOR TO THE WEATHER OVER THE NEXT COUPLE OF DAYS.
WATER VAPOR IMAGERY IS SHOWING ABUNDANT MOISTURE STREAMING
NORTHEAST OVER THE REGION BUT A BULK OF THE SHORTWAVE ENERGY IS
STILL HANGING BACK CLOSER TO THE UPPER TROUGH AXIS STRETCHING
NORTH/SOUTH FROM SOUTH DAKOTA TO NORTHERN TEXAS. THE FIRST WAVE OF
PRECIPITATION ASSOCIATED WITH THIS UPPER TROUGH IS SLIDING
NORTHEAST INTO THE REGION EARLY THIS MORNING. INITIAL PRECIPITATION
HAS BEEN STRUGGLING TO MAKE A DENT IN THE EXISTING DRY AIR SEEN
BETWEEN 800-550MB ON THE 00Z KGRB SOUNDING BUT IT IS GETTING INTO
NORTHEAST WISCONSIN AND SOUTH CENTRAL UPPER MICHIGAN. THIS
PRECIPITATION IS FORCED BY ISENTROPIC ASCENT ON 300-320K
SURFACES AND THE INITIAL WAVE WILL SLIDE NORTHEAST ACROSS THE
SOUTHEAST HALF OF UPPER MICHIGAN THIS MORNING. WITH THE ISENTROPIC
ASCENT STRETCHING TO THE WEST ACROSS NORTHERN WISCONSIN...COULD SEE
SHOWERS DEVELOPING THERE EARLY THIS MORNING...BUT THINK THE
PRECIPITATION CHANCES FOR THE WESTERN U.P. WILL BE TIED TO THE AREA
OF CONVECTION/SHOWERS IN SOUTHEAST MINNESOTA...NORTHEAST IOWA...AND
SOUTHWEST WISCONSIN. THESE SHOWERS HAVE BEEN MAKING A SLOW PUSH TO
THE NORTHEAST AND WOULD LIKELY PUSH NORTH ACROSS THE AREA LATE THIS
MORNING AND EARLY THIS AFTERNOON. BEHIND THESE TWO WAVES...THINK
THERE WILL A LULL IN THE PRECIP AS THE BEST LARGE SCALE FORCING IS
OFF TO THE WEST AND CLOSER TO THE UPPER TROUGH AXIS THAT WILL MOVE
INTO THE AREA TONIGHT. WITH NO SIGNIFICANT MID LEVEL THERMAL
ADVECTION BEHIND THE INITIAL WAVE THIS AFTERNOON...WONDERING IF
PORTIONS OF CENTRAL/EASTERN UPPER MICHIGAN WILL STAY DRY.

FARTHER TO THE WEST THIS AFTERNOON...A THE SURFACE-925MB TROUGH OR
WARM FRONT WILL SETUP OVER WESTERN LAKE SUPERIOR AND PORTIONS OF
WESTERN UPPER MICHIGAN. THIS LOW LEVEL FORCING WITH PLENTY OF
MOISTURE SHOULD BE ENOUGH TO KICK OFF SOME SHOWERS LATER THIS
AFTERNOON AND INTO THE EVENING HOURS. THIS AREA WILL CONTINUE TO BE
THE FOCUS INTO TONIGHT AS THE UPPER LEVEL TROUGH AND SURFACE LOW
(CURRENTLY WEST OF SIOUX FALLS) MOVE CLOSER TO THE AREA. THIS WILL
BRING BETTER DEEP FORCING AND MID LEVEL FGEN FROM WEST TO EAST
THROUGH THE NIGHT. THUS...WILL RAMP POPS UP TO DEFINITE VALUES OVER
THE WESTERN THIRD OF THE U.P. DURING THE EVENING AND SLOWLY SHIFT
THEM EAST WITH THE SURFACE/UPPER TROUGH.

AS FOR RAIN AMOUNTS...HAVE TRENDED THEM BACK FOR THE MORNING HOURS
TODAY (ESPECIALLY WEST) BASED OFF THE LATEST RADAR AND HIGH
RESOLUTION MODEL TRENDS. BEST OPPORTUNITY FOR MODERATE TO HEAVY
RAIN WILL COME TONIGHT OVER THE WESTERN HALF OF UPPER MICHIGAN
WHERE THE BEST FORCING IS LOCATED ALONG THE SURFACE TROUGH AND
EXTRA CONVERGENCE FROM THE SECONDARY TROUGH (CURRENTLY IN SOUTHERN
MANITOBA AND NORTH DAKOTA) THAT MERGES WITH THE EXISTING TROUGH.
THE HEAVY RAIN POTENTIAL IS ALSO AIDED BY PWAT VALUES ARE AROUND
1.5-1.75 INCHES OVER THE WEST (175 PERCENT OF NORMAL)...WARM CLOUD
LAYER OVER 11KFT...AND GENERALLY SLOW STORM MOTION VALUES. GOING
FORECAST HAS AROUND 0.75-1.00 INCH FOR MUCH OF WESTERN UPPER
MICHIGAN (MATCHING 03Z SREF 30 PERCENT PROBS OF 1IN/12HRS) AND THAT
COULD BE HIGHER WHERE ANY THUNDERSTORMS OCCUR. WILL CONTINUE THE
IDEA OF THE PREVIOUS SHIFT OF THUNDER STAYING SOUTH OF THE AREA FOR
THE FIRST PART OF THE MORNING...THEN STARTED TO NOSE SLIGHT CHANCES
IN THROUGH THE REST OF THE DAY BEHIND THE 925-850MB WARM FRONT.
TONIGHT...WILL TRANSITION TO CHANCE THUNDER ACROSS THE AREA DUE TO
THE BETTER FORCING AND MUCAPE VALUES BETWEEN 300-800 J/KG.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 328 PM EDT FRI AUG 29 2014

NAM SHOWS A SHORTWAVE OVER THE UPPER GREAT LAKES 00Z SUN WITH A
TROUGH OVER THE WESTERN U.S. A SHORTWAVE RIDGE MOVES INTO THE UPPER
GREAT LAKES ON SUN WITH TROUGHING MOVING INTO THE NORTHERN PLAINS
AND THIS TROUGH MOVES IN FOR SUN NIGHT INTO MON INTO THE AREA. NAM
BRINGS IN SOME 850-500 MB Q-VECTOR CONVERGENCE AND SOME MOISTURE SUN
NIGHT INTO MON ACROSS THE AREA. GFS AND ECMWF SHOW ABOUT THE SAME
THING AND WILL CONTINUE DIMINISHING POPS TREND FOR SAT NIGHT...DRY
FOR SUN AND THEN INCREASE POPS TO CATEGORICAL FOR SUN NIGHT INTO MON
FOR MOST OF THE CWA. DID NOT MAKE TOO MANY CHANGES TO THE GOING
FORECAST.

IN THE EXTENDED...GFS AND ECMWF SHOW A BROAD 500 MB TROUGH ACROSS
THE NORTHERN HALF OF THE U.S. WITH A RIDGE OVER THE SOUTHERN HALF
12Z TUE. UPPER PATTERN CHANGES LITTLE FOR 12Z WED WITH A STATIONARY
SFC FRONT ACROSS THE MID MISSISSIPPI AND OHIO VALLEYS. THE UPPER
RIDGE STARTS TO BUILD BACK TO THE NORTH 12Z THU AND 12Z FRI WITH A
WARM FRONT MOVING SLOWLY NORTH. WHAT THIS WILL MEAN IS A WARMING
TREND AND IT WILL BE DRY FROM TUE NIGHT THROUGH WED NIGHT BEFORE THE
WARM FRONT STARTS TO AFFECT THE AREA. MODELS SEEM OVERDONE ON POPS
FOR THEN. EVEN TUE...HAVING SOME DOUBTS THAT THERE WILL BE
POPS...BUT COULD SEE WITH UPPER TROUGHING IN THE AREA MAYBE SOME
ISOLATED INSTABILITY SHOWERS AND SLIGHT CHANCE POPS ARE WARRANTED
FOR THEN. TEMPERATURES WILL GO BACK TO NEAR NORMAL.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 140 PM EDT FRI AUG 29 2014

PERIOD OF SHOWERS AND LOW CIGS EXPECTED TO CONTINUE THROUGH THE
FORECAST PERIOD AT ALL SITES.

AT IWD...NO OBSERVATIONS IN OVER 48 HOURS HAVE MADE TAF PREPARATION
VERY DIFFICULT...BUT DO EXPECT POOR CONDITIONS TO PERSIST.

AT CMX...THINK THAT THE SITE WILL SEE RAIN MORE OFTEN THAN NOT...BUT
SOME DRY PERIODS WILL OCCUR WITH HIGHER CIGS AT THE TIME. THE TIMING
OF BETTER CONDITIONS IS DIFFICULT IF NOT IMPOSSIBLE TO PREDICT GIVEN
THE NATURE OF THE PRECIPITATION. THUNDER CHANCES SHOULD STAY SE OF
THE TAF SITE. CONDITIONS WILL IMPROVE ON SATURDAY...BUT IT SHOULD BE
AROUND OR AFTER THE END OF THE TAF PERIOD.

AT SAW...EXPECT SOME IMPROVEMENT THIS AFTERNOON/EVENING AS LOW LEVEL
MIXING INCREASES. CIGS SHOULD THEN GO BACK DOWN LATE THIS EVENING
THROUGH SATURDAY MORNING AS GREATER LOW LEVEL MOISTURE RETURNS.
THERE WILL BE DRY PERIODS WITH HIGHER CIGS...BUT TIMING THOSE OUT IS
DIFFICULT AT BEST. THUNDERSTORMS ARE POSSIBLE THIS EVENING DEPENDING
ON THE AMOUNT OF CLEARING AND INSTABILITY THAT CAN FORM.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 501 AM EDT FRI AUG 29 2014

HIGH PRESSURE CONTINUES TO SHIFT AWAY FROM THE UPPER GREAT LAKES
REGION THIS MORNING AND INTO THE NEW ENGLAND STATES TODAY. AS THIS
OCCURS...SOUTHEASTERLY FLOW WILL BE IN THE 15-20KT RANGE. THAT
SOUTHEASTERLY FLOW WILL CONTINUE OVER THE EASTERN HALF OF THE LAKE
TONIGHT...WHILE THE WESTERN HALF DIMINISHES BELOW 10KTS AS A
SURFACE TROUGH MOVES OVER THAT AREA. THIS TROUGH WILL PUSH
SOUTHEAST ACROSS THE REST OF THE LAKE BY SATURDAY AFTERNOON AND
SWITCHING WINDS TO THE NORTHWEST 10-20KTS. AFTER LIGHT WINDS
SATURDAY NIGHT...SOUTHEASTERLY WINDS WILL INCREASE ON SUNDAY AHEAD
OF THE NEXT TROUGH THAT WILL MOVE ACROSS LAKE SUPERIOR ON MONDAY.
WINDS UP TO 25KTS ARE POSSIBLE AHEAD OF THIS TROUGH SUNDAY NIGHT
INTO MONDAY.

FINALLY...AREAS OF FOG WILL DEVELOP OVER PORTIONS OF LAKE SUPERIOR
THIS AFTERNOON AND CONTINUE INTO SUNDAY MORNING. SOME LOCATIONS
COULD EXPERIENCE DENSE FOG...ESPECIALLY OVER NORTHEAST LAKE
SUPERIOR.
&&

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

$$

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





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