265  
FXUS63 KAPX 201100  
AFDAPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GAYLORD MI  
700 AM EDT SAT SEP 20 2014  
   
SYNOPSIS
 
 
ISSUED AT 247 AM EDT SAT SEP 20 2014  
 
OCCASIONAL WET WEATHER IS EXPECTED THIS WEEKEND...AS A COLD FRONT  
AND LOW PRESSURE SYSTEM MOVES ACROSS THE GREAT LAKES REGION. HIGH  
PRESSURE WILL PASS TO OUR SOUTH EARLY IN THE WORK WEEK...DRYING US  
OUT AND STARTING TO WARM US UP. AN EXTENDED PERIOD OF DRY AND WARM  
WEATHER IS EXPECTED FOR THE REST OF THE WORK WEEK.  
 

 
   
SHORT TERM
 
(TODAY THROUGH TONIGHT)  
ISSUED AT 247 AM EDT SAT SEP 20 2014  
   
..SHOWER AND THUNDERSTORMS EXPECTED TODAY AND TONIGHT
 
 
HIGH IMPACT WEATHER POTENTIAL: TYPICAL THUNDERSTORM CONCERNS  
(LIGHTNING/BRIEF HEAVY RAIN/GUSTY WINDS) RIGHT THROUGH TONIGHT.  
ISOLATED SEVERE STORM POSSIBILITIES THIS AFTERNOON?  
 
PATTERN SYNOPSIS/ANTICIPATED EVOLUTION: BRIEF INTERLUDE TO A MUCH  
MORE DEAMPLIFIED PATTERN CONTINUES...WITH A NEARLY ZONAL APPEARANCE  
TO MID AND UPPER LEVEL FLOW ACROSS THE NORTHERN CONUS/SOUTHERN  
CANADA. PLENTY OF ACTIVITY WITHIN THIS FLOW REGIME...WITH LEAD WAVE  
CUTTING ACROSS THE UPPER MISSISSIPPI VALLEY...WITH SECONDARY STRONGER  
WAVE DIVING SOUTHEAST INTO SASKATCHEWAN. BOTH OF THESE FEATURES WILL  
HAVE SIGNIFICANT IMPACT ON OUR WEATHER THROUGH THIS WEEKEND...WITH  
THE FORMER BRINGING SHOWERS AND EMBEDDED STORMS TODAY INTO THIS  
EVENING...WITH THE LATTER KEEPING CONDITIONS UNSETTLED LATER TONIGHT  
AND SUNDAY. ALREADY PLENTY OF SHOWERS ONGOING OVER PARTS OF THE  
NORTHERN LAKES WITH SHARP MOISTURE ADVECTION INTERACTING WITH  
APPROACHING MID LEVEL SUPPORT AND ATTENDANT COLD FRONT. SOME OF THIS  
ACTIVITY IS WETTING THE GROUND ACROSS THE NORTHWEST HALF OF OUR  
AREA...WITH SOUTHEAST AREAS REMAIN DRY (SO FAR AT LEAST). A MUCH  
MILDER NIGHT...WITH CURRENT READINGS MOSTLY IN THE 50S AND LOWER 60S.  
 
PRIMARY FORECAST CHALLENGES/CONCERNS: SHOWER AND STORM EVOLUTION  
TODAY AND TONIGHT. ADDRESSING THUNDERSTORM INTENSITY (ISOLATED  
SEVERE?) FOR THIS AFTERNOON.  
 
DETAILS: UNFORTUNATELY...JUST NOT AN OVERLY CONFIDENT FORECAST  
TODAY. FORCING REMAINS DISJOINTED...WITH SHARP MOISTURE  
ADVECTION/THETA-E GRADIENT OVERHEAD THIS MORNING...WELL AHEAD OF  
UPSTREAM COLD FRONT EXPECTED TO PASS LATE THIS AFTERNOON AND  
EVENING. SURFACE BASED INSTABILITY AHEAD OF THIS FRONT NEARLY  
COMPLETELY TIED TO BEING ABLE TO GENERATE SOME SUNSHINE...AND THAT  
IS ANYTHING BUT CERTAIN. AND IF THAT IS NOT ENOUGH TO GENERATE  
UNCERTAINTY...BEST MID LEVEL SUPPORT ARRIVES POST-FRONTAL...EXPECTED  
TO CROSS THE AREA LATE TONIGHT INTO THE START OF SUNDAY. HAVE SEEN  
THIS BEFORE...AND REALLY STARTING TO WONDER IF MOST SHOWERS/ELEVATED  
THUNDERSTORMS OCCUR THIS MORNING ALONG RAMPED-UP MOISTURE AXIS/LOW  
LEVEL JET SUPPORT...WITH WEAK FORCING ALONG FRONT LATER TODAY  
IGNITING JUST SOME SCATTERED ACTIVITY. WILL WAIT FOR FULL PERUSAL OF  
LATEST AND GREATEST GUIDANCE TRENDS...BUT STRONGLY LEANING TOWARD  
THIS LESS AGGRESSIVE AFTERNOON APPROACH. OF COURSE...THIS DOES NOT  
BODE WELL FOR SEVERE WEATHER POTENTIAL...WITH LIMITED DEEP LAYER  
FORCING AND PLENTY OF INSTABILITY CONCERNS. BEST FOCUS FOR SEVERE  
WEATHER REMAINS OFF TO OUR SOUTH...AND IN FULL SUPPORT OF SUCH GIVEN  
ABOVE DETAILS. IF SOME CLEARING/DESTABILIZATION IS REALIZED...  
OVERHEAD MID LEVEL SPEED MAX AND ASSOCIATED DEEP LAYER SHEAR VALUES  
DOES SUPPORT AN ISOLATED SEVERE WIND THREAT. BEST BET FOR THIS WILL  
BE ALONG/SOUTH OF M-55...BUT EVEN THIS SEEMS LIKE A LOW PROB  
SCENARIO AT THIS TIME.  
 
COLD FRONT EXITS THIS EVENING...LIKELY LEAVING BEHIND A QUIET  
STRETCH OF WEATHER THROUGH THE EARLY MORNING HOURS. STRONG VORT MAX  
APPROACHES QUICKLY TOWARD SUNRISE...WITH DEEP LAYER RESPONSE  
SUPPORTED BY LER UPPER JET DYNAMICS. SUSPECT SHOWERS WILL INCREASE  
IN COVERAGE ONCE AGAIN...TARGETING THE SOUTHERN THIRD OF THE AREA  
PER BEST UPPER JET SUPPORT. ELEVATED CAPE AND DECENT MID LEVEL LAPSE  
RATES IN LOCKSTEP WITH DEEPENING FORCING...SUPPORTING AT LEAST A  
CHANCE WORDING FOR ELEVATED THUNDER.  
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 247 AM EDT SAT SEP 20 2014  
   
..RAIN CHANCES SUNDAY FOLLOWED BY AN EXTENDED DRY PERIOD
 
 
VIGOROUS DIGGING SHORTWAVE WILL BE BARELY CLOSED OFF AS IT CROSSES  
LOWER MI ON SUNDAY. A WEAK SURFACE WAVE WILL BE JUST AHEAD OF THIS  
FEATURE...OVER CENTRAL LOWER MI SUNDAY MORNING BEFORE MOVING TOWARD  
THE THUMB AND EVENTUALLY LAKE ONTARIO. THIS TROF WILL OPEN UP AS IT  
DEPARTS SUNDAY NIGHT AND BEYOND...WITH STEADY HEIGHT RISES ALOFT. AT  
THE SURFACE...HIGH PRESSURE WILL BUILD FROM THE NORTHERN PLAINS TO  
THE OHIO VALLEY. SO...AFTER UNSETTLED WX SUNDAY...DRIER AND WARMER  
CONDITIONS WILL BE SEEN FOR MUCH OF THE WORK WEEK.  
 
SUNDAY...LOW LEVEL COLD ADVECTION WILL ALREADY BE UNDERWAY IN  
EASTERN UPPER MI ON NE FLOW TO START THE DAY. NORTHERLY FLOW WILL  
EXPAND ACROSS NORTHERN MI BY MID-AFTERNOON AS THE SURFACE LOW PULLS  
OUT. THERE IS STILL A WINDOW FOR WARM-SECTOR DEEP CONVECTION IN SE  
SECTIONS IN THE MORNING...ALONG WITH A QUICK SPIKE IN TEMPS INTO THE  
MID/UPPER 60S. OTHERWISE...THE ORGANIZING COLD CONVEYOR BELT WILL BE  
THE MAIN SOURCE FOR PRECIP. THIS FEATURE WILL SIT OVER FAR NORTHERN  
LOWER MI IN THE MORNING...ROTATE INTO NW LOWER BY MIDDAY...THEN PUSH  
SE-WARD DURING THE AFTERNOON. THE NAM IS FASTER TO ORGANIZE THE COLD  
CONVEYOR BELT THAN THE OTHER MODELS...AND IT/S POPS LOOK TOO HIGH.  
HOWEVER...WILL STILL INCREASE POPS TO LIKELY IN THE SE THIRD OF THE  
FORECAST AREA. MINIMAL POPS NEEDED IN CENTRAL/NORTHERN CHIPPEWA  
CO...WHERE THE SUN SHOULD APPEAR BY MID/LATE AFTERNOON. (REST OF  
EASTERN UPPER INTO NW LOWER SHOULD BREAK OUT OF CLOUDS TOWARD EARLY  
EVENING.)  
 
MAX TEMPS WILL RANGE FROM THE UPPER 50S TO NEAR 70F...MOSTLY IN THE  
MORNING. PM HOURS WILL BE SOMEWHAT BLUSTERY WITH STEADY TO FALLING  
TEMPS.  
 
SUN NIGHT/MONDAY...CLEARING WILL PROCEED APACE INTO N CENTRAL AND NE  
LOWER MI SUNDAY EVENING. MAINLY CLEAR OVERNIGHT. PRESSURE GRADIENT  
WILL RELAX SOMEWHAT...SUCH THAT PROTECTED INTERIOR LOCALES WILL NO  
DIFFICULTY DECOUPLING...WHILE COASTAL SITES MAINTAIN A NORTH BREEZE.  
MIN TEMPS WILL THUS VARY CONSIDERABLY...FROM LOW/MID 40S IN SOME  
COASTAL LOCALES...TO AROUND 30F IN THE COLDEST INTERIOR LOCALES (PLN  
A PRIME CANDIDATE). FROST REMAINS A THREAT IN THE LATTER PLACES...  
AND WILL CONTINUE TO BE HIGHLIGHTED IN THE HWO. MONDAY COULD SEE  
SOME MID/HIGH CLOUDS IN NORTHERN SECTIONS...AS THE PRESSURE  
GRADIENT/WARM ADVECTION INCREASES BETWEEN HIGH PRESSURE IN THE OHIO  
VALLEY AND A COLD FRONT SAGGING ACROSS FAR NORTHERN ONTARIO. THAT  
WON/T BE ENOUGH TO PREVENT A PARTLY TO MOSTLY SUNNY DAY. AFTER A  
COOL START...MAX TEMPS WILL REBOUND INTO THE UPPER 50S TO MID 60S.  
 
REST OF THE FORECAST...VERY QUIET TUE/WED AS A SHORTWAVE RIDGE  
BUILDS INTO THE CENTRAL LAKES. WITH LOW LEVEL WARM ADVECTION  
UNDERWAY AS HIGH PRESSURE SLIPS TO THE EAST COAST...MAX TEMPS WILL  
TAKE A RUN AT 70F IN PARTS OF NORTHERN LOWER. SUBSTANTIAL  
DISAGREEMENT AS TO HOW PROGRESSIVE THE UPPER FLOW WILL BE AFTER  
THIS. GFS/GEM ARE BOTH INCLINED TO CUT OFF THE NEXT PIECE OF  
ENERGY...LEAVING IT BACK IN THE CENTRAL PLAINS. THE ECMWF DOES BRING  
A DEAMPLIFYING TROF OVERHEAD THU AFTERNOON. EVEN IN THIS LATTER  
SCENARIO...WE ARE RATHER STARVED FOR MOISTURE...AND AM COMFORTABLE  
WITH A DRY FORECAST. REGARDLESS...ALL MODELS ARE INCLINED TO CLOSE  
OFF A 500MB HIGH OVER THE CENTRAL/EASTERN LAKES LATE IN THE  
WEEK...RESULTING IN DRY AND EVEN WARMER WX BY FRIDAY.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 700 AM EDT SAT SEP 20 2014  
 
EARLY MORNING SHRA/TSRA. PERIODS OF MVFR CONDITIONS.  
 
AREA OF SHRA/TSRA WILL CONTINUE TO TRANSIT NORTHERN LOWER MI EARLY  
THIS MORNING...BRINGING BRIEF MVFR TO IFR CONDITIONS. A MIX OF VFR  
TO MVFR CIGS WILL SETTLE IN BEHIND THE DEPARTING STORMS...AND IN  
ADVANCE OF A COLD FRONT NOW IN NW WI. SOME SHRA/TSRA ARE AGAIN  
POSSIBLE THIS AFTERNOON...THOUGH MAINLY S AND E OF THE TAF SITES.  
ANOTHER ROUND OF SHRA/TSRA IS AGAIN POSSIBLE LATE TONIGHT.  
 
GUSTY SW WINDS TODAY...BECOMING LIGHT TONIGHT AND VEERING NW TO N.  
 

 
   
MARINE
 
 
ISSUED AT 247 AM EDT SAT SEP 20 2014  
 
GUSTY SOUTHWEST WINDS VIA STRONG LOW LEVEL JET  
SUPPORT/APPROACHING COLD FRONT EXPECTED TO SLOWLY SUBSIDE HEADING  
THROUGH LATER THIS MORNING AND AFTERNOON...ESPECIALLY ACROSS CURRENT  
GALE AREAS OF NORTHERN LAKE MICHIGAN. INHERITED GALES END AT  
12Z...AND WILL SIMPLY LET THEM RUN THEIR COURSE. PLETHORA OF SCA/S  
ELSEWHERE THROUGH TODAY. WINDS REALLY SUBSIDE TONIGHT AS THEY VEER  
WEST TO NORTHWEST...ENDING ALL HEADLINES. BREAK LIKELY TO BE  
SHORT-LIVED...WITH GUSTY NORTHWEST WINDS DEVELOPING ONCE AGAIN  
SUNDAY...LIKELY NECESSITATING THE NEED FOR ADDITIONAL SCA/S FOR AT  
LEAST SOME OF THE BIG WATERS.  
 

 
   
APX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LH...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LHZ348-349.  
LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ323-341-  
342.  
GALE WARNING UNTIL 8 AM EDT THIS MORNING FOR LMZ344>346.  
LS...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THIS MORNING FOR LSZ321.  
 

 
 

 
 
SYNOPSIS...JZ  
SHORT TERM...MSB  
LONG TERM...JZ  
AVIATION...JZ  
MARINE...MSB  
 
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