470  
FXUS63 KAPX 210722  
AFDAPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GAYLORD MI  
322 AM EDT FRI JUL 21 2017  
   
NEAR TERM
 
(TODAY THROUGH TONIGHT)  
ISSUED AT 323 AM EDT FRI JUL 21 2017  
   
..WARM TODAY BEFORE RAIN CHANCES RETURN TONIGHT
 
 
HIGH IMPACT WEATHER POTENTIAL...LOCALLY DENSE EARLY-MORNING FOG.  
CHANCE FOR NON-SEVERE T-STORMS TONIGHT.  
 
A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM NE MN TO SW LOWER MI.  
QUIET WX AND MAINLY CLEAR SKIES ARE THE RESULT, THOUGH WE ARE SEEING  
SOME FOG FORM IN SPOTS. THE QUIET WX SHOULD HOLD THRU THIS EVENING.  
HOWEVER, EXTENDED STRETCHES OF DRY WX HAVEN'T REALLY BEEN OUR  
THING THIS SUMMER, AND THAT WON'T BE CHANGING. RETURN FLOW WEST OF  
THE RIDGE IS CONTRIBUTING TO MCS DEVELOPMENT IN THE NORTHERN  
PLAINS, DOWN TOWARD IOWA AND NORTHERN IL. THAT SORT OF ACTIVITY  
MAY START TO IMPACT NORTHERN MI TONIGHT.  
 
TODAY...DARKENING SEEN IN EARLY MORNING FOG IMAGERY SUGGESTS SOME  
FOG PATCHES OVER NORTHERN LOWER MI ARE RELATIVELY THICK. THAT  
SAID, JULY SUN WILL MAKE SHORT WORK OF THEM REGARDLESS. ANTICIPATE  
FOG WILL DISSIPATE BY 10-11AM, WITH PLENTY OF SUNSHINE FOR THE  
REST OF THE DAY. SOME CU WILL GET GOING, ESPECIALLY ALONG THE  
INLAND- MOVING LAKE BREEZE BOUNDARIES. MOISTURE POOLING ALONG  
THOSE BOUNDARIES WILL PUSH MLCAPE VALUES UP TO 200-300J/KG. COULD  
WE COOK SOMETHING OFF THIS AFTERNOON? IT'S NOT IMPOSSIBLE, AS  
THERE ISN'T MUCH OF A CAP. BUT SUSPECT WE WILL MIX OUT BL MOISTURE  
A BIT MORE THAN THE NAM THINKS. CAN'T REALLY FIND A CAM THAT  
PRODUCES ANY PRECIP THIS AFTERNOON, AND EVEN THE NAM ITSELF IS DRY  
HERE. WILL STICK WITH THAT. EVOLVING UPSTREAM MCSS WILL PUSH AS  
FAR EAST AS WESTERN OR EVEN CENTRAL WI, BUT RETURN FLOW AND  
INSTABILITY IS NON- EXISTENT FURTHER EAST. A LATE-DAY INCREASE IN  
CIRRUS IS LIKELY, BUT OTHERWISE NO IMPACT INTO EARLY EVENING.  
 
A WARM DAY AHEAD. MAX TEMPS NEAR 80 IN EASTERN UPPER, MAINLY IN THE  
80S IN NORTHERN LOWER MI (70S ON SOME OF THE BEACHES, WHILE A STRAY  
90F OR TWO IN NORTHERN LOWER ISN'T OUT OF THE QUESTION).  
 
TONIGHT...SO WILL THE UPSTREAM MCS(S) TAKE A RUN AT US? SURFACE  
RIDGE WILL MOVE TO THE EASTERN LAKES, ALLOWING RETURN FLOW TO AMP UP  
INTO NORTHERN MI (ESPECIALLY OVERNIGHT). LOW PRESSURE WILL MOVE FROM  
EASTERN SD TO THE IOWA/WI BORDER AREA, AND ONCE AGAIN THE WARM FRONT  
WILL NOT GET FURTHER NORTH THAN FAR SOUTHERN LOWER MI. MCS  
DEVELOPMENT WILL OF COURSE BE FAVORED NORTH OF THE FRONT. AN INITIAL  
E TO ESE MOTION IS EXPECTED, BUT EVENTUALLY A VEERING LLJ AND  
GROWING SURFACE COLD POOL WILL TURN THINGS TO THE RIGHT. THAT'S ALSO  
HERE ALL THE INSTABILITY IS; IN THIS STATE, SOUTH OF I-96 (PERHAPS  
/WELL/ SOUTH). SO, PER SPC, PRIMARY MCS TRACK WILL BE TO OUR SW  
(AGAIN). MIGHT PERHAPS BE GRAZED BY A STRONGER ELEVATED IN THE SW,  
DEPENDING ON HOW THINGS PLAY OUT, BUT OVERALL THIS LOOKS DOUBTFUL.  
MARGINAL RISK AREA FROM SPC JUST CLIPS THE MBL AREA; WILL NOT  
MENTION A SVR THREAT IN THE MORNING HWO.  
 
GIVEN THE ABOVE, AND GIVEN TRENDS IN RECENT EVENTS, AM RELUCTANT TO  
PUSH POPS TOO TERRIBLY HIGH. LIKELY POPS MAY STILL BE ORDER FOR MBL-  
CAD, BUT NOT AS FAR NORTH AS TVC/GLADWIN, WITH POPS DECAYING FURTHER  
AS YOU CONTINUE NORTH. INTERESTING THAT, EERILY SIMILAR TO HOW  
THINGS WENT LAST NIGHT, THE NAM SPROUTS SOME VERY LATE-NIGHT  
CONVECTION OVER FAR NE LOWER MI, SEPARATE FROM THE MAIN ACTION. A  
CONVECTIVELY-INDUCED SHORTWAVE OR TWO MAY HELP THAT ALONG. SO WILL  
EXPAND THE MENTION OF SHOWERS/T-STORMS A BIT FURTHER NORTH, INTO AT  
LEAST PARTS OF EASTERN UPPER MI. TIMING: RECENT TRENDS SUPPORT  
STAYING ON THE FASTER SIDE OF GUIDANCE. A CHANCE OF SHOWERS/T-STORMS  
COULD REACH SW SECTIONS BY MID/LATE EVENING, INCREASING AND  
EXPANDING FROM THERE.  
 
MILD MIN TEMPS; FROM THE UPPER 50S NEAR WHITEFISH BAY TO SOME UPPER  
60S IN THE FAR SOUTH.  
 

 
   
SHORT TERM
 
(SATURDAY THROUGH SUNDAY)  
ISSUED AT 323 AM EDT FRI JUL 21 2017  
   
..THUNDERSTORMS OVER THE WEEKEND
 
 
HIGH IMPACT WEATHER POTENTIAL...THUNDERSTORMS MARGINALLY SEVERE  
ALONG AND SOUTH OF M-55 SATURDAY.  
 
PATTERN SYNOPSIS/FORECAST...SEEMS WE HAVE BEEN GETTING OUR SHARE OF  
SFC LOWS MOVING IN FROM THE UPPER MISSISSIPPI VALLEY AND INTO OUR  
AREA WITH THE WARM FRONT MOVING NORTH DURING THE DAY. THIS AGAIN  
LOOKS TO BE THE CASE ON SATURDAY SO WILL EXPECT THAT THERE WILL BE  
THUNDERSTORM CHANCES. HOWEVER, THEY DON'T LOOK SEVERE EXCEPT MAYBE  
ALONG THE M-55 CORRIDOR. A 500 MB SHORTWAVE MOVES INTO THE UPPER  
GREAT LAKES SATURDAY NIGHT, AND MAY CONTRIBUTE MORE DURING THE  
EVENING, BUT AS WE MOVE AWAY FROM THE HEAT OF THE DAY, WILL EXPECT  
THAT THE OVERNIGHT WILL BE RAIN SHOWERS. SUNDAY, AS WE GET THE  
DIURNAL HEATING AND THE 500 MB LOW MOVES OVER THE FORECAST AREA,  
WILL EXPECT THAT THUNDER WILL AGAIN BREAK OUT, BUT PROBABLY NOT  
SEVERE, AS THE SFC WILL HAVE COLD ADVECTION FROM THE COLD FRONT  
MOVING THROUGH THE REGION BEHIND THE SFC LOW. HIGH PRESSURE THEN  
BUILDS INTO THE REGION OVERNIGHT.  
 
PRIMARY FORECAST CONCERNS...THE TRACK OF THE SFC LOW WILL MARK WHERE  
THERE WILL BE SEVERE WEATHER. IF THE SFC LOW MOVES TO THE NORTH WE  
COULD GET INTO THE WARM SECTOR AND THEN IT IS POSSIBLE THAT THE  
CHANCES FOR SEVERE WEATHER WILL GO UP. IF IT GOES SOUTH, THEN IT MAY  
EVEN TAKE OUR THUNDERSTORM CHANCES. IT SEEMS TO BE A LOW CONFIDENCE  
TRACK FORECAST.  
 

 
   
LONG TERM
 
(SUNDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 323 AM EDT FRI JUL 21 2017  
   
..DRY TO START THE WEEK
 
 
HIGH IMPACT WEATHER POTENTIAL...NONE.  
 
EXTENDED (MONDAY THROUGH THURSDAY)...MONDAY AND TUESDAY LOOK DRY AS  
HIGH PRESSURE BUILDS INTO THE REGION. TEMPERATURES AT THIS POINT  
LOOK TO BE BELOW NORMAL FOR MONDAY AS THE COOLER AIR FOLLOWING  
SUNDAY'S COLD FRONT MOVE INTO THE REGION. TUESDAY LOOKS MORE TO BE  
AROUND NORMAL WITH THE MID TO UPPER 70S AND EVEN AROUND 80.  
WEDNESDAY, THE NEXT FRONT MOVES INTO THE REGION WHICH COULD KICK OFF  
MORE SHOWERS, AND POSSIBLY THUNDERSTORMS, DEPENDING WHICH MODEL YOU  
BELIEVE. THURSDAY COULD INCLUDE SOME THUNDERSTORMS IF THE GFS IS  
RIGHT, THEN IT WOULD DRY OUT OVERNIGHT. THE ECMWF ON THURSDAY HAS IT  
DRY ALL DAY AND IS HINTING THAT IT WOULD BE DRY TO START THE WEEKEND  
AS WELL.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)  
ISSUED AT 1155 PM EDT THU JUL 20 2017  
 
OUTSIDE OF SOME EXPECTED FOG DEVELOPMENT TONIGHT, CONDITIONS WILL  
REMAIN VFR THIS TAF PERIOD WITH WEAKISH HIGH PRESSURE OVER THE  
REGION. W/NW AOB 10 KTS WILL GO NEAR CALM TONIGHT WITH LAKE  
BREEZES EXPECTED FRIDAY AFTERNOON. NEXT SHOT AT SHOWERS AND A FEW  
POSSIBLE STORMS ROLLS IN LATE IN THE TAF PERIOD, ATTM, BEST  
CHANCES AT MBL. WILL NOT MENTION IN THE FORECAST AT THIS TIME.  
 

 
   
MARINE
 
 
ISSUED AT 323 AM EDT FRI JUL 21 2017  
 
HIGH PRESSURE WILL CROSS MI TODAY, RESULTING IN LIGHT WINDS AND  
ONSHORE LAKE BREEZES. LOW PRESSURE WILL PASS TO OUR SOUTH ON  
SATURDAY, RESULTING IN DEVELOPING EAST WINDS. THESE WILL PICK UP  
LATE TONIGHT IN SATURDAY, AND NOT OUT OF THE QUESTION FOR SOME  
LOCALES (LIKE THE NE LOWER MI COAST) TO APPROACH SMALL CRAFT  
ADVISORY WIND/WAVES.  
 

 
   
APX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LH...NONE.  
LM...NONE.  
LS...NONE.  

 
 

 
 
NEAR TERM...JZ  
SHORT TERM...JL  
LONG TERM...JL  
AVIATION...SD  
MARINE...JZ  
 
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