336  
FXUS63 KAPX 241456  
AFDAPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GAYLORD MI  
1056 AM EDT SAT JUN 24 2017  
   
UPDATE
 
 
ISSUED AT 1056 AM EDT SAT JUN 24 2017  
 
BROAD UPPER TROUGHING ENGULFING THE GREAT LAKES THIS MORNING, WITH  
LATEST SATELLITE SHOWING ONE SHORTWAVE PRESSING ACROSS WISCONSIN  
AND INTO LAKE MICHIGAN, WHILE ANOTHER LARGER SHORTWAVE IS SEEN  
WORKING INTO MINNESOTA. THE FORMER WAVE IS WORKING ON AN AXIS OF  
HIGHER LOW LEVEL THETA-E AIR THAT IS NOW ALIGNED FROM LOWER  
MICHIGAN, BACK THROUGH WISCONSIN. THIS SEEN CLEARLY BY INCREASING  
AND THICKENING CLOUD FROM THE GTV BAY REGION BACK THROUGH  
WISCONSIN/WESTERN LAKE SUPERIOR WHERE THERE WAS SOME LIGHT SHOWER  
ACTIVITY.  
 
EARLY MORNING DISCUSSION HINTING OF POSSIBLE LIGHT SHOWER ACTIVITY  
ACROSS THE GTV BAY REGION THIS MORNING IS STILL A GREAT IDEA (PER  
SPRINKLES REPORTED AT EARLIER AT MBL. THIS SHOWER CHANCE WILL  
INCREASE EASTWARD THROUGH THE AFTERNOON, AND INTO NE LOWER AS THE  
SHORTWAVE TROUGHING AND THETA-E AXIS ARRIVE, WHILE SHOWER  
DEVELOPMENT BEING AIDED BY DIURNAL INSTABILITY GENERATED UNDER  
STEEPER LAPSE RATES/COOLER AIR ALOFT. COOL TEMPERATURES AND  
RELATIVELY LOW SFC TD'S ONLY LEADING TO UP TO 500-600J/KG OF  
MLCAPE. DID LOWER CHANCES FOR THUNDERSTORMS, BUT THERE WILL AT  
LEAST BE SOME ISOLATED ACTIVITY. NO SEVERE STORMS.  
 
THE UPSTREAM STRONGER SHORTWAVE STILL EXPECTED TO SWEEP ACROSS THE  
REGION TONIGHT WITH DECENT OVERALL DEEP AYER -DIVQ FOR CONTINUING  
SHOWER CHANCES, DESPITE LOSS OF DAYTIME HEATING.  
 

 
   
NEAR TERM
 
(TODAY THROUGH TONIGHT)  
ISSUED AT 404 AM EDT SAT JUN 24 2017  
   
..SUNNY EARLY BUT MORE CLOUDS/SHOWERS AS DAY PROGRESSES
 
 
HIGH IMPACT WEATHER POTENTIAL: MINIMAL OUTSIDE OF ONGOING HYDROLOGIC  
ISSUES.  
 
PATTERN SYNOPSIS/FORECAST: 03Z SURFACE/COMPOSITE ANALYSIS SHOWS  
MICHIGAN SANDWICHED BETWEEN A PAIR OF FRONTS...A NORTHEAST-SOUTHWEST  
ORIENTED COLD FRONT STRETCHED FROM THE LOWER GREAT LAKES INTO THE  
TENNESSEE VALLEY...A SECOND FRONT WAS DRAPED ACROSS NORTHERN ONTARIO  
TO THE NORTH OF LAKE SUPERIOR. MUCH DRIER AIR HAS SPREAD ACROSS THE  
AREA IN THE WAKE OF THE DOWNSTREAM COLD FRONT...WITH DEW POINTS  
FRIDAY AFTERNOON FALLING INTO THE UPPER 30S/40S INLAND FROM THE  
GREAT LAKES. WATER VAPOR IMAGERY SHOWS PLENTY OF MID LEVEL  
"WEAKNESS" SPINNING AROUND THE VICINITY OF THE UPPER GREAT LAKES.  
ONE SHORT WAVE TROUGH WAS MOVING THROUGH LOWER MICHIGAN INTO LAKE  
HURON...WITH A PAIR OF VORTICITY CENTERS OVER MINNESOTA... ANOTHER  
NORTH OF LAKE SUPERIOR...AND A LARGER UPPER LOW DIGGING INTO NORTH  
DAKOTA. POST-COLD FRONTAL DRYING EVIDENT IN 00Z APX SOUNDING WITH A  
DEEP (NEARLY UP TO 700MB) MIXED LAYER...BUT COLDER MID LEVEL  
TEMPERATURES UPSTREAM ALLOWING FROM SOME SKINNY INSTABILITY IN  
INL/YPL SOUNDINGS ALONG A LOW LEVEL THETA-E RIDGE AXIS THAT  
STRETCHES FROM NORTHERN ILLINOIS BACK TO THE NORTHWEST INTO THE  
NORTHWEST ONTARIO/SOUTHERN MANITOBA.  
 
UPPER LOW DROPPING INTO NORTH DAKOTA IS EXPECTED TO SPIN ACROSS THE  
UPPER MIDWEST TODAY...WHICH WILL ALSO PUSH AFOREMENTIONED VORTICITY  
CENTER OVER NORTHERN MINNESOTA EAST AS WELL. UPPER LOW WILL MAKE  
ITS WAY INTO LOWER MICHIGAN TONIGHT...WHILE BOUNDARY TO THE NORTH OF  
LAKE SUPERIOR SAGS ACROSS THE LAKE AND POSSIBLY INTO THE UPPER  
PENINSULA.  
 
PRIMARY FORECAST CONCERNS: MAINLY CLOUD AND SHOWER CHANCES TODAY  
WITH COOLING MID LEVEL TEMPERATURES AND APPROACHING SHORT WAVE  
TROUGH AND UPPER LOW. THE FORMER FEATURE IS ALREADY PUSHING ANOTHER  
MID CLOUD DECK (AND A FEW SPOTTY RADAR RETURNS) ACROSS WISCONSIN/  
WESTERN UPPER MICHIGAN AND WILL SPREAD INTO WESTERN LOWER MICHIGAN  
LATER THIS MORNING. COULD BE A FEW SPITS OF RAIN WITH THIS INITIAL  
CLOUD COVER LATER THIS MORNING INTO NORTHWEST LOWER...BUT DOES  
APPEAR THERE WILL BE AN ADDITIONAL DIURNAL COMPONENT TO CLOUD COVER  
TODAY...ESPECIALLY ACROSS NORTHERN LOWER...WHERE SOME SKINNY  
INSTABILITY WILL HELP GENERATE SOME SHOWERS DURING THE AFTERNOON. A  
LITTLE LESS CERTAIN ACROSS EASTERN UPPER WITH REGARD TO  
INSTABILITY...THOUGH LAKE MICHIGAN/HURON BREEZE MAY SERVE AS A FOCUS  
FOR SHOWERS PROBABLY ONLY ACROSS MACKINAC COUNTY. SHOULD ALSO BE A  
RISK FOR THUNDER ESPECIALLY SOUTH OF M-32 THIS AFTERNOON...WITH  
DIURNAL SHOWER COVERAGE DECREASING THIS EVENING. BUT WITH THE  
APPROACHING UPPER LOW...FAIRLY DEEP LAYER DEFORMATION AXIS EXPECTED  
TO SET UP ACROSS UPPER MICHIGAN WHICH IS EXPECTED TO FOCUS A  
CONTINUED THREAT FOR SHOWERS INTO TONIGHT. WILL PROBABLY ALSO SEE  
SOME ADDITIONAL SHOWERS WITH THE ARRIVAL OF THE PRIMARY MID LEVEL  
CIRCULATION AND ASSOCIATED DYNAMICS.  
 
FROM A HYDROLOGIC STANDPOINT...RIVERS IN THE RIFLE AND TOBACCO RIVER  
BASINS STILL RUNNING HIGH DUE TO RECENT RAINFALL. RIFLE RIVER NEAR  
STERLING HAS LEVELED OFF AND IS RUNNING BELOW THE CURRENT FORECAST  
SO WILL HAVE TO EVALUATE ONGOING WARNING. TOBACCO RIVER AT  
BEAVERTON ALSO APPEARS TO BE CRESTING JUST BELOW FLOOD STAGE  
(UPSTREAM GAUGE ON THE SOUTH BRANCH TOBACCO RIVER NEAR BEAVERTON  
ALSO LEVELING OFF LESS THAN A FOOT BELOW RECORD STAGE). ADDITIONAL  
RAINFALL TODAY/TONIGHT MAY SLOW THE RECESSION BUT OUTSIDE OF A SLOW  
MOVING CELL FALLING OVER THE RIGHT PART OF A BASIN...NOT EXPECTING  
ADDITIONAL RAINFALL TO CAUSE A BIG RISE IN RIVER LEVELS.  
 

 
   
SHORT TERM
 
(SUNDAY THROUGH MONDAY)  
ISSUED AT 404 AM EDT SAT JUN 24 2017  
   
..CONTINUED COOL WITH SHOWERS AND PERHAPS A FEW STORMS
 
 
HIGH IMPACT WEATHER POTENTIAL...A FEW NON-SEVERE THUNDERSTORMS  
POSSIBLE SUNDAY AND MONDAY AFTERNOONS.  
 
PATTERN SYNOPSIS/FORECAST...SUNDAY INTO MONDAY, MICHIGAN WILL BE IN  
LINE FOR A ONE-TWO PUNCH OF POTENT SHORTWAVES/VORT MAXES ROTATING  
AROUND A BROAD LONGWAVE TROUGH ENTRENCHED OVER THE GREAT LAKES. THE  
FIRST WILL EXIT THE THUMB BY SUNDAY AFTERNOON WHILE THE SECOND TAKES  
A MORE SOUTHERLY DIVE TOWARDS LAKE ERIE ON MONDAY. CLOSER TO THE  
SURFACE, A WEAK COLD FRONT WILL DROP SOUTH FROM ONTARIO ON SUNDAY,  
FOLLOWED BY A WEAK LOW WITH SOMEWHAT OF A SHORT-LIVED FRONTAL  
BOUNDARY THAT MOVE ACROSS NORTHERN LOWER SUNDAY NIGHT INTO MONDAY.  
THESE FEATURES WILL GENERATE SHOWERS AND POSSIBLY SOME AFTERNOON  
THUNDERSTORMS BOTH SUNDAY AND MONDAY.  
 
THE PARENT LONGWAVE TROUGH WILL BE QUITE DEEP WITH 500 MB HEIGHTS  
FALLING TO AROUND 558 DAM OVER NORTHERN MICHIGAN ON MONDAY...ABOUT 2  
TO 3 STANDARD DEVIATIONS BELOW THE MEAN FOR LATE JUNE. TEMPERATURES  
ALOFT FROM 925 TO 700 MB WILL ALSO BE AROUND 2 TO 3 STANDARD  
DEVIATIONS BELOW. SO, EXPECT A PROGRESSIVE COOL DOWN TO CONTINUE  
THROUGH THE START OF THE WORK WEEK AS PERSISTENT NW FLOW ADVECTS  
COOLER AIR INTO THE REGION. HIGHS WILL BE IN THE MID TO UPPER 60S ON  
SUNDAY AND GENERALLY A COUPLE DEGREES COLDER ON MONDAY. SUNDAY  
NIGHT'S LOWS WILL DROP INTO THE MID/UPPER 40S INLAND TO AROUND 50  
NEAR THE SHORES.  
 
PRIMARY FORECAST CONCERNS...RAIN AND THUNDER CHANCES WILL BE THE  
MAIN FORECAST CHALLENGE. LAPSE RATES ABOVE 600 MB ARE LOOKING A  
LITTLE WEAKER FOR SUNDAY AND MONDAY, AND PWATS WILL BE AROUND 0.8"  
OR A LITTLE LESS. GIVEN GENERAL NW FLOW PATTERN, EXPECT THE BETTER  
DIURNAL INSTABILITY WILL BE OVER NORTHEAST LOWER, THOUGH WE'RE ONLY  
TALKING SEVERAL HUNDRED J/KG OF MLCAPE AT MOST. SO, WHILE  
INGREDIENTS WILL BE SUFFICIENT FOR SCATTERED TO PERHAPS NUMEROUS  
SHOWERS (PARTICULARLY DURING THE DAYTIME HOURS), EXPECT ANY  
THUNDERSTORMS THAT MAY DEVELOP TO BE PRETTY ISOLATED, WEAK, AND  
SHORT-LIVED...ESPECIALLY GIVEN THE ABSENCE OF DEEP LAYER SHEAR.  
NORTHERN LOWER WILL SEE THE BEST FORCING AND HENCE HIGHER POPS THAN  
EASTERN UPPER.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 404 AM EDT SAT JUN 24 2017  
 
HIGH IMPACT WEATHER POTENTIAL...THUNDERSTORMS POSSIBLE AT TIMES  
WEDNESDAY AFTERNOON THROUGH FRIDAY.  
 
UPPER TROUGH AND UNSEASONABLY COOL AIRMASS FINALLY EJECT TO THE EAST  
MONDAY NIGHT WITH HEIGHTS RISING THROUGH MIDWEEK AS UPSTREAM RIDGE  
MAKES QUICK PROGRESS TOWARDS THE GREAT LAKES. INCREASING SUBSIDENCE  
FROM THIS RIDGE AND A SURFACE HIGH WILL LEAD TO A PERIOD OF DRY  
WEATHER THAT WILL LIKELY CONTINUE THROUGH WEDNESDAY MORNING. THE  
REMAINDER OF THE FORECAST PERIOD LOOKS RATHER ACTIVE AND WET AS  
MODELS TRACK SEVERAL DEVELOPING LOWS FROM THE CENTRAL/NORTHERN  
PLAINS INTO THE GREAT LAKES, INTERACTING WITH A POTENTIALLY VERY  
MOIST AIRMASS. BEING THIS FAR OUT, PLENTY OF QUESTIONS TO STILL BE  
ANSWERED, BUT PERIODS OF SHOWERS AND STORMS ARE LOOKING INCREASINGLY  
LIKELY FOR NORTHERN MICHIGAN THROUGH THE END OF THE WEEK.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 650 AM EDT SAT JUN 24 2017  
 
VFR CONDITIONS EXPECTED TODAY WITH MID CLOUDS INCREASING THIS  
MORNING. SOME SHOWERS THIS AFTERNOON ESPECIALLY FOR APN...MAY SEE  
SOME MVFR CEILINGS DEVELOP OVERNIGHT.  
 

 
   
MARINE
 
 
ISSUED AT 404 AM EDT SAT JUN 24 2017  
 
WINDS NOT EXPECTED TO BE SIGNIFICANT THIS WEEKEND AS GRADIENT  
WILL BE RELATIVELY WEAK. LAKE BREEZES LIKELY TO POP ALONG  
NORTHEAST LOWER AND SOUTHEAST UPPER SHORELINE THIS AFTERNOON. A  
LITTLE MORE PERSISTENT WEST/NORTHWEST WIND EXPECTED FOR SUNDAY.  
 

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

 
 

 
 
UPDATE...SMD  
NEAR TERM...JPB  
SHORT TERM...MEK  
LONG TERM...MEK  
MARINE...JPB  
 
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