935  
FXUS63 KAPX 131438  
AFDAPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GAYLORD MI  
1038 AM EDT THU AUG 13 2020  
   
UPDATE
 
 
ISSUED AT 1038 AM EDT THU AUG 13 2020  
 
SURFACE HIGH PRESSURE AND DRY LOWER LEVEL AIR REMAIN STEADFAST  
ACROSS THE GREAT LAKES THIS MORNING; 12Z APX SOUNDING REVEALS A  
FAIRLY DRY LAYER FROM THE SURFACE THROUGH NEARLY 15K FEET. ALOFT,  
SHARPENING SHORT-WAVE RIDGING EXTENDS THROUGH THE UPPER MIDWEST  
INTO ONTARIO. CONVECTIVELY INDUCED SHORT-WAVE IMPULSE (MCV) IS  
MAKING SLOW PROGRESS ACROSS THE FAR WESTERN GREAT LAKES DRIVING A  
GOOD AMOUNT OF MID/HIGH CLOUD COVER THROUGH THE REGION ALONG WITH  
SPOTTED DECAYING SHOWERS. GIVEN THE DRY AIR BELOW 15K FEET OR SO,  
MOST OF THE PRECIP INDICATED ON RADAR IS NOT REACHING THE GROUND,  
ALTHOUGH ESCANABA AND MENOMINEE DID REPORT SOME -RA UNDER THE  
HIGHEST RADAR RETURNS TO OUR WEST IN THE LAST HOUR OR SO.  
 
FURTHER WEST, STRONGER SOUTHERLY RETURN FLOW OF MOISTURE/  
INSTABILTY REMAINS CONTAINED UP THROUGH THE MIDWEST INTO THE  
NORTHERN PLAINS...WITH SOME CONVECTION CONTINUING TO FIRE IN  
CENTRAL WISCONSIN ALONG THE EASTERN FRINGE OF THE INSTABILITY  
GRADIENT. MOISTURE/INSTABILITY AXIS WILL REMAIN BOTTLED UP TO OUR  
WEST FOR AT LEAST THE NEXT FEW DAYS WITH NO RISK FOR CONVECTION  
HERE.  
 
MCV WILL MAKE VERY SLOW PROGRESS THROUGH THE REGION TODAY THROUGH  
FRIDAY WITH RECENT GUIDANCE TRENDS ACTUALLY STALLING/CUTTING THIS  
FEATURE OFF OVER NORTHERN LOWER MICHIGAN...WHILE SOME SEMBLANCE  
OF A BLOCKING PATTERN DEVELOPS ACROSS THE REGION. DECAYING SPOTTY  
SHOWERS/ELEVATED RADAR RETURNS WILL SLIDE ACROSS THE REGION  
THROUGH TODAY. BUT GIVEN THE DEGREE OF DRY LOWER LEVEL AIR ACROSS  
THE REGION, NOT ANTICIPATING MUCH (IF ANY) RAINFALL TO REACH THE  
GROUND. NOT IMPOSSIBLE THAT SOMEONE IN NW LOWER MICHIGAN GETS A  
FEW SPRINKLES OVER THE NEXT SEVERAL HOURS. BUT PLAN TO KEEP THE  
FORECAST DRY.  
 
CLOUD COVER IS ANOTHER MATTER HOWEVER ESPECIALLY ACROSS THE E.UP.  
WE'VE HAD SOME THINNING/CLEARING ACROSS NORTHERN LOWER MICHIGAN  
THIS MORNING. BUT PER SATELLITE TRENDS, CLOUD COVER WILL LIKELY  
FILL BACK IN TO VARYING DEGREES. SO AN OVERALL PARTLY TO MOSTLY  
CLOUDY DAY ANTICIPATED. I'VE TWEAKED FORECAST MAX TEMPS DOWNWARD A  
BIT AS A RESULT, AND MAY HAVE TO MAKE ADDITIONAL TWEAKS AS THE DAY  
PROGRESSES.  
 

 
   
NEAR TERM
 
(TODAY THROUGH TONIGHT)  
ISSUED AT 207 AM EDT THU AUG 13 2020  
 
IMPACTFUL WEATHER: NONE.  
 
PATTERN SYNOPSIS AND FORECAST:  
 
A SHORTWAVE IMPULSE/MCV IS LIFTING ENE ACROSS NRN WI/WESTERN LAKE  
SUPERIOR/UPPER MICHIGAN EARLY THIS MORNING, WITH DPVA AND WEAK 25KT  
LLJ LOW TO MID LEVEL THETA-E ADVECTION, RESULTING IN AN AREA OF  
SHOWERS WITH OCCASIONAL LIGHTNING, TRYING TO TRACK EASTWARD INTO AN  
ONLY SLIGHTLY DRIER AIR MASS. THIS WAS RESULTING IN SOME GRADUAL  
WEAKENING OF THE CONVECTION ON THE EASTERN END, BUT THERE HAS BEEN  
SOME REDEVELOPMENT ON THE WESTERN END OF THIS CONVECTION, AS THE LLJ  
REMAINS ORIENTED OUT OF THE SOUTH. HERE IN NRN MICHIGAN, SKIES WERE  
INCREASING IN HIGHER LEVEL CLOUDS, WITH LESS EROSION ON THE LEADING  
EDGE. FURTHER UPSTREAM BEHIND THIS SHORTWAVE, THERE WERE SOME MINOR  
RISES IN MID LEVEL HEIGHTS, WITH THE ONLY EXCITING WEATHER PHENOMENA  
BEING EXPANDING STRATUS ACROSS PARTS OF THE DAKOTAS AND MN.  
 
THE SHORTWAVE WILL WORK EASTWARD WITH TIME ACROSS LAKE SUPERIOR AND  
INTO NRN MICHIGAN THROUGH TODAY AND TONIGHT, SHALLOWING OUT AND  
WEAKENING WITH TIME, ALTHOUGH THERE IS SOME SEMBLANCE OF SOME SMALL  
CLOSED OFF CIRCULATION THAT SETTLES IN OVERHEAD TONIGHT. AM THINKING  
THAT CLOUDS WILL BE MORE PREVALENT TODAY THAN SEEN IN CURRENT  
FORECAST, AND WILL HAVE MOSTLY CLOUDY SKIES ACROSS PRIMARILY THE NRN  
HALF OF THE CWA TODAY. FCST SOUNDINGS SUPPORT THIS IDEA, WITH A  
PRETTY SOLID LAYER OF 700MB-500MB CLOUDS. THIS LAYER DOES THIN  
THROUGH TONIGHT ACROSS EASTERN UPPER, BUT DOES SETTLE SOUTHWARD INTO  
NRN LOWER. WHILE SKIES WILL LIKELY BE MORE CLOUDY THAN ORIGINALLY  
THOUGHT, THE AIR MASS BELOW 700MB IS VERY DRY. DPVA WANES THROUGH  
THE NIGHT, AND NRN MICHIGAN NEVER REALLY GETS INTO ANY GOOD LLJ  
THETA-E ADVECTION SINCE LOWER ATMOSPHERIC WINDS ARE WEAK. THIS WILL  
PREVENT ANY SHOWER ACTIVITY. EVEN IF THERE WERE SOME REFLECTIVITIES  
ALOFT, THE RAIN WOULD MORE THAN LIKELY NOT BE ABLE TO REACH THE  
GROUND.  
 
HIGHS TODAY WILL BE IN THE MIDDLE TO UPPER 80S MOST AREAS, SLIGHTLY  
COOLER LAKESHORES. LOWS TONIGHT WILL BE IN THE UPPER 50S TO  
LOWER 60S.  
 

 
   
SHORT TERM
 
(FRIDAY THROUGH SATURDAY)  
ISSUED AT 207 AM EDT THU AUG 13 2020  
 
HIGH IMPACT WEATHER POTENTIAL: LOW...RAIN/RUMBLE OF THUNDER SATURDAY  
NIGHT INTO SUNDAY  
 
PATTERN SYNOPSIS:  
 
AMPLIFIED RIDGING WILL EXPAND FROM THE GREAT LAKES OVER HUDSON BAY  
ON FRIDAY WHILE TROUGHING ENCROACHES FROM THE WEST AS IT TREKS  
ACROSS THE NORTHERN GREAT PLAINS. UPPER-LEVEL BLOCKING EVENTUALLY  
SLIDES EAST AT THE END OF THE WEEKEND AS THE LONGWAVE TROUGHING  
TRANSLATES OVERHEAD. AT THE SURFACE, ASCENT PROVIDED BY A SHORTWAVE  
IS EXPECTED TO RESULT IN LEE CYCLOGENESIS NEAR THE BLACK  
HILLS/BADLANDS OF SOUTH DAKOTA AND WILL QUICKLY MOVE/DEVELOP NE INTO  
HUDSON BAY BY SATURDAY. AN ASSOCIATED COLD FRONT WILL LIKELY SWEEP  
DOWN ACROSS THE REGION IN THE LATE SATURDAY/SUNDAY TIME FRAME.  
 
FORECAST/DETAILS:  
 
EASTERLY WINDS ON FRIDAY WILL BEGIN TO VEER MORE SOUTHERLY HEADING  
INTO THE WEEKEND AHEAD OF THE APPROACHING FRONT. LOW AND MID-LEVEL  
WINDS WILL BE RATHER MEAGER AS THE SYSTEM IS DISPLACED FAR FROM  
NORTHERN MICHIGAN, LEADING TO COMPARATIVELY WEAK MOISTURE ADVECTION  
INTO THE AREA TO THOSE WEST OF LAKE MICHIGAN. HOWEVER, THIS  
SOUTHERLY FLOW WILL HELP BRING THE CHANCE FOR SHOWERS AND A FEW  
RUMBLES OF THUNDER ARRIVING ACROSS EASTERN UPPER LATER SATURDAY.  
RAIN/THUNDER IS EXPECTED TO MAKE ITS WAY INTO NORTHERN LOWER LATE  
SATURDAY NIGHT/EARLY SUNDAY MORNING. NO SEVERE WEATHER IS EXPECTED  
WITH LITTLE INSTABILITY PRESENT AND VERY WEAK SHEAR ALOFT. ANY  
STRONGER, ORGANIZED THUNDERSTORMS WOULD STRUGGLE TO FORM/DEVELOP IN  
THIS ENVIRONMENT. OTHERWISE, CLOUD COVER WILL INCREASE INTO SATURDAY  
AS THE FRONT NEARS THE GREAT LAKES. HIGHS IN THE LOW TO MID 80S ON  
FRIDAY AND SATURDAY ARE ANTICIPATED, ALONG WITH HIGHS A FEW DEGREES  
COOLER ON SUNDAY AFTER THE COLD FRONT PASSES AND WINDS SHIFT  
NORTHEASTERLY.  
   
LONG TERM
 
(SATURDAY NIGHT THROUGH WEDNESDAY)  
ISSUED AT 207 AM EDT THU AUG 13 2020  
 
HIGH IMPACT WEATHER POTENTIAL: NONE  
 
LONGWAVE TROUGHING WILL ENCOMPASS THE AREA FROM HUDSON BAY DOWN INTO  
THE GREAT LAKES TO START MONDAY AS RIDGING TAKES HOLD OF THE CONUS  
WEST OF THE MISSISSIPPI RIVER. AT THE SURFACE, HIGH PRESSURE BUILDS  
ACROSS THE NORTH-CENTRAL CONUS UNDERNEATH SUBSIDENCE ALOFT PROVIDED  
AT THE RIDGE-TROUGH INFLECTION POINT. WITH LOW-LEVEL MOISTURE WIPED  
FROM THE AREA PRIOR TO THE START OF THE PERIOD AND SINKING AIR  
OVERHEAD, RAIN CHANCES WILL BE MUTED THROUGH AT LEAST THE FIRST HALF  
OF NEXT WEEK. THIS WILL BRING A BEAUTIFUL, COOLER START TO THE WORK  
WEEK AS HIGHS WILL DROP DOWN CLOSE TO 70 ACROSS NORTHERN MICHIGAN  
WITH PLENTIFUL SUNSHINE. OVERNIGHT LOWS COULD DROP DOWN INTO THE LOW  
TO MID 40S EARLY NEXT WEEK AS WELL. WEAK NORTHEASTERLY WINDS THROUGH  
THE FIRST HALF OF THE WEEK WILL KEEP MOISTURE RETURN AND WARMER  
TEMPS AT BAY HEADING TOWARDS THE WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)  
ISSUED AT 611 AM EDT THU AUG 13 2020  
 
HIGH PRESSURE FROM HUDSON BAY WORKS EASTWARD AND INTO QUEBEC TODAY  
THROUGH FRIDAY, WHILE AN AXIS OF HIGHER SFC PRESSURE EXTENDS BACK  
THROUGH THE GREAT LAKES. RELATIVELY DRY AIR IN THE LOWEST LEVELS OF  
THE ATMOSPHERE WILL RESULT IN NO SHOWER OR STORM THREATS AND VFR  
CONDITIONS WITH JUST PARTLY TO MOSTLY CLOUDY 10-15KFT CLOUDS OVER  
THE TAF PERIOD, PRIMARILY IMPACTING PLN. A GENERAL LIGHT EASTERLY  
WIND WILL TRY AND TURN MORE ONSHORE THIS AFTERNOON AT TVC/MBL.  
 

 
   
MARINE
 
 
ISSUED AT 207 AM EDT THU AUG 13 2020  
 
HIGH PRESSURE FROM HUDSON BAY WORKS EASTWARD AND INTO QUEBEC TODAY  
THROUGH FRIDAY, WHILE AN AXIS OF HIGHER SFC PRESSURE EXTENDS BACK  
THROUGH THE GREAT LAKES. RELATIVELY DRY AIR IN THE LOWEST LEVELS OF  
THE ATMOSPHERE WILL RESULT IN NO SHOWER OR STORM THREATS. GENERAL  
E/NE WINDS WILL SWITCH MORE OUT OF THE SE FRIDAY, AND WINDS AND  
WAVES WILL REMAIN UNDER ADVISORY LEVELS. NO MARINE CONCERNS  
FORESEEN.  
 

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

 
 

 
 
UPDATE...BA  
NEAR TERM...SMD  
SHORT TERM...DJC  
LONG TERM...DJC  
AVIATION...SMD  
MARINE...SMD  
 
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