552  
FXUS63 KAPX 290707  
AFDAPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GAYLORD MI  
307 AM EDT FRI AUG 29 2014  
   
SYNOPSIS
 
 
ISSUED AT 300 AM EDT FRI AUG 29 2014  
 
HIGH PRESSURE WILL SLIDE INTO NEW ENGLAND TODAY...ENDING UP OFF  
THE EAST COAST THIS WEEKEND. MEANWHILE...SLOW MOVING LOW PRESSURE  
WILL TRACK FROM THE CENTRAL PLAINS INTO THE GREAT LAKES BY  
SATURDAY. THIS PATTERN WILL DELIVER A COUPLE ROUNDS OF RAIN AND  
PERHAPS A FEW THUNDERSTORMS TODAY INTO SATURDAY...WITH A BRIEF  
BREAK EXPECTED ON SUNDAY AS HIGH PRESSURE RETURNS. CHANCES FOR  
SHOWERS AND THUNDERSTORMS WILL RETURN ON LABOR DAY...AS A COLD  
FRONT MARCHES THROUGH THE REGION.  
 

 
   
SHORT TERM
 
(TODAY THROUGH TONIGHT)  
ISSUED AT 300 AM EDT FRI AUG 29 2014  
   
..INCREASING RAIN CHANCES AND A FEW THUNDERSTORMS
 
 
IMPACTS: LIGHTNING POTENTIAL...BUT NO SEVERE WEATHER EXPECTED.  
 
CURRENT WEATHER AND SYNOPTIC PATTERN:  
 
UPPER FLOW IS SPLIT UPSTREAM WITH MORE ZONAL FLOW RIPPING THROUGH  
CANADA...AND A SHORTWAVE TROUGH AND ASSOCIATED SFC LOW IN THE  
CENTRAL PLAINS. A WARM FRONT EXTENDS ACROSS IA/IL WHERE DEEP LOW  
LEVEL MOISTURE...PWATS TO 2.00" AND UNIMPRESSIVE 6.0 C/KM MID LEVEL  
LAPSE RATES RESIDED. LOW LEVEL WARM ADVECTION WITH AN H8 LLJ OF  
30KTS WAS FEEDING MOISTURE UP INTO THE MID AND UPPER MISSISSIPPI  
VALLEY...AND IN TANDEM WITH THE ELEVATED WARM FRONT AND INITIAL  
VORTICITY EJECTED FROM THE TROUGH. THIS HAS RESULTED IN A THICKENING  
OF MID AND UPPER LEVEL CLOUDS IN OUR REGION...AND SOME WEAK RETURNS  
ON AREA RADARS AS WELL AS SOME ENCROACHING ON US. THE LOW LEVELS  
WERE STILL RATHER DRY HERE...AND MUCH OF THIS PRECIPITATION WAS  
EVAPORATING BEFORE REACHING GROUND. THE HEAVIER RAINFALL AND  
THUNDERSTORMS WERE WELL WEST AND SOUTH...CLOSER TO THE SFC/UPPER  
LOWS...WARM FRONT AND BETTER FORCING.  
 
SYNOPTIC PATTERN/WEATHER EVOLUTION:  
 
THE FASTER FLOW ALOFT WILL REMAIN TO OUR NORTH ACROSS CANADA...IN  
WHICH A BROAD SHALLOW WAVE WILL DRAW A VERY SHALLOW COLD FRONT OVER  
INTO EASTERN UPPER/WISCONSIN. AT THE SAME TIME...THE SHORTWAVE  
TROUGH WILL SLOWLY LIFT NE AND INTO THE WESTERN GREAT LAKES BY LATE  
TONIGHT...AND IT'S ASSOCIATED SFC LOW WILL RIDE ALONG THE FRONT  
THROUGH WISCONSIN. THIS IS FURTHER WEST THAN ORIGINALLY  
ANTICIPATED.  
 
PUTTING IT ALL TOGETHER...THE INITIAL EJECTED ENERGY WEAKENS AS IT  
RUNS INTO OUR RIDGE...WHILE WE CONTINUE TO DEEPEN MOISTURE AND CLOUD  
UP THIS MORNING. FORCING IS VERY WEAK...AND CAN FORESEE SOME VERY  
LIGHT RAIN SHOWERS OR SPRINKLES THIS MORNING FOR MUCH OF NRN  
MICHIGAN. MAYBE SOME MORE ORGANIZED RAINS ACROSS EASTERN UPPER...THE  
STRAITS AND NEARER LAKE MI...WHERE H8 LLJ FORCING IS STRONGER AND  
WITHIN THE BETTER MID LEVEL FLOW AND VORTICITY ADVECTION. ONCE THE  
AXIS OF DEEPER MOISTURE/GRADIENT LIFTS NE BY 18Z OR SO...WE ARE MORE  
HUMID BUT THERE IS A LACK OF FORCING THROUGH THIS EVENING. MOST  
LIKELY...THERE WILL NOT BE MUCH GOING ON. WITH PWATS STILL 1.5" OR  
HIGHER THOUGH...IT WON'T TAKE MUCH TO IGNITE A SHOWER. THE BETTER  
RAINFALL IS LIKELY NOT COMING UNTIL LATE TONIGHT AS THE SYNOPTIC  
FEATURES ARRIVE...THE SHORTWAVE AND SFC LOW. BETTER ORGANIZATION  
OF THE LLJ AND THETA-E ADVECTION SHOULD RESULT IN THE BEST FORCING  
AND GROWING INSTABILITY (SEVERAL HUNDRED J/KG MUCAPE) FOR SHOWERS  
AND STORMS. TOTAL QPF FOR MOST WILL NOT COME ANYWHERE CLOSE TO  
SOMETHING "HEAVY"...AT LEAST THROUGH THIS EVENING. AGAIN...THE  
BEST CHANCE FOR ANY SORT OF HEAVIER RAINFALL WILL BE OFF TO OUR  
NW...POSSIBLY SNAKING ACROSS WESTERN CHIP/MACK COUNTIES OF EASTERN  
UPPER...CLOSER TO THE FRONTAL ZONE.  
 
CLOUDY THIS MORNING WITH MAYBE SOME THINNING OF THE CLOUDS THIS  
AFTERNOON...HIGHS IN THE MIDDLE TO UPPER 60S EASTERN UPPER...TO THE  
LOWER AND MIDDLE 70S NRN LOWER.  
 
LOWS TONIGHT...MILD...WITH A GOOD DEAL OF CLOUDS AND INCREASED BL  
WINDS...IN THE 60S ALL AREAS.  
 

 
   
LONG TERM
 
(SATURDAY THROUGH THURSDAY)  
ISSUED AT 300 AM EDT FRI AUG 29 2014  
   
..A WET SENDOFF TO METEOROLOGICAL SUMMER
 
 
HIGH IMPACT WEATHER POTENTIAL: SEVERAL CHANCES FOR THUNDERSTORMS...  
PRIMARILY SATURDAY AND AGAIN FOR LABOR DAY ITSELF...WITH A SMALL  
LOCALIZED HEAVY RAIN THREAT...PARTICULARLY ACROSS NORTHWEST LOWER  
AND EASTERN UPPER MICHIGAN.  
 
PATTERN SUMMARY: A RATHER HEALTHY SEMI-CLOSED UPPER LEVEL TROUGH  
WILL MEANDER FROM THE CENTRAL PLAINS TODAY INTO THE NORTHERN GREAT  
LAKES SATURDAY NIGHT...FORCING AN ELEVATED WARM FRONT THROUGH THE  
REGION TODAY...OPENING THE GATES TO A MUCH MORE MOISTURE-LADEN  
AIRMASS THROUGH THE DAY ON SATURDAY. A WEAK SURFACE LOW AND  
ASSOCIATED COLD FRONT IS EXPECTED TO ARRIVE HERE LATE SATURDAY  
AFTERNOON OR EVENING...WITH HIGH PRESSURE TAKING OVER FOR THE DAY ON  
SUNDAY. HANG TIGHT THOUGH...AS ANOTHER STRONGER UPPER TROUGH AND  
ASSOCIATED COLD FRONT WILL BE KNOCKING ON THE DOOR BY LABOR  
DAY...USHERING IN A FAST ZONAL FLOW REGIME ACROSS MUCH OF THE  
COUNTRY FOR THE MAJORITY OF NEXT WEEK.  
 
A LOOK AT THE FORECAST DETAILS...  
 
SATURDAY: WEAKENING UPPER TROUGH WILL BE MAKING ITS APPROACH THROUGH  
THE DAY...AS OUR AIRMASS REMAINS VERY SOUPY WITH PWAT VALUES PUSHING  
1.75 INCHES (UP AROUND 2.5 SD ABOVE NORMAL AND NEARING THE 99TH  
PERCENTILE BY CLIMO STANDARDS). REALLY GETTING THE FEELING THAT THE  
MAJORITY OF THE HEAVY RAIN THREAT WILL EXIST FRIDAY NIGHT AS  
TIGHTENING MID LEVEL THERMAL REGIME FORCES A DYNAMIC JET RESPONSE  
OVER THE WESTERN LAKES...SUCH THAT MUCH OF THE WESTERN CWA GETS IN  
ON SOME MODEST UPPER JET DIVERGENCE TO HELP ENHANCE A TRAINING  
CONVECTIVE THREAT GIVEN STRONGLY PARALLEL DEEP LAYER WIND FIELDS TO  
THE FORCING BOUNDARY JUST TO OUR WEST. THAT WHOLE SETUP LOOKS LIKE  
IT WILL BREAK DOWN BY SATURDAY MORNING AS THE UPPER JET CORE SLIPS  
OVERHEAD...LEAVING THE SYNOPTIC FORCING COMPONENT TO A BETTER PUSH  
OF DPVA...ALSO HELPED ALONG TO A SMALL DEGREE TO WEAK LOWER LEVEL  
FRONTAL CONVERGENCE.  
 
HAVE LITTLE DOUBT THAT ALL AREAS WILL END UP WITH MEASURABLE RAINS  
AT SOME POINT THROUGH THE DAY...AND GOING CATEGORICAL POPS ARE MORE  
THAN WARRANTED. HOWEVER...THE SETUP LOOKS LIKE IT WILL FAVOR MORE OF  
A MORNING COMPONENT FOR WESTERN AREAS...WITH RAIN CHANCES TRANSITING  
EASTWARD THROUGH THE AFTERNOON WHERE A MORE CONVECTIVE COMPONENT MAY  
BE REALIZED PROVIDED WE CAN REALIZE SOME SNEAKY WARMER TEMPS OUT  
THAT WAY (WHICH APPEARS DOABLE). TEMPS WARMING THROUGH THE 70S  
COMBINED WITH DEW POINTS RISING THROUGH THE 60S (MAYBE LOWER 70S)  
WOULD SUPPORT MLCAPE VALUES PUSHING 1200 J/KG...SO A THUNDER MENTION  
IS MORE THAN JUSTIFIED...ESPECIALLY EAST OF I-75. SEVERE THREAT  
LOOKS LOW BUT WITH A WARM FRONT/WEAKLY BACKED FLOW NEARBY AND  
STRENGTHENING FLOW ALOFT INTO THE AFTERNOON...WOULDN'T BE SHOCKED TO  
SEE A FEW SNEAKY STRONGER STORMS...AGAIN PROVIDED WE CAN REALIZE  
ENOUGH INSTABILITY.  
 
SATURDAY NIGHT-SUNDAY NIGHT: ELONGATING WEAK DEFORMATION AXIS WITH  
THE UPPER TROUGH SHEARING OUT ALOFT SHOULD PROVIDE A CONTINUED  
THREAT FOR SHOWERS INTO MUCH OF SATURDAY NIGHT...ENDING WITH TIME AS  
SLIGHTLY DRIER AIR WORKS INTO THE PICTURE AND UPPER SUPPORT WANES.  
HOWEVER...WILL HAVE TO WATCH THE POSSIBILITY FOR ANOTHER COMPACT  
SHORTWAVE TO CROSS THE AREA ON SUNDAY...AS INCREASINGLY HINTED AT BY  
00Z GUIDANCE TRENDS. THAT FEATURE...COMBINED WITH A REMNANT SOUPY  
AIRMASS DOWN LOW WHILE DRYING OCCURS ABOVE 850MB...SUGGESTS WE MAY  
BE STUCK WITH SOME STUBBORN STRATUS AND MAYBE EVEN A LITTLE DRIZZLE  
LATE SATURDAY NIGHT INTO PART OF (MAYBE EVEN MUCH OF) SUNDAY. SHOULD  
THAT NEW FEATURE ACTUALLY COME TO FRUITION...A DIURNAL SHOWER THREAT  
MAY BE REALIZED CLOSER TO SAGINAW BAY BUT THE BETTER CHANCES LOOK TO  
BE ACROSS SOUTHEAST LOWER...WITH CONFIDENCE LOW ENOUGH IN SEEING  
ENOUGH SUNSHINE TO BOOST INSTABILITY TO MAINTAIN A DRY FORECAST FOR  
MUCH OF SUNDAY. CLOUD POTENTIAL ALSO MAKES FOR A TRICKY TEMPERATURE  
FORECAST...BUT HAVE TO BELIEVE WE CAN MUSTER SOME AFTERNOON SUNSHINE  
FOR MANY AREAS AS A QUICK ARRIVING SLUG OF MUCH DRIER AIR IS PROGGED  
TO ROLL IN THROUGH THE DAY. AS SUCH...GOING HIGHS RIGHT ABOUT CLIMO  
LOOK AS GOOD A GUESS AS ANY.  
 
MONDAY (LABOR DAY)-MONDAY NIGHT: ANOTHER PERIOD OF INTEREST GIVEN  
LOTS OF ONGOING OUTDOOR ACTIVITIES AS WE BID A FOND FAREWELL TO YET  
ANOTHER SUMMER SEASON. TIMING WILL BE EVERYTHING WHEN IT COMES TO  
THE BIG EVENT (MACKINAC BRIDGE WALK 2014)...BUT THE BASIC GIST IS  
FOR THE APPROACH OF ANOTHER SHARP UPPER TROUGH THROUGH THE WESTERN  
LAKES...AS A FAIRLY STRONG COLD FRONT GETS PUSHED TOWARD THE AREA BY  
LATE AFTERNOON. FROM A PATTERN RECOGNITION STANDPOINT...THIS ONE  
AGAIN LOOKS TO STAND A HIGH CHANCE OF PRODUCING RAIN ACROSS MOST OF  
THE AREA...AND AT THIS RANGE...LIKELY POPS ARE A GOOD WAY TO HANDLE  
IT. HOWEVER...THERE ARE TIMING DIFFERENCES AMONG THE GUIDANCE...WITH  
A CONSENSUS BLEND SUPPORTING A FRONTAL PASSAGE THROUGH LATE  
AFTERNOON. ANOTHER SURGE OF WARMTH/MOISTURE AHEAD OF THE FRONT  
COMBINED WITH INCREASINGLY STRONG WIND FIELDS BLEEDING OUT JUST  
AHEAD OF THE FRONT RAISE AN EYEBROW FROM A SEVERE STORM  
PERSPECTIVE...AND INDEED THIS ONE BEARS WATCHING OVER THE NEXT FEW  
DAYS. SHARP DRYING BEHIND THE FRONT MONDAY NIGHT SHOULD BRING A  
QUICK END TO PRECIP CHANCES BY 06Z...WITH ANOTHER SHOT OF COOLER AIR  
BEGINNING ITS ARRIVAL.  
 
TUESDAY-THURSDAY: A PERIOD OF MUCH QUIETER WEATHER APPEARS ON TAP AS  
WE HEAD INTO MIDWEEK AND SETTLE INTO THE FIRST FEW DAYS OF  
METEOROLOGICAL AUTUMN. HIGH PRESSURE AND A COOLER/DRYER CANADIAN  
AIRMASS SHOULD DELIVER A NICE DAY FOR BACK TO SCHOOL TUESDAY...WITH  
SIMILAR CONDITIONS ANTICIPATED INTO WEDNESDAY AS WELL...THOUGH  
LIKELY WITH SOME THICKENING CLOUDS. AFTER THAT...CONFIDENCE REALLY  
DECREASES TOWARD LATE WEEK WITH REGARD TO ADDITIONAL CHANCES FOR  
RAIN. ONE THING DOES APPEAR CERTAIN...WE ARE HEADING INTO A FASTER  
NORTHERN TIER ZONAL FLOW REGIME NOT REALLY SEEN AT ALL THIS SUMMER.  
THAT SETUP...COMBINED WITH WHAT SHOULD BE A RATHER TIGHT TEMPERATURE  
GRADIENT ALOFT NEARBY AND A STRONG LIKELIHOOD FOR SEVERAL SHORTWAVES  
WORKING THROUGH THE FLOW...SHOULD SUPPORT A COUPLE RAIN CHANCES  
TOWARD LATE WEEK. TIMING THOSE WAVES AND INDIVIDUAL RAIN CHANCES IS  
IMPOSSIBLE AT THIS RANGE...BUT A LOW CHANCE POP APPEARS WARRANTED BY  
THURSDAY.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)  
ISSUED AT 1147 PM EDT THU AUG 28 2014  
 
LIGHT RAIN FRIDAY MORNING/MIDDAY. MAINLY VFR.  
 
HIGH PRESSURE PRESENTLY OVER SOUTHERN ONTARIO MI WILL MOVE EAST.  
MOISTURE WILL QUICKLY SURGE NORTHWARD INTO THE REGION BEHIND THE  
HIGH. -RA IS EXPECTED TO ARRIVE AT ALL TAF SITES FRIDAY  
MORNING...AND WILL DIMINISH AFTER SEVERAL HOURS. SMALL CHANCE FOR  
MVFR CIGS...ESPECIALLY TOWARD THE TAIL END OF THE RAINY  
PERIOD...BUT FOR NOW THE TAFS WILL CONTAIN ONLY VFR CONDITIONS.  
 
LIGHT WINDS TONIGHT...A BIT OF A SE TO S BREEZE FRIDAY.  
 

 
   
MARINE
 
 
ISSUED AT 300 AM EDT FRI AUG 29 2014  
 
HIGH PRESSURE IS EXITING EAST WITH THE DEVELOPMENT OF A SOUTHERLY  
WIND...WHICH INCREASES TODAY AND TONIGHT AS THE PRESSURE GRADIENT  
TIGHTENS WITH THE APPROACH OF A WARM FRONT. ADVISORY LEVEL WINDS ARE  
POSSIBLE ACROSS WHITEFISH BAY AND PORTIONS OF LAKE MICHIGAN DUE TO  
AREAS OF COASTAL CONVERGENCE. HOWEVER...INCREASING STABILITY WILL  
LIKELY KEEP STRONGEST WINDS AT 20KTS. MAY EVENTUALLY NEED SOME  
ADVISORIES...BUT NONE PLANNED ATTM. MORE VARIABLE AND LIGHTER WINDS  
ARRIVE SATURDAY AND SATURDAY NIGHT WITH THE PASSAGE OF LOW PRESSURE.  
THE SRLY WIND INCREASES ONCE AGAIN MONDAY WITH A COLD FRONT PLANNED  
TO PASS THROUGH.  
 
PERIODS OF RAIN AND SOME EMBEDDED THUNDERSTORMS BEGIN TODAY...BUT  
ARE MOST LIKELY TONIGHT INTO SATURDAY EVENING. NO SEVERE WEATHER IS  
ANTICIPATED.  
 

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

 
 

 
 
SYNOPSIS...LAWRENCE  
SHORT TERM...SMD  
LONG TERM...LAWRENCE  
AVIATION...JZ  
MARINE...SMD  
 
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