586  
FXUS63 KAPX 251015  
AFDAPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GAYLORD MI  
615 AM EDT FRI JUL 25 2014  
   
SYNOPSIS
 
 
ISSUED AT 303 AM EDT FRI JUL 25 2014  
 
HIGH PRESSURE WILL GIVE WAY TO A FAST MOVING SYSTEM TONIGHT AND  
SATURDAY. CLOUDS WILL BE ON THE INCREASE TODAY...WITH A CHANCE FOR  
SHOWERS AND A FEW THUNDERSTORMS TONIGHT INTO THE START OF THE  
WEEKEND. A MUCH STRONGER SYSTEM WILL ARRIVE TO END THE WEEKEND...  
BRINGING BETTER POTENTIAL FOR SHOWERS SUNDAY AND SUNDAY NIGHT. A  
RETURN TO MUCH BELOW NORMAL TEMPERATURES ON MONDAY...WITH ONLY A  
SLOW MODERATION EXPECTED THROUGH THE REMAINDER OF THE WEEK.  
 

 
   
SHORT TERM
 
(TODAY THROUGH TONIGHT)  
ISSUED AT 303 AM EDT FRI JUL 25 2014  
   
..MORE CLOUDS AND A SHADE WARMER WITH STORM CHANCES TONIGHT
 
 
IMPACTS: LIGHTNING...BUT NO SEVERE WEATHER EXPECTED.  
 
CURRENT WEATHER AND SYNOPTIC PATTERN:  
 
BROAD UPPER RIDGING SEEN OVER THE SW PART OF THE COUNTRY WHILE  
TROUGHING IS STILL THE THEME OVER THE EASTERN CONUS. THE RIDGING HAS  
BEEN SQUASHED DUE TO A WRAPPED UP CLOSED LOW DRIFTS ACROSS SW  
CANADA. THIS HAS INDUCED LOW PRESSURE OVER EASTERN CANADA AND THE  
NRN PLAINS. AN AXIS OF DEEP THETA-E AIR...LEADING EDGE OF STEEP  
LAPSE RATES ALOFT (6.5C/KM-7.5C/KM) AND LLJ (45-55KT) CONVERGENCE  
AHEAD OF THE PLAINS SFC LOW HAS RESULTED IN POCKETS OF SHOWERS AND  
STORMS IN THE DAKOTAS DOWN TO NE. CLOSER TO HOME...AREA VAD WIND  
PROFILES AND RUC ANALYSIS SHOWING A TROUGH AXIS AND H8 MOISTURE  
ADVECTION FROM THE ARROWHEAD OF MN DOWN THROUGH WISCONSIN. THERE  
WERE A FEW ELEVATED RETURNS...BUT ONLY A FEW SPRINKLES HITTING  
GROUND PER AREA OBS. OVER NRN MICHIGAN...WE ARE STILL UNDER THE  
INFLUENCE OF SFC HIGH PRESSURE...BUT THOSE SAME VAD WIND PROFILES  
SHOW THAT THIS HAS SHIFTED JUST EAST OF US WITH A RETURN TO A SW  
WIND. AIR MASS IS STILL QUITE DRY WITH PWATS RELATIVELY LOWER THAN  
ANYWHERE NEARBY. ONLY A BAND OF HIGHER LEVEL CLOUD STREAMING DOWN  
THROUGH THE NW FLOW ALOFT. THE DRY AIR AND MOSTLY CLEAR SKIES HAVE  
ALLOWED TEMPERATURES TO FALL INTO THE LOWER HALF OF THE 40S IN THE  
LOW LYING AREAS...WHILE COASTAL AREAS AND SOME EXPOSED HIGHER  
TERRAIN ARE IN THE LOWER HALF OF THE 50S.  
 
SYNOPTIC PATTERN/WEATHER EVOLUTION:  
 
THE SFC HIGH GRADUALLY SINKS OFF TO THE SE TODAY...WHILE THE  
SOUTHERLY PRESSURE GRADIENT TIGHTENS AND DRAWS IN MORE LOW LEVEL  
MOISTURE THROUGH THE DAY AND NIGHT. THE INITIAL H8 TROUGH AND  
MOISTURE ADVECTION WILL DRIFT OVERHEAD TODAY...AND MAYBE SOME  
SPRINKLES ARE POSSIBLE EARLY THIS MORNING...BUT DAYTIME MIXING AND  
DRYING OF THE LOWER LEVELS WILL MOST LIKELY SEAL OFF ANY CHANCES FOR  
SPRINKLES TO HIT GROUND. THE MOISTURE WILL REVEAL ITSELF IN A HIGHER  
BASED CUMULUS FIELD...BUT ALSO MAY GET STUCK UNDERNEATH AN INVERSION  
IN FCST BFR SOUNDINGS. THIS COULD LEAD TO A PERIOD OF MOSTLY CLOUDY  
SKIES...BUT REALLY DOUBT THIS WILL HAVE MUCH AFFECT ON RISING TEMPS  
REACHING THE MIDDLE 70S MOST AREAS. THIS INVERSION AND DRY SFC TDS  
RESULT IN A PRETTY PRONOUNCED CAPPING FOR THE ENTIRE DAY...WITH  
LITTLE TO NO CHANCE FOR AFTERNOON CONVECTION.  
 
THERE ARE DIFFERENCES IN HOW THIS LID EVOLVES OVER THE NIGHT...BUT  
WE WILL AT LEAST BE TRENDING TOWARD MORE UNSTABLE CONDITIONS. SOME  
SHORTWAVE ENERGY/VORTICITY EJECTS FROM AFOREMENTIONED CLOSED LOW  
DRIFTING THROUGH SRN CANADA. THIS FORCING ARRIVES LATE EVENING AND  
OVERNIGHT. WEAK LOW PRESSURE AND A WARM FRONT LIFT UP TOWARD/INTO  
NRN MICHIGAN. THE SAME FCST BFR SOUNDINGS...IN A SCENARIO LIKE  
THIS...WOULD LIKELY ERODE/SUPPRESS THE CAP...UNLIKE THE GFS  
SUGGESTION. RATHER...WILL GO WITH SHOWERS AND EMBEDDED  
GARDEN-VARIETY THUNDERSTORMS DEVELOPING LATE EVENING/OVERNIGHT.  
NOTHING SEVERE ANTICIPATED...AS OUR LAPSE RATES AND OVERALL  
INSTABILITY WILL NOT MIRROR CURRENT ENVIRONMENT ACROSS THE NRN  
PLAINS. WE WILL ONLY HAVE SEVERAL HUNDRED J/KG MUCAPE WITH LAPSE  
RATES ALOFT 6-6.5C/KM. THE GREATEST MUCAPE LIKELY TO BE DOWN AROUND  
THE MANISTEE/CADILLAC AREAS...ALSO WHERE SOME ADDITIONAL LIFT  
ASSISTANCE WILL BE PROVIDED BY UPPER DIVERGENCE IN SOMEWHAT OF A  
DOUBLE JET STRUCTURE. WOULD GO WITH LIKELY CHANCES FOR SEEING  
PRECIPITATION...BUT BULK OF INSTABILITY AND LLJ FORCING WILL ONCE  
AGAIN BE ACROSS SRN WI/NRN IL/SRN LAKE MICHIGAN. THIS COULD BLOCK US  
FROM SEEING SOME OF THE ACTION. REGARDLESS...LIKELY TO BE SOME  
PRECIPITATION...BEST DESCRIPTION OF WHICH CAN BE PROVIDED BY LATER  
SHIFTS AS THE EVENT UNFOLDS.  
 
LOWS TONIGHT WILL LIKELY BE MILD WITH THICKENING CLOUDS...LOWER HALF  
OF THE 60S MOST AREAS.  
   
LONG TERM
 
(SATURDAY THROUGH THURSDAY)  
ISSUED AT 303 AM EDT FRI JUL 25 2014  
 
...RAINY END TO THE WEEKEND/COOL TEMPERATURES ON THE WAY FOR THE  
START OF NEXT WEEK...  
 
HIGH IMPACT WEATHER POTENTIAL: NOT A BUNCH. CHANCES FOR A FEW  
NON-SEVERE THUNDERSTORMS HEADING THROUGH THE WEEKEND.  
 
PATTERN SYNOPSIS/ANTICIPATED EVOLUTION: WHILE STILL PLENTY OF THE  
FINER DETAILS TO WORK OUT...MUCH TALKED ABOUT TRANSITION TO A MORE  
MERIDIONAL NOAM UPPER FLOW PATTERN STILL ON TARGET TO DEVELOP HEADING  
INTO AND THROUGH NEXT WEEK. NO LINGERING DOUBT MICHIGAN WILL BE  
CENTERED IN UNSEASONABLY CHILL PRODUCING TROUGH AXIS...WHICH WILL BE  
A SLOW ONE TO DEPART ONCE IT DEVELOPS. PLAYERS FOR SUCH UNUSUAL  
DEVELOPMENTS ALREADY ON THE TABLE...WITH LARGE NORTHERN QUEBEC GYRE  
SIMPLY STUCK IN PLACE...ALL THE WHILE STRONG PACIFIC SHORTWAVE MAKES  
STEADY EAST PROGRESS ACROSS THE SOUTHERN CANADIAN ROCKIES. THE  
LATTER WILL SIMPLY REINFORCE AND EXTEND THE FORMER AS IT  
SLING-SHOTS AROUND IT THROUGH EARLY NEXT WEEK. COMBINE THAT WITH  
DEVELOPMENT OF FULLY MATURE GULF OF ALASKA TROUGH/WEST NOAM RIDGE  
COUPLET (NOT TO MENTION ONE REALLY AMPLIFIED ATLANTIC RIDGE)...AND  
ONE CAN SEE WHY A PATTERN MUCH MORE RESEMBLING THE COOL SEASON IS  
EXPECTED.  
 
PRIMARY FORECAST CONCERNS/CHALLENGES: TEMPERATURE TRENDS THROUGHOUT  
AND EVOLUTION OF PERIODIC RAIN CHANCES. THUNDERSTORM POTENTIAL AND  
INTENSITY WILL ALSO NEED ADDRESSING THIS WEEKEND.  
 
DETAILS: SATURDAY CONTINUES TO REMAIN A CHALLENGE...WITH TIGHT  
THETA-E GRADIENT AND SURGE OF BEST UPPER JET FORCING EXITING STAGE  
RIGHT RATHER QUICKLY DURING THE MORNING. LEFT BEHIND WILL BE A MUCH  
MORE MOIST LOW LEVEL AIRMASS...WITH DEWPOINTS EXPECTED TO BE UP IN  
THE MID AND PERHAPS UPPER 60S. KINDA EXPECT WHAT EVER PUNCHES  
THROUGH HERE TONIGHT WILL LARGELY EXIT DURING THE MORNING  
HOURS...LEAVING NEXT LOW AMP WAVE AND DIURNAL DRIVEN DESTABILIZATION  
TO DRIVE ADDITIONAL SHOWER AND STORM DEVELOPMENT. MOISTURE CROSS  
SECTIONS SHOW GOOD TO EXCELLENT MOISTURE DEPTH UP THROUGH H7...WITH  
AGGRESSIVE DRYING ABOVE THIS LAYER. MANIPULATING MODEL DERIVED  
SOUNDINGS WITH ANTICIPATED DEWPOINTS/TEMPERATURES DOES YIELD  
DEVELOPMENT OF UPWARDS OF 1K-1.5K J/KG OF ML CAPE DURING THE  
AFTERNOON. THINK THIS MIGHT BE A TOUCH AGGRESSIVE...EXPECTING LOW  
LEVELS TO BE NOT QUITE AS SATURATED AS GUIDANCE WOULD SUGGEST. WHILE  
BEST DYNAMICS WILL HAVE EXITED...NOT ALL IS LOST...WITH MID LEVEL  
JET ROTATING THROUGH THE SOUTHWEST LAKES...COMBINING WITH LAKE  
INDUCED LOW LEVEL CONVERGENCE /PARTICULARLY IN NORTHEAST LOWER AND  
INTERIOR EASTERN UPPER MICHIGAN/ AND SAID WEAK WAVE. ABOVE  
DEFINITELY SUPPORTS SOME ADDITIONAL CONVECTIVE POTENTIAL...  
ESPECIALLY IN CLIMATOLOGICALLY FAVORED AREAS. INHERITED FORECAST  
ALREADY WELL TRENDED IN THIS DIRECTION...WITH ONLY SOME MASSAGING  
NEEDED TO POP/WEATHER GRID. DECENT DEEP LAYER SHEAR OF 30 TO 40  
KNOTS LARGELY OFFSET BY LIMITED MID LEVEL LAPSE RATES AND SKINNY  
CAPE PROFILE UP THROUGH HAIL GROWTH ZONE. SO...IF STORMS CAN DEVELOP  
(A BIG IF)...WOULD EXPECT THEM TO REMAIN BELOW SEVERE LIMITS.  
 
LOSS OF INSTABILITY AND RAPID APPROACH OF SHORTWAVE RIDGING EXPECTED  
TO BRING A MOSTLY DRY SATURDAY NIGHT. RATHER VIGOROUS CURRENT  
SOUTHERN CANADA WAVE QUICKLY FOLLOWS FOR SUNDAY...AND WHEN COMBINED  
WITH GOOD SLUG OF LEFT EXIT REGION UPPER JET DYNAMICS...LOOKS TO  
BRING A RATHER WIDESPREAD SHOWER EVENT SUNDAY INTO SUNDAY NIGHT.  
SYSTEM EVEN LOOKS TO TAKE ON COLD SEASON CHARACTERISTICS...WITH MORE  
STEADY RAIN POTENTIAL IN FAVORED NORTH SIDE DEFORMATION FIELD. SOME  
THUNDER THREAT REMAINS SUNDAY WITH OPPORTUNITY FOR SOME  
DESTABILIZATION BEFORE BETTER FORCING ARRIVES.  
 
TROUGHING DIGS IN AND STAYS THERE-ON-AFTER...PERHAPS LASTING THROUGH  
ALL OF NEXT WEEK. COLDEST ANOMALIES EXPECTED TO SLIDE JUST OFF TO  
OUR NORTHEAST. THAT SAID...COLD AIR ADVECTION ON FRONTSIDE OF  
SPRAWLING NORTHERN PLAINS HIGH WILL BE IMPRESSIVE INDEED...ONCE  
AGAIN NOT ALLOWING TEMPERATURES TO GET OUT OF THE 60S ON MONDAY. A  
VERY SLOW MODERATION TO FOLLOW...WITH HIGHS WARMING A FEW DEGREES  
EACH DAY THROUGH THURSDAY (EVEN BY THURSDAY...HIGHS WILL STILL BE A  
FEW DEGREES BELOW NORMAL). DESPITE TROUGHING...JUST NOT OVERLY  
IMPRESSED WITH RAIN CHANCES AFTER SUNDAY NIGHTS WAVE PASSAGE. DEEP  
LAYER FLOW WILL REMAIN NORTH TO NORTHWEST...AND MID LEVEL  
TEMPERATURE REALLY NEVER GET TOO COLD...REACHING THE NEGATIVE UPPER  
TEENS AT H5 LATER MONDAY INTO TUESDAY. OF COURSE...ANY WAVES  
ROTATING THROUGH WILL ONLY HELP THE SHOWER CAUSE...BUT TIMING AND  
MAGNITUDE OF SUCH NOT POSSIBLE TO DETERMINE JUST YET. NO REASON TO  
CHANGE THAT WHICH WAS INHERITED...FEATURING JUST ISOLATED/LOW CHANCE  
SHOWER POTENTIAL DURING THE DAYTIME HOURS. THIS WILL CHANGE...OF  
COURSE...BUT PLENTY OF TIME TO FIGURE THOSE DETAILS OUT IN THE  
COMING DAYS.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)  
ISSUED AT 609 AM EDT FRI JUL 25 2014  
   
..MAINLY VFR WITH CHANCES FOR SHOWERS AND STORMS TONIGHT
 
 
SFC HIGH PRESSURE HAS EXITED SOUTHEAST ALLOWING FOR A LIGHT SW  
RETURN FLOW. THIS GRADIENT TIGHTENS A TOUCH TODAY WITH GUSTS UP TO  
15-18KTS EXPECTED...MAINLY ACROSS NW LOWER. CUMULUS AND SOME  
HIGHER CLOUD EXPECTED TO ROLL ON THROUGH TODAY AND POSSIBLY GET  
STUCK UNDERNEATH AN INVERSION FOR A PERIOD OF MORE CLOUDY  
CONDITIONS. WEAK LOW PRESSURE AND A WARM FRONT ARRIVE TONIGHT WITH  
THE CHANCE FOR SHOWERS AND STORMS AHEAD OF IT. EXACT EVOLUTION OF  
THE PRECIPITATION NEBULOUS RIGHT NOW...WILL INCLUDE A VCSH FOR THE  
NIGHT.  
 
NO SEVERE WEATHER ANTICIPATED. BRIEF HEAVY RAIN AND LIGHTNING  
HOWEVER.  
 

 
   
MARINE
 
 
ISSUED AT 303 AM EDT FRI JUL 25 2014  
 
SW WINDS WILL INCREASE HEADING THROUGH TONIGHT...AHEAD OF SFC LOW  
PRESSURE AND A WARM FRONT...WHICH WILL BRING AREAS OF SHOWERS AND  
GARDEN-VARIETY STORMS TO THE GREAT LAKES. NOTHING SEVERE....AND  
WINDS TO REMAIN ABOVE ADVISORY LEVELS. EXPECTING NO MORE THAN  
20KTS..WHICH WILL LARGELY RESIDE ACROSS LAKE MICHIGAN. WINDS REMAIN  
UNDER ADVISORY LEVELS SATURDAY AND SUNDAY IN WEAK GRADIENT. ANOTHER  
SFC LOW CROSSES SUNDAY MORNING WITH A BETTER CHANCE FOR SHOWERS AND  
STORMS...AND MUCH COOLER AIR SET TO ARRIVE THROUGH THE DAY SUNDAY  
AND SUNDAY NIGHT.  
 

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

 
 

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