372  
FXUS63 KDTX 230958  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
558 AM EDT FRI AUG 23 2019  
 
   
AVIATION
 
 
HIGH PRESSURE BUILDING INTO THE REGION WILL RESULT IN VFR CONDITIONS  
THROUGH THE TAF PERIOD. COULD BE SOME SUB 5KFT CIGS POSSIBLE THIS  
AFTERNOON AS DIURNAL CU FIELD DEVELOPS WITH THE AID OF NORTHEASTERLY  
FLOW OFF THE LAKES PUSHING LOW LEVEL MOISTURE ACROSS THE AREA.  
OVERALL THE SOUNDING LOOKS VERY DRY ABOVE 7KFT THUS DEEP MIXING  
SHOULD ERODE THE CLOUD FIELD EASILY THIS EVENING. WINDS WILL REMAIN  
NORTH/NORTHEAST WITH SPEEDS TO ABOUT 10 KNOTS IN BEST MIXING THIS  
AFTERNOON.  
   
DTW THRESHOLD PROBABILITIES
 
 
* MEDIUM FOR CIGS AOB 5KFT FOR A PERIOD OF TIME FRIDAY AFTERNOON.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 402 AM EDT FRI AUG 23 2019  
 
DISCUSSION...  
 
CONTINUED INFLUENCE OF LARGER SCALE HIGH PRESSURE STARTS THE DAY  
ACROSS LOWER MICHIGAN BUT NOT WITHOUT SOME INTERACTION FROM THE  
GREAT LAKES THAT BECOMES MORE EVIDENT DURING THE MORNING. SURFACE  
AND MODEL ANALYSIS FIELDS SUGGEST A HYBRID BACKDOOR FRONT/AGGREGATE  
TROUGH ACROSS SUPERIOR AND NORTHERN HURON THAT MARKS A SLIGHT  
REINFORCEMENT OF COOL AIR. CLOUDS ALONG AND NORTH OF THE SURFACE  
TROUGH EXTEND WELL NORTH INTO ONTARIO AND ARE MORE OF THE MID LEVEL  
VARIETY SUPPORTED BY THE TROUGH AXIS AROUND 500 MB. THIS TROUGH AXIS  
PIVOTS SOUTHEASTWARD DURING THE MORNING AND PULLS THE SUPERIOR/HURON  
SURFACE TROUGH SOUTHWARD INTO SOUTHERN LAKE HURON AND THUMB REGION.  
THE UPSTREAM CLOUDS THEN REPRESENT ADEQUATE MOISTURE FOR SCATTERED  
SHOWERS DUE TO INSTABILITY OVER THE WARM LAKE WATER AND FROM DAYTIME  
HEATING OVER THE LAND BY LATE MORNING THROUGH AFTERNOON. HI RES  
MODEL SOLUTIONS HELP IDENTIFY THE AFFECTED LAND AREA LIMITED TO THE  
THUMB REGION BEFORE SHOWERS DISSIPATE TOWARD EVENING. THIS LEAVES  
ANOTHER NICE DAY ACROSS THE REST OF SE MICHIGAN WITH SOME POCKETS OF  
MID CLOUDS DURING THE MORNING GIVING WAY TO CUMULUS THIS AFTERNOON  
ALONG WITH A COMPONENT OF CLOUDS MOVING SOUTHWARD FROM THE THUMB.  
GUIDANCE TEMPERATURE PROJECTIONS REMAIN ON THE LOW SIDE OF NORMAL  
VALUES THAT ARE IN THE UPPER 70S TO AROUND 80 FOR HIGHS AND IN THE  
UPPER 50S TO AROUND 60 FOR LOWS TODAY THROUGH THIS WEEKEND.  
 
ANY REMNANT OF THE SURFACE TROUGH FILLS AND RELEASES INLAND IN A  
HYBRID LAKE BREEZE FASHION WITH THE LOSS OF DAYTIME HEATING DURING  
THE EVENING. A REINFORCEMENT OF SLIGHTLY MODIFIED BUT STILL COOLER  
AIR THEN WASHES OVER THE REGION DURING THE NIGHT ON LIGHT BUT STEADY  
NE WIND THAT IS SUPPLIED BY HIGH PRESSURE STRENGTHENING OVER  
NORTHERN ONTARIO. BOTH THE SURFACE HIGH AND RIDGE ALOFT DRIFT ACROSS  
THE GREAT LAKES AND COMBINE FOR IDEAL LATE SUMMER WEATHER DURING THE  
WEEKEND. TEMPERATURES REMAIN SLIGHTLY BELOW NORMAL SATURDAY AND THEN  
MODERATE SLIGHTLY BY SUNDAY.  
 
PROSPECTS FOR RAIN INCREASE MONDAY THROUGH THE EARLY WEEK AS THE  
UPPER LEVEL BLOCKING PATTERN SLOWLY MATURES. THE CURRENT UPPER LEVEL  
LOW AND TROUGH OVER THE ROCKIES MAKE IT INTO THE PLAINS BY MONDAY  
AND LATCH ON TO THE FRONT STALLED NEAR THE GULF COAST. THAT LEAVES  
LITTLE DOUBT ABOUT THE MOISTURE SUPPLY AS THE LEAD WAVE MOVES INTO  
THE GREAT LAKES AND ACROSS SE MICHIGAN MONDAY AFTERNOON AND NIGHT.  
UNSETTLED WEATHER CONTINUES THROUGH TUESDAY AS A STRONG PACIFIC COLD  
FRONT SURGES ACROSS THE REGION. GLOBAL MODEL SOLUTIONS PROJECT  
DEVELOPMENT OF A LARGE AND STRONG LOW PRESSURE SYSTEM OVER CENTRAL  
CANADA AND THE NORTHERN PLAINS WHICH LIKELY HAS HIGH PREDICTABILITY  
OVERALL BUT STILL WITH TIMING QUESTIONS ON THE FRONTAL PASSAGE  
ACROSS SE MICHIGAN. THUNDERSTORM POTENTIAL WILL BE DEPENDENT ON  
REFINEMENT OF THIS TIMING TUESDAY INTO TUESDAY NIGHT.  
 
MARINE...  
 
CANADIAN HIGH PRESSURE WILL BECOME CENTERED OVER THE NORTHERN GREAT  
LAKES TODAY BEFORE DEPARTING TO EASTERN CANADA OVER THE WEEKEND.  
THIS SYSTEM WILL INFLUENCE THE REGION THROUGH THE END OF THE  
WEEKEND. A WEAKENING GRADIENT WILL ATTEMPT TO KEEP WINDS DOWN BUT  
LIGHT TO MODEST NORTHERLY WINDS WILL PERSIST THROUGH THIS EVENING AS  
COLD AIR ADVECTION PRODUCES UNSTABLE CONDITIONS. WINDS AND WAVES  
SHOULD STAY JUST BELOW SMALL CRAFT CRITERIA. THIS DEVELOPING  
INSTABILITY WILL ALSO SUPPORT A CHANCE FOR WATERSPOUTS TODAY.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LAKE HURON...NONE.  
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

 
 
AVIATION.....DRK  
DISCUSSION...BT  
MARINE.......DRK  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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