593  
FXUS63 KDTX 140704  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
304 AM EDT MON OCT 14 2019  
   
DISCUSSION
 
 
 
CONDITIONS TODAY WILL REMAIN GOVERNED BY COLD WEAKLY CYCLONIC FLOW,  
AS SOUTHEAST MICHIGAN CONTINUES TO RESIDE WITHIN THE SOUTHERN  
PERIPHERY OF A SPRAWLING MID LEVEL CYCLONE LIFTING ACROSS EASTERN  
ONTARIO. THIS UNDERLYING PATTERN AUGMENTED BY THE DOWNSTREAM  
ADVECTION OF MOISTURE OFF LAKE MICHIGAN AND DAYTIME HEATING WILL  
SUPPORT A HIGHER COVERAGE OF STRATUS/STRATOCU THROUGHOUT THE  
DAYLIGHT PERIOD. THE LIMITED INSOLATION POTENTIAL WILL EFFECTIVELY  
REINFORCE AN ALREADY COLD RESIDENT ENVIRONMENT - EXISTING LOW LEVEL  
THERMAL TROUGH DEFINED BY 850 MB TEMPERATURES NEAR -4C. THIS  
SUPPORTS HIGHS OF UPPER 40S TO LOWER 50S...OR A SOLID 10 DEGREES  
BELOW AVERAGE.  
 
SURFACE RIDGING MARKING THE TRANSITION TOWARD DEEPER LAYER STABILITY  
AS UPPER LEVEL FLOW TURNS WEAKLY ANTICYLONIC TAKES RESIDENCE  
TONIGHT. THIS PROCESS FAVORS A PROGRESSIVE CLEARING OF ANY LINGERING  
STRATOCU COINCIDENT WITH THE LOSS OF DIURNAL SUPPORT THIS EVENING,  
WITH SIMPLY SOME THINNER HIGH CLOUD OVERNIGHT. A CORRESPONDING  
REDUCTION IN THE NEAR SURFACE GRADIENT AND INCREASING DEPTH/  
MAGNITUDE OF DRY AIR CONTINUE TO SIGNAL A RESPECTABLE RADIATIONAL  
COOLING OPPORTUNITY. THIS WILL BRING MOST LOCATIONS DOWN INTO THE  
MIDDLE 30S EARLY TUESDAY MORNING, ALLOWING FOR WIDESPREAD FROST  
FORMATION. A FROST ADVISORY NOW IN EFFECT TO HIGHLIGHT THIS  
EXPECTATION. RESIDENT THERMAL PROFILE SEEMINGLY JUST A TOUCH TOO  
WARM TO SUPPORT A HIGHER COVERAGE OF LOW TEMPERATURES OF FREEZING,  
ALTHOUGH THE VERY COLDEST LOCALES MAY NEAR THIS VALUE. THIS WILL  
PRECLUDE CONSIDERATION OF A FREEZE HEADLINE.  
 
NORTHERN STREAM SHORTWAVE NOW EJECTING OUT OF BRITISH COLUMBIA WILL  
STRENGTHEN OVER THE NEXT 36 HOURS AS IT DIGS SOUTHEAST ACROSS THE  
NORTHERN CONUS. THE RESULTING DEEP MID LEVEL CIRCULATION WILL THEN  
PIVOT ACROSS THE GREAT LAKES TUESDAY NIGHT INTO EARLY WEDNESDAY. A  
PERIOD OF MODEST WARM AIR ADVECTION WILL EMERGE DOWNSTREAM OF THESE  
HEIGHT FALLS TUESDAY. THIS WILL NET ROUGHLY A 10 DEGREE WARMING  
TREND FROM READINGS NOTED MONDAY - HIGHS MID 50S NORTH TO LOWER 60S  
SOUTH. WHILE DEEP LAYER NORTHWARD MOISTURE TRANSPORT WILL GENERALLY  
BE LACKING WITH THIS SYSTEM GIVEN THE MEAN WESTERLY MID LEVEL FLOW,  
THERE EXISTS A WINDOW /MAINLY LATE IN THE DAY/ FOR SHOWERS TO EMERGE  
WITHIN THE ONGOING ISENTROPIC ASCENT. GREATER POTENTIAL WITH  
NORTHWARD EXTENT WITH ANY LEAD ACTIVITY. HIGHER LIKELIHOOD FOR  
RAINFALL /LESS THAN 0.25"/ TUESDAY NIGHT TIED TO THE ATTENDANT COLD  
FRONTAL PASSAGE AND ASSOCIATED INCREASE IN MID LEVEL DYNAMICS WITH  
THE INBOUND UPPER CIRCULATION.  
 
COLD CYCLONIC FLOW WILL AGAIN GRIP SOUTHEAST MICHIGAN WEDNESDAY.  
INITIAL PERIOD OF POST-FRONTAL COLD AIR ADVECTION CURRENTLY  
PROJECTED TO LACK THE STRENGTH NOTED FOR TODAY /850 MB TEMPERATURES  
NEAR -1C/, BUT WILL EFFECTIVELY MAINTAIN BELOW NORMAL CONDITIONS.  
THE ONGOING CYCLONIC VORTICITY ADVECTION CAPITALIZING ON A DIURNALLY  
ENHANCED STEEP LAPSE RATE ENVIRONMENT WILL LIKELY SUPPORT A FEW  
SHOWERS THROUGH THE DAY. MODEST MIXING OF A FIRM WEST TO NORTHWEST  
GRADIENT WILL BRING GUSTY CONDITIONS FOR THE AFTERNOON -  
POTENTIALLY IN EXCESS OF 30 MPH AT TIMES.  
 
RESIDENT COLDER PATTERN HOLDS FIRM WEDNESDAY NIGHT THROUGH THURSDAY  
NIGHT, AS DEEP LAYER NORTHWEST FLOW DICTATES CONDITIONS. MAINTENANCE  
OF A SUFFICIENT BOUNDARY LAYER GRADIENT PRECLUDES FROST CONCERNS  
WEDNESDAY NIGHT, WITH GREATER POTENTIAL THEN AGAIN THURSDAY NIGHT AS  
SURFACE RIDGING BUILDS BACK IN. SUBSTANTIAL HEIGHT RISES CONCURRENT  
WITH INCREASING SOUTHERLY FLOW WILL THEN TRANSLATE INTO A SOLID  
WARMING TREND STARTING FRIDAY, WITH LATEST MODEL GUIDANCE SUGGESTING  
THIS TREND CONTINUES RIGHT INTO NEXT WEEKEND. HIGHS OVER THE WEEKEND  
BACK INTO THE 60S.  
 

 
   
MARINE
 
 
ELEVATED WESTERLY GRADIENT REMAINS IN PLACE ACROSS LAKE HURON TODAY  
AS THE CENTER OF BROAD LOW PRESSURE CONTINUES TRACKING TOWARD JAMES  
BAY AND HIGH PRESSURE BUILDS INTO THE OHIO VALLEY. AMPLE COLD AIR  
MOVING OVER THE REGION IN THE WAKE OF THE DEPARTING SYSTEM MAKE  
WATERSPOUTS POSSIBLE TODAY, PARTICULARLY ACROSS NORTHERN LAKE HURON.  
WINDS WEAKEN TONIGHT INTO EARLY TUESDAY, THEN BACK TO THE SOUTHEAST  
AND RESTRENGTHEN IN ADVANCE OF A DEVELOPING LOW PRESSURE SYSTEM  
SET TO TRACK THROUGH THE NORTHERN GREAT LAKES TUESDAY NIGHT. FRESH  
COLD ADVECTION AND STRONG NORTHWEST FLOW IN THE WAKE OF THE SYSTEM  
WILL HAVE GOOD POTENTIAL TO PRODUCE GALES BY LATE WEDNESDAY.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 1155 PM EDT SUN OCT 13 2019  
 
AVIATION...  
 
COLD CORE OF UPPER LEVEL LOW IS CURRENTLY BULLDOZING THROUGH  
SOUTHEAST MICHIGAN. STRONG 900-800MB COLD ADVECTION WILL BEGIN JUST  
AFTER THE START OF THE FORECAST PERIOD LEADING TO STOUT STRATUS DECK  
FOR ALL AREAS. OBSERVATION TRENDS UPSTREAM OVER PORTIONS OF  
SOUTHWEST MICHIGAN SUPPORTS THIS IDEA. THE STRATUS DECK IS EXPECTED  
TO BLANKET THE AREA THROUGH THE MORNING AND TRANSITION INTO  
STRATOCUMULUS AS DAYTIME HEATING RAISES CLOUD BASES. PRESSURE  
GRADIENT REMAINING IN PLACE WILL ALLOW WINDS TO INCREASE MODESTLY  
10-20 KNOTS AGAIN MONDAY.  
 
DTW THRESHOLD PROBABILITIES...  
 
* HIGH FOR CIG AOB 5KFT TONIGHT AND MONDAY MORNING.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR MIZ047>049-053>055-  
060>063-068>070-075-076-082-083.  
 
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 AM EDT THIS MORNING FOR LHZ421-422-  
441.  
 
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

 
 
DISCUSSION...MR  
MARINE.......TF  
AVIATION.....CB  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MI Page Main Text Page