957  
FXUS63 KDTX 241419  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
1019 AM EDT SAT JUN 24 2017  
   
UPDATE
 
 
LARGE UPPER LEVEL COLD POOL/CIRCULATION ENTERING WESTERN MINNESOTA,  
WITH LEAD UPPER WAVE EMBEDDED WITHIN THE NEGATIVE TILTED TROUGH AXIS  
EXITING CHICAGO, WHICH WILL MOVE THROUGH LOWER MICHIGAN, SENDING 500  
MB TEMPS TOWARD -20 C DURING PEAK HEATING OF THE DAY, WITH THE NOTED  
INVERSION SEEN IN THE 12Z DTX AT 700 MB ALSO COOLING/WEAKENING. WITH  
SURFACE DEW PTS SOMEWHAT ELEVATED IN THE 55-58 DEGREE RANGE RIGHT  
NOW, LOOKS LIKE SURFACE BASED CAPES WILL EASILY EXCEED 1000 J/KG,  
WITH MLCAPES EXCEEDING 500 J/KG, AND PLANNING ON RAISING POPS AND MAX  
TEMPS SLIGHTLY, BUT OVERALL LIMITED MOISTURE (PW VALUES AROUND 0.75  
INCHES) QUALITY AND DRY MID LEVELS SHOULD LIMIT AREAL EXTENT. NONE-  
THE-LESS, FAVORABLE FREEZING LEVELS FOR HAIL, AND THERE MAY ALSO BE  
JUST ENOUGH LINGERING 0-6 KM WIND SHEAR (EXITING 60 KNOT MAX) TO  
SUPPORT SINGLE SEVERE/PULSE TYPE STORM. WILL BE WATCHING DEW PTS  
CLOSELY, AS THEY SHOULD MIX DOWN IN THE AFTERNOON.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 540 AM EDT SAT JUN 24 2017  
 
AVIATION...  
 
MOSTLY CLEAR SKIES WILL PREVAIL THROUGH THE MORNING HOURS. DAYTIME  
HEATING AND AN UPPER LEVEL DISTURBANCE WORKING ACROSS THE AREA WILL  
THEN ALLOW FOR A BKN VFR CU FIELD THIS AFTERNOON. ISOLATED TO  
SCATTERED SHOWERS ARE ALSO EXPECTED TO DEVELOP, WITH GREATEST  
COVERAGE UP TOWARDS MBS AND FNT. A FEW THUNDERSTORMS WILL ALSO BE  
POSSIBLE ACROSS SOUTHEAST MICHIGAN, BUT PROBABILITY IS TOO LOW TO  
INCLUDE IN TAFS. LOSS OF DAYTIME HEATING AND SUBSIDENCE BEHIND THE  
EXITING UPPER WAVE SHOULD ALLOW CLOUDS TO SCATTER OUT THIS EVENING.  
OTHERWISE, WESTERLY WINDS WILL GUST TO 25 KNOTS THIS AFTERNOON.  
 
FOR DTW...POTENTIAL FOR SHOWERS WILL EXIST BETWEEN 17-00Z, BUT  
COVERAGE SHOULD BE ISOLATED. THE CHANCE FOR A THUNDERSTORM IN THE  
AIRSPACE IS LOW THIS AFTERNOON/EVENING, BUT POSSIBLE.  
 
//DTW THRESHOLD PROBABILITIES...  
 
* LOW CONFIDENCE IN CEILINGS AOB 5KFT THIS AFTERNOON AND EVENING.  
 
* LOW CONFIDENCE IN THUNDERSTORMS AT DTW THIS AFTERNOON AND EVENING.  
 
PREV DISCUSSION...  
ISSUED AT 350 AM EDT SAT JUN 24 2017  
 
DISCUSSION...  
 
BROAD MID LEVEL TROUGHING WILL GRIP THE GREAT LAKES REGION  
THROUGHOUT THE UPCOMING WEEKEND. THE SUBSEQUENT SUPPRESSION OF THE  
MEAN THICKNESS FIELD UNDER PREVAILING DEEP LAYER WEST-NORTHWEST FLOW  
WILL MAINTAIN A COOLER AND LESS HUMID RESIDENT ENVIRONMENT DURING  
THIS TIME. THE COMBINATION OF COOLER MID LEVEL TEMPERATURES AND  
NEAR SURFACE DIABATIC HEATING WILL ESTABLISH A STEEP LAPSE RATE  
ENVIRONMENT FOR SUBSTANTIAL DIURNAL CU GROWTH TODAY. THIS ASCENT  
WILL BE AUGMENTED THIS AFTERNOON BY THE ARRIVAL OF A SHORTWAVE AND  
COLD POOL, AS ENERGETIC NORTHWEST FLOW DIRECTS A SERIES OF  
PERTURBATIONS INTO THE BASE OF THE MEAN TROUGH OVER THE NEXT SEVERAL  
DAYS. RECENT MODEL GUIDANCE REMAINS SUPPORTIVE OF AN INCREASE IN  
SHOWER COVERAGE AS WEAK INSTABILITY EMERGES BENEATH THE INBOUND COLD  
POOL AND WITH THE SMALL SCALE INCREASE IN CYCLONIC FLOW. HIGHER  
PROBABILITY OF DEVELOPMENT WITH NORTHWARD EXTENT GIVEN FAVORABLE  
POSITIONING, WHICH SHOULD TRANSLATE INTO A SCATTERED COVERAGE OF  
SHOWERS WITH ISOLATED THUNDERSTORMS LARGELY IMPACTING THE TRI-  
CITIES/THUMB DOWN THROUGH THE I-69 CORRIDOR. MLCAPE REACHES  
UPWARDS OF 800 J/KG, PERHAPS SUFFICIENT TO GENERATE A DEEP ENOUGH  
UPDRAFT TO SUPPORT SMALL HAIL GIVEN THE LOWER FREEZING LEVELS.  
PALTRY DEEP LAYER WIND FIELDS WILL PRECLUDE A GREATER RISK OF  
ORGANIZED DEVELOPMENT.  
 
A STRONGER WAVE WILL LIFT ACROSS CENTRAL LOWER MI LATE TONIGHT INTO  
EARLY SUNDAY. THIS WILL YIELD A PERIOD OF GREATER FORCED ASCENT,  
POTENTIALLY CAPITALIZING ON SUFFICIENT MOISTURE AND STEEP LAPSE  
RATES AT THE MID LEVELS TO PRODUCE ANOTHER ROUND OF SCATTERED  
SHOWERS/ISOLATED THUNDERSTORMS. SHOULD THE TIMING PROVE A TOUCH  
SLOWER ALLOWING FOR GREATER DIURNALLY DRIVEN LOW LEVEL  
DESTABILIZATION, THEN A LOCALIZED REGION OF HIGHER COVERAGE WILL BE  
PLAUSIBLE. THIS WAVE WILL LEAD IN A SECONDARY PERIOD OF COLD AIR  
ADVECTION FOR SUNDAY, AS 850 MB TEMPERATURES DIP INTO THE 5-6C  
RANGE. THIS WILL PLACE HIGHS IN VICINITY OF 70 DEGREES ALL  
LOCATIONS, OR A GOOD 10 DEGREES BELOW NORMAL.  
 
TIMING OF ANY SUBSEQUENT SHORTWAVES REMAINS TOO ILL-DEFINED TO  
PROVIDE GREATER DETAIL, BUT IT GENERALLY APPEARS SE MICHIGAN WILL  
REMAIN SUSCEPTIBLE TO ADDITIONAL BOUTS OF HEIGHTENED CVA AND COLD POOL  
INTRUSIONS THROUGH MONDAY. A SCATTERED SHOWER/ISOLATED THUNDER  
MENTION REMAINS HIGHLIGHTED FOR THE MONDAY PERIOD. NEUTRAL  
TEMPERATURE ADVECTION UNDER THIS RELATIVELY STATIC PATTERN WILL  
AGAIN ENSURE TEMPERATURES REMAIN WELL BELOW NORMAL TO BEGIN THE WORK  
WEEK. AIRMASS MODIFICATION COMMENCES BEGINNING TUESDAY AS THE UPPER  
TROUGH AXIS EASES EASTWARD AND UPPER HEIGHTS BEGIN TO RECOVER. WARM  
AIR ADVECTION THEN RAMPS UP WEDNESDAY, WITH TEMPERATURES RETURNING  
TO AROUND AVERAGE FOR MIDWEEK.  
 
MARINE...  
 
WEST TO NORTHWEST FLOW WILL BE MAINTAINED THROUGH THE WEEKEND  
BETWEEN LOW PRESSURE OVER EASTERN CANADA AND HIGH PRESSURE BUILDING  
THROUGH THE PLAINS AND INTO TENNESSEE VALLEY. THE HIGHEST SPEEDS  
WILL BE OVER WESTERN LAKE ERIE WHERE THE GRADIENT WILL BE A LITTLE  
TIGHTER, RESULTING IN GUSTS THAT WILL JUST TOP 20 KNOTS BOTH THIS  
AFTERNOON AND SUNDAY AFTERNOON. SCATTERED SHOWERS, AND POSSIBLY A  
THUNDERSTORM, ARE ALSO EXPECTED EACH AFTERNOON. WEAK LOW PRESSURE  
TRACKING THROUGH THE AREA WILL BRING SCATTERED TO NUMEROUS SHOWERS  
AND A FEW THUNDERSTORMS MONDAY.  
 

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

 
 

 
 
UPDATE.......SF  
AVIATION.....HLO  
DISCUSSION...MR  
MARINE.......HLO  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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