844  
FXUS63 KDTX 262304  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
604 PM EST WED NOV 26 2014  
 
   
AVIATION
 
 
//DISCUSSION...  
 
A DEEP INVERSION BASED AROUND 4K FT AGL IS EXPECTED TO PERSIST  
THROUGH THE NIGHT AND INTO EARLY THURS AFTERNOON. THIS WILL SUSTAIN  
A 3500-4500 FT STRATUS DECK ACROSS SE MI. THERE HAS ALSO BEEN A  
SECOND CLOUD DECK BASED BETWEEN 2500 FT AND 3000 FT WITH SOME  
FLURRIES. IN TERMS OF SE MI...THESE LOWER CLOUDS AND FLURRIES HAVE  
BEEN MORE PREVALENT IN AND AROUND METRO DETROIT WHERE SOME BETTER  
LOW LEVEL MOISTENING FROM THE EAST HAS OCCURRED THIS AFTERNOON. THE  
LOW LEVEL FLOW WILL BACK FROM NORTHEAST THIS EVENING TO NORTHWEST  
OVERNIGHT. SOME ADDED HEAT FLUX OFF LAKE HURON OVERNIGHT MAY BOOST  
THE INVERSION A LITTLE BIT. THE TREND TOWARD NORTHWEST FLOW MAY ALSO  
ADD JUST A LITTLE DRYING TO THE LOW LEVELS. THESE FACTORS SUGGEST A  
TREND TOWARD PREVAILING LOW END MVFR CLOUD BASES /3500-4500 FT/  
OVERNIGHT...ALTHOUGH FLUCTUATING CEILINGS COULD STILL BE POSSIBLE  
THROUGH DAYBREAK THURS.  
 
//DTW THRESHOLD THREATS...  
 
* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FT THROUGH TONIGHT AND  
THURSDAY MORNING.  
 

 
   
PREV DISCUSSION
 
ISSUED 351 PM EST WED NOV 26 2014  
 
SHORT TERM...TONIGHT  
 
NORTHEAST GRADIENT WRAPPING AROUND THE EAST COAST CYCLONE WILL  
FUNNEL LIGHT NORTHEASTERLY WINDS INTO ONTARIO THROUGH TONIGHT. LAKE  
TROUGHING OVER LAKE HURON WILL NUDGE THE FLOW TOWARD A MORE VEERED  
EASTERLY FETCH AS IT APPROACHES THE SHORELINE OF THE THUMB TONIGHT.  
INCREASED CONVERGENCE WITHIN THE LAKE-INDUCED TROUGH AND ALONG THE  
SHORELINE MAY YET SUPPORT A PARTIAL COVERAGE OF SNOW SHOWERS WORKING  
INLAND. THERMODYNAMIC PROFILES LEAVE A LOT TO BE DESIRED,  
PARTICULARLY WITH REGARD TO A RESPECTABLE DEPTH OF SATURATION WITHIN  
THE DENDRITE GROWTH LAYER, SO NOT EXPECTING MORE THAN MINOR  
ACCUMULATIONS IN HURON AND SANILAC COUNTIES WITH THE MOIST RESIDENT  
AIRMASS SUPPORTING PATCHES OF FLURRIES ELSEWHERE. STOUT INVERSION  
EVIDENT ON THIS MORNING'S 12Z DTX SOUNDING AND ONGOING MOIST  
EASTERLY FETCH THROUGH TODAY YIELD CONTINUED HIGH CONFIDENCE IN LOW  
CLOUD COVER TONIGHT WHICH WILL CONTAIN OVERNIGHT LOWS TO THE  
MID/UPPER 20S.  
 
LONG TERM...THURSDAY THROUGH TUESDAY  
 
FAIRLY UNSTABLE/PROGRESSIVE UPPER LEVEL PATTERN LOOKING TO SET UP  
ACROSS THE CONUS THIS WEEK AS THE CURRENT TROUGH EXITS EAST BY THE  
WEEKEND. WITH THE EXIT OF THE AMPLIFIED TROUGH...A MUCH MORE ZONAL  
FLOW SETUP WILL DEVELOP AS AN UPPER LOW STALLS OFF THE COAST OF  
CALIFORNIA AND ANOTHER WOBBLES ABOUT ITSELF OVER NORTHERN CANADA.  
THIS WILL STEER THE FLOW EASTERLY BY NEXT WEEK WITH THE MAIN  
BAROCLINIC ZONE LINING UP VERY NEAR TO THE AREA. THIS RESULTS IN A  
LOWER CONFIDENCE FORECAST AS A SLIGHT WOBBLE NORTH OR SOUTH COULD  
LEAD TO NOTABLE CHANGES IN THE FORECAST.  
 
THE CURRENT TROUGH WILL BE DRIFTING EASTWARD ON THANKSGIVING WITH  
THE UPPER LEVEL TROUGH AXIS TRAVERSING THE AREA IN THE MORNING AND A  
MID LEVEL TROUGH PASSING OVERHEAD IN THE AFTERNOON. THIS WILL USHER  
IN A VERY COLD AIRMASS WHICH IS BELOW -22C AT 850MB OVER  
SOUTH/CENTRAL CANADA BUT WILL BE MODIFIED A BIT TO AROUND -17C BY  
THE TIME IT REACHES SE MI THURSDAY NIGHT. DURING THE DAY THURSDAY WE  
WILL HAVE A CHANCE OF LIGHT SNOW SHOWERS DUE TO THE COMBINATION OF  
THE MID LEVEL TROUGH PASSING AND WESTERLY FLOW AIDING IN A FEW LAKE  
EFFECT SHOWERS LATER IN THE DAY. DOES NOT LOOK TO MUCH IN THE WAY OF  
ACCUMULATION WITH THIS SCENARIO AS THE TROUGH PUSHES THE BETTER  
MOISTURE...A MEAGER 0.25-0.30 PWAT...EARLIER IN THE DAY WITH THE  
COLDER AIR ALOFT AND BETTER LL LAPSE RATES COMING LATER IN THE DAY.  
MODEL RH FIELDS SHOW A DRAMATIC DROP OFF IN MOISTURE THROUGHOUT THE  
COLUMN LATER IN THE DAY AS WELL AS THE SHORTWAVE RIDGE BUILDS INTO  
LOWER MI. THIS SHOULD SHUT OFF ANY LINGERING SNOW SHOWERS LATER  
THURSDAY EVENING LEADING TO A DRY OVERNIGHT PERIOD. KEPT  
ACCUMULATIONS LESS THAN A HALF INCH THROUGH THE DAY.  
 
BETTER CHANCE OF SNOWFALL ON FRIDAY AS RIDGING BUILDS EASTWARD  
THROUGH THE CENTRAL CONUS PUSHES THE ACTIVE JET NORTH INTO THE GREAT  
LAKES. THIS WILL DIRECT THE LEAD EDGE OF A SHEARING PV ANOMALY INTO  
SOUTHERN MI COINCIDENT WITH A BAND OF ISENTROPIC ASCENT ON THE  
ELEVATED WARM FRONT ACROSS CENTRAL MI ON THE NOSE OF A MORE THETA  
E RICH AIRMASS. MODELS HAVE TRENDED A BIT FURTHER SOUTH WITH THE  
BEST FGEN/ISENTROPIC ASCENT BAND THUS SLIGHTLY INCREASED THE  
POP/QPF/SNOW AMOUNTS SOUTHWARD AS WELL. START OF THE SNOW IS IN  
QUESTION AS MODELS STRUGGLE TO KEEP THE LOW LEVELS  
SATURATED...EVEN SEVERAL HOURS AFTER THE COLUMN SATURATES ABOVE  
800MB. STILL THINK IT LOOKS LIKE A DECENT SETUP FOR SOME LIGHT  
ACCUMULATIONS AS THE FLOW ALIGNS WITH THE AXIS OF THE FORCING  
GIVING IT A BETTER RESIDENCE TIME. WITH MODELS IN FAIR AGREEMENT  
WITH AROUND 0.10 INCHES OF QPF FRI-FRI NIGHT...THINKING A 1-2 INCH  
SNOWFALL FORECAST SEEMS FAIR.  
 
A ZONAL PATTERN WITH MODERATE WARM AIR ADVECTION WILL HOLD  
THROUGH THE WEEKEND. THIS WILL BOOST TEMPS TO SLIGHTLY ABOVE NORMAL  
FOR SUNDAY. A MID-LEVEL WAVE WILL THEN DYNAMICALLY FORCE A COLD FRONT  
ACROSS THE REGION SUNDAY EVENING/NIGHT...WITH MUCH COLDER AIR THEN  
FILTERING IN. STRONG 1044 MB HIGH PRESSURE SYSTEM WILL USHER IN COLD  
CANADIAN/ARCTIC AIR EARLY NEXT WEEK. THAT PATTERN WILL HOLD THROUGH  
THE 7 DAY FORECAST WITH TEMPS TRENDING COLDER THAN NORMAL AND PRECIP  
CHANCES QUITE LOW.  
 
MARINE...  
 
WEAK AREA OF HIGH PRESSURE WILL RESULT IN LIGHT EASTERLY WINDS AND  
LOW WAVE HEIGHTS THROUGH TONIGHT. ON THURSDAY...AN ARCTIC COLD FRONT  
WILL DROP THROUGH THE GREAT LAKES USHERING IN A COLDER AND MORE  
UNSTABLE AIRMASS. THIS WILL RESULT IN WINDS INCREASING AS THE BECOME  
NORTHWESTERLY DURING THE DAY. CURRENT GUIDANCE OFFERS NO CLEARER  
PICTURE FOR THE POTENTIAL GALE FORCE WINDS OVER CENTRAL LAKE HURON  
THURSDAY AFTERNOON. WINDS STILL LOOK TO INCREASE RAPIDLY IN THE  
AFTERNOON BUT DO NOT LOOK TO STAY ELEVATED FOR VERY LONG BEFORE  
SLOWLY DECREASING THROUGH THE NIGHT AS THE COLD AIR CONTINUES TO  
ADVECT OVER THE WATERS. WILL HOLD ONTO THE GALE WATCH UNTIL MORE  
CONFIDENCE CAN BE RESOLVED. FLOW THEN TURNS TO THE SOUTHWEST ON  
FRIDAY AS A WARM FRONT LIFTS NORTH THROUGH THE AREA. THIS WILL AGAIN  
INTRODUCE GUSTY WINDS ACROSS THE EASTERN LAKES.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LAKE HURON...GALE WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY EVENING FOR  
LHZ362-363.  
 
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

 
 
AVIATION.....SC  
SHORT TERM...JVC  
LONG TERM....DRK/MM  
MARINE.......DRK  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).  
 
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