Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 261100 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 600 AM EST WED NOV 26 2014 .AVIATION... //DISCUSSION... EXTENSIVE MVFR STRATUS DECK WILL HOLD FIRM FOR A GOOD PORTION OF THE DAY AS SURFACE RIDGING SHIFTS THROUGH. LOWER CONFIDENCE EXISTS ON THE POTENTIAL FOR BREAKS TO EMERGE WITHIN THIS DECK TODAY...AS DEVELOPING EASTERLY FLOW REINFORCES THE MOISTURE BELOW A DEEP INVERSION. THEREFORE WILL LEAN MORE PESSIMISTIC WITH MVFR TO LOWER VFR CEILINGS EXISTING THROUGH THE DAYLIGHT PERIOD. //DTW THRESHOLD THREATS... * HIGH CONFIDENCE IN CEILINGS BELOW 5000 FT THROUGH THIS AFTERNOON. && .PREV DISCUSSION...ISSUED 308 AM EST WED NOV 26 2014 SHORT TERM... TODAY AND TONIGHT WEAK SURFACE RIDGING TUCKED BENEATH LOWER AMPLITUDE MID LEVEL TROUGHING WILL DEFINE CONDITIONS ACROSS SE MICHIGAN TODAY. EXTENSIVE STRATUS CANOPY HOLDING FIRM EARLY THIS MORNING WITHIN THE LINGERING 925 MB THERMAL TROUGH...A SOLID DECK WITH A DEFINED CLEARING LINE JUST NOW EXITING NORTHEAST IL. RECENT TRENDS PROVIDE GROWING PESSIMISM TOWARD THE CLOUD FORECAST HEADING INTO TODAY. LINGERING THERMAL TROUGHING WILL MOVE LITTLE TODAY...SUGGESTING A STATIC THERMODYNAMIC PROFILE CARRYING A SOLID INVERSION LAYER. RECENT MODEL RH FIELDS RETAIN A HIGHER DEGREE OF MOISTURE JUST BENEATH THE INVERSION...SOME REINFORCEMENT OCCURRING BY THIS AFTERNOON/EVENING AS DEVELOPING LIGHT EAST/SOUTHEAST FLOW INTRODUCES A WEAK LAKE ERIE/HURON COMPONENT. A PERIOD OF INCREASING MOISTURE DEPTH MAY BECOME ADEQUATE TO SUPPORT SOME FLURRIES DURING THIS TIME. INCREASING CONVERGENCE ACROSS LAKE HURON AS GREATER LAKE AGGREGATE TROUGHING TAKES HOLD IS FORECAST TO DRIFT WESTWARD WITH TIME WITHIN THIS EASTERLY GRADIENT. POTENTIAL DOES EXIST FOR THIS FORCING TO BRIEFLY WORK INTO THE EASTERN THUMB THIS EVENING/TONIGHT. WORTHY OF A LOWER PROBABILITY MENTION OF SNOW SHOWERS AT THIS STAGE...MINOR ACCUMULATION. COLD RESIDENT AIRMASS VARIES LITTLE FROM THAT NOTED YESTERDAY... HIGHS THIS AFTERNOON ARRIVING IN THE LOWER AND MIDDLE 30S. LOWS TONIGHT MID 20S. LONG TERM... COLD (ZERO TO -20 F AT THE SURFACE) AND DRY AIR CLEARLY ON THE MOVE OVER SOUTH CENTRAL CANADA...AS STRONG UPPER WAVE DROPS SOUTHEAST THROUGH THE MIDWEST EARLY THIS MORNING. REALLY MODEST MOISTURE AXIS/850-700 MB THETA-RIDGE MOVING THROUGH SOUTHEAST MICHIGAN ON THANKSGIVING...WITH PW VALUES ONLY AROUND 0.25 INCH...AHEAD OF 500 MB SHORTWAVE TROUGH AXIS/UPPER LEVEL PV FILAMENT. 925-850 MB AVERAGE TEMP OF -8 C THROUGH MOST OF THE DAY...WITH THE COLDER AIR STILL LAGGING THROUGH 21Z...THUS EXPECT ACCUMULATING SNOW SHOWERS TO STRUGGLE TO MAKE IT OVER SOUTHEAST MICHIGAN. MORE FAVORABLE THERMAL PROFILES ARRIVE LATE IN THE DAY...BUT THEN THE CRASHING INVERSION HEIGHTS AND DRY NATURE OF ARCTIC AIRMASS OVERWHELMS THE CENTRAL GREAT LAKES...AND WOULD EXPECT ANY LINGERING LIGHT SNOW SHOWERS TO TAPER OFF TO FLURRIES OR END...AS GOOD DRYING SEEN OCCURRING AT THE 850 MB LEVEL. HOWEVER...WILL HAVE TO WATCH FOR BRIEF PERIOD OF NORTHERLY LOW LEVEL CONVERGENCE OFF LAKE HURON GLANCING NORTHEAST THUMB REGION EARLY THURSDAY EVENING WITH LIGHT SNOW ACCUMULATIONS BEFORE SURFACE RIDGE ARRIVES TOWARD FRIDAY MORNING. AIRMASS WILL BE VERY COLD...AS INDICATED BY THE NEGATIVE LOWER TEEN TEMPS AT 925 MB...BUT LACK OF SNOW COVER OVER THE CWA PRECLUDES GOING FOR SINGLE NUMBERS...AND WILL HOLD MINS IN THE TEENS. STILL LOOKING FOR SHEARED OUT UPPER WAVE/WARM ADVECTION PATTERN FOR FRIDAY...BUT THERE IS BARELY A BUCKLE IN THE 500 MB HEIGHT FIELDS...WITH THE UPPER WAVE WEAKENING/DAMPENING OUT. SO...CONFIDENCE IS NOT HIGH WE WILL BE ABLE TO SATURATE THE LOW LEVELS FROM THE DEPARTING ARCTIC AIRMASS COINCIDENT WITH THE MID LEVEL FORCING...AND WILL MAINTAIN JUST A CHANCE OF SNOW LATE FRIDAY INTO FRIDAY NIGHT. GOOD POST WARM FRONT SOUTHWEST FLOW OVER THE CENTRAL GREAT LAKES OVER THE WEEKEND...SUPPORTING SOLID WARMUP...AS TEMPERATURES APPROACH AT LEAST 50 DEGREES ON SUNDAY...WITH 00Z EURO 925 MB TEMPS (7-10 C) INDICATING THE POTENTIAL TO BE EVEN MILDER...DEPENDENT ON TIMING OF NEXT COLD FRONT AND ASSOCIATED SHOWERS. MARINE... VERY LIGHT WINDS AROUND TODAY AS HIGH PRESSURE WILL BE IN CONTROL. TOMORROW WILL BE A MUCH DIFFERENT STORY...AS AN ARCTIC FRONT SLIDES THROUGH THE CENTRAL GREAT LAKES DURING THE DAY. A BRIEF PERIOD OF GALE FORCE WINDS APPEARS LIKELY FOR THE CENTRAL PORTIONS OF LAKE HURON BY 00Z FRIDAY...BUT THE DURATION IS IN QUESTION...AND NOT SURE IF THEY WILL LAST 3 HOURS OR MORE. NONE-THE-LESS....ELECTED TO ISSUE A GALE WATCH TO COVER THIS POSSIBILITY. THE COLD AIRMASS STREAMING IN THURSDAY NIGHT WILL ALLOW FOR JUST A SLOW DECREASE IN THE NORTHWEST WINDS...AS THE WANING PRESSURE GRADIENT IS OFFSET BY THE INCREASING BOUNDARY LAYER DEPTH OVER THE OPEN LAKE. A WARM FRONT LIFTING INTO THE REGION FRIDAY WILL FLIP THE WINDS TO THE SOUTHWEST/SOUTH BY FRIDAY EVENING...WITH GUSTS OF 25 TO 30 KNOTS EXPECTED OVER MUCH OF LAKE HURON BEFORE MILDER AIR AND GREATER STABILITY ARRIVES OVER THE WEEKEND. && .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.....MR SHORT TERM...MR LONG TERM....SF MARINE.......SF YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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