Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 281940 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 240 PM EST FRI NOV 28 2014 .SHORT TERM...THIS AFTERNOON AND TONIGHT FORECAST HAS PLAYED OUT PRETTY MUCH AS EXPECTED THUS FAR AS DRIER AIR FROM 850-600MB HAS QUELLED LIGHT SNOW SHOWERS TO THIS POINT. RADAR TRENDS DO SUGGEST THAT THIS LAYER IS GRADUALLY SATURATING AND VARIOUS ENHANCED FGEN BANDS ARE BEGINNING TO BRING LIGHT SNOW INTO PORTIONS OF THE AREA. THIS UPTICK IN SNOW SHOWER ACTIVITY SHOULD PERSIST INTO THIS EVENING...PARTICULARLY FROM M 59 NORTH WHERE THE BREAK BETWEEN THIS INITIAL SURGE OF LIFT/MOISTURE AND THE NEXT PERIOD OF ENHANCED LIFT...THIS EVENING INTO TONIGHT...ASSOCIATED WITH STRONG WARM AIR ADVECTION AND LIFT FROM RIGHT ENTRANCE OF JET STREAK IS SHORTER. THIS IS SUPPORTED SO FAR BY REGIONAL RADAR LOOP FROM THE GREAT LAKES INTO THE UPPER MIDWEST AS THE TRAJECTORY OF NEW LIGHT SNOW DEVELOPMENT OVER MINNESOTA AND WISCONSIN SEEMS TO AIM MORE AT THE NORTHERN HALF OF THE CWA. WILL MAINTAIN THE SAME GENERAL SNOWFALL TOTALS FROM LATE TODAY INTO LATE TONIGHT WITH 1 TO 2 INCHES EXPECTED THRU THE MIDDLE OF THE CWA AND LESSER AMOUNTS SOUTH OF I 94. THERE STILL MAY BE LOCAL AMOUNTS APPROACHING 3 INCHES IN THE GENERAL VICINITY OF THE I 69 CORRIDOR...ESPECIALLY IF SOME LOCATIONS RECEIVE ON THE ORDER OF HALF AN INCH PRIOR TO 00Z. THE OTHER ASPECT OF THIS SYSTEM THAT NEEDS TO BE MENTIONED IS THE POTENTIAL FOR A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE FROM LATE TONIGHT. AS THE MAIN BAND(S) OF LIGHT SNOW END LATE TONIGHT...AND DEEPER MOISTURE IS STRIPPED AWAY...THERE WILL BE A 2-4 HOUR PERIOD WHERE SURFACE TEMPERATURES WILL HOVER IN THE 29-32F RANGE BEFORE THE PRECIPITATION SUBSIDES COMPLETELY. GIVEN THE FACT THAT SURFACES WILL BE WET AND/OR SNOW COVERED FROM OVERNIGHT LIGHT SNOW...DO NOT EXPECT THIS TO BE TOO BIG OF AN ISSUE AT THIS TIME. WILL REMAIN FOCUSED ON THE SNOW POTENTIAL MORE SO FOR THIS FORECAST PACKAGE...WITH THE ASSUMPTION THAT THE MAIN BANDS OF LIGHT PRECIPITATION REMAIN ALL OR MOSTLY SNOW LATE TONIGHT BEFORE TAPERING OFF QUICKLY EARLY SATURDAY MORNING. GIVEN THE FACT THAT SNOW ACCUMULATIONS OF 1 TO 2 INCHES WILL BE THE RULE OVER ROUGHLY A 15-18 HOUR TIME FRAME...NO HEADLINE IS ANTICIPATED AT THIS TIME. && .LONG TERM... WING OF ISENTROPIC ASCENT SUPPORTING OVERNIGHT SNOWFALL WILL EXIT THE CWA TO THE NORTHEAST AROUND SUNRISE SATURDAY MORNING. LEE CYCLONE POSITIONED OVER THE FAR NORTHERN GREAT PLAINS IS THEN FORECAST TO LIFT NORTH OF LAKE SUPERIOR TOWARD JAMES BAY SATURDAY EVENING INTO SUNDAY AS THE UPPER WAVE OVER THE PACNW EJECTS ACROSS SOUTH-CENTRAL CANADA. THIS WILL RESULT IN THE ESTABLISHMENT OF MOIST RETURN FLOW OVER THE CENTRAL UNITED STATES AND A STOUT AXIS OF SUB- 1KM MOISTURE ADVECTION THAT WILL FOCUS ON SOUTHEAST MICHIGAN MIDDAY SATURDAY THROUGH MUCH OF SUNDAY. DESPITE DRY MID-LEVELS, ONGOING WARM ADVECTION WILL SUPPORT A BACKGROUND OF LIGHT ISENTROPIC ASCENT BENEATH A STRENGTHENING INVERSION AND ABUNDANT LOW-LEVEL MOISTURE. THIS WILL BE SUPPORTIVE OF A BROKEN COVERAGE OF SHOWERS OR PERHAPS AN EXTENDED PERIOD OF DRIZZLE SAT AFTN INTO SUNDAY. MOISTURE ADVECTION ALONE WILL FORCE SATURDAY`S HIGHS INTO THE UPPER 30S AS DEWPOINTS RISE. TEMPERATURES WILL FALL LITTLE, IF ANY, SATURDAY NIGHT AS PERSISTENT THETA-E ADVECTION CONTINUES AND TEMPERATURES ULTIMATELY RISE INTO THE UPPER 40S TO AROUND 50 BY DAYBREAK SUNDAY MORNING. THE COLD FRONT ASSOCIATED WITH THE AFOREMENTIONED CYCLONE PASSING WELL TO OUR NORTH WILL THEN TRANSIT THE AREA LATE SUNDAY WITH A CONTINUED SHOWER/DRIZZLE THREAT IN THE MEANTIME. HIGHS WILL BE SENSITIVE TO TIMING OF FROPA. LOW/MID 50S SEEM A SAFE BET FOR NOW. THIS REPRESENTS AN ECMWF/GEM WEIGHTED COMPROMISE FOR SUNDAY`S TEMPS, AS LESS CREDENCE WAS GIVEN TO THE OFT FAST GFS/NAM. FRONTAL PASSAGE WILL LARGELY BE DRY AS SYSTEM MOISTURE WILL BE MINIMAL, BUT THE STRENGTHENING UPPER JET CENTERED OVER THE GREAT LAKES MAY INDUCE JUST ENOUGH DEEPER FGEN WITHIN THE PRE- FRONTAL MOISTURE AXIS TO SQUEEZE OUT SOME PREFRONTAL SHOWERS OVER THE SOUTHERN CWA ON SUNDAY EVENING AS ADVERTISED BY THE 12Z NAM. STRONG COLD ADVECTION WILL CAUSE H85 TEMPS TO PLUMMET BACK TO - 10C BY 12Z MONDAY HELPING OVERNIGHT LOWS SUNDAY NIGHT FALL BACK INTO THE 20S. AS THE COLD FRONT EXITS THE REGION SUNDAY NIGHT...A STRONG 1044 MB HIGH PRESSURE SYSTEM BUILDING OVER THE AREA...WILL CONTINUE TO USHER IN COLD CANADIAN/ARCTIC AIR. THIS PATTERN IS EXPECTED TO HOLD THROUGH THE 7 DAY FORECAST PERIOD. TEMPERATURES WILL REMAIN BELOW NORMAL WITH LOW CHANCES FOR PRECIPITATION. && .MARINE... DEVELOPING MODERATE SOUTHERLY WINDS WILL BECOME FRESH AT TIMES SATURDAY THROUGH SATURDAY NIGHT WITH GUSTS OCCASIONALLY APPROACHING 30 KNOTS MAINLY OVER THE SOUTHERN LAKE HURON BASIN. WINDS WILL GRADUALLY VEER TO A MORE WESTERLY DIRECTION ON SUNDAY BEFORE RAMPING UP OUT OF THE NORTHWEST AS A COLD FRONT TRAVERSES THE WATERS SUNDAY EVENING. GUSTS TO NEAR-GALES OR WEAK GALES AND BUILDING WAVES ARE LIKELY BY SUNDAY NIGHT. && .AVIATION...ISSUED 1248 PM EST FRI NOV 28 2014 //DISCUSSION... INITIAL BANDS OF -SHSN WILL EVENTUALLY WORK INTO TERMINALS AS DRY LAYER BETWEEN H85-H6 SATURATES THIS AFTERNOON INTO THIS EVENING. GIVEN THE AMOUNT OF DRY AIR...EXPECT MOST OF THIS ACTIVITY TO REMAIN RATHER LIGHT. BETTER LIFT/MOISTURE THEN SPREAD BACK INTO AREA THIS EVENING INTO THE OVERNIGHT...SO -SN SHOULD BE PREVALENT IN THE 03Z- 09Z TIME FRAME OR SO...ESPECIALLY FROM KPTK NORTH. THE SOUTHERN EDGE OF THE MOST PERSISTENT ACTIVITY SHOULD SET UP VERY CLOSE TO THE I 94 TERMINALS TONIGHT. THIS ACTIVITY WILL PRETTY MUCH END LATE TONIGHT WITH LINGERING ACTIVITY CHANGING TO SPRINKLES/-DZ SATURDAY MORNING. THERE MAY BE A BRIEF PERIOD OF -FZDZ BEFORE TEMPERATURES WARM ABOVE FREEZING SATURDAY MORNING...BUT WITH WET AND/OR SNOW COVERED SURFACES...THIS SHOULD NOT BE A BIG ISSUE. EXPECT CIGS TO FALL TO MVFR/LOWER VFR WITH THIS ACTIVITY. FOR DTW...WHILE FLURRIES WILL BE POSSIBLE LATER THIS AFTERNOON...THE BETTER CHANCE OF -SN WILL COME AFTER 03Z AND PERSIST UNTIL PERHAPS 09Z. EXPECT MVFR CIGS/VSBYS BY TONIGHT. //DTW THRESHOLD THREATS... * HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THIS EVENING INTO EARLY SATURDAY MORNING. * HIGH CONFIDENCE PRECIPITATION TYPE WILL BE ALL SNOW THROUGH 09Z SATURDAY...WITH LOWER CONFIDENCE THEREAFTER AS PRECIPITATION TAPERS OFF. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MICHIGAN WATERS OF LAKE ERIE...NONE. && $$ SHORT TERM...DG LONG TERM....JVC/DE MARINE.......JVC AVIATION.....DG YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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