000 FXUS63 KDTX 190857 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 357 AM EST TUE FEB 19 2008 .SHORT TERM...TODAY SNOW SHOWERS WILL CONTINUE THROUGH THE MORNING HOURS ACROSS A GOOD MAJORITY OF SOUTHEAST LOWER MICHIGAN...AS AN UPPER LEVEL SHORTWAVE CURRENTLY NEAR CHICAGO RACES EAST THROUGH THE AREA BETWEEN 12-15Z. IN ADDITION...SFC/THERMAL TROUGH ELONGATED FROM WEST TO EAST ROUGHLY BETWEEN SAGINAW AND HOUGHTON LAKE WILL CONTINUE TO SUPPLY AN ENHANCED CONVERGENT ZONE TO FOCUS HEAVIER SNOW SHOWER ACTIVITY PRIMARILY FOR THE SAGINAW VALLEY AND THUMB REGION. WILL TAPER POPS ACCORDINGLY FOR THIS MORNING FROM CATEGORICAL NORTH OF I-69...TO SCATTERED TOWARD THE OHIO BORDER. BASED ON CURRENT RADAR TRENDS AND VISIBILITY...WILL MAINTAIN ADDITIONAL ACCUMULATIONS UP AN INCH FOR THE SAGINAW VALLEY AND THUMB REGION...WITH THE BULK OF THIS FALLING PRIOR TO 15Z. ELSEWHERE...ADDITIONAL ACCUMS LOOK TO BE MINOR. WEAK SHORTWAVE RIDGING/SUBSIDENCE IN THE WAKE OF THE SHORTWAVE WILL BRING A RAPID DIMINISHING TREND TO THE ACTIVITY THIS AFTERNOON... WITH ANY ADDITIONAL -SHSN/FLURRIES COMING VIA ANY UPSTREAM LAKE EFFECT DEVELOPMENT UNDER A PERSISTENT WESTERLY GRADIENT. THIS GRADIENT WILL REMAIN STRONG...WITH A TIGHTENING PRESSURE FIELD AND WEAK COLD AIR ADVECTION CONTRIBUTING TO OCCASIONAL GUSTS OVER 25 MPH. THIS CERTAINLY WILL MAKE FOR A RAW DAY...AS TEMPERATURES STRUGGLE TO REACH MUCH ABOVE 20F...LEADING TO WIND CHILL READINGS IN THE SINGLE DIGITS THROUGHOUT THE DAY. && .LONG TERM...TONIGHT THROUGH MONDAY MAIN ISSUE OF THE LONG TERM CENTERS ON WINTRY WEATHER IMPACTING SOUTHEASTERN MICHIGAN FOR MUCH OF THE WORKWEEK. THE PERIOD WILL BEGIN WITH MODEST DEAMPLIFICATION OF THE FULL LATITUDE TROUGH THAT IS CURRENTLY IN PLACE ACROSS THE EASTERN HALF OF THE CONTINENTAL UNITED STATES. THIS WEAKENING TREND...LARGELY RESULTS FROM THE LIFTING OF A +160 KNOT JET STREAK ALIGNED OVER A LARGE PORTION OF THE ATLANTIC SEABOARD. THIS HAS MAJOR IMPLICATIONS FOR OUR WEATHER TONIGHT SINCE THE VIGOROUS/COMPACT VORTICITY MAXIMUM NOW DROPPING SOUTH THROUGH MANITOBA/ONTARIO DRAMATICALLY SHEARS OUT PRIOR TO ARRIVAL. LATEST MODEL GUIDANCE CONTINUES TO SUGGEST A SOUTHERN NEAR MISS OF THE ASSOCIATED SURFACE REFLECTION AND BAROCLINIC INSTABILITY. IN ADDITION...THE BEST COLLOCATION OF DEEPER FRONTOGENETIC FORCING AND THETA E RIDGING SLIDES THROUGH NORTHERN INDIANA/OHIO. THERMODYNAMICS REMAIN UNSPECTACULAR OVERNIGHT...ALTHOUGH THERE IS A BRIEF PERIOD OF SATURATION THROUGH 600MB AND STEEPER LAPSE RATES. BOTTOM LINE...LOOKING AT CHANCE POPS THROUGHOUT THE CWA AFTER 6Z WITH GREATEST LIKELIHOOD ACROSS THE FAR SOUTH. ACCUMULATIONS OF LESS THAN ONE INCH WILL BE POSSIBLE SOUTH OF I 96...WITH LITTLE TO NO ACCUMS EXPECTED ACROSS THE NORTH. WITH THE SYNOPTIC SUPPORT FOR OPTICALLY THICKER CLOUDS...HAVE NUDGED TEMPERATURES UPWARD A COUPLE OF DEGREES. LOWS WILL RANGE FROM SINGLE DIGITS ABOVE ZERO ACROSS THE NORTH TO AROUND 10 ABOVE ACROSS THE SOUTH. THERE WILL BE ONE LAST DAY FOR POTENTIAL LAKE EFFECT SNOWS ON WEDNESDAY AS WESTERN GREAT LAKES AGGREGATE TROUGHING HAS ONE LAST GASP. IT NEEDS TO BE STRESSED MOST AREAS WILL NOT ACCUMULATE ANYTHING AS WINDS QUICKLY TURN NORTHWEST BEHIND THE SECONDARY COLD SURGE/FRONTAL PASSAGE. CONSEQUENTLY DRIER AIR BECOMES MORE ESTABLISHED THROUGHOUT THE DAY WITH A LOWERING OF THE SUBSIDENCE INVERSION AND BUILDING SURFACE HIGH PRESSURE. NOTE...THE NAM12 IS SUGGESTING THAT A LAKE HURON MESOLOW OR MATURE MID LAKE HURON BAND MAKES LANDFALL ACROSS THE EASTERN THUMB COUNTIES AS SURFACE WINDS RAPIDLY VEER. ATTM...WILL JUST RAISE POPS TO HIGH CHANCE FOR THAT AREA...GIVEN THE LOW CONFIDENCE AND SENSITIVITY. HIGH PRESSURE WEDNESDAY NIGHT WILL ALLOW TEMPERATURES TO TANK...RANGING FROM ZERO ACROSS THE NORTH TO THE UPPER SINGLE DIGITS ABOVE SOUTH. THERE MAY BE ENOUGH OF A GRADIENT WIND TO GENERATE WIND CHILLS OF -10 TO -15 DEGREES NORTH OF M 59 WEDNESDAY NIGHT/THURSDAY MORNING. UNCERTAINTY STILL EXISTS FOR FRIDAY WITH GUIDANCE ALL OVER THE BOARD IN REGARDS TO RETURN FLOW AND PHASING OF SIGNIFICANT SHORTWAVES. WHILE ALL MODELS SUGGEST THE MAJORITY OF THE ENERGY MISSES SOUTHEASTERN MICHIGAN TO THE SOUTH...EVIDENCE IS MOUNTING THAT ENOUGH MOISTURE WILL BRUSH THE SOUTH. THE 00UTC CANADIAN IS FAR AND AWAY THE MOST BULLISH ON SNOWFALL WHILE THE NAM BRINGS THE PRECIPITATION THROUGH THE TENNESSEE RIVER VALLEY. WILL SAY THERE IS ONE THING GOING ON HERE THAT HASN/T HAPPENED THIS WINTER...PRECEDING LARGE SURFACE HIGH PRESSURE PASSING THROUGH THE GREAT LAKES UNABATED. WITH THE EXTREMELY LOW CONFIDENCE...WILL LEAVE POPS ALONE. && .MARINE... TIGHTENING PRESSURE GRADIENT AND WEAK COLD AIR ADVECTION IN THE WAKE OF AN UPPER LEVEL DISTURBANCE WILL MAINTAIN GUSTY WEST WINDS TODAY. AS A RESULT...A BRISK WIND ADVISORY WILL REMAIN IN EFFECT FOR ALL NEARSHORE AREAS TODAY...WITH GUSTS OF 25 TO 30 KNOTS COMMON THROUGH THIS EVENING. WINDS WILL DIMINISH TONIGHT AS HIGH PRESSURE BRIEFLY NOSES INTO THE SOUTHERN GREAT LAKES. SURFACE TROUGH DROPPING ACROSS LAKE HURON WILL ALLOW WINDS TO SHIFT TOWARD THE NORTH AND INCREASE ON WEDNESDAY...WITH GUSTS UP TO 30 KNOTS ON THE OPEN WATERS. LARGE AREA OF HIGH PRESSURE WILL THEN MOVE ACROSS THE GREAT LAKE BY THURSDAY...MAINTAINING WEAKER WINDS DURING THIS TIME. && .PREV DISCUSSION...ISSUED 1154 PM EST MON FEB 18 2008 AVIATION... PERIODIC MVFR AND IFR CEILINGS AND VISIBILITIES IN SNOW SHOWERS WILL PERSIST THROUGH THE EARLY MORNING HOURS DUE TO THE COMBINATION OF A MID LEVEL SHORT WAVE MOVING ACROSS SOUTHERN MICHIGAN...A SURFACE TROUGH DROPPING DOWN FROM THE NORTH...AND INSTABILITY OFF LAKE MICHIGAN. THROUGH 09Z...THE BULK OF THE SNOW SHOWERS ACTIVITY WILL BE FOCUSED NEAR MBS. THE SURFACE TROUGH WILL SLIDE THROUGH FNT AROUND 12Z...THEN BASICALLY WASH OUT BY 15Z AS IT APPROACHES DETROIT. CONDITIONS WILL IMPROVE AFTER 15Z AS THE UPPER WAVE MOVES EAST ALLOWING LARGE SCALE SUBSIDENCE TO ENVELOP SOUTHEAST MICHIGAN. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON... BRISK WIND ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON...UNTIL 7 PM TUESDAY. LAKE ST CLAIR... BRISK WIND ADVISORY...UNTIL 7 PM TUESDAY. MI WATERS OF LAKE ERIE... BRISK WIND ADVISORY...UNTIL 7 PM TUESDAY. && $$ SHORT TERM...MR LONG TERM....CB MARINE.......MR AVIATION.....SC YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).