658 FXUS63 KDTX 190500 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 100 AM EDT TUE MAR 19 2013 .AVIATION... //DISCUSSION... SCATTERED SNOW SHOWER OR FLURRIES WILL ACCOMPANY A RUSH OF COLDER AIR INTO SE MICHIGAN DURING THE EARLY MORNING. THIS WILL SUPPORT MVFR CONDITIONS IN ONE OR BOTH CEILING AND VISIBILITY THROUGH THE DAY BUT WITH STEADILY INCREASING WIND GUSTS AS DAYTIME HEATING DEEPENS THE BOUNDARY LAYER. THE AIR WILL BE TOO COLD TO NOT PICK UP SOME STRATOCU AND SNOW SHOWERS FROM LAKE MICHIGAN, BUT THESE WILL TEND TO BE FOCUSED FRONT FNT NORTHWARD IN THIS WIND REGIME. THE BOUNDARY LAYER WILL THEN REMAIN WELL MIXED ENOUGH FOR GUSTS TO PERSIST DURING TUESDAY NIGHT BUT NOT ENOUGH TO SCOUR STUBBORN MVFR CEILING. FOR DTW... INCREASING SOUTHWEST TO WEST WIND, WHILE NOT AN EXCESSIVE CROSS WIND COMPONENT, WILL BE THE PRIMARY AVIATION CONCERN DURING THE EARLY MORNING THROUGH TUESDAY NIGHT. GUSTS TO 35 KNOTS LOOK EASILY WITHIN REACH AS DAYTIME SURFACE HEATING GETS UNDERWAY BY AFTERNOON. //DTW THRESHOLD THREATS... * HIGH CONFIDENCE IN CEILING BELOW 5000 FEET FOR MOST OF TONIGHT AND THROUGH TUESDAY NIGHT. && .PREV DISCUSSION...ISSUED 945 PM EDT MON MAR 18 2013 UPDATE... THE LATEST UPDATE BROUGHT THE FORECAST DOWN FROM EVENING CATEGORICAL POPS NOW THAT THE OCCLUDED FRONT IS SWEEPING THE MAIN MOISTURE AXIS OUT OF SE MICHIGAN. THAT WILL OPEN THE DOOR ON INCREASING SOUTHWEST WIND AND FALLING TEMPERATURES FOR THE OVERNIGHT HOURS. GUSTS AROUND 35 KNOTS WILL BE POSSIBLE WITH THE ONSET OF STRONG COLD ADVECTION DURING THE EARLY MORNING HOURS, BUT JUST FOR AN HOUR OR TWO WITH THE MAIN ISALLOBARIC PUSH, AND THEN SETTLE INTO THE 25-30 KNOT RANGE THROUGH THE DAYLIGHT HOURS OF THE MORNING. UPSTREAM OBSERVATIONS OF GUSTS IN THE MID 30 KNOT RANGE ARE MOST COMMON WITH A FEW HIGHER GUSTS AROUND THE SOUTH END OF LAKE MICHIGAN AT STATIONS WITH BOTH HIGHER ELEVATION AND EXPOSURE TO OPEN WATER. OTHERWISE, THE SURFACE ISALLOBARIC GRADIENT LEADING IN A 3-4 MB 3-HOUR PRESSURE RISE, AND TRIALING DOWNWARD MOMENTUM TRANSPORT ASSOCIATED WITH COLD ADVECTION, DO NOT SUPPORT A WIND HEADLINE AT THIS POINT. PREV DISCUSSION...ISSUED 357 PM EDT MON MAR 18 2013 SHORT TERM...THROUGH TONIGHT THE NEGATIVELY TILTED UPPER LEVEL TROUGH IS NOW OVER THE WESTERN GREAT LAKES PER LATEST WATER VAPOR IMAGERY WITH ASSOCIATED SFC LOW APPROACHING WESTERN LAKE SUPERIOR. A SECONDARY/WEAKER MID LEVEL WAVE AND SFC REFLECTION OVER THE OHIO VALLEY WILL LIFT NE ACROSS EXTREME SE MI THIS EVENING. A PAIR OF FRONTAL BOUNDARIES WILL PASS THROUGH THE AREA THROUGH TONIGHT WITH THESE SYSTEMS. THE FIRST WILL LIFT NORTHEASTWARD THIS EVENING AS PSEUDO WARM FRONT WITH A COLD FRONT SWEEPING THOUGH BETWEEN 03Z-06Z. FORCING WILL BE SOMEWHAT FAVORABLE THIS EVENING AS THE FIRST FRONT LIFTS NORTH WITH A REGION OF ISENTROPIC ACCENT BETWEEN 295-305K COINCIDENT WITH WEAK MID LEVEL DIFFLUENCE AND BROAD LIFT FROM THE BASE OF THE TROUGH SWINGING THROUGH. THE BULK OF THE PRECIPITATION WILL LIKELY STAY TIED CLOSER TO THE TROUGH ITSELF SWINGING THROUGH NORTHERN MI AND EXTENDING SOUTH TOWARD SAGINAW. OBSERVATIONS UPSTREAM SHOW SOME MODERATE SNOWFALL AND VSBYS DROPPING UNDER 1SM FOR A FEW HOURS. THIS WILL HAVE A CHANCE TO BRING SOME ACCUMULATIONS TO AT LEAST THE NORTHERN HALF OF THE CWA THROUGH THE NIGHT. TOTAL ACCUMULATIONS OF 1 TO 2 INCHES CAN BE EXPECTED FURTHER NORTH AND TAPERING OFF QUICKLY SOUTHWARD TOWARD FNT AND BEYOND AS THERE DOES NOT APPEAR TO BE MUCH QPF AT ALL TO WORK WITH MID LEVEL DRY AIR WORKING INTO THE REGION. SOME LINGERING LIGHT DZ/RA WILL HOLD INTO THE EVENING BEFORE THE COLD FRONT PASSES AND COLD WESTERLY FLOW ADVANCES INTO THE AREA. WINDS WILL VEER FROM EAST...TO SOUTH...AND FINALLY WEST TONIGHT AND BECOME GUSTY. THE COLD FRONT WILL ALSO CHANGE PTYPE BACK TO ALL SNOW AS 850MB TEMPS FALL RAPIDLY TOWARD -15C. LONG TERM... TUESDAY THROUGH SUNDAY MID LEVEL TROUGH AXIS PIVOTING THROUGH THE GREAT LAKES TONIGHT WILL CLOSE OFF NORTH OF LAKE SUPERIOR ON TUESDAY AS ADDITIONAL ENERGY FUNNELS INTO THE FALLING HEIGHT FIELD. THIS MASS ADJUSTMENT WILL COINCIDE WITH THE DEVELOPMENT OF ANOTHER DEEP CLOSED MID LEVEL CIRCULATION OFF THE NEW ENGLAND COAST. THIS EVOLUTION WILL DRIVE A FIRM TRANSITION TOWARD A HIGH AMPLITUDE BLOCKING PATTERN THROUGHOUT THE NORTHERN CONUS/SOUTHERN CANADA...WITH THE GREAT LAKES EFFECTIVELY LOCKED INTO A PROLONGED STRETCH OF COLD CONDITIONS EMBEDDED WITHIN THE EXTENSIVE LOWER HEIGHT FIELD AND PREVAILING NORTHWEST FLOW. INITIAL COLD AIR ADVECTION COMMENCES TONIGHT...WITH A SECONDARY AND STRONGER SURGE OF COLD AIR THEN ACCOMPANYING THE PASSAGE OF A SHORTWAVE ROTATING THROUGH THE MEAN TROUGH BASE EARLY TUESDAY. 850 MB TEMPERATURES ARE EXPECTED TO DROP INTO THE -14 TO -16C RANGE BY AFTERNOON. GIVEN LIMITED PROSPECTS FOR ANY REAL DIURNAL HEATING CONTRIBUTION UNDER AN EXTENSIVE STRATOCU DECK...THE STRENGTH OF THIS AIRMASS WILL ENSURE THE TEMPERATURE RECOVERY IS MINIMAL WITH READINGS HOLDING MAINLY IN THE MID-UPPER 20S. IN ADDITION...SFC CYCLOGENESIS ONGOING TO THE NORTH WILL MAINTAIN A TIGHT POST-FRONTAL WEST-SOUTHWEST PRESSURE GRADIENT LOCALLY ON TUESDAY. THIS COMBINED WITH A RELATIVELY DEEP MIXED LAYER SUPPORTED BY THE COLD AIR ADVECTION AND STEEP LAPSE RATES WILL BRING WINDY CONDITIONS THROUGHOUT THE DAY. LOOKING AT A RAW DAY...WITH THIS WIND FIELD SUPPORTING PEAK GUSTS IN THE 40 MPH RANGE...PERHAPS MARGINALLY APPROACHING LOW END WIND ADVISORY CONDITIONS ACROSS SOUTHERN SECTIONS LATE IN THE DAY. THE COLD CYCLONIC FLOW AND SUPPORTIVE MOISTURE DEPTH...AIDED BY SOME DEGREE OF MOISTURE FLUX OFF THE UPSTREAM LAKES...WILL SUPPORT THE DEVELOPMENT OF NUMEROUS SNOW SHOWERS THROUGH THE DIURNAL HEATING CYCLE. AN AREA OF MORE PERSISTENT CONVERGENCE AND MOISTURE TRANSPORT WILL TEND TO ALIGN BETWEEN M-59 AND SAGINAW VALLEY WITHIN THE PREVAILING WEST- SOUTHWEST GRADIENT. THE GREATEST POTENTIAL FOR SOME VERY LOCALIZED HIGHER ACCUMULATION TOTALS /INCH RANGE/ WILL EXIST WITHIN THIS CORRIDOR...ALTHOUGH ALL LOCALES WILL BE SUSCEPTIBLE TO AT LEAST A LIGHT COATING SHOULD A FEW HEAVIER BURSTS EMERGE. CLOSED LOW OVER LAKE SUPERIOR WILL PIVOT THROUGH SE MICHIGAN AS TWO SEPARATE FRAGMENTED PIECES WEDNESDAY AND THURSDAY. THIS WILL YIELD ADDITIONAL REINFORCING SURGES OF COLD AIR /850 TEMPS HOLD IN THE NEGATIVE MID TEENS/...ENSURING TEMPERATURES REMAIN WELL BELOW NORMAL THROUGH THIS TIME. HIGHS NEAR TO BELOW FREEZING EACH DAY. AN ALREADY SUPPORTIVE BACKGROUND ENVIRONMENT FOR SNOW SHOWER DEVELOPMENT WILL RECEIVE AN ADDED BOOST ON WEDNESDAY VIA THE PASSAGE OF THE LEAD AND STRONGER PV ANOMALY COINCIDENT WITH THE DIURNAL COMPONENT. STRONGEST ASCENT/CVA ATTACHED TO THE WAVE WILL EXIST TOWARD THE NORTH...LENDING SUPPORT FOR GREATER COVERAGE AND MINOR ACCUMULATION POTENTIAL ALONG/NORTH OF THE M-59 CORRIDOR. LITTLE VARIATION FROM THIS PATTERN IS EXPECTED RIGHT THROUGH THE END OF THE WEEK...AND POSSIBLY INTO NEXT WEEKEND...AS THE WESTERN EXTENSION OF THE SOUTHEAST CANADIAN CLOSED LOW MAINTAINS A POSITION ACROSS THE GREAT LAKES. ANY SLIGHT MODERATION IN TEMPERATURES THROUGH THIS TIME WILL COME VIA THE GRADUAL INCREASE IN UPPER HEIGHTS AND PERHAPS A GREATER DEGREE OF INSOLATION AS A DRYING NORTH-NORTHEAST FLOW WORKS TOWARD SCOURING OUT THE STRATUS. REGARDLESS...PATTERN FAVORS THE MAINTENANCE OF A TEMPERATURE FIELD THAT SIDES ON THE COOLER END OF NORMAL FOR THE 3RD WEEK IN MARCH. MARINE... A PAIR OF LOW PRESSURE SYSTEMS TO OUR SOUTH AND WEST ADVANCING INTO THE GREAT LAKES HAS TIGHTENED THE PRESSURE GRADIENT ACROSS NORTHERN LAKE HURON AS IT RUNS UP AGAINST A STRONG AREA OF HIGH PRESSURE OVER QUEBEC. COLD AIR ALOFT WITH A FAVORABLE FETCH NORTH OF THE TROUGH CONNECTING THESE TWO SYSTEMS WILL PRODUCE GALE FORCE WINDS ACROSS NORTHERN LAKE HURON THROUGH THIS EVENING UNTIL THE TROUGH PASSES AND WINDS RELAX TEMPORARILY. THE NORTHERN SFC LOW TRACKING ACROSS LAKE SUPERIOR WILL SWEEP A COLD FRONT THROUGH THE GREAT LAKES TONIGHT WHICH WILL VEER THE WINDS TO THE WSW. STRONG CAA AND A TIGHT GRADIENT WILL ALLOW GUSTY WESTERLY WINDS TO DEVELOP OVERNIGHT AND THROUGH TUESDAY WITH GALES FORCE GUSTS LIKELY FOR THE SOUTH HALF OF LAKE HURON...LAKE ST CLAIR...AND LAKE ERIE. WINDS WILL VEER TO THE NW TUESDAY NIGHT WHICH WILL ALLOWING GUSTS TO DROP BACK BELOW GALES BUT WILL STILL BE ELEVATED WITH GUSTS TO 30KTS POSSIBLE. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON... GALE WARNING...LHZ363-LHZ421-LHZ422-LHZ441-LHZ442-LHZ443-LHZ462- LHZ463-LHZ464...UNTIL 10 PM TUESDAY. LAKE ST CLAIR... GALE WARNING...UNTIL 10 PM TUESDAY. MI WATERS OF LAKE ERIE... GALE WARNING...UNTIL 10 PM TUESDAY. && $$ AVIATION.....BT UPDATE.......BT SHORT TERM...DRK LONG TERM....MR MARINE.......DRK YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).