591 FXUS63 KDTX 200358 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1158 PM EDT WED MAR 19 2014 .AVIATION... //DISCUSSION... LOW PRESSURE CONTINUES TO TRACK AWAY FROM THE CENTRAL GREAT LAKES OVERNIGHT. IN ITS WAKE MVFR CIGS RULE THE TAF SITES WITH SOME POST COLD FRONTAL SNOW SHOWERS TO THE WEST AND NORTH. UPSTREAM OBSERVATIONS INDICATE THE SNOW SHOWERS ARE NOT MAKING MUCH INROADS INLAND...THEREFORE WILL CONTINUE TO LEAVE OUT OF THE TAFS WITH THIS ISSUANCE. CONTINUED FLOW OFF THE GREAT LAKES WILL KEEP CEILINGS AROUND 3000 FT DURING THE DAYTIME HOURS UNTIL RIDGING CLEARS OUT THE CLOUDS THURSDAY EVENING. //DTW THRESHOLD THREATS... * HIGH CONFIDENCE IN CEILINGS BELOW 5KFT THROUGH THURSDAY. && .PREV DISCUSSION...ISSUED 354 PM EDT WED MAR 19 2014 SHORT TERM...THROUGH TONIGHT A LOW PRESSURE SYSTEM CENTERED DIRECTLY OVER LOWER MI WILL RESULT IN A VARIETY OF WEATHER CONDITIONS THROUGH THE OVERNIGHT. ALL OF SE MI IS IN THE WARM SECTOR WITH GOOD SW FLOW YIELDING TEMPS UP TO 50 DEGREES. THE COLD FRONT ASSOCIATED WITH THE LOW IS NOW JUST COMING ONSHORE OVER WESTERN MI AND WILL MOVE THROUGH THE AREA THIS EVENING. A PREFRONTAL BAND OF RAIN WILL WORK THROUGH SE MI THIS AFTERNOON BEFORE CAA USHERS SLIGHTLY DRIER AIR IN TO THE AREA. CURRENT DEW POINTS ARE IMPRESSIVELY IN THE LOW TO MID 40S WHICH HAS LEAD TO PATCHY FOG AT TIMES. SCATTERED SHOWERS WILL PERSIST INTO THE OVERNIGHT BEFORE A TROWEL AXIS WRAPS AROUND THE DEPARTING LOW BRINGING ONE MORE SHOT OF PRECIP..THIS TIME IN THE FORM OF SNOW AS THE CAA WILL LOWER THE TEMPS BELOW FREEZING BY THIS TIME. NEITHER MOISTURE AMOUNTS OR FORCING ARE OVERLY IMPRESSIVE WITHIN THE TROWEL SO THINKING UP TO AN INCH WILL BE POSSIBLE ACROSS THE THUMB AND SAGINAW VALLEY WITH AMOUNTS DECREASING RAPIDLY AS YOU HEAD SOUTH. THE OTHER ISSUE TO NOTE IN THIS FORECAST IS THE WIND. THE ATMOSPHERE IS WELL MIXED JUST ABOVE THE INVERSION...AROUND 950MB...BUT WE HAVE JUST BARELY BEEN ABLE TO TAP INTO THAT FOR A FEW GUSTS TIMES AFTERNOON AROUND 25 KNOTS. AS THE LOW WORKS NE...A TIGHTER PRESSURE GRADIENT WILL SLIDE OVER THE AREA ALONG WITH A STRONG SUBSIDENCE REGION BEHIND THE COLD FRONT. THIS COMBINATION WILL BRING DOWN SOME HIGHER WINDS WHICH WILL GUST UP TO AROUND 35 MPH AROUND 00Z. LOOKING AT THE GEOSTROPHIC WIND IN THE LOWEST 50 TO 100MB AND WIND SPEEDS AROUND THE INVERSION...THE HIGHEST WIND SPEEDS SHOULD ONLY LAST A FEW HOURS...BUT WINDS WILL STAY AROUND 10 TO 15 MPH THOUGH THE REST OF THE NIGHT. LONG TERM... THE LONG TERM PERIOD WILL PICK UP ON THURSDAY MORNING WITH THE THERMAL TROUGH SETTLED DIRECTLY OVER THE AREA. WITH 850MB TEMPERATURES IN THE NEIGHBORHOOD OF -10C AND LIGHT COLD ADVECTION PERSISTING THROUGH THE DAY, TEMPERATURES WILL STRUGGLE TO REBOUND MUCH FROM EARLY MORNING LOWS AROUND 30 DEGREES. THIS WILL ESPECIALLY BE THE CASE GIVEN THAT STEEP SURFACE-BASED LAPSE RATES AND RESIDUAL SYSTEM MOISTURE ARE EXPECTED CONTRIBUTE TO AN EXTENSIVE LAYER OF STRATOCU THAT WILL LINGER FOR MUCH OF THE DAY. LATE AFTERNOON HIGHS NEAR 40 MAY STILL BE ACHIEVABLE THANKS TO LATE CLEARING AS HIGH PRESSURE ADVANCES INTO THE REGION FROM THE WEST, BUT OTHERWISE LOOKING AT A DAY MAINLY CHARACTERIZED MAINLY TEMPERATURES IN THE MID 30S. AFOREMENTIONED RIDGE OF HIGH PRESSURE WILL REMAIN PROGRESSIVE GIVEN THE RELATIVELY QUICK-MOVING/ZONAL UPPER FLOW AND IS FORECAST TO TRANSIT SOUTHEAST MICHIGAN ON THURSDAY NIGHT. SKIES SHOULD BE LARGELY CLEAR FOR MOST OF THE NIGHT JUDGING FROM MID/UPPER LEVEL MODEL RH FIELDS AND THE EXPECTATION FOR LATE CLEARING OF BOUNDARY LAYER CLOUDS. IN ADDITION, THE SURFACE PRESSURE GRADIENT SHOULD FALL OFF AND ALLOW FOR QUICK DECOUPLING AFTER SUNSET. LOWERED TEMPS BY A FEW DEGREES ACROSS THE BOARD, BUT THE POTENTIAL FOR A SNEAKY COLD NIGHT MAY WARRANT AN ADDITIONAL DOWNWARD ADJUSTMENT IN FUTURE FORECAST CYCLES. SHORTWAVE COMING ONSHORE OVER THE PACNW TODAY WILL EVENTUALLY UNDERGO SOME DEGREE OF PHASING WITH THE TRAILING SHEAR MAX CURRENTLY DEVELOPING OVER THE NORTHEAST PACIFIC OCEAN. THE NWP HAVE COME INTO PRETTY GOOD AGREEMENT CONSIDERING THE SMALL SPATIAL FOOTPRINT OF THESE TWO PRIMARY FEATURES. THE GENERAL CONSENSUS APPEARS TO BE ONE OF ONLY A PARTIAL PHASING OVER THE WESTERN GREAT LAKES AND A MORE NORTHWARD DISPLACEMENT OF FORCING. THE GEM IS NOW ON THE FAR NORTH END OF THE MODEL ENVELOPE WITH THE ECMWF AND GFS FURTHER SOUTH...THOUGH IT IS DIFFICULT TO ARGUE FOR MORE THAN 1-3" NORTH OF I-69 FROM ANY SOLUTION, ESPECIALLY GIVEN THE POTENTIAL FOR WARM SOUTHERLY FLOW IN ADVANCE OF THE LOW TO SEND HIGHS WELL INTO 40S. LEFT A GENERAL MENTION OF RAIN/SNOW MIX AS MOST LOCATIONS WILL PROBABLY SEE SOME LINGERING SNOW SHOWERS FRIDAY NIGHT AS COLDER AIR WRAPS BACK INTO THE AREA, BUT TOOK ANOTHER WHACK AT ACCUMS LEAVING 1-3" FROM THE SAGINAW VALLEY TO THE THUMB AND INCH OR LESS SOUTH. MAIN STORY IN THE EXTENDED WILL BE THE UNSEASONABLY COLD TEMPERATURES. LOW LEVEL COLD AIR ADVECTION WILL ENSUE EARLY SATURDAY IN THE WAKE OF FRIDAY NIGHT'S SYSTEM BEFORE ADVECTION BECOMES MORE NEUTRAL LATER IN THE DAY. THE COLD ADVECTION WILL BECOME REINVIGORATED SATURDAY NIGHT INTO SUNDAY AS SHORTWAVE ENERGY MOVES INTO THE GREAT LAKES...POSSIBLY TOUCHING OFF A FEW LOW-IMPACT LIGHT SNOW SHOWERS. FROM SUNDAY ON...GLOBAL MODELS AND THEIR ENSEMBLE MEMBERS ARE IN VERY GOOD AGREEMENT ON AN EXPANSIVE LONGWAVE UPPER TROUGH BECOMING ENTRENCHED OVER THE EASTERN TWO THIRDS OF THE CONUS. H85 TEMPS ARE ADVERTISED TO STAY BELOW -12C...AND REACH AS LOW AS THE -16C TO -20C RANGE OVER SE MI...WHICH IS APPROACHING 2 SD BELOW NORMAL. SURFACE HIGH PRESSURE WILL PROVIDE GENERALLY DRY CONDITIONS...THOUGH PERIODIC LIGHT SNOW SHOWERS CANNOT BE RULED OUT WITH QUICK SHORTWAVES EMBEDDED WITHIN THE LONGWAVE TROUGH. MARINE... WESTERLY GALES ARE STILL EXPECTED TO DEVELOP OVER NORTHERN LAKE HURON LATE TONIGHT INTO THURSDAY AS LOW PRESSURE LIFTS OUT OF THE REGION. REMAINING LOCATIONS WILL SEE SEVERAL HOURS OF NEAR GALES BEGINNING WITH STRENGTHENING SOUTHERLY FLOW THIS EVENING BEFORE A TRANSITION TO WESTERLY LATE. WINDS WILL SUBSIDE LATE THURSDAY EVENING AS HIGH PRESSURE BUILDS ACROSS THE GREAT LAKES. GUSTY WINDS WILL RETURN ON SATURDAY AS COLDER AIR RETURNS THE AREA IN THE WAKE OF ANOTHER LOW PRESSURE SYSTEM. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON... GALE WARNING...LHZ361-LHZ362...FROM 4 AM THURSDAY TO 6 PM THURSDAY. BRISK WIND ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON INCLUDING SAGINAW BAY...UNTIL 8 PM THURSDAY. LAKE ST CLAIR... BRISK WIND ADVISORY...UNTIL 8 PM THURSDAY. MI WATERS OF LAKE ERIE... BRISK WIND ADVISORY...UNTIL 8 PM THURSDAY. && $$ AVIATION.....KURIMSKI SHORT TERM...DRK LONG TERM....JVC/DT MARINE.......JVC YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).