000 FXUS63 KDTX 172035 AFDDTX SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 334 PM EST THU JAN 17 2002 THE KDTX AND KGRR RADAR LOOPS SHOWING LAKE EFFECT FLURRIES ACROSS SOUTHEAST MICHIGAN. THE WATER VAPOR LOOP SHOWS A SHORT WAVE TROUGH OVER MANITOBA AND NORTH DAKOTA. ANOTHER WEAKER SHORT WAVE CENTERED OVER WISCONSIN IS LENDING TO SOME AREAS OF -SN JUST UPSTREAM OF LAKE MICHIGAN. THE SHOWS THIS SHORT WAVE SHEARING OUT AS IT CROSSES LAKE MICHIGAN THIS EVENING. MAIN FORECAST CONCERN WILL BE WITH THE LAKE ENHANCEMENT AS THE MUCH STRONGER SHORT WAVE OVER MANITOBA MOVES INTO THE REGION LATE TONIGHT. THE 12Z MODELS ARE IN GOOD AGREEMENT WITH TIMING THE SHORT WAVE ACROSS REGION TONIGHT...THEN THE MODELS SHOW A FAIRLY BENIGN PATTERN INTO THE WEEKEND. TONIGHT...WESTERLY BOUNDARY LAYER WINDS OVER LAKE MICHIGAN WILL CONTINUE TO ADVECT LAKE STRATO CU AND SCT FLURRIES INTO SE MICHIGAN THIS EVENING. THE SHORT WAVE TROUGH OVER MANITOBA WILL QUICKLY MOVE INTO NORTHERN WI/WESTERN LAKE SUPERIOR BY 06Z...THEN PUSH EAST INTO WESTERN LAKE HURON AROUND 12Z. WEAK SYNOPTIC LIFT WILL THUS SPREAD ACROSS THE REGION BETWEEN 06Z AND 12Z AHEAD OF THE SHORT WAVE. QVECTOR ANALYSIS AND OMEGA FIELDS ARE NOT ALL THAT STRONG SINCE THE WAVE WEAKENS AS IT APPROACHES THE AREA WITH THE BEST FORCING NORTH OF THE TRI CITIES. FROM A SYNOPTIC STANDPOINT...I WOULD ONLY EXPECT FLURRIES AT BEST WITH THIS SYSTEM. HOWEVER...GIVEN LAKE TO 850MB DELTA TS AROUND 18C...LAKE INSTABILITY SHOULD ENHANCE SNOWFALL ACROSS LOWER MICHIGAN. WITH MESO ETA MODEL SOUNDINGS OVER LAKE MICHIGAN SHOWING EQUILIBRIUM LEVELS AROUND 7K FT AT 06Z WITH 700MB RH INCREASING TO 70 PCT...WILL LIKELY SEE ENHANCEMENT OFF THE LAKES. WESTERLY WINDS OVER SOUTHERN LAKE MICHIGAN...WITH WEST-SOUTHWESTERLY SURFACE WINDS OVER NORTHERN IN/FAR SOUTHERN LOWER MICHIGAN WILL FAVOR A DOMINATE E-W BAND PUSHING WELL INLAND OF LAKE MICHIGAN. THE 6KM ETA SHOWS THE DEVELOPMENT OF THIS BAND ALONG THE 1-96 TO M-59 CORRIDOR IN ITS LOW LEVEL CONVERGENCE PARAMETERS AND IN ITS PROJECTED QPF. I WILL THEREFORE MENTION MINOR ACCUMULATIONS IN THIS AREA...WITH NOTHING MORE THAN A DUSTING ELSEWHERE. FRIDAY...THE SHORT WAVE QUICKLY PUSHES TO THE EAST IN THE MORNING. WILL LIKELY SEE SOME LINGERING LAKE ENHANCED SNOW SHOWERS EARLY BEFORE STRONG SYNOPTIC SCALE DESCENT WORKS IN ACROSS THE AREA. MODEL SOUNDINGS SHOW INVERSION HEIGHTS FALLING BELOW 4K FT DURING THE AFTERNOON. LOWER INVERSIONS WITH VERY DRY AIR ATOP THE MIXED LAYER AND SURFACE FLOW SLOWLY BECOMING MORE ANTICYCLONIC OVER THE SOUTHERN LAKES SHOULD BE ABLE TO SCOUR OUT SOME OF THE LAKE CLOUDS ENOUGH TO MENTION PARTLY SUNNY SKIES IN THE AFTERNOON. FRIDAY NIGHT...MAIN CONCERN FRIDAY NIGHT WILL BE WITH LOW TEMPS AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN GREAT LAKES. DESPITE WEAKENING PRESSURE GRADIENT AND SNOW COVER...MODEL SOUNDINGS SHOW MID LEVEL MOISTURE INCREASING OVERNIGHT AHEAD OF STRONG ISENTROPIC ASCENT IN THE OHIO VALLEY. I WILL THEREFORE KEEP MIN TEMPS CLOSE TO GUIDANCE. SATURDAY AND SUNDAY...SE MICHIGAN WILL LIE IN BETWEEN SOUTHERN STREAM SYSTEM AND NORTHERN STREAM TROUGH ON SATURDAY. ETA IS A LITTLE FARTHER SOUTH WITH THE TROUGH OVER THE NORTHERN GREAT LAKES ON SATURDAY THAN THE AVN AND IS SUGGESTIVE OF SOME SCT LAKE EFFECT WORKING INTO THE NORTHERN COUNTIES. THE AVN HAS BEEN A LITTLE MORE CONSISTENT WITH THIS SYSTEM. THUS I WILL CONTINUE WITH JUST THE CHANCE OF FLURRIES IN THE NORTH. A GRADUAL WARM AIR ADVECTION PATTERN WILL DEVELOP THROUGH THE REST OF THE WEEKEND IN ADVANCE OF THE NEXT SHORT WAVE POISED TO MOVE INTO THE UPPER MISSISSIPPI RIVER VALLEY/WESTERN GREAT LAKES SUNDAY EVENING. EXTENDED DISCUSSION...THE MEDIUM RANGE MODEL SUITE CONTINUES TO SHOW THE POLAR VORTEX OVER HUDSON BAY THROUGH EARLY NEXT WEAK...WITH A ZONAL FLOW ACROSS THE CONUS. THE BULK OF THE COLD AIR IS STILL PROGGED TO BE LOCKED UP IN CANADA...SO EXPECT TEMPS TO RUN NEAR TO SLIGHTLY ABOVE NORMAL. THE MODELS THEN SHOW THE POLAR VORTEX PUSHING INTO NORTHERN CANADA WITH THE DEVELOPMENT OF A LONG WAVE TROUGH OVER THE WESTERN US AND HEIGHT RISES ACROSS THE EASTERN US. THE ENSEMBLES INDICATE A GOOD DEAL OF UNCERTAINTY WITH RESPECT TO THE PLACEMENT OF THIS UPPER TROUGH. OF ALL THE MEDIUM RANGE MODELS...THE MRF IS THE LEAST AMPLIFIED. EVEN THE MRF ENSEMBLE MEANS SHOW A LITTLE MORE AMPLIFICATION TO THE LONG WAVE PATTERN. THUS I WILL BOOST TEMPS UP FOR MID TO LATE WEEK. A SHORT WAVE COMES THROUGH THE REGION ON MONDAY (FORCING DOES NOT APPEAR ALL THAT STRONG WITH THIS) WHICH WILL PROVIDE A CHANCE FOR SNOW. THE ENSEMBLES INDICATE THAT THE LONG WAVE TROUGH WILL BE FAIRLY PROGRESSIVE LATE IN THE WEEK...WITH A SURFACE LOW DEVELOPING IN THE LEE OF THE ROCKIES. DUE TO MODEL UNCERTAINTY WITH RESPECT TO PLACEMENT OF THE UPPER TROUGH...TIMING AND TRACK OF THE SURFACE LOW IS UNCERTAIN. THE MRF ENSEMBLES SUGGESTS THE LOW MAY TRACK INTO THE GREAT LAKES ON THURSDAY. COORDINATED WITH KGRR. .DTX...NONE. CONSIDINE