FXUS63 KDTX 150147 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 946 PM EDT THU OCT 14 2004 .UPDATE... A DEEP UPPER LOW IS CURRENTLY LOCATED OVER FAR WESTERN KENTUCKY...WITH A SURFACE LOW OVER SW INDIANA. THE 00Z UPPER AIR PLOTS SHOWED A 120KT 250MB JET LOCATED SOUTHEAST OF THE UPPER LOW. THE CURRENT WATER VAPOR LOOP INDICATED THIS UPPER LOW IS STILL SLOWLY LIFTING NORTHEAST. THE STRONGER MID LEVEL LIFT ASSOCIATED WITH THIS UPPER LOW AND THE UPPER DIVERGENCE WITHIN THE LEFT EXIT REGION OF THE UPPER JET WILL NOT MOVE INTO THE SOUTHERN PORTIONS OF SE MICHIGAN UNTIL AFTER 08Z...WITH THE BEST LIFT REACHING THE FORECAST AREA BY 12Z. TRENDS IN THE RADAR DATA OVER THE LAST SEVERAL HOURS HAVE SHOWN PRECIP DIMINISHING AS IT MOVE ACROSS NORTHEAST INDIANA. THE 00Z DTX SOUNDING ALSO SHOWED SOME SLIGHTLY DRYER AIR BETWEEN 900 AND 800MB. SO WILL LIKELY HAVE TO WAIT UNTIL THE STRONGER FORCING AND DEEPER MOISTURE ARRIVES LATE TONIGHT/EARLY FRI MORNING BEFORE THE WIDESPREAD RAINFALL AFFECTS SE MICHIGAN. A SECONDARY WEAKER SURFACE LOW IN THE THUMB REGION HAS ALLOWED SOME LOW LEVEL MOISTURE AND SHOWERS TO ADVECT INTO THE SAGINAW VALLEY FROM SAGINAW BAY. THIS LOW WILL LIFT NORTH INTO LAKE HURON OVERNIGHT...WHICH WILL DIMINISH THE SCATTERED SHOWER ACTIVITY IN THIS REGION. HOWEVER...SURFACE OBS INDICATE QUITE A BIT OF LOW LEVEL MOISTURE BELOW 1500 FT FROM FLINT THROUGH THE TRI CITIES. THIS MOISTURE SHOULD REMAIN IN PLACE THROUGH THE NIGHT... COUPLED WITH SOME WEAK BOUNDARY LAYER CONVERGENCE... WOULD EXPECT SOME AREAS OF DRIZZLE TO PERSIST IN THIS REGION. WILL UPDATE THE PRECIP WORDING IN THE ZONES/GRIDS TO REFLECT THESE CHANGES. OTHERWISE...GOING FORECAST LOOKS IN GOOD SHAPE. && CONSIDINE .PREV DISCUSSION...ISSUED AT 327 PM. SATELLITE IMAGERY SHOWS LOW PRESSURE CIRCULATING OVER THE SOUTH END OF LAKE HURON THIS AFTERNOON WHILE ANOTHER STRONG LOW MOVES THROUGH THE MID MS VALLEY. THE MID MS VALLEY LOW WILL SPREAD MORE MOISTURE INTO LOWER MICHIGAN TONIGHT AND FRIDAY AND THEN GET A BOOST FROM THE CENTRAL CANADIAN WAVE FOR STRONG WINDS FRIDAY NIGHT AND SATURDAY. ADVISORY CRITERIA WIND GUSTS ON LAND AND GALES ON THE LAKES ARE STILL POSSIBLE. THE 12Z MODEL RUNS ARE IN GOOD AGREEMENT SHOWING MOISTURE RELOADING OVER THE MID MS VALLEY AND OHIO VALLEY, AND HEADING THIS WAY DURING THE EVENING. A 120 KT UPPER JET WILL HELP THE TN VALLEY UPPER LOW BECOME NEGATIVELY TILTED OVERNIGHT AND FRIDAY. FORCING FOR VERTICAL MOTION OVER SE MICHIGAN WILL BE DOMINATED BY CYCLOGENESIS AND OCCLUSION DYNAMICS IN AN ENVIRONMENT OF CONVECTIVE INSTABILITY. THE MODELS SHOW A WELL DEVELOPED THETA-E RIDGE WRAPPING AROUND THE NORTH AND WEST FLANK OF THE LOW OVERNIGHT THROUGH FRIDAY. THIS MORE THAN JUSTIFIES THE INCREASED MODEL QPF OBSERVED IN THE 12Z RUNS, 0.5 TO 0.75 INCH FOR THE EVENT, BUT NOT QUITE ENOUGH FOR THUNDER AT THIS POINT. IT WILL TAKE MOST OF FRIDAY EVENING FOR THE WRAP-AROUND MOISTURE TO MOVE NORTH AND EAST OF OUR AREA, THEN THE WIND WILL BECOME THE MAIN STORY AS THE SYSTEM DEEPENS TO AROUND 980 MB BY 12Z SATURDAY NEAR THE NORTH END OF LAKE HURON. THE ETA STILL SHOWS THE BEST ISALLOBARIC GRADIENT OCCURRING FRIDAY NIGHT AND CONTINUED COLD ADVECTION ON SATURDAY. THE COMBINATION OF LOW LEVEL COLD ADVECTION AND DAYTIME HEATING ON SATURDAY WILL ALLOW MIXING INTO A LAYER OF WINDS CLOSE TO 40 KNOTS DURING THE AFTERNOON. THE ETA IS A LITTLE WEAKER ON THE LOW LEVEL WIND FIELD COMPARED TO THE GFS, BUT BOTH ARE CLOSE ENOUGH TO WIND ADVISORY CRITERIA TO CAUSE CONCERN. GALES ON THE LAKES ARE A DONE DEAL. PREFER THE ETA SOLUTION ON SATURDAY AND SATURDAY NIGHT FOR ITS ABILITY TO MODEL THE LAKE COMPONENT OF QPF. EXPECT LAKE TO 850 DELTA-T TO APPROACH 20C ON SATURDAY WITH LITTLE OR NO INVERSION UNTIL SATURDAY EVENING. DURING SATURDAY NIGHT AND SUNDAY, DRY AIR AND WARM ADVECTION WILL DEVELOP AND BRING AN END TO LAKE EFFECT PRECIP AND EVENTUALLY SCOUR OUT THE LOW CLOUDS FOR A WHILE ON SUNDAY. THE UPPER LEVEL LONG WAVE TROF WILL BROADEN OR RETROGRADE WESTWARD AROUND THE MONDAY PERIOD WITH THE HELP OF A SERIES OF SHORT WAVES DIGGING FROM THE GULF OF ALASKA. THERE IS GOOD MODEL AGREEMENT ON THE LARGE SCALE PATTERN WITH THE USUAL TIMING DIFFERENCES ON THE SHORT WAVES, BUT EVEN THESE ARE NOT SIGNIFICANT. MORE IMPORTANT IS THE POSITION OF THE SURFACE FRONTAL ZONE AND STORM TRACK TO OUR SOUTH DURING THE PERIOD WHICH WILL LIMIT ANY BIG WARMING TRENDS. OUTSIDE OF RAIN CHANCES WITH THE SHORT WAVE SUNDAY NIGHT AND MONDAY, WE'LL HOLD OFF ON ADDING POPS TO THE MID WEEK PERIOD AS THE PREPONDERANCE OF MODEL EVIDENCE SUGGESTS HIGH PRESSURE WILL BE IN CONTROL WITH THE SURFACE SYSTEMS MOVING TO OUR SOUTH AND EAST. THE GFS SHOWS A STRONGER SYSTEM MOVING IN ON THURSDAY THAT WILL BE MONITORED FOR OVER THE NEXT FEW CYCLES FOR MODEL TRENDS. && .DTX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ BT EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT HTTP://WWW.CRH.NOAA.GOV/DTX (ALL LOWER CASE)