000 FXUS63 KDTX 031738 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1238 PM EST THU FEB 3 2005 .AVIATION... RIBBON OF LOW-LEVEL MOISTURE ACROSS NORTHERN LOWER MICHIGAN ASSOCIATED WITH A WEAKENING SURFACE TROUGH IS GRADUALLY WORKING SOUTH. CEILINGS HAVE BEEN MAINLY MVFR, THUS FAR. CONVERGENCE ALONG THE TROUGH AXIS IS REMOISTENING THE BOUNDARY LAYER AS WELL- WHICH IS MANIFESTED IN SLIGHT REDUCTIONS IN VISIBILITY NEAR THE STRAITS. THE TROUGH AXIS WILL WASH OUT AS IT CROSSES SOUTHEAST MICHIGAN TONIGHT, LIKELY LEAVING BEHIND THE LOW-LEVEL MOISTURE. EXPECT THAT NOCTURNAL COOLING IN COMBINATION WITH THE MOISTURE ADVECTION WILL AID IN LOWERING THE CEILINGS AND VISIBILITIES ACROSS THE AREA DURING THE OVERNIGHT. ACROSS THE SOUTH, EXPECT THAT MORE WIDESPREAD FOG WILL DEVELOP ONCE AGAIN, GIVEN A LONGER DURATION OF SURFACE COOLING AS THE LOW-LEVEL MOISTURE AXIS ARRIVES LATER. THE CLOUDS AND FOG WILL ONCE AGAIN BE SLOW TO MIX OUT FRIDAY, AS THE FLOW REMAINS REASONABLY LIGHT THROUGH THE MORNING. && .SHORT TERM...THURSDAY AND THURSDAY NIGHT...ISSUED AT 305 AM FOG DEVELOPMENT EARLY THIS MORNING OVER THE FAR SOUTH AND ALONG THE ST CLAIR RIVER NOT MAKING MUCH PROGRESS AS STRATUS DECK PERSISTING OVER MUCH OF THE REGION...PREVENTING GOOD RADIATIONAL COOLING...SO LOOKS LIKE JUST PATCHY DENSE FOG THIS MORNING. ANOTHER TROUBLE SPOT IS THE SAGINAW VALLEY AND TIP OF THE THUMB AS STRATOCU DECK HAS STRIPPED AWAY...DENSE FOG SHOULD BE A LITTLE MORE WIDESPREAD IN THIS REGION. ETA-12 SHOWS A MINIMA IN THE 925 MB RH FIELD ACROSS THE CENTRAL PORTION OF THE CWA...AND GROUND TRUTH SHOWS THAT THIS SAME REGION IS SEEING ONLY MVFR FOG AT THIS TIME...HOWEVER TEMP/DEW PT SPREADS CLOSING AND ANTICIPATED ANOTHER 1-3 DEGREE COOLING...SO PATCHY DENSE FOG ALSO POSSIBLE IN THIS REGION. MODELS INDICATING THAT MOIST LAYER AND INVERSION DEPTH VERY SHALLOW CWA WIDE THIS MORNING...AND RUNNING AROUND 1K FEET. 00Z DTX SOUNDING SUPPORTS SHALLOW MOIST LAYER...BUT INVERSION DEPTH MUCH DEEPER THAN MODELS INDICATE...ESPECIALLY WITH SOME WARMING AT 850 MB. SO WILL CONTINUE WITH PERSISTENT FOG THROUGH 14Z AGAIN. WILL NOT HAVE TO DEAL WITH HIGH CLOUD COVER EARLY THIS MORNING...SO BURN OFF SHOULD NOT BE HINDERED LIKE IT WAS WEDNESDAY. UPPER WAVE OVER THE NORTHERN GREAT LAKES TO MOVE THROUGH THE CWA THIS AFTERNOON...SPREADING SOME MID LEVEL CLOUDS BACK INTO THE REGION. SURFACE TROF ASSOCIATED WITH THIS FEATURE FORECAST TO WEAKEN ON BOTH 00Z AND 06Z MODEL RUNS...SO WILL CONTINUE WITH IDEA OF JUST SCT TO BKN MID LEVEL CLOUDS AT THIS TIME. TEMPERATURES TODAY SHOULD ALSO REBOUND NICELY...WITH SOME SUN. 1000-850 MB THICKNESSES INCREASE TO NEAR 1300DM THIS AFTERNOON...WHICH RESULTED IN TEMPERATURES IN THE MID TO UPPER 30S OVER WISCONSIN ON WEDNESDAY. SO WILL LEAN TOWARD HIGHER MAV TEMPS FOR THIS AFTERNOON. SOUTHWEST FLOW IN SURFACE TROF AXIS OVER THE NORTHERN GREAT LAKES PRODUCING SOME HIGH STRATUS/STRATOCU EARLY THIS MORNING. ETA-12 INDICATES THAT THIS MOISTURE POOLING WILL BE CONSISTENT THROUGH 12Z FRIDAY AND DROP SOUTH OVER THE CWA TONIGHT. MODELS APPEAR TO BE BALLOONING THIS AREA A LITTLE AND TROF AXIS WEAKENS WITH TIME. HOWEVER MELTING SNOW TODAY SHOULD ADD SOME BOUNDARY LAYER MOISTURE OVER SOUTHEAST LOWER. SO WILL BRING STRATUS DECK INTO THE CWA OVERNIGHT...BUT WILL LIMIT TO 70 PERCENT CLOUD COVER AT THIS TIME. BOUNDARY LAYER FLOW STILL LOOKS WEAK ENOUGH FOR SOME FOG FORMATION AS WELL...ESPECIALLY SOUTH OF THE SAGINAW VALLEY. LOOKS LIKE HIGHER DEW POINTS WILL ALSO ADVECT INTO THE CWA TONIGHT AS WELL...LIMITING OVER NIGHT LOWS TO THE LOWER 20S OVER MOST OF THE CWA. THAT WILL ALSO MAKE IT EASIER FOR TEMPS TO FALL OFF TO AFTERNOON DEW POINT VALUES AND AID IN FOG FORMATION. && .LONG TERM...ISSUED AT 305 AM DRAMATIC PATTERN CHANGE THIS WEEKEND/EARLY NEXT WEEK AS THE SPLIT FLOW OVER THE CONUS IS EXPECTED TO TRANSITION TO MORE OF A PHASED PATTERN...WITH A LARGE UPPER LEVEL TROUGH/CUTOFF LOW SETTING UP OVER THE ROCKIES EARLY NEXT WEEK. DIGGING NORTHERN STREAM TROUGH OVER THE PACIFIC NORTHWEST ON FRIDAY...EXPECTED TO GRAB/KICK THE CUTOFF UPPER LOW JUST WEST OF BAJA CALIFORNIA OFF TO THE NORTHEAST. HIGH DEGREE OF UNCERTAINTY WITH THE EXACT DETAILS/THERMAL PROFILES OVER THE GREAT LAKES REGION EARLY NEXT WEEK....AS THERE IS PLENTY OF UPSTREAM WAVES WHICH WILL HAVE AN IMPACT ON WHEN PHASING OCCURS AND THE ULTIMATE POSITION OF THE MAIN TROUGH AXIS/COLD AIR. INTERESTING TO NOTE IS THE 00Z NOGAPS WHICH IS INDICATING MORE OF A ZONAL PATTERN EARLY NEXT WEEK...WITH THE NORTHERN STREAM JET JUST SOUTH OF THE GREAT LAKES REGION BY TUESDAY. THIS IS OBVIOUSLY A COLDER SOLUTION...BUT WOULD CALL FOR LESS SNOW WITH A FLATTER WAVE. 00Z CANADIAN MODEL IS DEEPER WITH THE TROUGH...WHICH RESULTS IN A FARTHER WEST TRACK OF THE SURFACE LOW...PLACING SOUTHEAST MICHIGAN IN SOMEWHAT MILD AIR FOR TUESDAY. FINALLY...THE 00Z EUROPEAN IS THE DEEPEST WITH THE UPPER LEVEL TROUGH AND CORRESPONDING SURFACE LOW. THE EUROPEAN IS MAINTAINING A STRONG CUTOFF LOW AT 500 MB. THIS RESULTS IN A SLOWER AND FARTHER WEST TRACK...WHICH IS THROUGH THE WESTERN GREAT LAKES ON WEDNESDAY. THIS SOLUTION IS CONSISTENT WITH THE 12Z RUN. WILL BE PUTTING SOME WEIGHT TO THE EUROPEAN...WHICH USUALLY IS THE BEST PERFORMING MEDIUM RANGE MODEL. PREFERENCE OUT OF HPC IS ALSO TOWARD THE EUROPEAN. WITH THAT SAID...WILL HAVE TO EXTEND PRECIPITATION CHANCES INTO WEDNESDAY. ALTHOUGH THE EUROPEAN IS IMPLYING AN ALL RAIN EVENT FOR TUESDAY...WILL HEDGE OUR BETS AND CALL FOR A CHANCE OF RAIN OR SNOW ACROSS THE NORTH. IN THE MEANTIME...IT CERTAINTY LOOKS LIKE WE WILL SEE 40+ DEGREES OVER THE WEEKEND...AS WARM 850 MB TEMPS (4 TO 8 C) STREAM INTO THE SOUTHERN GREAT LAKES. MADE FEW IF ANY CHANGES TO THE GRIDS FOR FRIDAY THROUGH SUNDAY. ETA BUFKIT SOUNDINGS AND BOUNDARY LAYER CONDENSATION PRESSURE CONTINUE TO ADVERTISE FOG AND/OR LOW STATUS SATURDAY MORNING. WITH THE WEAK PRESSURE GRADIENT...FAVORING MORE FOG. && .DTX WATCHES/WARNINGS/ADVISORIES... .MI...NONE. .LAKE HURON...NONE. .LAKE ST CLAIR...NONE. .MI WATERS OF LAKE ERIE...NONE. && $$ MANN