FXUS63 KDTX 261451 AFDDTX SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1051 AM EDT MON MAY 26 2003 PERSISTENT UPPER LEVEL LOW CAN BE SEEN JUST EAST OF GEORGIAN BAY ON ALL THE SATELLITE DATA. THE 12Z UPPER AIR OBS...CURRENT SURFACE OBS AND THE LATEST VISIBLE LOOP INDICATES THAT PLENTY OF MOISTURE IN THE LOW LEVELS CONTINUE TO WRAP AROUND THE UPPER LOW AND INTO SOUTHEAST MICHIGAN. WITH THE 12Z KDTX SOUNDING SHOWING NEAR SATURATED CONDITIONS IN THE 750-900MB LAYER...DIURNAL CU SHOULD BE QUITE WIDESPREAD THIS AFTERNOON. THE LATEST VISIBLE IMAGES ARE BEGINNING TO SHOW THIS MORNINGS BREAKS QUICKLY FILLING IN WITH CU. FOR THE MOST PART...AFTERNOON CU FIELD WILL REMAIN BROKEN. DIURNAL MIXING SHOULD HOWEVER BEGIN TO ALLOW MORE SUNSHINE BY LATE AFTERNOON. WITH THIS SAID AND WITH THE LATEST VISIBLE IMAGE STILL SHOWING CONSIDERABLY BREAKS IN THE CLOUDS...I WILL CONTINUE WITH AN OPTIMISTIC PARTLY SUNNY FORECAST. EXPECT VFR CONDITIONS WITH CU FIELD THIS AFTERNOON. THE EXCEPTION WILL BE ACROSS THE SAGINAW VALLEY AND THUMB WHERE A STRATUS DECK OFF OF LAKE HURON SHOULD MAINTAIN LOCALLY LOWER CIGS FOR THE NEXT 2 TO 3 HOURS...POSSIBLY LONGER OVER THE THUMB. UPDATED ZFPDTX AND GRIDDED FORECAST HAVE ALREADY BEEN ISSUED. I ADDED A MENTION OF A SLIGHT CHANCE OF AFTERNOON SHOWERS ACROSS THE ENTIRE FORECAST AREA GIVEN THE LATEST RUC AND MESO ETA SOUNDINGS SHOWING STEEP SFC TO 850MB LAPSE RATES WITH CAPE AROUND 100 J/KG BY LATE AFTERNOON. I ALSO LOWERED TEMPS ACROSS THE THUMB BASED ON CURRENT READINGS. PERSISTENT LAKE STRATUS AND NORTHEAST WINDS OFF LAKE HURON WILL HOLD TEMPS DOWN SEVERAL DEGREES FROM LOCATIONS FARTHER INLAND. CONSIDINE ..............PREVIOUSLY ISSUED AREA FORECAST DISCUSSION........... ...PERIODIC SHRA/TSRA CHCS BECOMING MAIN CHALLENGE... A VERY STAGNANT WX PATTERN WILL BE SHIFTING INTO AN ACTIVE ONE THIS WEEK AND MAYBE BACK TO STAGNATION NEXT WEEKEND? 00Z UAA SHOWED UPPER LOW NOW A FAR DISTANCE EAST OF CWFA...BUT MODELS STILL WOBBLE IT BACK THIS WAY FOR TUE/WED. THEREAFTER A SERIES OF DISTURBANCES RACE INTO THE AREA ON NW FLOW FROM THE NRN PACIFIC...THE FIRST OF WHICH IS NOW PROGGED INTO THE AREA WED NIGHT/THU AM...A BIT FASTER. THIS STILL KICKS THE CURRENT UPPER LOW OUT OF AREA...BUT REALLY DOESN/T CHANGE THE BLOCKING PATTERN APPRECIABLY...SAVE A FEW DAYS LATE THIS WEEK. RIDGE REMAINS ANCHORED OVER WRN CONUS AND TROFFING CONTINUES OFF THE WEST COAST. WILL CHANGE VERY LITTLE IN THIS FORECAST. FOR THE FIRST FIVE DAYS. NOT MUCH HAS CHANGED IN MODEL PROGS SO ONLY MINOR TWEAKS NEEDED. THEREAFTER...THE BUSINESS OF THE BLOCKING PATTERN MORE OR LESS HOLDING BECOMES AN ISSUE. AFTER SVRL NW FLOW WAVES RACE THRU AREA...GFS NOW DROPS A BIG CHUNK OF COOL AIR DOWN FROM CANADA AS RATHER DEEP UPPER LOW DEVELOPS OVER THE LAKES REGION NEXT WEEKEND INTO EARLY NEXT WEEK. CMC AND UKMET SUPPORT THIS GENERAL IDEA...BUT ARE NOT QUITE AS BULLISH WITH DROPPING HGHTS THAT FAR SOUTH INTO THE REGION. GIVEN THESE ARE DAYS 6/7...NOT WILLING TO BITE HOOK/LINE/SINKER...BUT WILL TREND SUNDAY COOLER. THIS WOULD BE A RATHER UNFORTUNATE DVLPMNT IF THINGS SHAPE UP IN THIS GENERAL WAY...EXTENDING AN ALREADY COOL/ DAMP SPRING INTO JUNE. AGAIN...NOT MUCH CHANGE TO GOING FORECAST W/ TEMPS PUSHING 70 TODAY THEN DROPPING BACK 5 OR SO DEGREES ON TUESDAY WITH UPPER LOW WOBBLE THEN EDGING BACK UP TO 70 THU AND INTO THE 70-75 RANGE FRI/SAT. BEST SHOTS AT PRECIP WILL BE SOME SHRAS ON TUE W/ UPPER LOW...SCT SHRAS AND TSRAS WED NIGHT/THU AND FRI NIGHT/SAT WITH NW FLOW WAVES. WE/LL SEE HOW THINGS SHAPE UP AFTER THAT. .DTX...NONE. $$ GURNEY EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT HTTP://WWW.CRH.NOAA.GOV/DTX (ALL LOWER CASE)