FXUS63 KDTX 072111 AFDDTX SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 410 PM EST FRI MAR 7 2003 12Z RAOBS/WATER VAPOR LOOP SHOW NEARLY ZONAL PATTERN ACROSS THE NORTHERN CONUS FOR NOW...WITH LOW NORTH OF LAKE WINNIPEG. A SERIES OF SHORTWAVES IN THIS FAST FLOW ALONG +100KT JET OBSERVED AT 300MB. ONE JUST UPSTREAM MOVING INTO NORTHERN LOWER...WITH A WEAKER ONE BACK ACROSS MINNESOTA. NEXT SHORTWAVE OF INTEREST HAS MOVED ONSHORE IN THE PACIFIC NORTHWEST. SURFACE ANALYSIS SHOWS WEAKENING COLD FRONT OVER NORTHERN LOWER...WITH WEAK RIDGE INTO THE WESTERN GREAT LAKES FROM COLD ARCTIC HIGH OVER NORTHWEST CANADA. NEXT SURFACE LOW OVER THE HIGH PLAINS ALONG WESTWARD EXTENT OF ARCTIC BOUNDARY. CONVECTIVE-LOOKING RETURNS ON DTX RADAR AHEAD OF THE FIRST SHORTWAVE...BUT WITH ONLY A FEW REPORTS OF HEAVIER THAN FLURRY TYPE SNOW FROM ACROSS THE NORTHERN CWA. MAIN QUESTION FOR THIS PACKAGE IS WITH SYSTEM OVER THE HIGH PLAINS APPROACHING FOR SATURDAY/SATURDAY NIGHT. FOR TONIGHT...SHORTWAVE WILL MOVE EAST OF THE STATE BY MIDNIGHT. EXPECT HEAVIER ECHOES TO BE CLEAR OF THE CWA DURING THE NEXT HOUR...SO SHOULD BE ABLE TO GET BY WITH SCATTERED FLURRIES CARRIED OVER TO START THE EVENING. TRAILING SHORTWAVE OVER MINNESOTA LEADING TO A COUPLE FLURRIES AND MAINLY SOME CLOUDS BACK ACROSS WISCONSIN/NORTHERN ILLINOIS. MAY TAKE SOME TIME FOR THE CLOUDS TO CLEAR OUT...BUT STILL EXPECT AT LEAST PARTLY CLOUDY SKIES OVERNIGHT. TEMPERATURES WILL BE TRICKY YET AGAIN WITH CONTINUED WARM/MOIST ADVECTION DESPITE SOME CLEARING. WILL KEEP LOWS A TOUCH BELOW GUIDANCE GIVEN THEIR SOMEWHAT OVERDONE TEMPERATURES FOR THIS AFTERNOON...WITH CURRENT READINGS JUST BREAKING INTO THE LOW 30S. SHORTWAVE OVER THE NORTHWEST WILL SWING THROUGH THE NORTHERN PLAINS AND INTO THE GREAT LAKES BY SATURDAY EVENING...GAINING ENERGY FROM THE UPPER LOW NEAR LAKE WINNIPEG AS IT SHIFTS TOWARDS HUDSON BAY. SOME MODEL DISCREPANCIES BETWEEN THE ETA AND GFS...WITH THE ETA FARTHER NORTH WITH THE TRACK OF THE SURFACE LOW. ETA HAS TRENDED SIGNIFICANTLY NORTH COMPARED TO PREVIOUS RUNS...WHILE THE GFS HAS BEEN MORE CONSISTENT. GENERALLY LEANING MORE TOWARD THE FARTHER SOUTH GFS SOLUTION. IT LOOKS TO HAVE HAD A BETTER INITIALIZATION OF THE STRENGTH OF THE INITIAL SHORTWAVE WHEN COMPARED TO SATELLITE IMAGERY...AND ALSO HAS A BETTER INITIALIZATION OF THE SURFACE WAVE OVER WYOMING. IN FACT BOTH ETA/GFS WERE TOO WEAK WITH THE CURRENT WAVE...AND LOOK TOO WEAK WITH THE SHORTWAVE AS WELL. ALSO THERE IS A LOT OF COLD AIR SETUP OVER CANADA WAITING TO RUSH DOWN. 12Z RAOB FROM CYQD /THE PAS MANITOBA...NORTHERN LAKE WINNIPEG/ HAS AN 850MB TEMPERATURE OF -37C. AS YOU CAN IMAGINE THERE IS A VERY TIGHT BAROCLINIC ZONE ACROSS THE NORTHERN PLAINS. WOULD TEND TO BELIEVE THAT THE COLD AIR WOULD MAKE MORE PROGRESS SOUTHWARD...AS HAS SEEMS TO HAVE BEEN THE CASE THIS SEASON. CONSEQUENTLY WILL LEAN MORE TOWARD THE GFS SOLUTION...WHICH BRINGS THE SURFACE WAVE THROUGH THE CWA RATHER THAN NORTH OF US. ONE CAVEAT THOUGH IS THE UPPER JET STRUCTURE. BOTH ETA/GFS TRY TO BRING A SOMEWHAT COUPLED JET ACROSS THE NORTHERN GREAT LAKES. BEST UPPER DIVERGENCE WOULD TRACK THROUGH NORTHERN LOWER/UPPER MICHIGAN...WHICH WOULD ACCOUNT FOR THE ETA TAKING THE WAVE FARTHER NORTH. AS FOR WEATHER ON SATURDAY...STRONG WARM ADVECTION CONTINUES THROUGH MUCH OF THE DAY. PROFILES CONTINUE TO WARM ABOVE 0C EVEN IN FARTHER SOUTH GFS. GOOD ISENTROPIC LIFT/THETA-E ADVECTION AHEAD OF THE SYSTEM ON +50KT 850MB JET...AS WELL AS STRONG 700MB-500MB FRONTOGENESIS ALONG THE BAROCLINIC ZONE. GOOD ELEVATED CONVECTIVE POTENTIAL AS WELL WITH 700MB-500MB LAPSE RATES APPROACHING 8C/KM. BEST FORCING PASSES NORTH OF THE CWA...BUT STILL EXPECT ENOUGH TO WARRANT HIGH LIKELY POPS THROUGHOUT THE AREA. PRECIP TYPE WILL BE AN ISSUE WITH GOOD WARMING. 1000MB-850MB THICKNESSES/FORECAST PROFILES STILL SUPPORT RAIN IN THE SOUTH/MIXED PRECIP IN THE NORTH EVEN WITH THE COLDER GFS TRACK. WILL KEEP ALL SNOW ACROSS THE NORTHERN COUNTIES...BUT CUT BACK A BIT ON ACCUMULATIONS WITH BETTER FORCING SHIFTED NORTHWARD. GOOD MOISTURE THROUGH THE CWA WITH SPECIFIC HUMIDITIES AROUND 3G/KG...BUT WITH LITTLE IN THE WAY OF ACCUMULATION FARTHER SOUTH WITH THE MIXED PRECIP. THE QUICK SHOT OF LIFT SATURDAY AFTERNOON WILL SLIP EAST WITH THE COLD FRONT AND IT SWINGS THROUGH THE CWA DURING THE EVENING. WILL KEEP LIKELY POPS EARLY SATURDAY NIGHT FOR NOW WITH A POSSIBLE SLOWER TIMING TREND. ALTHOUGH WILL CUT TIMING BACK TO EARLY IN THE PERIOD AS MOISTURE/LIFT QUICKLY SHIFTS EASTWARD. FORECAST SOUNDINGS/PROFILES SHOW DECENT LOW-LEVEL MOISTURE WITH NORTHWEST FLOW...AND WILL HOLD ON TO SCATTERED SNOW SHOWERS FOR NOW. COLD AIR WILL POUR SOUTHWARD YET AGAIN WITH 850MB TEMPERATURES DROPPING TO -20C BY 12Z SUNDAY. WILL DROP LOWS SATURDAY NIGHT A FEW MORE DEGREES. IF WE SEE STRONGER SUBSIDENCE THAN INDICATED BY EITHER MODEL WITH THIS COLD ADVECTION...WE MAY BREAK OUT AND RADIATE EVEN FURTHER. SUNDAY STILL LOOKS TO BE A COLD DAY WITH TEMPERATURES NEARLY 15-20F BELOW NORMAL. SOME LOW-LEVEL MOISTURE WITH OVER LAKE INSTABILITY...BUT WITH LOW INVERSION HEIGHTS AND TIMING THIS LATE IN THE YEAR DO NOT SEE MORE THAN SCATTERED FLURRIES. HIGH PRESSURE SHIFTS EAST THROUGH THE OHIO VALLEY SUNDAY NIGHT INTO MONDAY...BUT WITH ONLY MINOR WARMING AHEAD OF THE NEXT CLIPPER FOR EARLY-MID WEEK. ZONAL PATTERN BECOMES MORE AMPLIFIED FOR THE EXTENDED AS SHARPER TROUGH DEVELOPS OVER THE GULF OF ALASKA...WITH DOWNSTREAM RIDGE OVER THE WEST COAST AND TROUGH ACROSS THE EASTERN CONUS. BROAD CYCLONIC UPPER FLOW CONTINUES ACROSS THE GREAT LAKES FOLLOWING THE SYSTEM THIS WEEKEND. REINFORCING ENERGY DROPS DOWN THE WESTERN RIDGE TO HELP DIG BACK THE EASTERN TROUGH. 00Z RUNS OF THE GFS/LOCAL ETA-XX HAVE BEEN TOWARD A MORE COMPACT AND SLOWER SHORTWAVE...WHICH MAY LEAD TO A DRY DAY ON TUESDAY. HOWEVER 06Z/12Z GFS ARE FASTER AND MORE STRUNG OUT WITH THE ENERGY...LEADING TO PRECIP ON TUESDAY/TUESDAY NIGHT AS OPPOSED TO WEDNESDAY. 06/12Z ECMWF SUPPORTS THE 00Z RUNS WITH A SLOWER AND MORE COMPACT CLIPPER. 00Z CANADIAN IS SIMILAR TO THE 12Z GFS...FASTER WITH THE SHORTWAVE AND EVEN WITH NO SURFACE WAVE...JUST A FRONT PASSING THROUGH THE REGION. WILL MAINTAIN THE CURRENT FORECAST WITH A CHANCE OF SNOW TUESDAY/WEDNESDAY...THEN DRY AS HIGH PRESSURE BUILDS ACROSS THE REGION. 00Z GFS STILL KEEPS MORE OF A PROGRESSIVE PATTERN BRINGING THE UPPER RIDGE INTO THE CENTRAL CONUS BY THE END OF THE WEEK. ENSEMBLE MEMBERS ARE STILL SPLIT...WITH A GOOD CLUSTER HOLDING THE RIDGE BACK ALONG THE WESTERN CONUS LONGER INTO THE WEEKEND. WILL PLAY THE CURRENT FORECAST A BIT COOLER THAN GUIDANCE WOULD INDICATE...WARMING BACK INTO THE 30S BUT STILL JUST BELOW NORMAL HIGHS AROUND 40F. .DTX...NONE. $$ BRAVENDER EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT HTTP://WWW.CRH.NOAA.GOV/DTX (ALL LOWER CASE)