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

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