Damaging Wind in Michigan, May 29, 2002

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION...RETRANSMITTED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
247 PM EDT WED MAY 29 2002

RESENT TO ADD EXTENDED DISCUSSION...

THE CURRENT WATER VAPOR LOOP SHOWS DEEP LAYER MOISTURE ACROSS THE
MISSISSIPPI VALLEY SURGING NORTHWARD INTO THE GREAT LAKES AHEAD OF A
DEEP SOUTHERN STREAM TROUGH OVER EASTERN TEXAS. SEVERAL SHORTWAVES
ARE NOTED UPSTREAM OF THE GREAT LAKES. ONE IN NORTHERN LAKE MICHIGAN
IS CONTRIBUTING TO SHOWERS AND THUNDERSTORMS OVER NORTHERN LAKE
HURON. A WEAKER SHORT WAVE IS ALSO NOTED OVER EASTERN IOWA. THE
STRONGER SHORT WAVE MOVING INTO THE NORTHERN DAKOTAS WILL BE
THURSDAYS MAIN WEATHER CONCERN.

TRENDS IN THE VISIBLE SATELLITE LOOP AND RADAR COMPOSITE HAVE
INDICATED THAT BREAKS IN THE CLOUD COVER HAVE ESTABLISHED SOME
DIFFERENTIAL HEATING BOUNDARIES. THE CONVERGENCE ALONG THESE
BOUNDARIES IN COMBINATION WITH THE INSTABILITY IN PLACE ACROSS THE
REGION (SFC DEWPOINTS IN THE LOW TO MID 60S) HAS ALLOWED CONVECTION
TO DEVELOP (MAINLY ACROSS THE NORTH HALF OF THE CWA). LAPS MODEL
SOUNDINGS CONTINUE TO SHOW CAPES RISING TO 1500 TO 2200 J/KG
(ESPECIALLY NEAR THESE DIFFERENTIAL HEATING BOUNDARIES). CELLS HAVE
BEEN MORE OR LESS PULSE DUE TO THE WEAK WIND FIELDS AND VERY LOW
DEEP LAYER SHEER. THE MAIN THREAT WITH THESE STORMS STILL APPEARS TO
BE SMALL HAIL...BRIEF GUSTY WINDS AND HEAVY RAIN (WITH PRECIPITABLE
WATER AROUND 1.3 INCHES). THE SLOW MOVEMENT OF THESE STORMS COMBINED
WITH THE HEAVY RAINFALL MAY LEAD TO SOME MINOR LOCALIZED FLOODING
THIS EVENING. I WILL CONTINUE TO TAPER PRECIP TO JUST CHANCE OF
SHOWERS OVERNIGHT AS THERE IS VERY LITTLE FORCING AVAILABLE OTHER
THAN SOME WEAK LIFT AHEAD OF A SHORT WAVE. WITH SFC DEWPOINTS NOW IN
THE LOW TO MID 60S...THINK GUIDANCE TEMPS MAY BE A LITTLE TOO
LOW...SO I WILL UP THEM A COUPLE DEGREES.

ON THURSDAY...MODELS ARE IN GOOD AGREEMENT IN BRINGING THE SHORT
WAVE OVER THE DAKOTAS INTO WISCONSIN BY AFTERNOON. AT THE
SURFACE...A COLD FRONT WILL MOVE INTO WISCONSIN. THERE WILL STILL BE
PLENTY OF LOW LEVEL MOISTURE AHEAD OF THIS SYSTEM ACROSS THE REGION
THURSDAY...WITH SFC DEWPOINTS IN THE MID 60S AND 850MB DEWPOINTS
AROUND +10C. MODEL SOUNDINGS HINT AT SOME MID LEVEL DRYING WORKING
INTO THE REGION BETWEEN 21 AND 00Z WHICH BRING CAPE VALUES UP
BETWEEN 1500 AND 2000 J/KG PER MODEL SOUNDINGS. 0-6KM SHEAR VALUES
ARE STILL PROGGED TO BE RELATIVELY WEAK (AROUND 20 M/S). HOWEVER THE
COMBINATION OF LIFT AHEAD OF THE SHORT WAVE TROUGH...SOME BOUNDARY
LAYER CONVERGENCE WITHIN DIFFERENTIAL HEATING BOUNDARIES (AS SEEN
THIS AFTERNOON)...AND SOME UPPER DIVERGENCE IN LFQ OF UPPER JET WILL
ALLOW FOR MORE ORGANIZED CONVECTION. THUS SPC OUTLOOK PLACES ALL OF
SE MICHIGAN IN A SLIGHT RISK FOR SEVERE WEATHER. I WILL SIDE WITH
THE COOLER MAV NUMBERS FOR HIGHS THINKING THAT THE CLOUD COVER WILL
SUPPRESS AFTERNOON MAX TEMPS (AS IS BEING OBSERVED TODAY).

MODEL DIFFERENCES BEGIN TO ARISE FOR THURSDAY NIGHT. THE ETA
SOLUTION IS MUCH FASTER AT BRINGING THE SURFACE COLD FRONT INTO SE
MICHIGAN. IT ALSO SHOWS MUCH MORE LOW LEVEL CONVERGENCE AND
INSTABILITY AHEAD OF THE FRONT. THIS IS LIKELY DUE TO THE ETA
SOLUTION BRINGING ANOTHER SHORT WAVE INTO WISCONSIN THURSDAY NIGHT
ALONG WITH A FARTHER SOUTH POSITION ON THE UPPER JET. THE AVN
SOLUTION HAS SHOWN MORE CONSISTENCY. THE AVN BRINGS FAIRLY WEAK
DYNAMICS ACROSS THE REGION OVERNIGHT AND BRINGS A MUCH WEAKER SFC
FRONT THROUGH ON FRIDAY AFTERNOON. GIVEN THAT THE AVN HAS SHOWN MORE
CONSISTENCY AND THE NGM AND CANADIAN SOLUTIONS ARE IN BETTER
AGREEMENT WITH THE AVN...I WILL FOLLOW THE AVN SOLUTION THURSDAY
NIGHT INTO FRIDAY. THUS...I WOULD EXPECT THE BETTER PRECIP CHANCES
TO OCCUR THURSDAY EVENING AS OPPOSED TO OVERNIGHT.

THE AVN SHOWS SOME GOOD SUBSIDENCE AND DRYING WORKING IN BEHIND THE
WEAK FRONT FRIDAY AFTERNOON. COLD AIR ADVECTION IS REALLY NOT THAT
IMPRESSIVE BEHIND THE BOUNDARY. THUS...I DO NOT EXPECT TEMPS TO FALL
OFF ALL THAT MUCH. WEAK HIGH PRESSURE AND SLIGHTLY ABOVE NORMAL
TEMPS WILL THEN CARRY INTO THE WEEKEND.

EXTENDED DISCUSSION...THERE IS STILL GOOD AGREEMENT AMONG MEDIUM
RANGE MODEL SOLUTIONS THAT AN EAST-WEST ORIENTED FRONTAL BOUNDARY
WILL PUSH INTO THE SOUTHERN GREAT LAKES BY THE END OF THE WEEKEND
AND EARLY NEXT WEEK. THIS FRONT WILL BE ASSOCIATED WITH A DEVELOPING
SURFACE LOW OVER THE PLAINS IN ADVANCE OF A CUT OFF UPPER LOW OVER
THE SW UNITED STATES. PRECIP SHOULD BE SCATTERED AT BEST ON SUNDAY
GIVEN THE CONFLUENT FLOW ALOFT AND DRY SW LOW LEVEL TRAJECTORIES.
CONVERGENCE ALONG THE FRONT AND SOME INSTABILITY WILL WARRANT CHANCE
OF THUNDER. THE FRONT IS PROGGED TO LINGER ACROSS SOUTHERN LOWER MI
THROUGH MONDAY. AVN/MRF...UKMET AND ECMWF SOLUTIONS SHOW THE SW
UPPER LOW FILING IN AS IT MOVES EAST THROUGH MIDWEEK...AS SFC HIGH
PRESSURE SINKS SOUTH INTO THE GREAT LAKES AND PUSHES THE FRONT SOUTH
OF THE REGION ON TUESDAY. THE ETAXX SOLUTIONS IS MUCH SLOWER AND
ACTUALLY KEEPS THE FRONTAL BOUNDARY AROUND THROUGH TUESDAY. TRENDS
IN THE MRF AND ENSEMBLE MEANS ACTUALLY SUPPORT A SLOWER SOLUTION. I
WILL KEEP TUESDAY DRY FOR THE TIME BEING...HOWEVER CHANCE POPS MAY
HAVE TO BE ADDED AT A LATER ISSUANCE.

.DTX...NONE.

CONSIDINE