000
FXUS63 KDTX 080731
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
331 AM EDT MON SEP 8 2008
.SHORT TERM...TODAY
A WEAK SHORTWAVE RIPPLING EASTWARD ACROSS LAKE SUPERIOR WITHIN THE
BROAD NORTHERN CONUS LONGWAVE TROUGH ALLOWING A WEAK COLD FRONT TO
DROP SOUTHEAST...WITH LATEST SFC ANALYSIS PLACING THIS BOUNDARY IN
THE VICINITY OF LAKE MICHIGAN. FRONT WILL EVENTUALLY DRIFT INTO
SOUTHEAST LOWER MI TODAY...BEFORE STALLING AS THE BAROCLINIC ZONE
BEGINS TO STRENGTHEN IN RESPONSE TO A STRONGER SHORTWAVE AND
ASSOCIATED SFC WAVE EJECTING OUT OF THE PLAINS. LOW LEVEL
CONVERGENCE/LARGE SCALE ACCENT REMAINS WEAK...BUT CURRENT RADAR
TRENDS WOULD SUGGEST THE POTENTIAL FOR A FEW LIGHT SHOWERS TO IMPACT
MAINLY THE SAGINAW VALLEY/NORTHERN THUMB REGION THIS MORNING.
OTHERWISE...RAIN CHANCES WILL REMAIN SLIM (LESS THAN 20%) FOR MOST
OF THE DAY. THE ONSET OF DEEPER MOISTURE TRANSPORT/ISENTROPIC
ACCENT IN ADVANCE OF THE AFOREMENTIONED SFC FEATURE WILL COMMENCE BY
LATE AFTERNOON/EVENING...SUPPORTING A CHANCE POP (MAINLY NORTHWEST
OF FLINT) AFTER 20Z.
MODEL THERMAL FIELDS SHOWING ONLY SLIGHT MODIFICATION IN THE AIRMASS
TODAY...WITH VERY SLIGHT POST-FRONTAL COLD AIR ADVECTION DEVELOPING
ACROSS THE NORTH...WHILE SOUTHERN AREAS SEE BETTER MODERATION UNDER
A PERSISTENT LOW LEVEL SOUTHWEST FLOW. FACTORING IN THE LIMITED
INSOLATION UNDER A BKN-OVC HIGH CLOUD DECK...WILL DEPICT HIGHS
WITHIN A RANGE FROM NEAR 70F ACROSS THE FAR NORTH TO UPPER 70S NEAR
THE OHIO BORDER.
&&
.LONG TERM...
WATER VAPOR IMAGERY SHOWS A SHORTWAVE TROUGH OVER THE NORTHERN
ROCKIES...WHICH WILL BE UNDERGOING SOME AMPLIFICATION/DEEPENING AS A
SERIES OF SHORTWAVES CONSOLIDATE OVER THE GREAT LAKES REGION.
HOWEVER...THE RAMP UP/CYCLOGENESIS APPEARS TO TAKE A BIT LONGER THAN
INDICATED YESTERDAY...WHICH RESULTS IN A FASTER AND FLATTER SURFACE
WAVE TRACKING THROUGH THE EASTERN GREAT LAKES. THE MAJORITY OF THE
MODEL SOLUTIONS (00Z NGM/NAM/CANADIAN GLOBAL/UKMET) CLUSTERING THE
TRACK JUST SOUTHEAST OF THE BORDER...WHILE THE 00Z GFS REMAINS THE
STRONGEST AND FARTHEST NORTH (CLOSE TO DETROIT). WILL FOLLOW THE
LEAD OF THE MAJORITY OF THE MODELS AND FORECAST THE TRACK SOUTHEAST
OF THE BORDER. THE SIGNIFICANCE TO THIS IS THE SEVERE THREAT WOULD
BE NIL...WITH JUST A SLIGHT CHANCE OF THUNDERSTORMS EXPECTED...AS
THE MAIN INSTABILITY REMAINS SOUTH OF THE AREA. REGARDLESS...IT IS
GOING TO RAIN TONIGHT WITH THE GOOD LARGE SCALE FORCING/FGEN IN
PLACE.
ANY MORNING RAIN WILL QUICKLY COME TO AN END ON TUESDAY. EVEN WITH
SOME AFTERNOON SUNSHINE...LOOKING FOR LOW LEVEL COLD ADVECTION TO
HELP OFFSET THE WARMING...AND WILL CONTINUE WITH MAXES IN THE MID
60S TO AROUND 70 DEGREES. HIGH PRESSURE SETTLING OVER SOUTHEAST
MICHIGAN TUESDAY NIGHT WILL ALLOW FOR A GOOD RADIATING NIGHT AND NO
BIG COMPLAINTS WITH THE LATEST MAV GUIDANCE...WHICH INDICATES MINS
IN THE UPPER 30S TO LOWER 40S FOR MUCH OF THE CWA. MOSTLY SUNNY
SKIES ON WEDNESDAY SHOULD LEAD TO A GOOD DIURNAL REBOUND...INTO THE
UPPER 60S TO LOWER 70S.
RETURN FLOW WILL THEN BEGIN TO KICK IN BY THURSDAY...WITH 850/700 MB
THETA-E RIDGE MOVING OVER THE AREA THURSDAY NIGHT...JUSTIFYING
MODERATE POPS WITH APPROACHING WEAK COLD FRONT/UPPER LEVEL
TROUGH...WHICH IS EXPECTED TO MOVE THROUGH FRIDAY MORNING...PER 00Z
EUROPEAN/CANADIAN GLOBAL.
&&
.MARINE...
WINDS WILL SHIFT TOWARD THE NORTHWEST AND STRENGTHEN TONIGHT AS A
LOW PRESSURE SYSTEM LIFTS ACROSS LOWER MICHIGAN. WHILE THE
POTENTIAL FOR GALE FORCE WINDS IS NOW LOOKING LESS LIKELY...WINDS
WILL GUSTS OVER 25 KNOTS AT TIMES THROUGH EARLY TUESDAY...PROMPTING
THE ISSUANCE OF A SMALL CRAFT ADVISORY FOR ALL NEARSHORE MARINE
LOCATIONS. WHILE WINDS WILL BEGIN DECREASING BY TUESDAY
NIGHT...EXPECT WAVES TO REMAIN HIGH AS COLDER AIR MOVES ACROSS THE
WATER LAKE WATERS. MORE FAVORABLE BOATING CONDITIONS WILL RETURN BY
WEDNESDAY AS HIGH PRESSURE BUILDS ACROSS THE GREAT LAKES. WILL NEED
TO MONITOR THE POTENTIAL FOR WATERSPOUTS TO FORM OVER LAKE HURON
WEDNESDAY MORNING...AS CONVERGENCE DEVELOPS ALONG DEVELOPING LAKE
BREEZE BOUNDARIES AND OVERLAKE INSTABILITY BECOMES MORE
FAVORABLE.
&&
.PREV DISCUSSION...ISSUED 136 AM EDT MON SEP 8 2008
AVIATION...
WITH THE LOSS OF DAYTIME HEATING, SHOWERS WILL CONTINUE TO DIMINISH
THIS EVENING AND HAVE LITTLE OR NO IMPACT ON AVIATION OPERATIONS
TONIGHT. VFR CONDITIONS WILL BE ON PLACE THROUGH THE OVERNIGHT HOURS
UNTIL THE COLD FRONT ARRIVES FROM WISCONSIN. THIS FRONT WILL REACH
MBS AROUND SUNRISE AND WILL HAVE JUST SPOTTY PATCHES OF SHOWERS AND
MVFR CEILING BEFORE MAKING ITS WAY THROUGH THE REST OF SE MICHIGAN.
A BROKEN VFR CEILING IS THEN EXPECTED LATER IN THE MORNING AND EARLY
IN THE AFTERNOON AS THE FRONT SLIDES EASTWARD AND SOUTHWARD. A LIGHT
SW WIND WILL INCREASE MODESTLY FROM THE WEST BEHIND THE FRONT,
GENERALLY AT 15 KNOTS OR LESS.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
HURON INCLUDING SAGINAW BAY...FROM 4 AM TUESDAY TO 8 AM
WEDNESDAY.
LAKE ST CLAIR...
SMALL CRAFT ADVISORY...FROM 4 AM TUESDAY TO 8 PM TUESDAY.
MI WATERS OF LAKE ERIE...
SMALL CRAFT ADVISORY...FROM 4 AM TUESDAY TO 8 PM TUESDAY.
&&
$$
SHORT TERM...MR
LONG TERM....SF
MARINE.......MR
AVIATION.....BT
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