FXUS63 KDTX 061637
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1243 PM EDT MON OCT 6 2008

.AVIATION...

VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES THROUGH THE PERIOD
EXCEPT FOR POSSIBLY A BRIEF PERIOD OF MVFR CEILINGS AROUND 3K FT AT
THE BEGINNING OF THE TAFS AT MBS/FNT AS SUN WILL CREATE A QUICK CU
FIELD OF SCT-BKN BEFORE MIXING OUT WITH DRIER AIR. DRY AIR WORKING
IN ON A EASTERLY FLOW FROM HIGH PRESSURE OVER ONTARIO WILL BRING A
GRADUAL DECREASE IN CLOUDS THIS AFTERNOON FROM NORTHEAST TO
SOUTHWEST.

&&

.UPDATE...

UPDATED TO LOWER TEMPS A FEW DEGREES AND DELAY CLEARING A BIT BASED
ON SATELLITE/RADAR TRENDS AND NEW GUIDANCE. MID LEVEL FORCING WILL
CONTINUE TO WEAKEN AS IT PUSHES SOUTHWESTWARD DURING THE AFTERNOON
AS ENTRANCE REGION OF UPPER JET MOVES TO THE EAST. HIGH PRESSURE
DROPPING SOUTH INTO ONTARIO WILL SEND DRIER AIR FILTERING IN FROM
THE NORTHEAST THIS AFTERNOON WHICH WILL ERODE CLOUD COVER FROM
NORTHEAST TO SOUTHWEST ACROSS SOUTHEAST MICHIGAN. LIGHT RAIN IS
TRANSITIONING TO SPRINKLES ACROSS THE FAR SOUTHEAST CORNER AND
SHOULD BE GONE BY EARLY AFTERNOON.

&&



.PREV DISCUSSION...ISSUED 531 AM EDT MON OCT 6 2008

SHORT TERM...TODAY

LATEST WATER VAPOR AND UPPER AIR ANALYSIS SHOWING SOUTHEAST LOWER MI
SANDWICHED BETWEEN THE BACK END OF AN UPPER TROUGH AXIS SWINGING
ACROSS SOUTHERN ONTARIO/QUEBEC AND UPPER RIDGING EXTENDING INTO THE
MID MS VALLEY. AN ELONGATED AREA OF WEAK ISENTROPIC ACCENT AND MID
LEVEL FRONTOGENESIS SUPPORTING A NARROW CORRIDOR OF VERY LIGHT RAIN
STRETCHING FROM EAST-CENTRAL WI INTO THE SOUTHERN THIRD OF THE
FORECAST AREA. BOTH THE 12Z NAM AND GFS INDICATE THIS FORCING WILL
QUICKLY DIMINISH THROUGH THE MORNING HOURS...ALLOWING ANY LINGERING
PCPN TO RAPIDLY TAPER OFF. THE RATHER MODEST LOOKING MOISTURE
PROFILES...AS WELL AS CURRENT RADAR TRENDS...WOULD SUGGEST LITTLE
MORE THAN A COUPLE HUNDREDTHS OF RAIN AT MOST. HIGHEST POPS WILL
FOCUS WITHIN THE OWOSSO-HOWELL-ANN ARBOR CORRIDOR...WITH NO MENTION
TOWARD THE THUMB.

RESIDUAL HIGH CLOUDINESS WILL GRADUALLY THIN THROUGH THE AFTERNOON
AS THE LARGE SCALE FORCING WANES AND UPPER RIDGING BUILDS TOWARD THE
REGION. SOME INCREASING INSOLATION LATE WILL HELP COUNTER A
PREDOMINANT LOW LEVEL EASTERLY FLOW RESULTING FROM HIGH PRESSURE
CENTERED OVER SOUTHERN ONTARIO. RISING UPPER HEIGHTS WILL ALLOW THE
AIRMASS TO MODERATE DESPITE THE EASTERLY FLOW...ALTHOUGH PERHAPS NOT
QUITE TO THE EXTENT PROJECTED BY EITHER THE NAM OR GFS. GENERALLY
WILL SEE HIGHS AROUND OR JUST BELOW SEASONAL NORMS...WITH READINGS
MAINLY IN THE LOWER 60S (UPPER 50S IN THE THUMB).

LONG TERM...

NOT A WHOLE LOT OF CHANGES MADE TO THE PREVIOUS FORECAST...AS
MILDER TEMPERATURES REMAINS THE WEATHER STORY.

THE TREND OF THE UPPER LEVEL LONGWAVE TROUGH OVER THE ROCKIES IS TO
BE A BIT FASTER/MORE PROGRESSIVE AS THE DAY SHIFT EXPECTED. THE
UPPER WAVE AT THE BOTTOM OF THE TROUGH STRUGGLES TO CUTOFF FROM THE
NORTHERN STREAM...WITH ZONAL FLOW BECOMING ESTABLISHED OVER THE
NORTHERN CONUS ON WEDNESDAY. MODELS (00Z UKMET/GFS) SHOWING SOME
SEMBLANCE OF A WEAK SURFACE LOW/WAVE OR AT THE VERY LEAST A SURFACE
TROUGH (NAM/EUROPEAN) LIFTING NORTHEAST THROUGH LOWER MICHIGAN
DURING WEDNESDAY...AND HAVE RAISED POPS TO 50 PERCENT. DAY SHIFT
ALREADY INTRODUCED CHANCE POPS LATE TUESDAY NIGHT WHICH ALSO LOOKS
GOOD AS SHARP 850-700 MB THETA-E GRADIENT MOVES IN AROUND 12Z
WEDNESDAY. IN THE MEANTIME...RATHER AMPLIFIED UPPER LEVEL RIDGE IN
PLACE ON TUESDAY WILL PROVIDE A MILD DAY AS LOW LEVEL WARM ADVECTION
KICKS IN...ALLOWING 850 MB TEMPS TO REACH AND EXCEED 12 C. THE MAV
GUIDANCE LOOKS GOOD...UPPER 60S TO AROUND 70 ON TUESDAY. CLOUDS AND
SHOWERS ON WEDNESDAY WILL PROBABLY HOLD MAX TEMPS DOWN A BIT...IN
THE MID 60S. HOWEVER...WITH THE WEAK COLD FRONT WASHING OUT ON
THURSDAY...UPPER 60S TO NEAR 70 DEGREES SEEMS ATTAINABLE ONCE AGAIN
AS 925 MB TEMPS SEEN WARMING INTO THE LOW TO MID TEENS.

MARINE...

A PROLONGED PERIOD OF EASTERLY WINDS WILL DEVELOP ACROSS ALL MARINE
AREAS TODAY AS HIGH PRESSURE BUILDS ACROSS THE EASTERN GREAT LAKES
AND LOW PRESSURE MOVES THROUGH THE PLAINS. THESE WINDS MOVING
ACROSS THE LONG LAKE HURON FETCH WILL RESULT IN HIGHER WAVES TODAY.
THESE CONDITIONS WILL DEVELOP ACROSS THE MICHIGAN WATERS OF LAKE
ERIE BY TONIGHT AND SMALL CRAFT ADVISORIES ARE NOW IN EFFECT HERE AS
WELL. WAVES WILL GRADUALLY DIMINISH ON TUESDAY AS WINDS SHIFT
TOWARD THE SOUTHEAST AND DECREASE. AN APPROACHING COLD FRONT WILL
BRING THE NEXT CHANCE OF RAIN ON WEDNESDAY...ALTHOUGH WIND AND WAVE
CONDITIONS WILL REMAIN GENERALLY FAVORABLE ACROSS ALL MARINE AREAS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
SMALL CRAFT ADVISORY...SAGINAW BAY AND THE NEARSHORE WATERS FROM
PORT AUSTIN TO PORT SANILAC...UNTIL 10 AM TUESDAY.

SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT SANILAC TO PORT
HURON...FROM 2 PM MONDAY TO 10 AM TUESDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...
SMALL CRAFT ADVISORY...FROM 6 PM MONDAY TO 10 AM TUESDAY.

&&

$$

UPDATE.......DRC
AVIATION.....DRC
SHORT TERM...MR
LONG TERM....SF
MARINE.......MR


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