Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 301954
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
354 PM EDT TUE SEP 30 2014

.SHORT TERM...TONIGHT

CURRENT MODEL RUNS ARE STILL SHOWING SURFACE RIDGING TO BUILD ACROSS
THE REGION TONIGHT HELPING TO PUT AN END TO ANY LINGERING DRIZZLE
AND RAIN SHOWERS BY EARLY EVENING. ORIGINAL THINKING WAS FOR CLOUDS
TO ALSO DIMINISH SLIGHTLY...HOWEVER...WITH ABUNDANT MOISTURE AROUND
FROM RAIN AND DRIZZLE THROUGHOUT THE DAY...CONFIDENCE IS HIGH IN CLOUD
COVER REMAINING OVERCAST TONIGHT. THIS LOW LEVEL MOISTURE COMBINED
WITH SOME WEAK WARM AIR ADVECTION WILL RESULT IN A HIGHER
PROBABILITY OF LOW STRATUS AND EVEN SOME FOG DEVELOPMENT ESPECIALLY
IN LOW LYING AREAS. ONLY MAJOR CONCERN TO WATCH OUT FOR DURING THE
NEXT FORECAST SHIFT IS THE UNCERTAINTY ABOUT HOW DENSE THE FOG WILL BE
OVERNIGHT. OVERCAST SKIES OVERNIGHT WILL RESULT IN TEMPERATURES TO
ONLY DROP A FEW DEGREES FROM TUESDAYS HIGH TEMPS INTO THE UPPER 40S
AND LOW 50S ACROSS SOUTHEAST MICHIGAN.

&&

.LONG TERM...WEDNESDAY THROUGH MONDAY

LONGWAVE PATTERN TO UNDERGO SOME BIG CHANGES THROUGH THE REST OF THE
WEEK LEADING TO A VERY COOL WEEKEND AS A DEEP TROUGH OVERTAKES THE
REGION. THE MIDWEEK TIME FRAME WILL BE THE TRANSITION PERIOD FOR THE
PATTERN AS THE FIRST STRONG WAVE COMES ASHORE THE NW CONUS. THIS
WILL CARVE OUT A TROUGH OVER THE MOUNTAIN WEST WHICH WILL ABSORB A
CUTOFF LOW AS IT MOVES FURTHER EAST. NARROW RIDGE AXIS IN ADVANCE OF
THE TROUGH WILL PASS OVER THE GREAT LAKES WEDNESDAY. MEANWHILE AT
THE SFC...SOUTHERN PERIPHERY OF HIGH PRESSURE OVER ONTARIO/QUEBEC
REMAINS IN CONTROL AT THE SFC BUT WILL DRIFT EAST LOOSENING ITS
GRIP. COOL EASTERLY FLOW WILL BE REPLACED WITH WARMER AND MOISTER
SOUTH/SOUTHWEST FLOW AS THE DEEPENING TROUGH REACHES THE PLAINS
STATES. PATTERN STALLS OVER THE UPPER MISSISSIPPI VALLEY AS A STRONG
WAVE DIVES THROUGH THE TROUGH CHANGING IT FROM A POSITIVE TO NEUTRAL
TILT. AS THE WAVE LIFTS NE OUT OF THE TROUGH...CYCLOGENESIS WILL
ENSUE ALONG A COLD FRONT EXTENDING FROM ONTARIO DOWN INTO OKLAHOMA.
THIS SFC LOW WILL UNDERGO RAPID INTENSIFICATION...DEEPENING FROM
1004MB 18Z THURSDAY DOWN TO 988MB 12Z FRIDAY WHICH IS NEARLY 1
MB/HR. BUT THIS SFC LOW WILL HAVE LITTLE FORWARD PROPAGATION DUE TO
THE UPPER LEVEL TROUGH STALLING.

NOW FOR WHAT THIS MEANS FOR SE MI WEDNESDAY AND THURSDAY. WEDNESDAY
WILL START OFF VERY CLOUDY AS MODEL CONSENSUS KEEPS A VERY MOISTURE
LADEN BL UNDER A STRONG BUT WEAKENING INVERSION. INCREASING HEIGHTS
WITH RIDGE AXIS OVERHEAD WILL PROMOTE SOME WARMING ALONG WITH THE
MORE FAVORABLE WIND DIRECTION. EAST WINDS WILL VEER AROUND SOUTH
LATE IN THE DAY BECOMING SOUTHWEST OVERNIGHT. CURRENT THINKING KEEPS
TEMPS IN THE MID 60S. WILL BE SOME ADDITIONAL POTENTIAL FOR TEMPS TO
JUMP A DEGREE OR TWO WITH WARMER AIR ALOFT BUT MODEL SOUNDINGS SHOW
MIXING DEPTHS STRUGGLING TO TAP INTO THAT AIR. THERE WILL LIKELY BE
A SHARP GRADIENT IN PRECIPITATION ON THURSDAY AS A PREFRONTAL LINE
OF SHOWERS APPROACHES SE MI. THE RIDGE WILL HOLD IT TO THE WEST FOR
MOST OF THE DAY WITH ONLY OUR WESTERN COUNTIES HAVING A CHANCE FOR
ANY SHOWERS. THE STRONGEST OF THE SHORTWAVES THUS FAR WILL SURGE
THROUGH THE TROUGH FORCING THE COLD FRONT THROUGH LOWER MI LATE
THURSDAY NIGHT INTO FRIDAY. GOOD SW FLOW AHEAD OF THE FRONT WILL
RAMP UP WAA WITH TEMPS IN THE MID 70S WHICH WILL DROP OFF
SIGNIFICANTLY POST FRONTAL AS WE EXPERIENCED TODAY FROM THE MOST
RECENT COLD FRONT.

DEEPENING LOW PRESSURE AND ASSOCIATED COLD FRONT WILL CROSS THROUGH
THE STATE ON FRIDAY. THIS FEATURE WILL SPREAD RAIN...BRISK
WINDS...AND A SHARP TEMPERATURE DROP TO THE AREA. EXPECT LOW
STRATUS...DRIZZLE...AND MUCH COOLER TEMPERATURES FOR THE WEEKEND IN
THE POST FRONTAL/UPPER TROUGH PATTERN. TEMPS WILL BE HOVERING AROUND
10 DEGREES BELOW NORMAL FOR THE WEEKEND INTO EARLY NEXT WEEK.

&&

.MARINE...

A TIGHT NORTHERLY GRADIENT REMAINS OVER CENTRAL LAKE HURON KEEPING
WIND SPEEDS UP LONGER INTO THE AFTERNOON. THESE WINDS WILL CONTINUE
TO BUILD WAVES UP TO SMALL CRAFT CRITERIA ALONG THE LAKE HURON
SHORELINE OF THE THUMB. SMALL CRAFT ADVISORIES WILL CONTINUE THROUGH
THIS EVENING TO ACCOUNT FOR THAT. WINDS WILL DIMINISH TONIGHT AS
HIGH PRESSURE LESSENS THE GRADIENT OVER THE LAKES BUT THE PERSISTENT
NORTHEAST FLOW WILL KEEP SOME ELEVATED WAVES HEIGHTS INTO THE
OVERNIGHT HOURS. LIGHT WINDS AND LOW WAVES WILL PERSIST WEDNESDAY
INTO THURSDAY. HOWEVER...SOUTHERLY WINDS DEVELOPING AHEAD OF A COLD
FRONT LATE THURSDAY COULD RESULT IN WINDS UP TO 30 KNOTS OVER THE
OPEN WATERS OF LAKE HURON THURSDAY NIGHT.

&&

.AVIATION...ISSUED 115 PM EDT TUE SEP 30 2014

//DISCUSSION...

FOR THE MOST PART DRIZZLE IS COMING TO AN END ACROSS SOUTHEAST
MICHIGAN. HOWEVER...RECENT RADAR IMAGERY STILL IS SHOWING SOME
SPOTTY DRIZZLE TRYING TO FORCE INTO THE REGION. THEREFORE...HAVE
KEPT A TEMPO OF DRIZZLE IN THE FORECAST UNTIL 22Z. CEILINGS WILL
REMAIN OVERCAST AND BELOW 2000 FEET THROUGH THE WEDNESDAY
AFTERNOON AS LOW LEVEL MOISTURE CONTINUES TO FILTER ACROSS THE TAF
SITES.

FOR DTW...LINGERING DRIZZLE WILL BE POSSIBLE AT METRO THIS
AFTERNOON. CURRENTLY EXPECTING THE CHANCE FOR DRIZZLE DEVELOPMENT TO
END BY 22Z...HOWEVER LOW CLOUDS /BELOW 2000 FEET/ WILL STICK AROUND
THROUGH WEDNESDAY MORNING.

//DTW THRESHOLD THREATS...

* HIGH PROBABILITY THAT CEILINGS WILL REMAIN BELOW 5000 FT THROUGH WEDNESDAY.

&&

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

LAKE HURON...
     SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS
     FROM PORT AUSTIN TO HARBOR BEACH...UNTIL 10 PM TUESDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...RK
LONG TERM....DRK/MM
MARINE.......DRK
AVIATION.....RK


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).






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