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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 171651
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1251 PM EDT FRI MAY 17 2013


.AVIATION...

-- Changed Discussion --
//DISCUSSION...

HIGH PRESSURE TO THE NORTH AND AN ABUNDANCE OF LOW-LEVEL DRY AIR
WILL SUSTAIN LIGHT/STABLE EASTERLY FLOW AND VFR CONDITIONS THROUGH
THE TAF PERIOD. CONVECTIVE ACTIVITY OVER WISCONSIN IS NOT EXPECTED
TO SURVIVE ITS TREK EAST, ALTHOUGH PERIODS OF MID/HIGH CLOUDS ABOVE
5KFT CAN BE EXPECTED AS THE ASSOCIATED CLOUD COVER IS DRAWN
EASTWARD. FAR NORTH AND WEST LOCATIONS SUCH AS KMBS MAY SEE A BRIEF
PERIOD OF LIGHT RAINFALL OUT OF THIS ACTIVITY WITH NO RESTRICTION TO
VISIBILITY, WHILE REMAINING LOCATIONS WILL STAY DRY WITH PASSING MID
AND HIGH CLOUDS. IMPROVING MID-LEVEL MOISTURE QUALITY WILL BRING A
CHANCE FOR A CEILING BELOW 5KFT BY MORNING, BUT CONFIDENCE REMAINS
QUITE LOW AS STABILITY AND DRY AIR IN THE LOWEST 6KFT ARE EXPECTED
TO REMAIN LARGELY DOMINANT.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILINGS BELOW 5KFT ON SATURDAY MORNING
-- End Changed Discussion --

&&

.PREV DISCUSSION...ISSUED 345 AM EDT FRI MAY 17 2013

SHORT TERM...TODAY AND TONIGHT

QUIET DAY IN STORE AS WE REMAIN UNDER THE SOUTHERN PERIPHERY OF
CANADIAN HIGH PRESSURE AT THE SFC WITH MID LEVEL HEIGHTS BUILDING
THROUGH THE DAY. LOOKING ALOFT...THERE ARE TWO DISTURBANCES TRYING
TO MOVE INTO THE GREAT LAKES. THE FIRST IS A CLOSED MID LEVEL LOW
DRIFTING THROUGH THE CENTRAL CONUS WITH A SLIGHT NE TRAJECTORY
TOWARD THE OHIO VALLEY. THE SECOND IS A SHORTWAVE ROUNDING THE APEX
OF THE MID LEVEL RIDGE OVER IA/MN/WI. MOST MODELS KEEP THE FIRST TO
OUR SOUTH AND TAKE THE LATTER ON A NE TRACK THROUGH NORTHERN MI.
MANY MODELS...KEEP SE MI DRY THROUGH TONIGHT BUT THE NAM/GFS STILL
HANG ONTO A SOME PRECIP AFTER MIDNIGHT TONIGHT. WITH A CONSTANT FEED
OF DRY AIR IN THE LOW LEVELS WITH THE NE FLOW FROM THE SFC
HIGH...BOTH SYSTEM WILL HAVE A TOUGH TIME GETTING ANY PRECIP TO HIT
THE GROUND. THERE IS A BAND OF ELEVATED FGEN NEAR THE 700MB THETA E
GRADIENT WHICH HAS BEEN PRODUCING SHOWERS TO OUR WEST AND WHICH THE
TAIL END WILL SWEEP NORTHWARD THROUGH THE SAGINAW VALLEY. THIS IS
ENOUGH TO KEEP SOME MENTION OF SHOWERS WHILE GIVING THE DAY CREW A
CHANCE TO LOOK AT HIRES MODELS TODAY AND GET A BETTER HANDLE OF
THINGS. SHIFTED THE INHERITED SLIGHT CHANCE NORTH ACROSS THE SAGINAW
VALLEY AND THUMB AS THIS REGION STAND THE BEST CHANCE OF SATURATING
LATE TONIGHT. THE POSITIONING OF THE SFC RIDGE WILL LEAD TO EASTERLY
WINDS THROUGH TONIGHT WHICH WILL KNOCK TEMPS DOWN A BIT FROM THE
LAST FEW DAYS...EVEN MORE FOR LOCATIONS CLOSE TO THE LAKE HURON
SHORELINE. ADDITIONALLY...THE MID AND HIGH CLOUDS STREAMING INTO THE
REGION FROM THE MIDWEST SHORTWAVE WILL HELP KEEP INSOLATION FROM
MAXIMIZING.

LONG TERM...SATURDAY THROUGH THURSDAY

LONGWAVE RIDGE WILL AMPLIFY DURING THE WEEKEND AND KEEP THE WEATHER
RELATIVELY QUIET ACROSS THE CENTRAL GREAT LAKES. ALTHOUGH THERE IS
AN OUTSIDE CHANCE OF AN ISOLATED SHOWER...CONDITIONS ARE EXPECTED TO
BE DRY AND STABLE. EASTERLY SURFACE WINDS AND ABUNDANT MID TO HIGH
LEVEL CLOUDS UNDERNEATH THE RIDGE WILL KEEP TEMPERATURES IN THE 70S
ON SATURDAY. WINDS WILL TURN SOUTHERLY ON SUNDAY AS THE SURFACE
RIDGE HEADS OFF TO THE EAST WITH HIGH TEMPERATURES TOPPING OUT
AROUND 80 DEGREES SUNDAY AFTERNOON.

A LONGWAVE TROUGH...CURRENTLY SHOWN ON WATER VAPOR IMAGERY MAKING
LANDFALL ON THE CALIFORNIA COAST...WILL CONTROL THE WEATHER FOR MUCH
OF NEXT WEEK. THIS LONGWAVE TROUGH IS FORECAST TO MOVE EAST DURING
THE WEEKEND...EMERGING EAST OF THE ROCKIES ON MONDAY AND CLOSING OFF
ACROSS THE NORTHERN PLAINS. ALTHOUGH THERE IS UNCERTAINTY REGARDING
THE PLACEMENT OF THE AFOREMENTIONED LOW...THERE SEEMS TO BE A
CONSENSUS IN GENERATING QUITE A BIT OF SHOWERS AND THUNDERSTORMS AS
A WARM STABLE ATMOSPHERE SETTLES OVER THE CENTRAL GREAT LAKES DURING
THE MONDAY THROUGH WEDNESDAY TIME FRAME. DURING THIS TIME FRAME
MUCAPE VALUES RISE TO 1000 TO 2000 J/KG...INCREASING THE THREAT FOR
ORGANIZED THUNDERSTORM ACTIVITY. HODOGRAPHS ARE RATHER UNIMPRESSIVE
ON MONDAY WITH A NEARLY UNIDIRECTIONAL SOUNDING. THERE ARE BETTER
HODOGRAPHS TUESDAY AND WEDNESDAY AS THE LOW ITSELF TRACKS THROUGH
THE REGION. HOWEVER WITH THE LOW TRACK BEING UNCERTAIN THE THREAT
FOR SEVERE THUNDERSTORMS IS UNCERTAIN GIVEN THE SHEAR VALUES ARE
VASTLY DIFFERENT DEPENDING ON THE TRACK OF THE LOW. ALTHOUGH THE
SITUATION BEARS CLOSE ATTENTION...THERE IS NOT ENOUGH CONFIDENCE
EITHER WAY REGARDING SEVERE POTENTIAL NEXT WEEK.

TEMPERATURES TAKE A NOTABLE TUMBLE BEHIND THE DEPARTING LOW ON
THURSDAY AS 850 MB TEMPERATURES FALL BACK INTO THE SINGLE DIGITS
ABOVE ZERO. THIS WOULD BRING HIGH TEMPERATURES BACK DOWN BELOW
NORMAL LATE NEXT WEEK WITH HIGH TEMPERATURES IN THE 60S.

MARINE...

THE SOUTHERN PERIPHERY OF A CANADIAN HIGH PRESSURE SYSTEM WILL
PRODUCE LIGHT NORTHEASTERLY WINDS OVER THE GREAT LAKES TODAY. WINDS
WILL VEER MORE EASTERLY ON SATURDAY AND SOUTHEASTERLY SUNDAY BUT
WILL REMAIN LIGHT. THIS WILL LEAD TO FAVORABLE MARINE CONDITIONS
THROUGH THE WEEKEND AS THE HIGH SLOWLY WORKS ACROSS THE REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....JVC
SHORT TERM...DRK
LONG TERM....KURIMSKI
MARINE.......DRK


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