Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 280046
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
846 PM EDT SAT JUN 27 2015

.UPDATE...

THE 00Z SURFACE ANALYSIS PLACES A 1002MB LOW OVER CLEVELAND. THE
00Z DTX SOUNDING SHOWED 50KT WINDS AT 3K FT. THE AXIS OF STRONG
LOW LEVEL WINDS WILL REMAIN OVER THE ERN THIRD OF SE MI FOR THE
REST OF THE EVENING BEFORE THE GRADIENT STARTS TO RELAX AS THE SFC
LOW SLOWLY EXITS TO THE EAST. WHILE MARGINAL LOW LEVEL STABILITY
IS NOT BRINGING THE 50 KNOT WINDS TO THE SURFACE...FREQUENT WIND
GUSTS IN THE 30-40 MPH RANGE HAVE OCCURRED SINCE THIS AFTERNOON
AND WILL CONTINUE OVER THE EASTERN HALF OF THE FORECAST AREA
DURING THE REST OF THE EVENING BEFORE WEAKENING. WHILE NOT
ADVISORY LEVEL...THERE HAVE BEEN SEVERAL REPORTS OF SMALL LIMBS
DOWN AND NUMEROUS POWER OUTAGES...ESPECIALLY ACROSS METRO DETROIT.
THERE HAS BEEN ENOUGH BACKING OF THE WINDS TOWARD THE NNW TO ALLOW
WATER LEVELS ALONG LAKES ERIE AND ST CLAIR TO BEGIN A DOWNWARD
TREND THIS EVENING. GIVEN THIS AND WITH WINDS DIMINISHING
OVERNIGHT...THE LAKE SHORE FLOOD WARNINGS WILL NOT BE EXTENDED
PAST THIS EVENING.

MID LEVEL DEFORMATION BECAME ANCHORED OVER LENAWEE/HILLSDALE
COUNTIES AND POINTS SOUTH THIS AFTERNOON/EVENING. THIS LED TO
SEVERAL INCHES OF RAINFALL IN THIS REGION. BASED ON AVAILABLE
SPOTTER REPORTS...RADAR STORM TOTALS ARE A LITTLE UNDERESTIMATED.
THIS ANCHOR POINT HAS SINCE RELOCATED EASTWARD TOWARD MONROE AND
TOLEDO. THE BETTER DEFORMATION HAS ALSO BECOME FOCUSED ALONG THE
EDGE OF THE MID LEVEL THETA E GRADIENT...EXTENDING FROM MONROE TO
THE CITY OF DETROIT TO PORT HURON. THIS IS WHERE THE MORE
WIDESPREAD RAIN WILL BE CONCENTRATED THROUGH THE REMAINDER OF THE
EVENING BEFORE GRADUALLY EXITING TO THE EAST OVERNIGHT.
OVERALL...THE GOING FORECAST REMAINS VALID. AN UPDATE WILL BE
FORTHCOMING JUST TO MAKE SOME MINOR ADJUSTMENTS TO POPS BASED ON
RECENT TRENDS.

&&

.AVIATION...ISSUED 704 PM EDT SAT JUN 27 2015

THE STRONG NNE GRADIENT OVER SE MI ASSOCIATED WITH THE DEEP SFC LOW
OVER NRN OHIO WILL SUSTAIN GUSTY WINDS THROUGH THE EVENING. THE SFC
LOW WILL SLOWLY DEPART TO THE EAST OVERNIGHT...LEADING TO A GRADUAL
DROP IN WIND SPEEDS AND CAUSING WINDS TO BACK SLIGHTLY TOWARD THE
NNW. IFR CLOUD BASES HAVE THUS FAR BEEN CONFINED TO THE PORT HURON
AREA. THIS IS LIKELY DUE TO THE AMOUNT OF LOW LEVEL DRY AIR TO THE
NORTH WHICH HAS BEEN FUNNELING INTO SE MI. THERE WILL STILL BE AN
OPPORTUNITY FOR SOME REDEVELOPMENT OF LOW CLOUDS DURING THE
OVERNIGHT...ALTHOUGH CONFIDENCE IS NOT TOO HIGH AT THIS POINT. THE
HEAVIEST RAIN WILL DIMINISH LATE THIS EVENING...LEAVING JUST LIGHT
SHOWERS ACROSS THE AREA DURING THE OVERNIGHT.

FOR DTW...THE STRONGEST WINDS...WITH GUSTS POSSIBLY UP TO 35
KNOTS...WILL PERSIST THROUGH ROUGHLY 04 OR 05Z BEFORE THE
GRADIENT RELAXES.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS BELOW 5000 FEET THROUGH EARLY SUNDAY AFTERNOON.
* LOW IN A THUNDERSTORM AFFECTING THE NEAR TERMINAL AIRSPACE TONIGHT.

&&

.PREV DISCUSSION...ISSUED 323 PM EDT SAT JUN 27 2015

SHORT TERM...THIS EVENING AND TONIGHT

LAST PHASE OF THE MATURE CYCLONE AFFECTING THE REGION IS ABOUT TO
COMMENCE OVER SOUTHEAST LOWER MICHIGAN. DEFORMATION AXIS IS
REORIENTING OVER SOUTH CENTRAL LOWER AND REPOSITIONING FARTHER EAST
WHERE THE BETTER THETA-E OVERLAP IS PRESENT IN THE 850-700MB LAYER.
DECENT ELEVATED CONVECTIVE RESPONSE OCCURRED NEAR THE MI/IN/OH STATE
INTERSECTION THIS AFTERNOON CLOSER TO THE MID/UPPER LEVEL DRYING.
THIS WILL SERVE AS THE ANCHOR POINT FOR THE DEFORMATION SIGNAL
THROUGH THE EVENING HOURS. EXPECT THE GREATEST CONTINUOUS RESPONSE
WILL EXIST ALONG A FLINT TO ADRIAN LINE - MORE FEEDER WAVE STRUCTURE
IS EXPECTED TO THE EAST OF THE DEFORMATION AXIS.  LATEST GUIDANCE
SUITE SUGGESTS THE DEFORMATION WILL BECOME OVERSTRETCHED AND DECAY
TOWARD MIDNIGHT AS IT SLOWLY WORKS EASTWARD TOWARD THE CANADIAN
BORDER.  AFTER WHICH...SCATTERED SHOWERS ARE STILL POSSIBLE UNTIL
DAYBREAK ACROSS THE FAR EAST.

THE OTHER MAIN SYSTEM CHARACTERISTIC IMPRESSING ITSELF UPON THE
REGION IS THE STRONG NORTH/NORTHEAST WINDS. THE BEST GUST POTENTIAL
WILL BE LATE THIS AFTERNOON INTO THIS EVENING AS THE LOW CONTINUES
TO DEEPEN - FORCING 50KTS AT 925MB. HOWEVER...NOT EXPECTING MIXING
WILL REALLY BE AN ISSUE TO GET UP INTO THE REALLY STRONG LOW-LEVEL
FLOW.  THE SURFACE PRESSURE GRADIENT SHOULD SUFFICE ALONE TO
MAINTAIN THE FIRM WIND FIELD. AS SUCH...WILL CONTINUE TO ADVERTISE
HIGH WATER LEVELS ALONG THE LAKE ERIE AND LAKE ST CLAIR SHORELINES
WITH THE ONSHORE GALES FORCING ON TOP OF THE RECENTLY HIGHER WATER
LEVELS.

LONG TERM...

OUR WELL DEFINED MID LEVEL CIRCULATION/500 MB LOW WILL SLOWLY WORK
THROUGH THE EASTERN GREAT LAKES ON SUNDAY. THE KEY WORD IS
SLOWLY...AS HEIGHTS WILL GRADUALLY RISE. DEEP MOISTURE TO START THE
DAY (POSSIBLE SPRINKLES/LEFTOVER LIGHT RAIN SHOWERS EAST OF U.S 23
)...AS 1000-500 MB MEAN RH STARTS OUT IN EXCESS OF 80 PERCENT. WITH
ALL THE RAIN TODAY AND TONIGHT SATURATING THE GROUND AND THE
STUBBORN CYCLONIC FLOW...WOULD EXPECT MOSTLY CLOUDY SKIES OVER
EASTERN AREAS THROUGH AT LEAST THE EARLY AFTERNOON HOURS BEFORE
RIDGING/DRYING TAKES BETTER HOLD. HOWEVER...CONFIDENCE IN THE
DEVELOPING AFTERNOON SUNSHINE IS NOT HIGH ENOUGH TO GO FOR MAXES OF
80 DEGREES WHICH IS THE AIRMASS POTENTIAL (850 MB TEMPS APPROACHING
12 C)...AND THUS WILL CARRY MID TO UPPER 70S INSTEAD...IN LINE WITH
LATEST MET GUIDANCE.

ANOTHER SEASONABLY STRONG UPPER WAVE CURRENTLY DIVING SOUTHEAST
THROUGH SOUTHERN MANITOBA WILL TRACK INTO THE UPPER MISSISSIPPI
RIVER VALLEY TONIGHT/SUNDAY MORNING...THEN MAKING THE TURN TO THE
EAST DURING THE DAY INTO THE NORTHERN OHIO VALLEY SUNDAY
EVENING/NIGHT. YET MORE UPPER LEVEL ENERGY COMING DOWN FROM THE SAME
LOCATION MONDAY MORNING CARVING OUT HIGHER AMPLITUDE TROUGH AXIS
OVER THE WESTERN GREAT LAKES MONDAY EVENING AS UPPER LEVEL RIDGE
ALONG THE WEST COAST BUILDS INTO WESTERN CANADA.

AS A RESULT...DEVELOPING RAIN SHOWERS APPEAR LIKELY MONDAY
AFTERNOON/EVENING OVER SOUTHEAST MICHIGAN AS THE CLOSED 500 MB LOW
OR OPEN UPPER LEVEL TROUGH AND ASSOCIATED SURFACE LOW SLOWLY TRACKS
THROUGH SOUTHERN LOWER MICHIGAN...WITH SUFFICIENT MOISTURE AS PW
VALUES RISE TO AT LEAST 1.5 INCHES...POTENTIALLY AROUND 1.75 INCHES
PER 12Z NAM. MORE SUBSTANTIAL INSTABILITY LOOKS TO BE REMAINING
SOUTH OF THE BORDER ALONG WITH THE MID LEVEL JET...BUT STRENGTH OF
LOW LEVEL JET/MOISTURE ADVECTION CERTAINLY WARRANTS A CHANCE OF
THUNDERSTORMS. MUCH LIKE THIS LAST SYSTEM...MOVEMENT WILL BE
SLOW...AS THE GFS STILL SHOWING TROUGH AXIS LINGERING OVERHEAD ON
TUESDAY...IN LINE WITH THE 12Z EURO. THE CHANCE FOR SHOWERS AND
THUNDERSTORMS WILL CONTINUE DURING THE DAY. HIGHS LOOK TO BE IN THE
70S BOTH TUESDAY AND WEDNESDAY...ULTIMATELY DEPENDENT ON CONVECTION
INITIATION TIMES.

NORTHWEST UPPER FLOW OVER THE LOCAL AREA ON WEDNESDAY AS THE CENTER
OF THE UPPER TROUGH CONTINUES TO SHIFT EASTWARD. THIS IS EXPECTED TO
LEAD TO HIGH PRESSURE AT THE SURFACE AND DRY CONDITIONS. THERE ARE
SIGNS THAT THE TROUGH WILL REESTABLISH ITSELF OVER THE WESTERN GREAT
LAKES FRIDAY INTO NEXT WEEKEND COINCIDENT WITH AN INCREASE IN PWATS.
WILL CARRY CHANCE POPS FRIDAY NIGHT INTO NEXT WEEKEND. TEMPS LOOK TO
REMAIN BELOW NORMAL WITH THE TROUGHINESS IN PLACE.

MARINE...

STRONG LOW PRESSURE HAS JUST ABOUT FINISHED BOTTOMING OUT OVER
NORTHEAST OHIO THIS AFTERNOON. SUBSEQUENTLY...THE STRONGEST WINDS
ACROSS LAKE ERIE AND LAKE ST CLAIR HAVE LIKELY ALREADY OCCURRED. AS
WINDS SHIFT TO A MORE NORTHERLY DIRECTION THIS EVENING...STILL
EXPECT WINDS TO INCREASE TO GALE FORCE ACROSS EXTREME SOUTHERN LAKE
HURON...BUT THESE STRONGER WINDS WILL BE THE EXCEPTION...WITH THE
OVERALL TREND OF GRADUALLY DIMINISHING WINDS OCCURRING THIS
EVENING...AND ESPECIALLY TONIGHT. DECREASING WINDS WILL CONTINUE ON
SUNDAY...WITH WINDS 10 KNOTS OR LESS BY SUNDAY EVENING AS A WEAK
SURFACE RIDGE ARRIVES. THE NEXT LOW PRESSURE SYSTEM LOOKS TO BE
TRACKING THROUGH SOUTHERN LOWER MICHIGAN MONDAY NIGHT...BRINGING
ANOTHER ROUND OF SHOWERS AND POSSIBLE THUNDERSTORMS. DEPENDING ON
THE STRENGTH OF THE LOW...SOUTHWEST WINDS SOUTH OF THE LOW OVER LAKE
ST CLAIR AND LAKE ERIE COULD GUST TO 25 KNOTS...WITH POSSIBLE
NORTHWEST GUSTS TO AROUND 25 KNOTS BEHIND THE LOW OVER LAKE HURON ON
TUESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT UNTIL 8 AM EDT SUNDAY FOR MIZ049-055-063-
     083.

     LAKESHORE FLOOD WARNING UNTIL 10 PM EDT THIS EVENING FOR MIZ070-076-
     083.

LAKE HURON...GALE WARNING UNTIL 4 AM EDT SUNDAY FOR LHZ443-464.

     SMALL CRAFT ADVISORY UNTIL 8 AM EDT SUNDAY FOR LHZ421-422-441-442.

LAKE ST CLAIR...GALE WARNING UNTIL 4 AM EDT SUNDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...GALE WARNING UNTIL 4 AM EDT SUNDAY FOR LEZ444.

&&

$$

UPDATE.......SC
AVIATION.....SC
SHORT TERM...MANN
LONG TERM....SF/DT
MARINE.......SF


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


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