Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 201945
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
345 PM EDT SUN JUL 20 2014

.SHORT TERM...THROUGH TONIGHT

UPPER HEIGHT RISES WILL COMMENCE THROUGH TONIGHT AS THE UPPER RIDGE
OVER THE CONUS AMPLIFIES AND STARTS TO SLIDE EAST. AT THE
SURFACE...HIGH PRESSURE OVER THE NEW ENGLAND WILL CONTINUE TO EXPAND
BACK ACROSS MICHIGAN. SUBSIDENCE PROVIDED BY HIGH PRESSURE AT THE
SURFACE AND ALOFT WILL ALLOW DIURNAL CU FIELD TO DISSIPATE AROUND
SUNSET...WITH JUST SOME HIGH CLOUDS EXPECTED TO START WORKING IN
FROM THE NORTHWEST LATE TONIGHT. CLEARING SKIES AND LIGHT WINDS WILL
ONCE AGAIN ALLOW SHALLOW SURFACE-BASED INVERSIONS TO FORM. EXPECT
AREAS OF FOG TO DEVELOP ONCE AGAIN WITH SURFACE DEWPOINTS CLOSE TO
60 LATE TONIGHT. FOG SHOULD BE SLIGHTLY LESS DENSE THAN LAST NIGHT
WITH LOW-LEVEL FLOW FROM THE WEST INSTEAD OF THE EAST OFF THE LAKES.
MIN TEMPS WILL RUN SLIGHTLY WARMER THAN LAST NIGHT WITH JUST A
SLIGHT BOOST IN THE LOW-LEVEL THERMAL FIELDS/THICKNESSES...FROM THE
UPPER 50S TO LOW 60S.

&&

.LONG TERM...MONDAY THROUGH NEXT SUNDAY

THERE CONTINUES TO BE MODEL AGREEMENT WITH THE BUILDING RIDGE FOR
MONDAY AND INTO TUESDAY...THEN FOR A BREAKDOWN OF THAT RIDGE ON
WEDNESDAY WITH THE PASSAGE OF A COLD FRONT EARLY DURING THE DAY ON
WEDNESDAY.

THE UPPER WAVE OVER SC CANADA AND MN WILL MOVE OVER THE BUILDING
RIDGE AND MAY BRING SOME HIGH CLOUD TO THE NE PORTION OF THE FORECAST
AREA.  ALSO EXPECT MORE AFTERNOON CU ON MONDAY...BUT NOTHING TO STOP
A MOSTLY SUNNY FORECAST. REALLY NOT MUCH ON MONDAY NIGHT EITHER AND
WOULD EXPECT CLEAR SKIES. CANNOT ARGUE WITH MOS TEMPS FOR BOTH
PERIODS. THE DEW POINTS ARE A LITTLE LOWER FOR MONDAY NIGHT THAN
PREVIOUS FORECASTS AND WILL FOLLOW MOS TO GO A LITTLE COOLER.

TUESDAYS CLOUD AND HIGH TEMPERATURE ARE ALL PREDICATED ON THE AMOUNT
OF DEBRIS CLOUD FROM THE UPPER MS RIVER CONVECTION LATE MONDAY AND
MONDAY NIGHT. ALL MODELS ARE SUGGESTING THAT THE DEBRIS CLOUD
DISSIPATES INTO THE UPPER RIDGE BEFORE IT GETS TO THE FORECAST AREA.
THE 850 MB TEMPS GET CLOSE TO OR UP TO 20C. WHEN THE EML ADVECTS
OVER THE LAKES REGION...THAT TENDS TO BE A TIME WHEN WE GET A LITTLE
HIGHER THAN GUIDANCE. GIVEN THE EXPECT MOSTLY SUNNY SKIES FOR THE
BULK OF THE DAY...WILL GO JUST ABOVE GUIDANCE FOR TUESDAY.

TUESDAY NIGHT INTO WEDNESDAY MORNING HAS THE WIND FIELD AND MOISTURE
INCREASING.  MLCAPES GET UP TO 1200-1800 J/KG ON TUESDAY IN A CAPPED
ENVIRONMENT.  THOSE MLCAPES HOLD ABOVE 1000 J/KG DURING THE NIGHT.
MODELS INDICATE ANOTHER WAVE IN THE INCREASING FLOW OVER IA/MN ON
TUESDAY MOVING ESE TO SW LOWER/INDIANA BY 12Z WEDNESDAY WITH THE
APPROACH OF THE SURFACE FRONT. GIVEN THE UNCERTAINTY IN THE EXACT
PLACEMENT OF THE UPPER WAVES WHICH WILL BE LARGELY DICTATED BY THE
UPSTREAM CONVECTION ON BOTH MONDAY AND TUESDAY...WILL KEEP WITH THE
CHANCE POPS TUESDAY NIGHT AND WEDNESDAY MORNING.

ALL MODELS...EXCEPT THE GFS WITH ITS CONVECTIVE FEEDBACK...SUGGESTS
THE FRONT MOVES THROUGH THE FORECAST AREA FROM ABOUT 12Z TO 18Z
WEDNESDAY. BEHIND THE FRONT IS FAIRLY IMPRESSIVE LOW LEVEL COLD AIR
ADVECTION. THIS SHOULD BRING SOME BREEZY CONDITIONS FOR THE
AFTERNOON AND KEEP SOME STRATOCU AROUND UNTIL THE DRIER LOW LEVEL
AIR WORKS INTO THE REGION TOWARD EVENING.

HIGH PRESSURE WILL QUICKLY BUILD INTO THE GREAT LAKES REGION OUT OF
CANADA BY WEDNESDAY EVENING. THIS HIGH WILL REMAIN SITUATED OVER
SOUTHEAST MICHIGAN THROUGH FRIDAY EVENING RESULTING IN DRY AND
PLEASANT CONDITIONS ACROSS THE CWA. THE HIGH WILL FINALLY DRIFT
EASTWARD ON SATURDAY MORNING AS THE NEXT LOW PRESSURE SYSTEM
APPROACHES FROM THE WEST. THIS LOW WILL BRING A RETURN OF RAIN
SHOWERS FOR THE SATURDAY NIGHT AND SUNDAY TIMEFRAME. HIGH
TEMPERATURES WILL HOVER IN THE MID TO UPPER 70S WITH LOW
TEMPERATURES IN THE UPPER 50S TO LOW 60S FROM WEDNESDAY EVENING
THROUGH THE WEEKEND.

&&

.MARINE...

A BROAD REGION OF HIGH PRESSURE EXTENDING ACROSS SOUTHEAST LOWER MI
AND THE EASTERN LAKES WILL MAINTAIN LIGHT WINDS AND FAVORABLE WAVE
CONDITIONS SOUTHERN LAKE HURON...LAKE ST. CLAIR AND LAKE ERIE WHILE
NORTHERN LAKE HURON WILL MAINTAIN A LIGHT S-SE WIND. LIGHT S-SW
WINDS WILL DEVELOP ON MONDAY AND STRENGTHEN A LITTLE ON TUESDAY IN
ADVANCE OF A SLOW MOVING FRONTAL BOUNDARY OVER THE NORTHERN PLAINS.
WARM AIR ADVECTION WILL LEAD TO STRONG STABILITY OVER THE LAKES
DURING THIS TIME FRAME. THIS WILL KEEP WINDS GENERALLY AT OR BELOW
15 KNOTS.

A COLD FRONT WILL PASS THROUGH THE REGION TUESDAY NIGHT OR
EARLY WEDNESDAY...PROVIDING A CHANCE FOR THUNDERSTORMS. THERE IS
LIKELY TO BE A NOTABLE WIND SHIFT TO THE N-NW WITH THE PASSAGE OF
THE FRONT WITH UNSTABLE CONDITIONS DEVELOPING. THIS WILL LEAD TO
WINDS 15 TO 25 KNOTS AND BUILDING WAVES...ESPECIALLY FOR LAKE HURON.

&&

.AVIATION...ISSUED 123 PM EDT SUN JUL 20 2014

//DISCUSSION...

MOISTURE TRAPPED UNDER AN INVERSION WILL CONTINUE TO GENERATE A CU
FIELD AS DAYTIME HEATING PEAKS. THERE IS SOME UNCERTAINTY TO HOW
WIDESPREAD THIS CLOUD FIELD BETWEEN 4000-6000 FEET WILL BECOME
HOWEVER AS DRIER AIR TRIES TO MIX INTO THE LAYER OF MOISTURE SETTLED
UNDER THE INVERSION. BEST POTENTIAL FOR BKN CEILINGS WILL INITIALLY
BE OVER THE MOST INLAND PORTIONS OF THE LOWER PENINSULA EARLY THIS
AFTERNOON...WHERE SOME LOW-LEVEL WIND CONVERGENCE EXISTS. THIS AREA
OF CONVERGENCE WILL SHIFT SLOWLY EAST THROUGH THE LATE
AFTERNOON...INCREASING POTENTIAL FOR BKN CEILINGS AT MBS AND FNT. BY
THE TIME THIS CONVERGENCE AXIS SHIFTS TOWARDS THE DETROIT
AREA...DAYTIME HEATING WILL BE WANING AND THE CU FIELD WILL START TO
DISSIPATE. OTHERWISE...ONLY EXPECTING PATCHY CIRRUS AND A LITTLE BIT
OF SMOKE FROM THE WESTERN WILDFIRES...BOTH OF WHICH WILL LAST INTO
THE OVERNIGHT HORUS. SKIES SHOULD BECOME CLEAR ENOUGH HOWEVER FOR
FOG/BR TO FORM AGAIN AS WINDS GO LIGHT. FOG/BR LOOKS TO BE A LITTLE
LESS DENSE THAN LAST NIGHT HOWEVER AS LIGHT FLOW OVER THE GREAT
LAKES TURNS WEST AS OPPOSED TO EAST OFF THE NEARBY LAKES LIKE LAST
NIGHT.

FOR DTW...FOG/BR TRENDS WILL BE THE MAIN CONCERN FOR THE 18Z TAF
PERIOD. THE BEST POTENTIAL FOR MVFR BR IS BETWEEN 07Z AND 13Z...WITH
SOME IFR CONDITIONS POSSIBLY SETTLING IN AROUND 09Z.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE WITH CEILINGS BELOW 5000 FEET THROUGH 01Z TODAY.

* LOW CONFIDENCE IN FOG BELOW 1/2 MILE OR CEILINGS AT OR BELOW 200
FEET FROM 09-13Z MON.

&&

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

&&

$$

SHORT TERM...HLO
LONG TERM....RBP/RK
MARINE.......RBP
AVIATION.....HLO


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





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