Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 240726
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
326 AM EDT MON AUG 24 2015

.SHORT TERM...TODAY AND TONIGHT

COOLER WEATHER CAN BE EXPECTED TODAY AS A LARGE LOW PRESSURE SYSTEM
SLOWLY TRACKS EASTWARD ACROSS THE NORTHERN GREAT LAKES. MAINLY CLEAR
SKIES WILL TRANSITION INTO PARTLY/MOSTLY CLOUDY CONDITIONS AS LOW
LEVEL MOISTURE IN THE FORM OF STRATUS/STRATO-CU WRAPS INTO NORTHERN
AREAS AROUND THIS LOW PRESSURE CENTER. ADDITIONAL STRATO-CU WILL
ALSO EXPAND INTO SOUTHERN AREAS AS UPPER LEVEL COLD POOL MOVES OVER
THE AREA. GIVEN LOCATION OF THE LOW TO THE NORTHERN...EXPECT THE
MOST CLOUDINESS TO EXIST I-69 NORTH WITH A FEW INSTABILITY SHOWERS
POSSIBLE LATE TODAY. SKIES WILL TREND TO PARTLY CLOUDY SOUTHWARD TO
THE MICHIGAN AND OHIO STATE LINE.

AS BOUNDARY LAYER MIXING INCREASES THIS MORNING...EXPECT GUSTY WEST
TO SOUTHWEST WINDS TO DEVELOP WITHIN DECENT PRESSURE GRADIENT
BETWEEN THIS LOW AND HIGH PRESSURE OVER THE PLAINS/MID MISSISSIPPI
VALLEY. THESE DOWNSLOPING WINDS SHOULD ADD A DEGREE OR TWO TO HIGHS
THIS AFTERNOON FROM DETROIT SOUTH...AND WILL ADJUST FORECAST INTO
THE 75F TO 77F RANGE. FURTHER NORTH...LOWER 70S ALONG I-69 WILL GIVE
WAY TO UPPER 60S OVER PARTS OF THE SAGINAW VALLEY WHERE CLOUDINESS
WILL BE THE GREATEST.

&&

.LONG TERM...TUESDAY THROUGH SUNDAY

UPPER AND SURFACE LOW PRESSURE WILL CONTINUE TO TRACK EAST ACROSS
ONTARIO AND INTO QUEBEC TUESDAY AND WEDNESDAY. MOIST CYCLONIC FLOW
AROUND THIS SYSTEM WILL PROVIDE MAX TEMPERATURES 10 TO 15 DEGREES
BELOW NORMAL AND PLENTY OF CLOUDS...ESPECIALLY AS THE COOL AIR RIDES
OVER THE WARMER WATERS OF THE GREAT LAKES. UPPER COLD POOL WILL
PROVIDE INSTABILITY FOR SHOWERS...ESPECIALLY DURING THE DAY WHEN
SURFACE HEATING STEEPENS LOW-LEVEL LAPSE RATES. WILL ALSO SEE SOME
CONTRIBUTION FROM OFF THE GREAT LAKES.

UPPER SHORTWAVE PIVOTING AROUND UPPER LOW WILL DROP THROUGH LOWER
MICHIGAN TUESDAY INTO TUESDAY NIGHT...BRINGING A REINFORCING SHOT OF
COLD AIR AND A BOOST TO UPWARD FORCING. THIS SHOULD PROVIDE A MORE
SCATTERED COVERAGE OF SHOWERS COMPARED TO TODAY. A SURFACE RIDGE
WILL THEN GRADUALLY BUILD IN FROM THE WESTERN GREAT LAKES WEDNESDAY
AND WEDNESDAY NIGHT...AS IT BECOMES POSITIONED AHEAD OF AN UPPER
RIDGE EXTENDING UP THROUGH THE CENTRAL U.S. AND CANADA. EXPECTING TO
SEE A LOWER COVERAGE OF SHOWERS BY WEDNESDAY AND ESPECIALLY BY
WEDNESDAY NIGHT AS THE LOW AND ASSOCIATED MOISTURE BEGIN TO PULL
AWAY FROM THE AREA AND SUBSIDENCE OVER LAKE MICHIGAN BRINGS LESS
FAVORABLE CONDITIONS FOR LAKE EFFECT SHOWERS/CLOUDS.

MEDIUM RANGE MODELS SHOW SURFACE HIGH PRESSURE CENTERED OVER THE
AREA ON THURSDAY...WHILE COLDEST AIR ALOFT SHIFTS TO OUR EAST. DRY
WEATHER IS EXPECTED AS TEMPERATURES WARM ALOFT AND A STRONG
SUBSIDENCE INVERSION FORMS. UPPER RIDGING WILL GRADUALLY SHIFT INTO
THE EASTERN U.S. BY THE END OF THE WEEK...ALTHOUGH GFS/EURO/GEM SHOW
AN UPPER SHORTWAVE TRACKING ACROSS THE GREAT LAKES AND OHIO VALLEY
FOR THE WEEKEND. TIMING AND TRACK OF THIS FEATURE STILL VARIES QUITE
A BIT BOTH MODEL TO MODEL AND RUN TO RUN...AND LOW CHANCE POPS OVER
THE WEEKEND STILL LOOK MOST APPROPRIATE UNTIL MODELS CAN GET A
BETTER FEEL FOR THE UPPER WAVE AS IT DEVELOPS OVER THE SOUTHWEST
DURING THE NEXT FEW DAYS. OTHERWISE...AN OVERALL WARMING TREND IS
EXPECTED THROUGH THE WEEKEND...BACK CLOSER TO SEASONAL NORMALS.

&&

.MARINE...

WINDS WILL TURN SOUTHWEST AND INCREASE TODAY AS ANOTHER COLD FRONT
DROPS THROUGH THE CENTRAL GREAT LAKES. GUSTS UP TO 30 KNOTS ARE
EXPECTED...AND SMALL CRAFT ADVISORIES ARE IN EFFECT FOR ALL
NEARSHORE WATERS FROM LATE MORNING THROUGH EVENING. WAVE HEIGHTS
OVER SAGINAW BAY LOOK TO INCREASE INTO THE 3 TO 5 FOOT RANGE...WHILE
WAVES OVER THE REMAINDER OF THE NEARSHORE WATERS REMAIN LOWER AS
THEY ARE SHELTERED BY LAND. WINDS AND WAVES WILL GRADUALLY DECREASE
THROUGH THE EVENING BEHIND THE COLD FRONT.

A POOL OF COLD AIR WILL ALSO REMAIN OVER THE CENTRAL GREAT LAKES
TODAY THROUGH WEDNESDAY AS AN AREA OF UPPER LEVEL LOW PRESSURE
SLOWLY MOVES THROUGH ONTARIO. THE COLDER AIR ABOVE THE WARM LAKE
WATERS WILL CREATE FAVORABLE CONDITIONS FOR WATERSPOUTS TODAY
THROUGH WEDNESDAY.

&&

.AVIATION...ISSUED 1241 AM EDT MON AUG 24 2015

SKIES HAVE BECOME MOSTLY CLEAR ACROSS SOUTHEAST MI. SOME STRATOCU
TRYING TO MAKE IT TOWARD MBS BUT IT CONTINUES TO STRUGGLE AND EXPECT
THAT TO CONTINUE THROUGH THE NIGHT. EXPECT DIURNAL CU TO EXPAND
ACROSS SE MI MONDAY MORNING AND AFTERNOON AS GOOD LEVEL MOISTURE IN
COMBINATION TO LOW LEVEL INSTABILITY WITH A GOOD COOL FALL AIRMASS.
SHOULD BE BKN CIGS BETWEEN 4K AND 6K FEET THROUGH THE DAY. ALSO
DIURNAL WEST WINDS WILL INCREASE DURING THE MORNING WITH GUSTS IN
EXCESS OF 25 KTS.

FOR DTW...QUICK CLEARING BEHIND COLD FRONT WILL LAST THROUGH THE
NIGHT. CLOUDS ARE THEN EXPECTED TO STRUGGLE FILL BACK ON MONDAY.
MAINLY SCT AROUND 6K FEET BUT BECOMING BKN CIGS AROUND 6K FEET
TOWARD MONDAY EVENING. WEST SOUTHWEST WINDS WILL BECOME STRONG (25
KNOTS) DURING THE DAY.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR CEILINGS AT OR BELOW 5000 FT THROUGH 22Z MONDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT FROM 10 AM EDT THIS MORNING THROUGH THIS
     EVENING FOR MIZ049.

LAKE HURON...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 9 PM EDT THIS
     EVENING FOR LHZ421-422-441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 9 PM EDT THIS
     EVENING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 9 PM EDT THIS
     EVENING FOR LEZ444.

&&

$$

SHORT TERM...DG
LONG TERM....HLO
MARINE.......HLO
AVIATION.....DG


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


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