Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 241653
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1253 PM EDT MON AUG 24 2015

.AVIATION...

A SECONDARY SURGE OF COOLER AIR WILL MOVE FROM WISCONSIN THROUGH
LOWER MICHIGAN DURING THE REST OF THE AFTERNOON AND EVENING
PROVIDING CONTINUED SUPPORT FOR GUSTY WEST WIND AND VFR CEILING. A
FEW LIGHT/VFR RAIN SHOWERS ARE ALSO POSSIBLE...MAINLY IN THE FNT TO
MBS REGION. PLAN TO MONITOR RADAR TRENDS ON SHOWER COVERAGE AS
EXPECTATIONS REMAIN THAT COVERAGE WILL BE TOO LOW TO INCLUDE AT THE
TERMINAL LOCATIONS. THE CLOUD PATTERN WILL HOLD THROUGH MUCH OF
TONIGHT AT VFR LEVELS BUT AT THE LOW END OF THE RANGE. A HINT OF
MVFR IS POSSIBLE LATE TONIGHT THROUGH MID TUESDAY MORNING BUT
POTENTIAL WILL BE BETTER WEST OF THE TERMINAL CORRIDOR DEPENDING ON
CONTRIBUTIONS FROM LAKE MICHIGAN.

FOR DTW... CEILING OF SHALLOW CUMULUS ABOVE 5000 FT IS EXPECTED TO
SETTLE BELOW 5000 FT BY EVENING AS A SECONDARY FRONT MOVES THROUGH
THE REGION. THE FRONT WILL ALSO SUPPORT CONTINUED GUSTY WEST WIND
AROUND 25 KNOTS THROUGH MID EVENING. EXPECT CEILING BELOW 5000 FT TO
HOLD THROUGH TUESDAY MORNING.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR CEILING 5000 FT OR LESS THROUGH MID AFTERNOON...MEDIUM
  LATE AFTERNOON/EVENING THROUGH TUESDAY MORNING.

* LOW FOR EXCEEDING CROSS WIND THRESHOLD ON 25 KNOTS GUSTS
  AVERAGING FROM 250 DURING AFTERNOON AND 280 DURING EVENING.

&&

.PREV DISCUSSION...ISSUED 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.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...BEACH HAZARDS STATEMENT UNTIL 9 PM EDT THIS EVENING FOR MIZ049.

LAKE HURON...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR LHZ421-422-
     441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR LEZ444.

&&

$$

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


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