Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 240358
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1158 PM EDT WED JUL 23 2014


.AVIATION...

//DISCUSSION...

VFR CIGS BETWEEN 6-10KFT OR SO WILL SHIFT OUT OF TERMINALS EARLY IN
THE FORECAST PERIOD AS HIGH PRESSURE IS USHERED INTO AREA BEHIND
PASSING SHORTWAVE TROUGH. DRIER AIR ASSOCIATED WITH THIS HIGH WILL
LIKELY LIMIT THE AMOUNT OF DIURNAL CU/STRATO-CU ON THURSDAY WITH
GENERALLY SCT CLOUDS. WITH THIS HIGH BECOMING THE MAIN FEATURE OVER
THE AREA...WINDS WILL ALSO REMAIN LIGHT...GENERALLY UNDER 10 KNOTS.

//DTW THRESHOLD THREATS...

* NONE.

&&

.PREV DISCUSSION...ISSUED 353 PM EDT WED JUL 23 2014

SHORT TERM...THROUGH TONIGHT

SURFACE HIGH PRESSURE HAS BEGUN BUILDING INTO THE AREA IN THE WAKE
OF THIS MORNINGS COLD FRONT. THIS HIGH WILL MOVE EASTWARD FROM
SOUTHERN MANITOBA TOWARD THE WESTERN GREAT LAKES BY MORNING. THIS
WILL KEEP US UNDER WEAK NORTHERLY CAA FLOW THROUGH THE OVERNIGHT
WHILE ADVECTING DRIER AIR INTO THE AREA. THE HEALTHY DIURNAL CU
FIELD SHOULD ERODE QUICKLY AFTER SUNSET WITH THE DRY MID LEVEL AIR
MOVING IN LEAVING MOSTLY CLEAR SKIES FOR THE OVERNIGHT WITH ONLY
SOME HIGH CLOUDS AROUND. A MID LEVEL PV ANOMALY WILL SURGE SE ACROSS
THE STATE PULLING THE THERMAL TROUGH AXIS OVER SOUTHERN MI BY EARLY
THURSDAY MORNING. 850MB TEMPS WILL DROP FROM ABOUT 14C AT PRESS TIME
DOWN TO AROUND 7C BY 12Z THURSDAY. MIN TEMPS TONIGHT MAY BE TRICKY
AS THE DRY COOL AIR...BUILDING HIGH PRESSURE...AND DECREASING MID
LEVEL HEIGHTS WILL WANT TEMPS TO FALL PRETTY GOOD BUT 15-20 KNOT
FLOW IN THE 850-950MB LAYER WILL KEEP THE LAYER FAIRLY MIXED WHICH
SHOULD CURB DECOUPLING IN THE BL. OVERALL EXPECT TEMPS TO FALL
INTO THE LOW 50S...BUT MAY TAKE A WHILE TO GET THERE AND LAST ONLY A
COUPLE HOURS BEFORE MORNING. IF WINDS SHOULD DROP OFF MORE THAN
MODELS ARE ADVERTISING...A FEW COLDER LOCATIONS MY DIP INTO THE
UPPER 40S TO 50. AT THAT POINT DEWPOINTS WILL STEP IN TO LIMIT THE
AMOUNT OF COOLING.

LONG TERM...

MASS GRADIENT BETWEEN THE HIGH AMPLITUDE WESTERN U.S. RIDGE AND THE
NORTHEAST CANADA VORTEX WILL DRIVE STRONGLY CONFLUENT UPPER FLOW
ACROSS THE GREAT LAKES REGION FOR THE REMAINDER OF THE WORK WEEK.
ASSOCIATED SURFACE HIGH PRESSURE WILL TRANSLATE ACROSS THE REGION
DURING THIS TIME AS THE UPSTREAM RIDGE AXIS DEAMPLIFIES AND FOLDS
EAST IN ADVANCE OF THE COMPACT PAC NW LOW, WHICH IS PROGGED TO EJECT
ACROSS THE CANADIAN ROCKIES. THE DOMINANCE OF SURFACE HIGH PRESSURE
MEANS THE RESIDENT AIRMASS WILL HANG TIGHT THROUGH FRIDAY WITH ONLY
AN INCREMENTAL 2-3 DEGREES OF MODERATION EACH DAY. THE COOL NATURE
OF THE AIRMASS WILL SUPPORT DEEP DIURNAL BOUNDARY LAYER GROWTH.
THUS, BOTH THURS AND FRI ARE FORECAST TO FEATURE A HEALTHY COVERAGE
OF HIGH-BASED FAIR WEATHER CU TO ALONG WITH HIGHS IN THE MID/UPPER
70S.

PACNW LOW IS PROGGED TO HAVE SIGNIFICANTLY DAMPENED THE UPSTREAM
RIDGE BY FRIDAY NIGHT. INCREASING LOW-LEVEL FLOW IN ADVANCE OF THIS
APPROACHING COMPACT CIRCULATION WILL ALLOW DEWPOINTS TO RISE INTO
THE UPPER 60S IN THE LOWER PENINSULA ON SATURDAY, LEADING TO MODEST
POTENTIAL FOR SOME DESTABILIZATION. CONVECTIVE POTENTIAL WILL BE
TIED TO UPSTREAM CONVECTIVE TRENDS, BUT WITH PORTIONS OF LOWER MI
INVOF THE INSTABILITY GRADIENT AND UNDER THE INCREASING INFLUENCE OF
ENERGETIC WESTERLY FLOW ALOFT, POTENTIAL FOR SHOWERS WARRANTS AT
LEAST A CHANCE POP WITH MENTION OF THUNDER FRI NIGHT THRU SAT.

WEAK LOW PRESSURE WILL EXIT TO THE NORTHEAST AND A BRIEF DRY PERIOD
WILL BEGIN STARING SATURDAY NIGHT. DRY CONDITIONS WILL CONTINUE INTO
SUNDAY MORNING BEFORE THE NEXT LOW PRESSURE SYSTEM SWINGS THROUGH
THE GREAT LAKES REGION. THIS LOW WILL BRING ANOTHER ROUND OF RAIN
SHOWERS AND THUNDERSTORMS TO SOUTHEAST MICHIGAN SUNDAY AFTERNOON
THROUGH SUNDAY NIGHT. HIGH PRESSURE THEN WILL BUILD INTO THE WESTERN
GREAT LAKES ON MONDAY AND EVENTUALLY BUILD INTO THE OHIO VALLEY WITH
DRY CONDITIONS RETURNING ONCE AGAIN THROUGH MID-WEEK. TEMPERATURE
WISE...HIGHS ON SUNDAY WILL BE IN THE LOW 80S BEFORE MUCH COOLER
TEMPS FILTER INTO THE REGION BRINGING HIGHS INTO THE LOW TO MID 70S
THROUGH WEDNESDAY. WHILE LOW TEMPERATURES WILL START OFF IN THE MID
60S ON SATURDAY NIGHT...THE COOLER AIR WILL DROP LOWS INTO THE MID
50S THROUGH THE REST OF THE EXTENDED PERIOD.

MARINE...

MODERATE NORTHERLY FLOW GUSTING TO AROUND 20 KNOTS WILL DECREASE
TONIGHT AS THE SURFACE PRESSURE GRADIENT WEAKENS AND THE INFLUX OF
COOL AIR ACROSS THE WATERS EASES. IT WILL...HOWEVER...BE ENOUGH TO
SUPPORT 3 TO 6 FOOT SIGNIFICANT WAVE HEIGHTS WITHIN THE EXPOSED
NEARSHORE WATERS OF THE THUMB THROUGH LATE TONIGHT. THE SMALL CRAFT
ADVISORY FOR THESE AREAS HAS BEEN EXTENDED AN ADDITIONAL 6 HOURS
ACCORDINGLY. WINDS WILL THEN REMAIN ON THE LIGHT SIDE THROUGH THE
WEEKEND BEFORE RAMPING UP AGAIN EARLY NEXT WEEK AS ANOTHER ROUND OF
COOL AIR SPREADS ACROSS THE GREAT LAKES.

&&

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

&&

$$

AVIATION.....DG
SHORT TERM...DRK
LONG TERM....JVC/RK
MARINE.......JVC


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).





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