Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 161925
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
325 PM EDT TUE SEP 16 2014

.SHORT TERM... THROUGH TONIGHT

QUIET NIGHT IN STORE FOR SE MI AS WEAKENING AREA OF HIGH PRESSURE
BUILDS ACROSS LOWER MI AND OHIO VALLEY. THIS HAS ALREADY BEGUN TO
INFLUENCE THE AREA WHICH IS EVIDENT IN THE QUALITY OF THE CU FIELD
THIS AFTERNOON...WHICH IS MUCH LESS DENSE THAN IT IS A BIT FURTHER
SOUTH OVER OHIO. THIS WILL ERODE SHORTLY AFTER SUNDOWN WITH THE
LOSS OF HEATING WHICH WILL LEAD TO A CLEAR NIGHT. SOME MODELS ARE
TRYING TO HANG ON TO SOME BL MOISTURE UNDER THE INVERSION DEVELOPING
A NOCTURNAL STRATUS DECK...BUT UPSTREAM OBS SUGGEST THEY AREA
OVERDOING THE LL MOISTURE THUS WILL CONTINUE THE CLEAR FORECAST.
GOOD RADIATIONAL COOLING SETUP AS THE HIGH TAKES HOLD WHICH WILL
ALLOW TEMPS DROP SEVERAL DEGREES LOWER THAN LAST NIGHT TO AROUND 40.
SOME LOCALLY COOLER SPOTS MAY SEE UPPER 30S WHEREAS THE DETROIT
METRO HEAT ISLAND WILL LIKELY STAY IN THE MID 40S.

&&

.LONG TERM...

A SHEAR MAX NOTED NEAR 70N OVER NUNAVUT WILL PROPAGATE AROUND THE
PERIPHERY OF THE LARGER SCALE PARENT CIRCULATION ANCHORED OVER HUDSON
BAY THROUGH THURSDAY, UNDERGOING A MODEST AMPLIFICATION AS IT DOES
SO. ALL RESPECTABLE MOISTURE AND DYNAMICS WITH THIS WAVE ARE PROGGED
TO REMAIN WELL NORTH. HOWEVER, THE ASSOCIATED "BACKDOOR FRONT" WILL
SLIDE THROUGH THE AREA ON WEDNESDAY NIGHT. WESTERLY FLOW AND DEEP
MIXING TO 850MB IN ADVANCE OF THE FRONT WILL ALLOW HIGHS TO EASILY
REACH THE MID/UPPER 60S ON WED AFTERNOON GIVEN NEARLY FULL SUN AND
H85 TEMPS NEAR 5C. BY WEDNESDAY NIGHT, NORTHEAST FLOW FILLING IN
BEHIND THE FRONT WILL ADVECT A SHALLOW AND NOTABLY COOLER AIRMASS
INTO THE AREA. 925MB TEMPERATURES ARE FORECAST TO FALL FROM NEAR 12C
WED AFTN TO 5C THURSDAY MORNING. WELL-MIXED NORTHEAST FLOW WILL BE
QUITE FAVORABLE FOR EXPANSION OF NOCTURNAL STRATOCU, ESPECIALLY
GIVEN ADDED MOISTURE FLUX OFF OF LAKE HURON. ALTHOUGH MODELED
SOUNDINGS INDICATE POTENTIAL FOR CLOUDS TO SCATTER BY THURSDAY
AFTERNOON, HIGHS SHOULD STRUGGLE TO REACH MUCH HIGHER THAN THE UPPER
50S IN MOST LOCATIONS PERSISTENCE OF COLD NORTHEAST FLOW FOR THE
BALANCE OF THE DAY. CLEARING SKIES AND A RELAXED SURFACE PRESSURE
GRADIENT WILL ALLOW TEMPERATURES TO POTENTIALLY FALL INTO THE MID OR
UPPER 30S THURSDAY NIGHT. THE EXCEPTION WILL BE ACROSS EASTERN AREAS
WHERE SOUTHEAST FLOW ABOVE THE NOCTURNAL LAND INVERSION WILL
POTENTIALLY ADVECT A STRATOCU DECK WITH ORIGINS OVER LAKE ERIE INTO
THE AREA.

HIGH PRESSURE WILL SLOWLY DRIFT EASTWARD ON FRIDAY AS THE NEXT LOW
PRESSURE SYSTEM TRACKS ACROSS THE NORTHERN PLAINS. THIS LOW WILL
DRAG A WARM FRONT ACROSS THE NORTHERN CWA ON FRIDAY NIGHT BRINGING A
CHANCE FOR SOME RAIN SHOWERS TO THE THUMB REGION. RAIN CHANCES
INCREASE ON SATURDAY AND INTO SUNDAY AS A COLD FRONT THEN MOVES
ACROSS THE REGION. TIMING ON THIS COLD FRONT IS STILL A BIT
UNCERTAIN. THEREFORE HAVE ONLY INCLUDED CHANCE POPS IN THE FORECAST
FOR THE DAYTIME ON SATURDAY AND SUNDAY AND LOW LIKELY POPS FOR
SATURDAY NIGHT WHEN THE BEST CHANCE FOR SHOWERS IS EXPECTED. THE
COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION BY SUNDAY NIGHT
WITH HIGH PRESSURE RETURNING TO SOUTHEAST MICHIGAN FOR THE BEGINNING
OF NEXT WEEK.

&&

.MARINE...

LIGHT WESTERLY WINDS TODAY WILL BACK TO MODERATE SOUTHWESTERLY FLOW
AHEAD OF AN APPROACHING FRONT BY EARLY WEDNESDAY. THE PASSAGE OF THE
FRONT ON WEDNESDAY NIGHT WILL RESULT IN MODERATE TO FRESH NORTHEAST
FLOW FORCING COOLER AIR TO SPREAD ACROSS AREA WATERS. GUSTS WILL
APPROACH 25 KNOTS. A SMALL CRAFT ADVISORY FOR BOTH WINDS AND WAVES
MAY BE NEEDED FOR NEARSHORE ZONES OF LAKE HURON ALONG THE THUMB
WEDNESDAY NIGHT INTO THURSDAY. WINDS WILL EASE THURSDAY NIGHT INTO
FRIDAY BEFORE SOUTHERLY WINDS BEGIN TO RAMP UP AHEAD OF THE NEXT
SYSTEM LATE FRIDAY.

&&

.AVIATION...ISSUED 132 PM EDT TUE SEP 16 2014

//DISCUSSION...

VFR CONDITIONS EXPECTED THROUGH THE TAF CYCLE AS HIGH PRESSURE
BUILDS INTO THE REGION. DIURNAL CU FIELD FORMING AS BOUNDARY LAYER
MOISTURE TRIES TO MIX OUT BUT IS STRUGGLING A BIT MORE THAN
EXPECTED. THIS IS ESPECIALLY TRUE FOR FNT/PTK WHICH ARE ON THE
HIGHER TERRAIN. LOSS OF HEATING WILL ALLOW CU TO QUICKLY CLEAR OUT
TONIGHT LEADING TO CLEAR SKIES. MINIMAL COVERAGE EXPECTED TOMORROW
DUE TO INCREASED MIXING.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILING BELOW 5KFT THIS AFTERNOON OR TOMORROW
AFTERNOON.

&&

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

&&

$$

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


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






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