Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250008
AFDDTX

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

.UPDATE...

QUICK UPDATE TO ACCOUNT FOR SHOWERS ALONG THE SECONDARY SURGE OF
COLDER AIR MAKING IT FARTHER SOUTH INTO THE M 59 AND I 94
COUNTIES. NOTHING HAS MEASURED YET THIS EVENING...SO THE SMALL
POPS SHOULD COVER THIS. ALSO TOOK CARE OF CLOUD WORDING NOW THAT
THE STRATOCU HAS OVERSPREAD THE ENTIRE FORECAST AREA.
OTHERWISE..TEMPS LOOK ON TARGET WITH NO CHANGES NECESSARY.

&&

.AVIATION...ISSUED 705 PM EDT MON AUG 24 2015

THE SECONDARY SURGE OF COOLER AIR HAS JUST ABOUT MOVED THROUGH ALL
OF LOWER MICHIGAN WITH ITS ASSOCIATED COLD POOL VFR CEILING
STRATOCU. A FEW LIGHT/VFR RAIN SHOWERS REMAIN POSSIBLE...MAINLY IN
THE FNT TO MBS REGION. EXPECT COVERAGE WILL CONTINUE TO BE TOO LOW
TO INCLUDE AT THE TERMINAL LOCATIONS. THE CLOUD PATTERN WILL HOLD
THROUGH 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. EXPECT MORE OF THE SAME THROUGH
TUESDAY AFTERNOON AS THE VFR CEILINGS LIFT JUST A BIT. WINDS WILL BE
CONSIDERABLY LIGHTER ON TUESDAY.

FOR DTW... CEILING OF STRATOCUMULUS ABOVE 5000 FT IS EXPECTED TO
SETTLE BELOW 5000 FT BY 04Z. THE FRONT WILL ALSO SUPPORT CONTINUED
GUSTY WEST WIND AROUND 25 KNOTS THROUGH MID EVENING. EXPECT CEILING
BELOW 5000 FT TO HOLD THROUGH TUESDAY.

//DTW THRESHOLD PROBABILITIES...

* MEDIUM FOR CEILINGS BELOW 5000 FT THROUGH TUESDAY.

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

&&

.PREV DISCUSSION...ISSUED 353 PM EDT MON AUG 24 2015

SHORT TERM... AFTERNOON THROUGH TONIGHT

A TOUCH OF FALL WEATHER WILL BECOME MORE FIRMLY ESTABLISHED DURING
THE REST OF TODAY THROUGH TONIGHT. THE IMPRESSIVE CLOSED UPPER LEVEL
LOW PRESSURE SYSTEM WILL CONTINUE TO DRIFT OVER NORTHERN ONTARIO AND
DIRECT COOLER AIR...CLOUDS...AND SCATTERED SHOWERS INTO SOUTHEAST
MICHIGAN ON MODERATE WESTERLY WIND.

SATELLITE IMAGERY AND MODEL ANALYSIS FIELDS INDICATE A SPOKE OF
HEIGHT FALLS AND ASSOCIATED VORTICITY MAX WILL ROTATE FROM OVER
WISCONSIN THROUGH LOWER MICHIGAN DURING THE LATE AFTERNOON AND
EVENING. THE SURFACE PRESSURE REFLECTION WILL MARK A SECONDARY COLD
FRONT/TROUGH THAT WILL CARRY A REINFORCING SURGE OF COOL AIR INTO
THE REGION AND TAKE TEMPERATURES DOWN ANOTHER STEP AFTER THE FRONT
THAT MOVED THROUGH YESTERDAY. GUIDANCE MIN TEMPERATURES IN THE LOWER
TO MID 50S WILL BE ON TARGET CONSIDERING CLOUD COVER AND MODERATE
WIND HOLDING UP THROUGH THE NIGHT. MODEL TEMPERATURE PROJECTIONS
ALOFT ARE HIGHLIGHTED BY READINGS DROPPING TO ABOUT 6C ON AVERAGE AT
850 MB AND TO NEAR -15C AT 500 MB OVER THE SAGINAW VALLEY AND
NORTHERN THUMB TONIGHT. THESE READINGS ARE NEAR RECORD LOWS IN THE
DTX UPPER AIR DATABASE THAT ARE 5.6C AND -15.6C RESPECTIVELY FOR THE
00Z 8/25 UPPER AIR RUN. A DEEPER MOISTURE PLUME ASSOCIATED WITH THE
COLD POOL WILL SLIDE OVER CENTRAL LOWER MICHIGAN DURING THE EVENING
AND MAINTAIN SOME INSTABILITY EVEN AFTER SUNSET...PERHAPS WITH A
SMALL BOOST FROM LAKE MICHIGAN. CHANCE POPS/SCATTERED COVERAGE LOOKS
GOOD BASED ON MESOSCALE MODEL OUTPUT DOWN TO ABOUT THE I-69
CORRIDOR. PLAN TO MAINTAIN DRY CONDITIONS IN THE DETROIT METRO AREA
TO THE OHIO BORDER FOR NOW AND MONITOR PROGRESS OF LAKE INFLUENCE
THROUGH THE NIGHT.

LONG TERM...

LARGE AND SEASONABLY COLD UPPER LEVEL CIRCULATION ENCOMPASSING THE
GREAT LAKES REGION/ONTARIO WILL BE SLOW TO BREAK DOWN AND TRACK EAST
OVER THE NEXT COUPLE OF DAYS. 12Z INL SOUNDING REVEALED AN 850 MB
TEMP OF 1 C. MODIFICATION OF THIS AIRMASS WILL OCCUR...BUT LOOKS
LIKE 850 MB TEMPS WILL BE IN THE 5 TO 6 C RANGE TO START THE DAY ON
TUESDAY. THIS COOL CYCLONIC FLOW COMING OFF LAKE MICHIGAN SHOULD BE
SUFFICIENT TO CARRY A MOSTLY CLOUDY FORECAST DURING THE DAY...WITH
SUFFICIENT LOW LEVEL LAPSE RATES/CAPE (100 J/KG) TO CARRY LIGHT
ISOLATED-SCATTERED SHOWERS...AS CLOUD DEPTHS LOOK TO BE ABOUT 6 KFT
FEET WITH EQL LEVELS REACHING 10 KFT. A SHORTWAVE IS ALSO DIVING
SOUTHEAST FROM CENTRAL CANADA INTO THE CIRCULATION...ROUNDING ALONG
THE SOUTHERN MICHIGAN BORDER AROUND 00Z WEDNESDAY. BLEND OF MAV/MET
GUIDANCE SUGGESTS HIGHS IN THE UPPER 60S TO AROUND 70 DEGREES.

HEIGHTS WILL BEGIN TO REBOUND ON WEDNESDAY...BUT STILL ENOUGH
RESIDUAL COLD AIR DOWN LOW...0 C AT 700 MB/6 C AT 850 MB TO SUPPORT
POSSIBLE LAKE MICHIGAN ENHANCED SPRINKLES/ISOLATED LIGHT RAIN
SHOWERS. COMPARABLE TO SLIGHTLY WARMER MAXES EXPECTED ON WEDNESDAY
COMPARED TO TUESDAY. ASSUMING LOW LEVEL ANTICYLONIC FLOW BUILDING IN
WEDNESDAY NIGHT IS ABLE TO SUPPORT CLEARING SKIES (A BIG IF OVER THE
THUMB REGION WITH NORTHERLY FLOW OFF LAKE HURON)...CHILLY MINS IN
THE 45 TO 55 DEGREE RANGE APPEAR IN THE OFFING AS WINDS ALSO DROP
OFF.

THURSDAY THROUGH MONDAY...HIGH PRESSURE OVER THE AREA AT THE END
OF THE WEEK WILL GIVE WAY TO A MID AND UPPER LEVEL TROUGH LATE
FRIDAY NIGHT. THIS WILL RESULT IN WIDESPREAD RAINSHOWERS AND
ISOLATED THUNDERSTORMS LATE FRIDAY NIGHT THROUGH SATURDAY MORNING.
SCATTERED SHOWERS COULD LINGER THROUGH MONDAY MORNING.

MARINE...

SOUTHWEST WINDS WILL EASE JUST A BIT TONIGHT...WITH GUSTS OF 25
KNOTS OR SLIGHTLY HIGHER EXPECTED TO BE CONFINED TO THE OPEN WATERS
OF LAKE HURON. ELEVATED WINDS GENERALLY IN THE 15 TO 25 KNOT RANGE
WILL PERSIST HOWEVER...SHIFTING TO THE NORTHWEST...AS POOL OF COLD
AIR REMAINS OVER THE CENTRAL GREAT LAKES THROUGH WEDNESDAY. THE
COLDER AIR ABOVE THE WARM LAKE WATERS WILL ALSO CREATE FAVORABLE
CONDITIONS FOR WATERSPOUTS THROUGH WEDNESDAY. EXPANSIVE HIGH
PRESSURE IN PLACE ON THURSDAY WILL LEAD TO LIGHTER WINDS...LINGERING
INTO FRIDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT UNTIL 11 PM EDT THIS EVENING FOR MIZ049.

LAKE HURON...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LHZ421-422-
     441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LEZ444.

&&

$$

UPDATE.......RBP
AVIATION.....RBP
SHORT TERM...BT
LONG TERM....SF/DE
MARINE.......SF


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