Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 292002
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
402 PM EDT SUN MAR 29 2015

.SHORT TERM...THIS AFTERNOON AND TONIGHT

A LINE OF PRECIPITATION AHEAD OF AN IMPRESSIVE SHORTWAVE IS
CURRENTLY PUSHING IN FROM WESTERN MICHIGAN TOWARDS THE CWA THIS
AFTERNOON. A SURFACE TROUGH WILL TRACK THROUGH ALONG WITH THIS LINE
OF PRECIPITATION...TURNING SOUTHERLY WINDS TO THE SOUTHWEST THIS
EVENING. UPSTREAM OBSERVATIONS SHOW A MIX OF RAIN...SNOW AND EVEN
SOME SLEET AS TEMPERATURES CRASH WITH WET BULBING GIVEN THE VERY DRY
LOWER LEVELS. THE BRIGHTER UPSTREAM RETURNS ON RADAR ARE INDICATIVE
OF THIS AFOREMENTIONED SLEET WITH SOME VERTICAL MOTION ASSOCIATED
WITH THE VIGOROUS SHORTWAVE TRACKING THROUGH THE GREAT LAKES. THE
THREAT FOR SLEET IS EXPECTED TO END AFTER THE INITIAL LINE TRACKS
THROUGH AND THE SHORTWAVE AND ENHANCED VERTICAL MOTION HEAD EAST.
THE SHORT AND INTERMITTENT NATURE OF THE SLEET PRECLUDES THE
ISSUANCE OF ANY HEADLINES WITH THIS INITIAL LINE OF ACTIVITY.

BEHIND THE MAIN TROUGH AND SHORTWAVE THE MAIN COLD FRONT WILL THEN
TRACK EAST DURING THE EVENING HOURS...CONTINUING THE CHANCE FOR
RAIN AND SNOW AS THE UPPER COLUMN COOLS BUT SURFACE TEMPERATURES
STAY ABOVE FREEZING. ONCE THE MAIN COLD FRONT TRACKS EAST
PRECIPITATION WILL COME TO AN END BY 06Z. ALTHOUGH DRIZZLE WILL
STILL BE A THREAT AFTER 06Z...DRY AIR ADVECTION WILL WORK AGAINST
THIS LATE TONIGHT. OVERALL NOT MUCH FROZEN PRECIPITATION IS EXPECTED
TO ACCUMULATE GIVEN SURFACE TEMPERATURES ARE EXPECTED TO REMAIN
ABOVE FREEZING WITH LIQUID MIXING IN WITH FROZEN PRECIPITATION FOR
THE BALANCE OF THE EVENT.

&&

.LONG TERM...

THE UPPER TROUGH WILL EXIT EAST BY EARLY TOMORROW...ALLOWING FLAT
RIDGING TO BRIEFLY OVERTAKE THE AREA BEFORE THE NEXT UPPER WAVE
EJECTING OUT OF BRITISH COLUMBIA DROPS DOWN THROUGH THE GREAT LAKES
MONDAY NIGHT AND TUESDAY.

LAPSE RATES WILL STEEPEN TOMORROW AS COLDER AIR ALOFT ARRIVES BEHIND
THE FRONT AND SURFACE HEATING TAKES PLACE DURING THE DAY. A WELL-
MIXED AND DEEPENING BOUNDARY LAYER WILL PROVIDE BREEZY CONDITIONS
FROM THE WEST-NORTHWEST...WITH GUSTS TO 35 MPH POSSIBLE THROUGH THE
AFTERNOON. RIDGING WILL THEN PROVIDE LIGHTER WINDS FOR THE EVENING
AND OVERNIGHT. SOME SUNSHINE AND A BETTER START TO THE DAY WITH MINS
ONLY IN THE 30S WILL PROVIDE WARMER TEMPERATURES...WITH MOS VALUES
FROM THE LOW TO UPPER 40S LOOKING REASONABLE FOR MONDAY AFTERNOON.

UPPER WAVE WILL THEN TRACK THROUGH THE SOUTHERN GREAT LAKES IN THE
EVENING AND OVERNIGHT...WITH PREFERENCE IN TRACK GIVEN TO THE
STRONGER CONSENSUS OF THE EURO/GFS. NAM STILL LOOKS TOO AGGRESSIVE IN
DEEPENING THE SYSTEM. ELEVATED PORTION OF THE FRONT THAT WILL DROP
THROUGH TONIGHT LOOKS TO REMAIN OVER MICHIGAN AS THIS UPPER WAVE
APPROACHES. EXPECTING TO SEE A NICE FGEN RESPONSE AS THE MID-LEVEL
WAVE AND SURFACE LOW TRACK ACROSS THE SOUTHERN GREAT LAKES...WITH
THE LOW CENTER EXPECTED TO PASS ALONG/JUST SOUTH OF THE MICHIGAN
BORDER. THE FGEN COMBINED WITH MID-LEVEL PVA AND SOME FORCING FROM
AN UPPER JET WILL WORK WITH 3 G/KG (AVERAGE) OF SPECIFIC HUMIDITY
ACROSS THE AREA TO GENERATE PRECIPITATION...MAINLY SOUTH OF A LINE
FROM SAGINAW TO PORT HURON. PRECIPITATION TYPE IS A LITTLE
TRICKIER...WITH DRY AIR PRECEDING THE SYSTEM IN THE LOWEST LEVELS
PROMOTING WET BULB EFFECTS. WENT WITH THERMAL FIELDS SIMILAR TO THE
GFS...BUT DID HEDGE THE FORECAST SLIGHTLY WARMER BASED ON THE EURO.
THE NAM WAS NOT USED. THIS KEEPS A RAIN/SNOW MIX IN THE
FORECAST...WITH THE BEST CHANCE FOR SNOW STILL NORTH OF FLINT. THIS
IS WHERE PRECIPITATION AMOUNTS ALSO TAPER OFF HOWEVER...AND DUE TO
THE SLIGHT SHIFT IN TRACK...FORECAST AMOUNTS DO NOT EXCEED AN INCH.

COLDER AIR FILTERING INTO THE AREA BEHIND LOW PRESSURE WILL FIGHT
DIURNAL HEATING ON TUESDAY. MUCH LOWER DEWPOINTS WILL ALSO
ARRIVE...KEEPING A CHANCE FOR RAIN SHOWERS TO MIX WITH SNOW (WET-
BULB EFFECTS) DESPITE MAX TEMPERATURES IN THE UPPER 30S AND LOW 40S.

HIGH PRESSURE WILL BE IN PLACE FOR WEDNESDAY RESULTING IN DRY
CONDITIONS AND CALM WINDS ACROSS SOUTHEAST MICHIGAN. WARM AIR
ADVECTION WILL ALLOW WARMER TEMPERATURES TO FILTER INTO THE REGION
WITH HIGHS ON WEDNESDAY IN THE UPPER 40S AND LOW 50S. WARMER
TEMPERATURES WILL CONTINUE INTO THURSDAY /HIGHS IN THE MID 60S FOR
MOST LOCATIONS/ HOWEVER...THE NEXT WEATHER SYSTEM ARRIVES THURSDAY.
THIS LOW PRESSURE SYSTEM TRACKING ACROSS THE NORTHERN GREAT LAKES
WILL DRAG A COLD FRONT ACROSS LOWER MICHIGAN. WITH TEMPERATURES WELL
ABOVE FREEZING...PRECIP WILL REMAIN ALL RAIN. TIMING ON THIS SYSTEM
IS A BIT UNCERTAIN THOUGH AND WILL HAVE TO BE FINE TUNED AS THE WEEK
PROGRESSES. DRY WEATHER RETURNS FOR FRIDAY AND SATURDAY AS WEAK HIGH
PRESSURE TRIES TO BUILD INTO THE REGION. RAIN POSSIBLY RETURNS FOR
SATURDAY NIGHT AS A WEAK LOW PRESSURE SYSTEM SLIDES JUST NORTH AND
EAST OF SOUTHEAST MICHIGAN.

&&

.MARINE...

A GALE WARNING IS NOW IN EFFECT FOR ALL OF LAKE HURON WITH UPSTREAM
OBSERVATIONS OVER LAKE MICHIGAN SUPPORTING MOSTLY GUSTS TO GALE
FORCE AS OF 300 PM. THE WARNING REMAINS IN EFFECT INTO TONIGHT FOR
ALL OF THE LAKE AS SOUTHERLY WINDS CONTINUE TO INCREASE AHEAD OF A
LOW PRESSURE SYSTEM TRACKING ACROSS ONTARIO. THE WARNING WILL THEN
REMAIN IN EFFECT FOR THE NORTHERN THIRD OF LAKE HURON OVERNIGHT AND
THROUGH MONDAY AFTERNOON AS WINDS FLIP TO THE NORTHWEST. COLDER AIR
SPILLING INTO THE AREA WILL ALLOW STRONGER WIND GUSTS TO MIX DOWN TO
THE SURFACE...CONTINUING THE THREAT FOR GALES OVER THE NORTHERN
PORTION OF THE LAKE AND ALLOWING GUSTS TO REACH ABOUT 30 KNOTS FOR
THE SOUTHERN TWO-THIRDS OF LAKE HURON.

FURTHER TO THE SOUTH...A SMALL CRAFT ADVISORY IS NOW IN EFFECT FOR
LAKE ST CLAIR AND WESTERN LAKE ERIE...WITH GUSTS TO 30 KNOTS
EXPECTED THIS EVENING.

BRIEF RIDGING WILL THEN ALLOW FOR LIGHTER WINDS ACROSS ALL OF THE
CENTRAL GREAT LAKES MONDAY EVENING BEFORE THE NEXT LOW PRESSURE
SYSTEM TRACKS ACROSS THE AREA MONDAY NIGHT AND TUESDAY. THIS SYSTEM
DOES NOT LOOK TO PRODUCE STRONG WINDS.

&&

.AVIATION...ISSUED 138 PM EDT SUN MAR 29 2015

A DRY ATMOSPHERE WILL BE IN PLACE EARLY THIS AFTERNOON AHEAD OF AN
APPROACHING TROUGH. A TIGHT PRESSURE GRADIENT HAS ALLOWED SOUTH
SOUTHWESTERLY SURFACE WINDS TO BECOME GUSTY WITH WINDSPEEDS OF 25 TO
30 KNOTS. PRECIPITATION IS EXPECTED TO ARRIVE BETWEEN 19 AND 21Z AT
ALL OF THE TAF SITES AS A LOW LEVEL JET AXIS RAPIDLY LIFTS MOISTURE
INTO THE REGION. STILL SOME QUESTION ON PRECIPIATION TYPE AS
UPSTREAM OBSERVATIONS HAVE SHOWN A MIX...BUT STRENGTH OF WARM AIR
ADVECTION AND DAYTIME TEMPERATURES SHOULD SUPPORT MORE LIQUID
HYDROMETEOR TYPE. HAVE INCLUDED A -SHRASN MENTION FOR PTK
NORTHWARD...BUT NO ACCUMULATION IS EXPECTED. SYSTEM MOTION IS
EXPECTED TO BE VERY FAST WHICH WILL LEAD TO A SHORT PRECIPITATION
DURATION. LOSS OF MIDLEVEL MOISTURE THEN SUGGESTS A 3 TO 6 HOUR
WINDOW FOR DRIZZLE AND BR DURING THE MID TO LATE EVENING.

FOR DTW...VFR UNTIL 22Z-23Z OR SO WHEN MVFR CIGS WITH -SHRA WILL
BECOME INCREASINGLY LIKELY. CONTINUED TO BE MORE PESSIMISTIC WITH
CIGS AFTER 00Z WITH NOCTURNAL COOLING CONTRIBUTIONS LIKELY LOWERING
CIGS INTO IFR. LACK OF MOISTURE DEPTH THEN BRINGS CONCERN FOR -DZ
FOR THE EVENING. SOUTHERLY WINDS FROM 190 TO 200 DEGREES WILL ALSO
GUST TO 25 KNOTS OR BETTER AT TIMES THIS AFTERNOON.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS AOB 5000 FEET AFTER 21Z-22Z TODAY.

* HIGH IN WIND GUSTS TO 25 KNOTS FROM 190-200 DEGREES THIS AFTERNOON.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING UNTIL MIDNIGHT EDT TONIGHT FOR LHZ363-421-422-441>443-
     462>464.

     GALE WARNING UNTIL 6 PM EDT MONDAY FOR LHZ361-362.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR LEZ444.

&&

$$

SHORT TERM...KURIMSKI
LONG TERM....HLO/RK
MARINE.......HLO
AVIATION.....KURIMSKI


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