Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250356
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1156 PM EDT TUE MAR 24 2015


.AVIATION...

LOW PRESSURE WILL BRING LOWER CIGS AND PRECIPITATION TO THE TAF
SITES LATE TONIGHT INTO EARLY WEDNESDAY. WHILE INITIAL PRECIP MAY
FALL AS -FZRA...TEMPERATURES WILL CLIMB ABOVE FREEZING AND ALLOW A
CHANGE TO ALL -RA INTO WEDNESDAY MORNING. EXPECT MVFR TO OCCASIONAL
IFR CIGS WITH THIS ACTIVITY. DRIER SOUTHWEST FLOW AROUND THE BASE OF
THIS LOW WILL SCOUR THIS MOISTURE OUT BY WEDNESDAY AFTERNOON WITH A
RETURN TO VFR CONDITIONS. WIND GUSTS WILL...HOWEVER...TOP OUT AROUND
25 KNOTS DURING THE AFTERNOON...BEFORE EASING CONSIDERABLY AT THE
FORECAST PERIOD/S END.

FOR DTW...CIGS WILL DROP TO NEAR 5000 FEET BY 09Z-10Z WITH A BRIEF
PERIOD OF -FRZA POSSIBLE AT THAT TIME. PRECIP WILL CHANGE TO -RA AND
PERSIST UNTIL 15Z WITH MVFR TO OCCASIONAL IFR CIGS. VFR CONDITIONS
WILL RETURN AS DRIER SOUTHWEST FLOW ENSUES. THIS FLOW WILL BRING THE
OCCASIONAL GUST OF 25 KNOTS DURING THE AFTERNOON.

//DTW THRESHOLD PROBABILITIES...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET 10Z-18Z WEDNESDAY
  MORNING.

* MEDIUM CONFIDENCE IN BRIEF PERIOD OF -FZRA BEFORE PRECIP CHANGES
  TO RAIN EARLY WEDNESDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 351 PM EDT TUE MAR 24 2015

SHORT TERM...THROUGH TONIGHT

SURFACE HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES AND
SHORTWAVE RIDGING ALOFT WILL KEEP DRY AND QUIET CONDITIONS OVER
SOUTHEAST MICHIGAN THROUGH MUCH OF TONIGHT. GOOD RADIATIONAL COOLING
CONDITIONS SHOULD ALLOW TEMPERATURES TO FALL INTO THE UPPER 20S BY
LATE THIS EVENING...BEFORE WARM AIR ADVECTION AND INCREASING CLOUDS
AND WINDS ALLOW TEMPERATURES TO BEGIN WARMING.

NEGATIVELY TILTED UPPER WAVE OVER THE CENTRAL PLAINS WILL LIFT UP
INTO THE WESTERN GREAT LAKES TONIGHT...ALLOWING A DEEPENING AREA OF
LOW PRESSURE TO REACH LAKE MICHIGAN BY 12Z. THIS WILL LIFT A FRONTAL
BOUNDARY NOW STRETCHED FROM MISSOURI DOWN THROUGH SOUTHERN
ILLINOIS/INDIANA UP ACROSS LOWER MICHIGAN EARLY WEDNESDAY MORNING.
STRONG ISENTROPIC ASCENT ALONG THIS FRONTAL BOUNDARY AND LEFT EXIT
REGION FORCING IN CONJUNCTION WITH GOOD WARMTH AND MOISTURE (PWAT
VALUES 0.8-0.9 INCHES) ADVECTION PUSHED UP BY THE NOSE OF A 50-60
KNOT LOW-LEVEL JET SHOULD ALLOW PRECIPITATION TO MOVE INTO LOWER
MICHIGAN AFTER ABOUT 07Z/3AM TONIGHT. FRONT WILL INITIALLY BE
ELEVATED OVER SOUTHEAST MICHIGAN BEFORE THE SURFACE FRONT WORKS
ACROSS..AND LATEST MODEL RUNS CONTINUE TO SHOW THE ELEVATED WARM
SECTOR FULLY ENCOMPASSING SOUTHEAST MICHIGAN BY THE TIME FORCING
WILL BE STRONG ENOUGH TO OVERCOME THE VERY DRY AIR ALREADY IN PLACE.

NAM SOUNDINGS BEFORE 12Z SHOW ABOVE FREEZING TEMPERATURES FROM 600-
900 FEET UP TO AROUND 6000 FEET MSL...AND ONLY FOR A FEW HOURS AT
EACH LOCATION BEFORE SURFACE TEMPERATURES IN THE LOWEST SEVERAL
HUNDRED FEET ALSO RISE ABOVE FREEZING. THIS SHOULD LIMIT THE AMOUNT
OF FREEZING RAIN THAT DEVELOPS...AND DO NOT FEEL DURATION OR AMOUNT
WILL BE ENOUGH TO WARRANT AN ADVISORY. EACH LOCATION MAY SEE A BRIEF
PERIOD OF FREEZING RAIN OR A MIX OF RAIN AND FREEZING RAIN FOR AN
HOUR...MAYBE TWO...BEFORE STRONG WARM AIR AND MOISTURE ADVECTION
(HIGHER DEWPOINTS) FULLY SUPPORT ALL RAIN. BIGGEST AREA OF CONCERN
WOULD BE NORTH OF I-69 AND WEST OF THE THUMB WHERE PRECIP SHOULD
ARRIVE BEFORE SUNRISE WEDNESDAY MORNING. THIS LOOKS TO BEST BE
HANDLED BY SPECIAL WEATHER STATEMENTS AND SOCIAL MEDIA...BUT LATER
SHIFTS WILL NEED TO WATCH. THERE IS ALSO SOME CONCERN THAT WHILE
PRECIP DOES HIT THE GROUND AS RAIN...THE ROAD TEMPS COULD BE COLD
ENOUGH FOR IT TO FREEZE ON THE SURFACE.

UPSTREAM OBSERVATIONS ALONG THE FRONT RIGHT NOW SHOW ONLY OCCASIONAL
FREEZING RAIN REPORTS OVER IOWA...AND PRECIPITATION SO FAR OVER
SOUTHERN ILLINOIS/INDIANA HAS BEEN RAIN AT ONSET DESPITE TEMPS IN
THE 30S AND SUB-FREEZING DEWPOINTS PRECEDING ARRIVAL OF
PRECIPITATION. BIGGEST CONCERN WOULD BE FOR MIDLAND COUNTY AS THEY
WOULD SEE TEMPERATURES BELOW FREEZING THE LONGEST. HOWEVER...EVEN
NAM BUFR SOUNDINGS (WHICH ARE COLDER THAN GFS NEAR THE SURFACE) FOR
A POINT IN MIDLAND COUNTY SHOWS VERY DRY AIR AT 09Z...WITH A QUICK
TRANSITION TO SATURATION BY 11Z BUT WITH A MAX TEMP IN THE WARM
LAYER OF 7C.

LONG TERM...WEDNESDAY THROUGH NEXT TUESDAY

SURFACE LOW PRESSURE WILL BE TRACKING THROUGH LOWER MICHIGAN BY 12Z
WEDNESDAY BRINGING WITH IT ABUNDANT MOISTURE AND A SURGE OF WARMER
TEMPERATURES. WARM AIR ADVECTION WILL ALLOW 850 MB TEMPS TO INCREASE
INTO THE 3-5 C DEGREE RANGE BY AFTERNOON RESULTING IN SURFACE TEMPS
TO MAKE A RUN AT HIGH TEMPS HITTING THE LOW 50S ON WEDNESDAY. THESE
WARM TEMPERATURES BOTH AT THE SURFACE AND ALOFT WILL ALL
PRECIPITATION TO REMAIN AS ALL RAIN THROUGH EARLY AFTERNOON. BESIDES
RAIN WEDNESDAY MORNING...THE OTHER MAJOR WEATHER CONCERN WILL BE AN
INCREASE IN WIND OVER SOUTHEAST MICHIGAN AS A LOW LEVEL JET MOVES
OVER THE REGION. WHILE WINDS WILL REMAIN BELOW ADVISORY
CRITERIA...GUSTS COULD STILL REACH AS HIGH AS 30 TO 35 MPH. WINDS
WILL FINALLY DIMINISH BY LATE AFTERNOON AS THE LOW PRESSURE SYSTEM
PUSHES OUT THE REGION. A BRIEF QUIET PERIOD WILL RESUME AS A RESULT
OF THE DRY SLOT FROM LATE WEDNESDAY AFTERNOON THROUGH THURSDAY
MORNING BEFORE THE NEXT SYSTEM IMPACTS PARTS OF SOUTHEAST MICHIGAN.

LOW PRESSURE WILL DEVELOP AND TRACK ACROSS THE OHIO VALLEY ON
THURSDAY MORNING...CLIPPING US ON THE NORTHERN END OF THE SYSTEM.
MODELS SEEM TO BE FAIRLY CONSISTENT ON THE TIMING OF THIS LOW
PRESSURE SYSTEM...HAVING PRECIPITATION BEGINNING BETWEEN 9-12Z.
THERE IS STILL QUITE A BIT OF DISCREPANCY ABOUT HOW FAR NORTH THE
PRECIPITATION WILL MOVE INTO SOUTHEAST MICHIGAN. FOR NOW...HAVE
LIKELY POPS ACROSS MONROE AND LENAWEE COUNTIES TAPERING UP TO ONLY
SLIGHT CHANCE POPS IN THE SAGINAW VALLEY. THE MAJOR CONCERN FOR THIS
SYSTEM WILL BE PRECIP TYPE. WITH TEMPERATURES IN THE MID 30S IN THE
EARLY MORNING HOURS...HAVE PUT IN A RAIN AND SNOW MIX TO ACCOUNT FOR
SOME WET SNOWFLAKES...HOWEVER...AS TEMPERATURES QUICKLY RISE AFTER
SUNRISE ON THURSDAY PRECIP SHOULD TURN OVER TO ALL RAIN. PRECIP WILL
END BY MID AFTERNOON ACROSS THE SOUTHERN COUNTIES AS THE LOW MOVES
OFF TO THE EAST. HIGH TEMPS WILL ONLY REACH INTO THE MID 40S.

FOR MOST OF THE CWA...WEATHER CONDITIONS WILL REMAIN QUIET FOR
THURSDAY NIGHT. THE EXCEPTION WILL BE THE NORTHERN THUMB REGION
WHERE SOME LIGHT LAKE EFFECT SNOW SHOWERS COULD BE POSSIBLE AS WINDS
BECOME NORTHERLY AND TEMPERATURES DROP TO BELOW FREEZING. FOR NOW
HAVE ONLY PUT ABOUT A HALF INCH ACCUMULATION OF SNOW MAINLY JUST FOR
HURON AND SANILAC COUNTIES. THIS WILL DEFINITELY HAVE TO BE
SOMETHING TO KEEP AN EYE ON SINCE IF IT HAPPENS IT WILL BE SUCH A
SMALL SCALE AND LOCALIZED FEATURE. LOW TEMPERATURES WILL BOTTOM OUT
IN THE LOW TO MID 20S ON THURSDAY NIGHT.

THE UPCOMING WEEKEND INTO THE BEGINNING OF NEXT WEEK WILL SEE
PERIODS OF PRECIP AND BELOW NORMAL TEMPERATURES.  THERE IS SOME HOPE
FOR MORE NORMAL TEMPERATURES AT THE END OF THE EXTENDED FORECAST
PERIOD.  LONGWAVE TROUGH WILL CONTINUE TO SAG ACROSS THE GREAT LAKES
AREA FRIDAY INTO SATURDAY JUST AS SURFACE HIGH PRESSURE OVER THE
NORTHERN PLAINS BUILDS IN.  THIS WILL KEEP NORTHEASTERLY FLOW OVER
THE REGION RESULTING HIGHS ON THE COOLER SIDE.  POTENTIAL EXISTS FOR
SOME SHOWER ACTIVITY ON FRIDAY AS THE TROUGH SLIDES ACROSS THE CWA.
NEXT WAVE THEN TRANSVERSES ACROSS THE NORTHERN GREAT LAKES SUNDAY
BRINGING THE NEXT ROUND OF PRECIPITATION TO THE CWA AS A COLD FRONT
SLIDES THROUGH DURING THE DAY.  SEASONAL TEMPERATURES THEN COME BACK
INTO THE PICTURE AS UPPER LEVEL RIDGING ALONG WITH SURFACE HIGH
PRESSURE MOVE IN FOR THE BEGINNING OF NEXT WEEK.

MARINE...

LOW PRESSURE WILL TRACK THROUGH THE GREAT LAKES REGION LATE TUESDAY
NIGHT. THIS LOW WILL BRING A CHANCE OF MIXED PRECIPITATION TO
NORTHERN LAKE HURON EARLY WEDNESDAY MORNING BEFORE QUICKLY CHANGING
OVER TO ALL RAIN AS TEMPERATURES RISE ABOVE FREEZING. MARINE AREAS
IN THE SOUTHERN LAKE HURON AREA AND SOUTH ACROSS LAKE ST. CLAIR AND
LAKE ERIE SHOULD REMAIN ALL RAIN THROUGHOUT THIS EVENT. WINDS ARE
EXPECTED TO INCREASE ON WEDNESDAY AFTERNOON WITH GUSTS UP TO 30
KNOTS. THE INCREASED WINDS HAS RESULTED IN A SMALL CRAFT ADVISORY
ACROSS THE NORTHERN SAGINAW BAY AND LAKE HURON NEARSHORE WATERS FROM
LATE MORNING UNTIL EARLY EVENING ON WEDNESDAY. ANOTHER LOW PRESSURE
TRACKS SOUTH OF THE MICHIGAN BORDER BRINGING A CHANCE OF SOME RAIN
AND SNOW MIX TO THE SOUTHERN GREAT LAKES ON WEDNESDAY NIGHT AND
THURSDAY MORNING. NORTHERLY WINDS COULD KICK UP SOME LAKE EFFECT
SNOW SHOWERS FOR THURSDAY NIGHT AND FRIDAY AS TEMPERATURES DROP TO
BELOW FREEZING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 11 AM TO 8 PM EDT WEDNESDAY FOR LHZ421-
     441.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....DG
SHORT TERM...HLO
LONG TERM....RK/SS
MARINE.......RK


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


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