Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 042310
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
710 PM EDT MON MAY 4 2015


.AVIATION...

SCT SHRAS ARE STILL EXPECTED EARLY THIS EVENING AS COLD FRONT SAGS
SOUTH THROUGH THE AREA. IN FACT...CONVERGENCE ALONG A LEAD SURFACE
TROUGH IS ALREADY ASSISTING IN SOME ISOLATED SHRA ACTIVITY AROUND
THE I-94 TERMINALS. WILL INCLUDE A TEMPO GROUP AS THE COLD FRONT
ADDS ADDITIONAL FORCING AND LIFT TO THE MOISTURE POOLED IN THIS
VICINITY. THE FRONT WILL SETTLE SOUTH OF THE AREA TONIGHT INTO EARLY
TUESDAY AND BRING VFR CONDITIONS DURING THAT TIME AS DRIER NORTHEAST
FLOW BECOMES ESTABLISHED. OVERRUNNING MOISTURE WILL THEN BRING MORE
SHRAS AND PERHAPS A FEW TSRAS BY 16Z-18Z OR SO...ESPECIALLY KPTK
SOUTH.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR CEILINGS AOB 5000FT TONIGHT...MEDIUM AFTER 12Z TUESDAY.

* LOW FOR THUNDERSTORMS 00Z-03Z THIS EVENING & AGAIN AFTER 16Z-18Z
  TUESDAY.

&&

.PREV DISCUSSION...ISSUED 326 PM EDT MON MAY 4 2015

SHORT TERM... TONIGHT

GOOD PUSH OF DRY AIR OVER THE WESTERN GREAT LAKES...AS SURFACE DEW
PTS HAVE FALLEN INTO THE 30S ACROSS MUCH OF WISCONSIN...UPPER
PENINSULA AND PARTS OF NORTHER LOWER MICHIGAN. WITH SURFACE HIGH
(1025-1027 MB) BUILDING OVER NORTHERN LOWER MICHIGAN TONIGHT...IT
APPEARS WE CAN LOWER POPS TONIGHT...AS MAJORITY OF CWA SHOULD END UP
DRY AS THE FRONT SINKS SOUTH OF THE BORDER. STILL NEED THE COLD
FRONT TO CLEAR SOUTHEAST MICHIGAN THIS AFTERNOON INTO THIS
EVENING...AND WITH SURFACE BASED CAPES CLIMBING TO AT LEAST 1000
J/KG (MID/UPPER 70S OVER MID/UPPER 50 DEW PTS)...ISOLATED-LOW
SCATTERED COVERAGE OF THUNDERSTORM/SHOWER ACTIVITY REMAINS
POSSIBLE...WITH 12Z REGIONAL GEM BEING ONE OF THE BIGGEST
PROPONENTS...WHILE THE NAM LITES UP THE FRONT AROUND 00Z...HELPED
OUT BY THE COOL MARINE LAYER PUSH OF LAKE HURON. COULD BE
EXPERIENCING SUBSIDENCE AT THE PRESENT TIME DUE TO DEPARTING
CIRCULATION OVER NORTHWEST OHIO. NONE-THE-LESS...WILL BE
MAINTAINING THE LOW CHANCE POPS ALONG AND SOUTH OF I-69 INTO THE
EVENING...THEN ALLOWING THE DRIER AIR TO TAKE HOLD AND CONFINE
CHANCE POPS TOWARD THE OHIO BORDER AS UPSTREAM ACTIVITY APPROACHES
TOWARD SUNRISE.

WILL HAVE TO KEEP AN EYE ON THE RADAR (ASSUMING CAPES REACH 1000+
J/KG) THROUGH DAYLIGHT HOURS FOR ISOLATED STRONG/MARGINAL SEVERE
ACTIVITY AS FREEZING LEVELS ARE IDEAL...AND FRONT IS CO-LOCATED
ALONG THE SHARP 0-6 KM SHEAR GRADIENT. SOLID NORTH-SOUTH MIN TEMP
GRADIENT (15 DEGREES) LIKELY TONIGHT WITH MOSTLY CLEAR SKIES/COOL
LAKE HURON INFLUENCE NORTH (AROUND 40/LOWER 40S)...WHILE
THICKER/LOWER CLOUDS LINGER SOUTH (LOW/MID 50S).

LONG TERM...TUESDAY THROUGH SUNDAY

TUESDAYS FORECAST IS SHAPING UP TO BE KIND OF TRICKY IN REGARDS TO
HOW FAR SOUTH A FRONTAL FEATURE WILL SLIDE DOWN ACROSS LOWER
MICHIGAN. CURRENT MODEL RUNS...WHILE OVERALL ARE TRENDING MORE TO
THE SOUTH...ARE VERY INCONSISTENT WITH EACH OTHER MAKING IT
DIFFICULT TO DETERMINE WHERE THE FRONT AND ASSOCIATED PRECIPITATION
WILL REMAIN FOCUSED. HAVE SHIFTED THE MAIN PRECIP AREA FURTHER TO
THE SOUTH...TO ACCOUNT FOR THE MODEL TREND...HOWEVER...HAVE ALSO
LEFT LOW CHANCE POPS /30 PERCENT/ TO THE NORTH /UP TO I-69/ TO
ACCOUNT FOR A MORE NORTHERLY TRACK. THE FRONTAL SET UP TUESDAY NOT
ONLY AFFECTS WHERE THE RAIN AND THUNDERSTORMS WILL DEVELOP...BUT
ALSO WILL PLAY A BIG PART ON OUR TEMPERATURES. IN THE NORTHERLY
SOLUTIONS...MORE CLOUD COVER WILL BE AROUND...CONSIDERABLY HAMPERING
OUR HIGH TEMPERATURES /HIGHS ONLY IN THE MID TO UPPER 50S/.
HOWEVER...IF THE FRONT SETTLES SOUTH OF THE OHIO BORDER...WE WILL
EXPERIENCE A MORE PARTLY CLOUDY FORECAST WITH RESULTING HIGHER MAX
TEMPS /MID TO UPPER 60S/. SINCE CURRENT TRENDS ARE FAVORING A MORE
SOUTHERLY SOLUTION...HAVE BUMPED UP TEMPERATURES BY A FEW DEGREES.
SIMILARLY...THE POSITION OF THE FRONT WILL AFFECT TUESDAY NIGHT
LOWS. FOR NOW UNTIL MORE CONFIDENCE ON WHERE THIS FRONTAL FEATURE
WILL SET UP...HAVE MAINTAINED THE MID TO UPPER 40 LOW TEMPERATURE
FROM THE PREVIOUS FORECAST.

FOR THE MOST PART...WEDNESDAY WILL REMAIN DRY AS UPPER LEVEL RIDGING
BUILDS INTO THE GREAT LAKES REGION RESULTING IN A SURFACE HIGH TO
DEVELOP OVER THE EASTERN GREAT LAKES. LOCATIONS THAT MAY SEE SOME
LIGHT SHOWER ACTIVITY...MAINLY IN THE MORNING HOURS...WOULD BE IN
THE EXTREME WESTERN COUNTIES /SHIAWASSEE...LIVINGSTON...WASHTENAW
..LENAWEE/. HAVE KEPT IN A SLIGHT CHANCE OF SHOWERS AND ISOLATED
THUNDERSTORMS FROM THE PREVIOUS FORECAST FOR THESE LOCATIONS.
ELSEWHERE ACROSS THE CWA...CURRENT MODEL RUNS SHOW ENOUGH DRY AIR
AND SUBSIDENCE TO KEEP THE FORECAST DRY...HOWEVER...PLENTY OF CLOUDS
WILL BE AROUND KEEPING TEMPERATURES ON THE COOLER SIDE FOR MOST OF
THE DAY /MID TO UPPER 60S/. A BRIEF SCATTERING OUT OF THE CLOUD DECK
TOWARDS LATE AFTERNOON AND EARLY EVENING WEDNESDAY COULD ALLOW
TEMPERATURES TO CREEP UP INTO THE LOW 70S TOWARDS THE END OF THE DAY
BEFORE TEMPS QUICKLY DROP AFTER SUNSET. PARTLY CLOUDY SKIES
OVERNIGHT WILL ALLOW TEMPERATURES TO DROP INTO THE UPPER 40S TO LOW
50S ON WEDNESDAY NIGHT.

HIGHLY AMPLIFIED FLOW WITH A TROUGH OUT WEST AND RIDGE OVER THE
GREAT LAKES AND EAST COAST FOR THE END OF THE WEEK WILL ALLOW FOR
WARM AND MAINLY DRY CONDITIONS. THIS PATTERN WILL BREAK DOWN A BIT
BY THE WEEKEND AS IMPULSES IN THE SOUTHWESTERLY FLOW WILL ALLOW FOR
DAILY SHOWER/TSTORM CHANCES INTO EARLY NEXT WEEK. AT THE
SURFACE...COLD FRONT WILL SLOWLY EASE INTO LOWER MICHIGAN BY
SATURDAY...PROVIDING A LOW-LEVEL FOCUS FOR PRECIPITATION AND
ALLOWING TEMPERATURES TO DECLINE SUNDAY AND MONDAY.

MARINE...

RAIN SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS THE SOUTHERN
GREAT LAKES AS A FRONTAL SYSTEM TRACKS ACROSS THE REGION.
NORTHWESTERLY WINDS WILL BECOME NORTHERLY BY TUESDAY MORNING...WITH
RAIN SHOWERS CONTINUING THROUGH TUESDAY AFTERNOON. HIGH PRESSURE
RETURNS FOR WEDNESDAY ALLOWING WINDS AND WAVES TO REMAIN CALM
THROUGH THURSDAY. A LOW PRESSURE SYSTEM ARRIVES LATE FRIDAY BRINGING
THE NEXT CHANCE OF RAIN AND THUNDERSTORMS TO THE GREAT LAKES.

&&

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

$$

AVIATION.....DG
SHORT TERM...SF
LONG TERM....RK/DT
MARINE.......RK


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



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