Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 301926
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
326 PM EDT TUE JUN 30 2015

.SHORT TERM...THIS EVENING AND TONIGHT

FORECAST REASONING HAS CHANGED RELATIVELY LITTLE FOR THIS AFTERNOON
WITH THE LONE NOTABLE EXCEPTION THAT A MESOSCALE LOW PROPAGATING
SOUTH OVER LAKE MICHIGAN HAS MODULATED THE FORCING FIELD OVER
CENTRAL AND SOUTHERN LOWER MICHIGAN SO FAR TODAY. AS A RESULT, THE
GENESIS REGION FOR SHOWERS AND THUNDERSTORMS HAS BEEN ALONG AND
SOUTH OF THIS FEATURE`S PSEUDO-WARM FRONT. POPS HAVE CORRESPONDINGLY
BEEN SHIFTED SOUTH IN ACCORDANCE WITH THE LATEST OBSERVATIONAL
EVIDENCE WHICH SUGGESTS AFTERNOON CONVECTIVE ACTIVITY FUNNELING INTO
THE I-69 TO I-94 CORRIDOR. 4KM SPC WRF RUN APPEARS USABLE THROUGH
LATE EVENING. SHEAR REMAINS QUITE LOW WHILE MLCAPE STILL LOOKS TO
MAX OUT AROUND 600 J/KG NEAR THE OHIO BORDER. NO SEVERE WEATHER
ANTICIPATED, BUT A LOCALIZED FLOODING THREAT COULD EVOLVE IN A
REGION OF TRAINING OF SLOW MOVING CELLS.

LARGE SCALE FORCING ASSOCIATED WITH THE MID-LEVEL CIRCULATION OVER
NORTHERN LOWER MICHIGAN WILL SHIFT EAST THROUGH THE LATE EVENING
BRINGING A GRADUAL END TO SHOWERS AFTER SUNSET. MARINE MODIFIED AIR,
AS NOTED STREAMING OFF OF LAKE SUPERIOR ALL DAY, WILL FILTER INTO
LOWER MICHIGAN WITHIN WESTERLY FLOW TONIGHT SUPPORTING LOW CLOUDS
THROUGH SUNRISE AND CONTAINING LOWS TO THE MID AND UPPER 50S.

&&

.LONG TERM...

LARGE UPPER LEVEL RIDGE CENTERED OVER THE CENTRAL ROCKIES THIS
AFTERNOON FOLDING OVER...WITH SHORTWAVE OVER EXTREME SOUTHERN
SASKATCHEWAN DIVING SOUTHEAST INTO THE MIDWEST TOMORROW MORNING.
SOUTHEAST MICHIGAN LOOKS TO BE UNDER GENERAL SUBSIDENCE AND DRYING
BEHIND THIS EVENINGS TROUGH AXIS PASSAGE...WITH HEIGHTS AND SURFACE
PRESSURE ON THE RISE. HOWEVER...A NORTHERN STREAM SHORTWAVE TROUGH
EXTENDING FROM THE LARGE UPPER LEVEL LOW OVER HUDSON BAY IS
FORECASTED TO SWEEP THROUGH THE NORTHERN GREAT LAKES LATE
WEDNESDAY/WEDNESDAY NIGHT...WITH SECOND PV EXTENSION ROTATING
THROUGH SOUTHERN LOWER MICHIGAN DURING THURSDAY. GOOD 500 MB PACKING
OF TEMPERATURES...BUT GFS INDICATING 925 MB COMPUTED LIS AND
SHOWALTER INDEX REMAINING SOLIDLY POSITIVE WEDNESDAY EVENING...WHILE
NAM LOWERS THE LIS TO AROUND ZERO AS WEAK FRONTAL PASSAGE OCCURS.
WITH POSSIBLE SLIGHT MOISTURE CONTRIBUTION FROM SAGINAW BAY...WOULD
NOT DISCOUNT THE POSSIBILITY OF ISOLATED CELLS GOING UP....BUT EVEN
NAM SOUNDINGS SHOW DIFFICULT TIME OVER COMING THE DRY MID LEVEL AIR.

DURING THURSDAY...SHORTWAVE AND SURFACE LOW EXPECTED TO TRACK ACROSS
THE OHIO VALLEY. ALTHOUGH MID LEVEL LAPSE RATES WILL BE RATHER STEEP
(6.5+ C FROM 700-500 MB NOTED) OVER LOWER MICHIGAN...LOW LEVEL
ANTICYLONIC FLOW WILL BE BUILDING IN...AND WILL CONTINUE WITH THE
DRY FORECAST. LIGHT NORTHEAST FLOW IN THE LOW LEVELS COUPLED WITH
PARTLY CLOUDY SKIES (SOUTH) EXPECTED TO HOLD MAXES UNDER 80 DEGREES
WITH 850 MB TEMPS AROUND 10 C.

WILL MAINTAIN A DRY FORECAST FRIDAY INTO THE HOLIDAY WEEKEND WITH
WEAK UPPER FLOW/LACK OF FORCING...LACK OF MOISTURE...AND WEAK
SURFACE HIGH PRESSURE SHOWN BY 12Z MODEL SUITE. TEMPERATURES ALSO
EXPECTED TO WARM BACK TO NEAR NORMAL AS THE NEGATIVE UPPER HEIGHT
ANOMALY IS REPLACED BY SLIGHTLY RISING HEIGHTS. MODELS DISAGREE
SUBSTANTIALLY EARLY NEXT WEEK WITH 12Z EURO TRACKING A STRONG UPPER
LOW THROUGH ONTARIO WHILE GFS/GEFS MEAN CUT THIS ENERGY OFF OVER
NORTHWESTERN CANADA. WILL KEEP POPS NEAR CLIMO IN THE LOWER CHANCE
RANGE UNTIL BETTER AGREEMENT CAN BE REACHED.

&&

.MARINE...

VERY LIGHT WINDS WILL PERSIST THROUGH TONIGHT WITH A FEW SHOWERS
AROUND INTO THE EVENING HOURS. A WEAK COLD FRONT LOOKS TO BE
DROPPING SOUTH THROUGH THE CENTRAL GREAT LAKES LATE
TOMORROW/TOMORROW NIGHT. LITTLE SHOWER/THUNDERSTORM ACTIVITY IS
EXPECTED WITH THE FRONT...WITH NORTHWEST WINDS INCREASING TO AROUND
15 KNOTS OVER LAKE HURON. HIGH PRESSURE BUILDING INTO THE REGION ON
THURSDAY WITH LOW PRESSURE TRACKING THROUGH THE OHIO VALLEY WILL
LEAD TO NORTHEAST FLOW....BUT STILL HOLDING AROUND 15 KNOTS.

&&

.AVIATION...ISSUED 130 PM EDT TUE JUN 30 2015

LOW VFR TO HIGH MVFR WILL PERSIST FOR THE REMAINDER OF THE DAY UNDER
A CANOPY OF EXTENSIVE LOW-LEVEL MOISTURE. SHOWERS OVER WESTERN LOWER
MICHIGAN REMAIN ALIGNED WITH FORCING ASSOCIATED WITH A MESOSCALE LOW
MOVING DOWN CENTRAL LAKE MICHIGAN. EVENTUALLY, SOME EASTWARD
EXPANSION AND PROPAGATION OF THIS ACTIVITY IS EXPECTED AS LARGER
SCALE FORCING AND DIURNAL HEATING TAKE OVER DURING THE AFTERNOON.
LOW INSTABILITY WARRANTED REMOVAL OF THUNDER FOR KMBS/FNT BUT LEFT
THE FORECAST IN TACT ELSEWHERE ALTHOUGH CHANCE OF THUNDER REMAINS
LOW FOR ALL LOCATIONS. COMBINATION OF SATURATED NEAR SURFACE LAYER
AND DEVELOPMENT OF A MARINE INVERSION WILL LEAD TO WIDESPREAD IFR
TONIGHT.

FOR DTW...BEST CHANCE FOR THUNDER REMAINS 20-23Z THIS EVENING. SOME
UNCERTAINTY EXISTS WITH REGARD TO TIMING OF LOWEST CEILINGS...BUT
CURRENT SATELLITE TRENDS DID WARRANT INTRODUCING AT LEAST MVFR FOR
MOST OF THE MID/LATE EVENING.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIGS AOB 5KFT

* LOW FOR TSTORM IMPACTING KDTW AIRSPACE

&&

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

$$

SHORT TERM...JVC
LONG TERM....SF/DT
MARINE.......SF
AVIATION.....JVC


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


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