Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 061111
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
711 AM EDT SUN JUL 6 2014


.AVIATION...

//DISCUSSION...

A DRY AIRMASS TO START THE DAY...BUT INCREASING SOUTHWEST
WINDS...GUSTING TO 20 KNOTS WILL ALLOW FOR INCREASE IN
MOISTURE...SUPPORTING 5000-7000 FOOT CU THIS AFTERNOON...LOWERING
THIS EVENING. NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
DEVELOP TONIGHT AS COLD FRONT SLIDES INTO THE AREA. HOWEVER...EXACT
COVERAGE AND TIMING OF THUNDERSTORMS REMAINS UNCERTAIN...AND TAFS
WILL FEATURE A PROB30 GROUP...MAINLY AFTER MIDNIGHT.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILING AOB 5000 FEET TODAY...HIGH CONFIDENCE
  TONIGHT.

* LOW CONFIDENCE IN THUNDERSTORMS DUE TO TIMING AND COVERAGE

&&

.PREV DISCUSSION...ISSUED 338 AM EDT SUN JUL 6 2014

SHORT TERM...TODAY AND TONIGHT

JUST ENOUGH MID CLOUDS YESTERDAY AFTERNOON FROM UPSTREAM MCV TO KEEP
SOUTHERN HALF OF THE CWA UNDER 80 DEGREES...AS 00Z DTX SOUNDING DID
COME IN WITH AN 850 MB TEMP OF 11 C. THE MID LEVELS WERE EXTREMELY
DRY...AS 700 MB DEW PT DEPRESSIONS CHECKED IN AT 41 C. MOISTURE WILL
BE ON THE INCREASE TODAY...BUT LIKELY TAKING MOST/ENTIRE DAY UNTIL
WE ARE CONCERNED WITH SHOWER/THUNDERSTORM DEVELOPMENT...AS 500 MB
HEIGHT FALLS DO NOT BEGIN TO TAKE PLACE UNTIL 00Z. 500 MB MAX HEIGHT
FALL CENTER WILL BE TRACKING NORTH OF THE CENTRAL GREAT LAKES...BUT
STILL SUFFICIENT HEIGHT FALLS EXTENDING SOUTH...ISENTROPIC ASCENT
AHEAD OF THE COLD FRONT...AND FURTHER MOISTURE ADVECTION (PW VALUES
1.75+ INCHES)...LOOKING AT DECENT AMOUNT OF INSTABILITY (-3 TO -5 C
SHOWALTER INDEX/1000+ J/KG OF CAPE)...AS 40 TO 45 KNOT JET AT 850 MB
TRAVERSES THROUGH THE AREA. SEEMS LIKE GOOD BET FOR SOME SHOWER AND
THUNDERSTORM ACTIVITY. CLOSER ARRIVAL TO 00Z OR DURING EARLY
EVENINGS HOURS...BETTER PROSPECT FOR A FEW SEVERE STORMS...AS MID
LEVEL LAPSE RATES (700-500 MB) ARE ABOVE 7 C DURING THAT TIME FRAME.
HOWEVER...THE PARALLEL NAM SUGGEST ACTIVITY WILL HOLD OFF UNTIL
AFTER 6Z.

TODAY`S MAXES WILL AGAIN LIKELY BE IMPACTED BY SOME CONVECTIVE
DEBRIS BLOWOFF...OTHERWISE...850 MB TEMPS OF 15+ C SUPPORT HIGHS IN
THE UPPER 80S WITH SOUTHWEST FLOW...BUT WILL BE CARRYING MID 80S DUE
TO INCREASE IN CLOUDS DURING PEAK HEATING. INCREASING DEW PTS AHEAD
OF THE COLD FRONT EXPECTED TO HOLD MINS IN THE UPPER 60S/AROUND 70.

LONG TERM...MONDAY THROUGH SATURDAY

BROAD MID LEVEL TROUGHING WILL TAKE SHAPE OVER THE REGION DURING THE
EARLY WEEK PERIOD...AS A SERIES OF STRONGER MID LEVEL WAVES OF
NORTHWEST CANADIAN ORIGIN PIVOT THROUGH THE MEAN TROUGH AXIS
ANCHORED TO THE NORTH.  NEXT ROUND OF HEIGHT FALLS WILL EASE INTO
THE LOWER PENINSULA ON MONDAY...WORKING THE ATTENDANT COLD FRONT
THROUGH DURING THE MIDDAY PERIOD.  EXISTING RIBBON OF HIGHER THETA-E
BISECTING SE MICHIGAN MONDAY MORNING WILL BE SWEPT EAST PRIOR TO THE
FRONTAL PASSAGE AS THE STRONGER BACKGROUND MID LEVEL DYNAMICS AND
LOW LEVEL JET SUPPORT RACE OFF TO THE NORTHEAST.  THIS WILL RESULT
IN A STEADY DIMINISHING TREND IN THE COVERAGE OF ONGOING SHOWERS AND
THUNDERSTORMS FROM NORTHWEST TO SOUTHEAST DURING THE LATTER HALF OF
THE MORNING.  THIS ALSO POINTS TO VERY LIMITED POTENTIAL FOR SOME
RENEWED DEVELOPMENT AS THE TRAILING FRONT SLIDES THROUGH...A
STEADILY DRYING AND MIXED COLUMN OFFSETTING A SOLID PRE-FRONTAL
TEMPERATURE RESPONSE AS HIGHS PUSH THE LOWER AND MIDDLE 80S.

NEXT MID LEVEL WAVE TAKES A MORE SOUTHERLY ROUTE THROUGH THE
EXISTING TROUGHING...DEEPENING IN THE PRESENCE OF FAVORABLE RIGHT
ENTRANCE REGION UPPER JET SUPPORT AS IT ENTERS THE GREAT LAKES ON
TUESDAY.  STRENGTHENING MID LEVEL DYNAMICS WILL PROMPT AT LEAST A
MODEST LOW LEVEL RESPONSE...A WEAK SURFACE WAVE REMAINS FORECAST TO
TRACK ACROSS NORTHERN LOWER MI TUESDAY AFTERNOON.   A SIZABLE UPTICK
IN MID LEVEL FORCING WITH A PERIOD OF STRONG MASS CONVERGENCE WITHIN
A BACKGROUND OF WEAKLY CYCLONIC FLOW WILL SUPPORT AN INCREASE IN
SHOWER AND THUNDERSTORM COVERAGE ON TUESDAY.  LATEST MODEL GUIDANCE
FAVORING AN EARLY DAY TIMING AT THIS STAGE.  MAIN AXIS OF
INSTABILITY WILL RESIDE SOUTH THE AREA...BUT SOME ORGANIZATION TO
ANY CONVECTIVE ELEMENTS REMAINS PLAUSIBLE GIVEN THE MAGNITUDE OF THE
WIND FIELD /0-6 KM BULK SHEAR IN EXCESS OF 40 KNOTS/.  THE OVERALL
EXTENT AND TIMING OF PRECIPITATION/CLOUD COVER WILL TEND TO CONFINE
HIGHS IN THE 70S.

MID LEVEL TROUGHING REMAINS PREVALENT THROUGH WEDNESDAY AS THE MEAN
TROUGH AXIS WORKS THROUGH.  DEPENDING ON THE TIMING...THE ASSOCIATED
INCREASE IN CVA AND STEEPENING LAPSE RATES AS MID LEVEL TEMPERATURES
LOWER MAY SUPPORT SOME DIURNAL SHOWER DEVELOPMENT LATE WEDNESDAY
/PARTICULARLY TRI-CITIES AND THUMB CORRIDOR/.  A COOLER AND LESS
HUMID ENVIRONMENT WILL SETTLE ACROSS THE GREAT LAKES TO THE FINISH
THE WEAK AS HIGH PRESSURE BUILDS IN.

MARINE...

STRENGTHENING SOUTHWEST WINDS WILL RESULT IN GUSTS TO 20 KNOTS
ACROSS ALL MARINE AREAS THIS AFTERNOON AND EVENING.  POTENTIAL FOR A
PERIOD OF HIGHER GUSTS ACROSS SAGINAW BAY NOW APPEARS WORTHY OF A
SMALL CRAFT ISSUANCE.  COLD FRONT DROPPING ACROSS THE REGION WILL
BRING A CHANCE OF THUNDERSTORMS LATE TONIGHT AND EARLY MONDAY.
ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE ON TUESDAY AS ANOTHER COLD
FRONT SWEEPS THROUGH.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...SAGINAW BAY...FROM 1 PM SUNDAY TO 10 AM
     MONDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....MR
SHORT TERM...SF
LONG TERM....MR
MARINE.......MR

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






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