Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 262258
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
658 PM EDT SAT JUL 26 2014


.AVIATION...

//DISCUSSION...

THERE WILL BE THE POTENTIAL FOR SCATTERED SHRAS OR ISOLATED TSRAS
EARLY THIS EVENING ALONG THE I 94 TERMINALS AS THETA-E RIDGE AXIS
DEEPENS OVER THE AREA AND LIFT FROM PASSING SHORTWAVE TROUGH ACT TO
FORCE THIS INCREASINGLY UNSTABLE AIRMASS. WHILE CONVECTION IS NOT
OUT OF THE QUESTION FURTHER NORTH...THE BEST FOCUS SEEMS TO BE OVER
THE SOUTHERN CWA WHERE OUTFLOW FROM EARLIER CONVECTION TO THE SOUTH
AND SOUTHEAST HAS ENHANCED LOW LEVEL CONVERGENCE NEARBY THE TAFS.
THE MUCH BETTER CHANCE OF SHRAS/TSRAS WILL COME BY SUNDAY AFTERNOON
AS MAJOR SHORTWAVE PIVOTS THROUGH THE AREA. THIS WAVE WILL INDUCE
THE FORMATION OF A SURFACE LOW OVER THE AREA BY THIS TIME AND EXPECT
AT LEAST MODERATELY UNSTABLE AIR TO REMAIN OVER THE AREA AS LOW
LEVEL MOISTURE POOLS NEAR THIS FEATURE.

FOR DTW...A FEW SHRAS/TSRAS WILL BE POSSIBLE EARLY IN THE FORECAST
PERIOD...BUT THE BETTER CHANCE WILL HOLD OFF UNTIL 20Z-22Z SUNDAY AS
A STRONG SYSTEM PIVOTS INTO THE CENTRAL GREAT LAKES. INCREASED LOW
LEVEL MOISTURE WILL ALSO LEAD TO PATCHY FOG OVERNIGHT INTO EARLY
SUNDAY.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS AT OR BELOW 5000 FEET THROUGH 02Z THIS
EVENING.

* LOW CONFIDENCE IN SCATTERED THUNDERSTORM DEVELOPMENT NEAR TERMINAL
  EARLY THIS EVENING...WITH HIGHER CONFIDENCE AFTER 20Z SUNDAY.

&&

.PREV DISCUSSION...ISSUED 328 PM EDT SAT JUL 26 2014

SHORT TERM...THIS AFTERNOON AND TONIGHT

A DIFFICULT FORECAST REMAINS OVER SOUTHEAST MICHIGAN THIS AFTERNOON
AND TONIGHT AS A MID LEVEL WARM FRONT APPROACHES SOUTHEAST MICHIGAN
THIS EVENING...EVIDENCED BY THE THUNDERSTORMS JUST TO OUR SOUTH.
ALSO EVIDENT BY CURRENT CONVECTION IS THE CAP IN PLACE OVER THE AREA
AS THE MAIN ACTIVITY IS WELL TO THE NORTH WITH A MID LEVEL SHORTWAVE
AND TO OUR SOUTH WITH THE MID LEVEL WARM FRONT. HI-RES MODEL RUNS
CONTINUE TO ERODE THIS CAP LATE THIS AFTERNOON AND THIS EVENING AS
THE SURFACE TROUGH ASSOCIATED WITH THE SHORTWAVE OVER THE UPPER
PENINSULA DIVES SOUTH BRINGING IN COOLER AIR ALOFT AS THE MID LEVEL
WARM FRONT NUDGES ITS WAY NORTH. EVEN WHEN THIS HAPPENS AREAL
COVERAGE OF THIS CONVECTION IS SPOTTY AT BEST AS THE MAIN FORCING
REMAINS TO THE NORTH AND SOUTH OF THE CWA. WITH THIS IN MIND WILL
MAINTAIN THE CHANCY POPS THIS AFTERNOON AND THIS EVENING.

SEVERE WEATHER POTENTIAL CONTINUES TO BE CONDITIONAL AS
THUNDERSTORMS WILL BE ABLE TO TAP INTO 1-2 J/G OF MUCAPE WITH AROUND
50 KNOTS OF 0-6 KM BULK SHEAR. THIS COULD CAUSE SOME STORMS TO BE
SEVERE...AS EVIDENCED BY THE CURRENT ACTIVITY OVER NORTHERN INDIANA
AND NORTHWESTERN OHIO. THE BEST CHANCE FOR THIS WILL BE ACROSS THE
FAR SOUTH WITH THE BETTER DYNAMICS AND INSTABILITY...HOWEVER THIS
WILL BE HIGHLY DEPENDENT ON WHEN AND IF THE CAP CAN BE BROKEN LATE
THIS AFTERNOON AND EARLY THIS EVENING.

AS THE AFOREMENTIONED TROUGH ACROSS THE NORTHWESTERN GREAT LAKES
WORKS ITS WAY EAST...DRIER COOLER AIR WILL WORK ITS WAY IN FROM THE
WEST...WHICH WILL EFFECTIVELY END PRECIPITATION CHANCES AROUND OR
SHORTLY AFTER MIDNIGHT. DESPITE THE ADVECTION OF COOLER AIR
ALOFT...THE MID LEVEL WARM FRONT WILL INCH NORTH...KEEPING OVERNIGHT
LOWS IN THE 60S.

LONG TERM...

HIGHLY AMPLIFIED UPPER LEVEL PATTERN NEXT WEEK...WITH RIDGE OVER THE
ROCKIES/TROUGH OVER THE APPALACHIANS...LEADING TO SOLIDLY BELOW
NORMAL TEMPERATURES FOR SOUTHEAST MICHIGAN...LIKELY ALLOWING DETROIT
TO SNEAK INTO THE TOP 10 COLDEST JULY`S ON RECORD...WITH THE AVERAGE
TEMPERATURE FOR THE MONTH AROUND 70.1 BASED ON THE CURRENT
FORECAST. BEFORE WE GET TO THE COOLER TEMPERATURES...MOISTEN LADEN
AIRMASS WILL BE DISPLACED BY THE STRONG PV ANOMALY/DEEP UPPER LEVEL
LOW/COLD POOL OVER SOUTHERN MANITOBA WHICH IS NOW SHOWING SIGNS OF
ACCELERATING OFF TO THE SOUTHEAST...AND APPEARS TO BE ON TRACK TO
SWING THROUGH SUNDAY EVENING. THIS TIGHT CIRCULATION SHOULD HELP
FOCUS HEAVY RAINFALL FOR A GOOD PART OF THE CWA AS IT MOVES
DIRECTLY THROUGH.

THERE WILL BE A WINDOW OF OPPORTUNITY TO MODERATELY DESTABILIZE ON
SUNDAY BEFORE AGGRESSIVE HEIGHT FALLS/SURFACE LOW/CONVERGENCE
ARRIVES DURING THE AFTERNOON. HOWEVER...MAIN JET CORE WILL BE
DISPLACED TO OUR SOUTH...WITH EVEN THE 0-1 KM WIND SHEAR
PREDOMINATELY BELOW 10 KNOTS OVER SOUTHEAST MICHIGAN...EXCEPT TOWARD
THE OHIO BORDER WHERE SHEAR QUICKLY INCREASES. FOR MAJORITY OF THE
CWA...HAIL WILL LIKELY BE THE BIGGEST SEVERE THREAT WITH THE
LOWERING FREEZING LEVELS. FOCUSED HEAVY RAINFALL ALONG CONVERGENCE
ZONES WITH 850 MB DEW PTS AROUND 11 C SUPPLYING AMPLE
MOISTURE....AND 1-2 INCHES RAINFALL TOTALS APPEAR ATTAINABLE.

THE 500 MB LOW/COLD CORE (-15 C AT 500 MB) SHOULD ALREADY BE LOCATED
OVER WESTERN PA BY 12Z MONDAY...WITH THE SURFACE COLD FRONT SOUTH OF
THE MICHIGAN BORDER...SO THE PROSPECTS FOR RAIN APPEARS LOW AS
STRONG NORTHERLY FLOW USHERS IN DRIER AIR. STILL ENOUGH RESIDUAL
MOISTURE TO LIKELY MAINTAIN SOME LOW CLOUDS THROUGH MUCH OF THE DAY
WITH THE COLD ADVECTION...WHICH LIKELY CAPS MAXES AROUND 70 DEGREES
WITH 850 MB TEMP OF 7-8 C ADVERTISED.

MINS MONDAY NIGHT WILL HAVE TO POTENTIAL TO DROP INTO THE 40S BASED
ON THE SURFACE DEW PTS...BUT SUSPECT THERE WILL BE JUST ENOUGH
NORTHERLY GRADIENT/MIXING TO KEEP MINS AROUND 50/LOWER
50S...ESPECIALLY OVER THE EASTERN THUMB REGION WITH LAKE HURON
INFLUENCE.

LONGWAVE PATTERN WILL CONTINUE TO BE DOMINATED BY THE WESTERN CONUS
RIDGE AND EASTERN CONUS TROUGH FOR THE REMAINDER OF THE FORECAST
PERIOD. THE EXTENSION OF THE CIRCULATION LOCATED NEAR JAMES BAY WILL
SLOWLY RETREAT NORTHWARD...BUT THE GREAT LAKES REGION WILL STILL BE
DOMINATED BY BELOW-NORMAL UPPER HEIGHTS AND GENERAL TROUGHINESS...TRANSLATING
INTO TEMPS REMAINING BELOW NORMAL. WITH THE UPPER COLD POOL IN PLACE
AND SHORTWAVE DISTURBANCES ROTATING AROUND THE LONGWAVE
TROUGH...EXPECT SCATTERED DIURNALLY-ENHANCED SHOWERS TO BE COMMON
INTO THE END OF THE WEEK.

MARINE...

STILL A CHANCE OF SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON INTO
THIS EVENING...BUT BULK OF ACTIVITY WILL HOLD OFF UNTIL TOMORROW.
SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON...CONTINUING INTO
SUNDAY NIGHT. SEVERE WEATHER POTENTIAL REMAINS GREATEST IN THE AREA
OF LAKE ST CLAIR AND WESTERN LAKE ERIE. WIND AND WAVE ACTION WILL
OTHERWISE BE FAVORABLE THROUGH SUNDAY BEFORE A COLD FRONT MOVES
THROUGH THE REGION SUNDAY NIGHT. NORTHERLY WINDS WILL RAMP UP BEHIND
THE FRONT...PEAKING AROUND 30 KNOTS OVER SOUTHERN LAKE HURON MONDAY.
SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED AS THE LONG NORTH FETCH
WILL BE FAVORABLE FOR BUILDING LARGE WAVES THAT WILL IMPACT THE
SOUTH HALF OF LAKE HURON AND NEARSHORE MARINE ZONES. COOL HIGH
PRESSURE WILL THEN BUILD INTO THE NORTHERN PLAINS AND GREAT LAKES
AND RETURN BENIGN MARINE WEATHER FOR THE MID WEEK PERIOD.

&&

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

&&

$$

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


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