Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 220358
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1158 PM EDT MON JUL 21 2014

.AVIATION...

//DISCUSSION...

CLEAR SKY AND LIGHT WIND AT ALL TERMINALS WILL BE THE RESULT OF
SUMMER HIGH PRESSURE IN FULL CONTROL OF AVIATION WEATHER AROUND SE
MICHIGAN. EXPECT LIGHT WIND AND PROXIMITY TO LAKE ERIE WILL HELP
PRODUCE MVFR FOG IN THE DTW AREA...BUT IT WILL QUICKLY DISSIPATE
WITH THE ONSET OF DAYTIME HEATING AND AS SOUTH WIND INCREASES.
FARTHER NORTH...THE WIND SPEED WILL REMAIN HIGH ENOUGH TO PREVENT A
RESTRICTION...ESPECIALLY AT MBS. MODEST CUMULUS DEVELOPMENT WILL
OCCUR AGAIN DURING TUESDAY AFTERNOON WITH SOME WIND GUSTS AROUND
20 KNOTS DEVELOPING BY MID AFTERNOON. THIS WILL BE PRIMARILY NORTH
OF PTK WHICH WILL BE CLOSER TO THE NEXT COLD FRONT ON SCHEDULE FOR
LATE TUESDAY NIGHT AND EARLY WEDNESDAY...PRECEDED BY SCATTERED
COVERAGE OF THUNDERSTORMS WHICH HAVE A CHANCE TO REACH THE MBS
AREA BY MIDNIGHT AND THE DTW AREA AFTER 06Z.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN THUNDERSTORM TIMING AFTER MIDNIGHT TUESDAY
NIGHT.

&&

.PREV DISCUSSION...ISSUED 329 PM EDT MON JUL 21 2014

SHORT TERM...THROUGH TONIGHT

UPPER LEVEL HEIGHTS CONTINUE TO RISE TODAY AS THE UPPER RIDGE
CENTERED OVER THE SOUTHERN PLAINS EXPANDS EASTWARD. WARM ADVECTION
AT LOW LEVELS HAS BEEN SLOW TO DEVELOP TODAY HOWEVER DUE TO A WEAK
SOUTHERLY GRADIENT. SOME DIURNAL CUMULUS HAS DEVELOPED...MAINLY
ALONG AND NORTH OF THE IRISH HILLS WHERE SLIGHTLY HIGHER DEWPOINTS
HAVE PREVAILED. HOWEVER...MIDLEVEL WARMING HAS GENERALLY RESULTED IN A LOWER
COVERAGE THAN THE PRIOR FEW DAYS. THE GRADIENT WILL STRENGTHEN VERY
SLIGHTLY LATE TONIGHT...MAINLY OVER THE NORTHWESTERN PORTION OF THE
FORECAST AREA...CAUSING LOWS TO REMAIN RELATIVELY ELEVATED IN THE
MID-60S OVER THE TRI-CITIES/FLINT AREAS. THE WEAKER GRADIENT OVER
THE SOUTHEAST MAY ALLOW SOME AREAS OF SHALLOW FOG TO DEVELOP IN
FAVORED SPOTS AS CLEAR SKIES PROMOTE RADIATIONAL COOLING. DUE TO
LIMITED COVERAGE AND EXTENT...LEFT IT OUT OF THE GRIDS. LOWS WILL BE
IN THE LOW TO MID-60S IN THIS REGION...ASIDE FROM THE URBAN HEAT
ISLAND WHERE UPPER 60S ARE ANTICIPATED.

LONG TERM...

THE UPPER LEVEL RIDGE (592 DAM AT 500 MB) IN PLACE WILL SLOWLY BREAK
DOWN ON TUESDAY AS ENERGY EJECTS OUT OF THE NORTHERN ROCKIES...WITH
THE ACCELERATED HEIGHT FALLS NOT OCCURRING UNTIL TUESDAY NIGHT. EVEN
THEN...MAX HEIGHT FALL CENTER WILL BE DISPLACED WELL TOO OUR NORTH
(NORTH OF LAKE HURON). THE DAYTIME HOURS LOOK CAPPED...AS WARM AIR
OUT AHEAD OF THE COLD FRONT LOOKS TOO MUCH TO OVERCOME...AS 700 MB
TEMPS CLIMB INTO THE LOWER TEENS..WITH 850 MB TEMPS RISING INTO THE
UPPER TEENS TO NEAR 20 C SUPPORTING HIGHS AROUND 90 DEGREES. THE
MOISTURE AXIS/850 MB DEW PT RIDGE IN THE MID TO UPPER TEENS LOOKS
VERY NARROW TUESDAY EVENING/NIGHT...AND CONFIDENCE IN SHOWERS AND
THUNDERSTORMS REMAINS A BIT MUTED...WITH THE BETTER FORCING NORTH.
STILL...MID LEVEL LAPSE RATES LOOK PRETTY GOOD WITH AROUND 1000 J/KG
OF CAPE TO WORK WITH...BUT UNCERTAINTY REMAINS IN THE AMOUNT OF
FORCING/MOISTENING OF THE LOW LEVELS...AND PREFER TO MAINTAIN THE
CURRENT HIGH CHANCE POPS. 0-6 KM SHEAR IS DECENT IN THE 20 TO 25
KNOT RANGE...BUT UNFAVORABLE TIMING WILL LIKELY LIMIT SEVERE THREAT.

THE FRONTAL BOUNDARY SHOULD BE SOUTH OF THE BORDER AROUND 12Z
WEDNESDAY...AND ANY LINGERING ACTIVITY WILL COME TO AN END AS
NORTHERLY WINDS USHER IN DRIER AIR. STILL ENOUGH LINGERING LOW LEVEL
MOISTURE FOR DECENT CU UP DURING AFTERNOON HOURS...PER NAM 850 MB RH
FIELDS...AND PROBABLY WILL HOLD TEMPS IN THE 70S (EXCEPTION NEAR
OHIO BORDER) WITH THE SURFACE NORTHERLY COLD ADVECTION THROUGH THE
DAY...HELPED OUT BY THE COOLER WATERS OF LAKE HURON.

BROAD LARGE SCALE UPPER LEVEL TROUGH OVER THE GREAT LAKES/NEW
ENGLAND ON THURSDAY WITH SPRAWLING SURFACE HIGH PRESSURE IN PLACE
OVER LOWER MICHIGAN...ASSURING DRY AND SEASONABLY COOL WEATHER
THURSDAY AND FRIDAY...AS 850 MB TEMPS SEEN SLIPPING JUST BELOW 10 C
ONCE AGAIN...LIKELY HOLDING MAXES IN THE MID TO UPPER 70S.

HIGH PRESSURE OVER THE GREAT LAKES REGION WILL SLOWLY DRIFT EASTWARD
FRIDAY NIGHT AND SATURDAY MORNING AS THE NEXT LOW PRESSURE SYSTEM
APPROACHES FROM THE WEST. THIS LOW WILL BRING A RETURN OF RAIN
SHOWERS FOR THE SATURDAY NIGHT AND SUNDAY NIGHT TIMEFRAME AS IT
STALLS OVER THE GREAT LAKES. HOWEVER...THERE IS STILL QUITE A BIT OF
DISAGREEMENT AMONG THE MODELS REGARDING THE TRACK OF THIS LOW
PRESSURE. THEREFORE HAVE ONLY INCLUDED CHANCE POPS IN THE FORECAST
FROM SATURDAY NIGHT THROUGH MONDAY MORNING. HIGH TEMPERATURES WILL
BE IN THE UPPER 70S ON SATURDAY AND SUNDAY AND DROP SLIGHTLY INTO
THE MID 70S BY MONDAY. LOW TEMPERATURES HOWEVER WILL HOVER IN THE
LOW TO MID 60S THROUGH THE EXTENDED PERIOD.

MARINE...

WARM SOUTHERLY FLOW OVER THE CENTRAL GREAT LAKES TOMORROW...BUT
STRONG STABILITY OVER THE LAKES MAINTAINING WINDS UNDER 20 KNOTS.
A COLD FRONT WILL PASS THROUGH THE REGION TUESDAY NIGHT...TRIGGERING
SCATTERED THUNDERSTORMS. A STRONG WEST TO NORTH WIND POP AROUND 30
KNOTS IS EXPECTED LATE TUESDAY NIGHT OVER THE NORTH HALF OF LAKE
HURON AS COLDER AIR RACES IN...WITH MARGINALLY UNSTABLE CONDITIONS
DEVELOPING. NORTHWEST WINDS WILL SLOWLY EASE DURING WEDNESDAY...BUT
WAVES WILL REMAIN ELEVATED OVER SOUTHERN LAKE HURON WITH THE LONGER
FETCH. A RETURN TO IDEAL BOATING CONDITIONS WILL OCCUR THURSDAY AND
FRIDAY AS LARGE SURFACE HIGH DOMINATES.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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


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