Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 180351
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1151 PM EDT WED SEP 17 2014


.AVIATION...

//DISCUSSION...

A COLD FRONT WHICH HAS BEEN DROPPING SOUTH THROUGH NORTHERN MICHIGAN
THIS EVENING WILL TRACK ACROSS SE MI DURING THE PRE DAWN HOURS.
LIGHT N-NE WINDS WILL DEVELOP BEHIND THE FRONT. POST FRONTAL
STRATUS HAS BEEN SLOWLY TRICKLING SOUTH. THESE CLOUDS ARE BEING
DUCTED UNDER A DEEPENING LOW LEVEL INVERSION COURTESY OF SHALLOW
POST FRONTAL COLD AIR ADVECTION. IN LIGHT OF UPSTREAM OBSERVATIONS...
CLOUD BASES LOOK TO PRIMARILY FALL INTO THE MVFR RANGE. ADDED
MOISTURE FLUX OFF LAKE HURON DURING THE MORNING SHOULD SUSTAIN LOW
END MVFR CIGS FOR PTK/FNT/MBS. THE ADDED UPSLOPE MAY STILL RESULT
IN SOME IFR INTO PTK. CLOUD BASES SHOULD ONLY SLOWLY LIFT DURING
THE AFTERNOON UNDER DIURNAL HEATING CONSIDERING THE STRENGTH OF
THE LOW LEVEL INVERSION.

FOR DTW...THE LOW LEVEL INVERSION IS NOT EXPECTED TO BE AS DEEP
AROUND METRO DETROIT. THIS AND THE ADDED DOWNSLOPE INTO METRO UNDER
N-NE WINDS MAY BE ENOUGH TO HOLD OFF LOW CLOUDS UNTIL AFTER 12Z.
THERE SHOULD BE SOME DEGREE OF DIURNAL CU DEVELOPMENT DURING THE
LATE MORNING AS DAYTIME MIXING GETS UNDERWAY AND MOISTURE
CONTINUES TO STREAM IN OFF LAKE HURON.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS BELOW 5000 FT DEVELOPING AFTER 13Z.

&&

.PREV DISCUSSION...ISSUED 327 PM EDT WED SEP 17 2014

SHORT TERM... THROUGH TONIGHT

HIGH PRESSURE AT THE SURFACE HELPED SCOUR OUT SOME OF THE LL
MOISTURE THAT HAS BEEN PREVALENT OVER THE LAST FEW DAYS. THIS WAS
EVIDENT IN THE AFTERNOON CU FIELD WHICH STRUGGLED TO DEVELOP OVER
OUR EASTERN PARTS. EARLY CU DEVELOPMENT OVER WESTERN MI DID MAKE A
PUSH EAST INTO SAGINAW VALLEY AND FNT WHICH THEN EXPANDED THROUGH
THE THUMB. THIS WILL QUICKLY DISSIPATE THIS EVENING AFTER SUNSET
ALLOWING CLEAR SKIES TO TAKE US INTO THE OVERNIGHT.

A FAST MOVING SHORTWAVE  EMBEDDED IN THE NORTHWEST FLOW ALOFT
TRACKED THROUGH ONTARIO THIS MORNING LAYING OUT A COLD FRONT ACROSS
THE UPPER PENINSULA. CAA ADVECTION BEHIND THE FRONT BROUGHT
FREEZING TEMPERATURES AND EVEN SOME SNOW TO PARTS OF ONTARIO. THIS
FRONT WILL CONTINUE ITS SOUTHWARD PUSH THROUGH THE OVERNIGHT
REACHING MBS AROUND 10Z AND DTW CLOSER TO 12Z. CAA BEHIND THE FRONT
COMBINED WITH MOISTURE ADVECTION FROM NE FLOW OVER LAKE HURON WILL
RESULT IN A LOW STRATUS DECK FOR MOST OF THE AREA. AS THE FRONT
DRIFTS SOUTH IT WILL BECOME MORE DIFFUSE WHICH WILL LESSEN THE
IMPACTS FURTHER SOUTH. THERE WILL LIKELY BE A DEGREE OF LIGHT FOG AS
WELL BUT WITH THE AMPLIFIED WINDS ASSOCIATED WITH THE
FRONT...LEANING MORE TOWARD LOW STRATUS. THIS WILL BE A DRY FROPA IN
TERMS OF PRECIP AS HIRES MODELS SHOW PWATS ONLY AROUND A HALF INCH
WITH THE MOISTURE DENSITY LOCATED IN THE LOWEST 5KFT OF THE COLUMN.
THE CLOUDS WILL HOLD MIN TEMPS UP IN THE MID 40S TONIGHT AS THE COLD
FRONT...AND CAA...WILL HOLD OFF TIL AFTER 12Z FOR MOST
LOCATIONS.

LONG TERM...THURSDAY THROUGH TUESDAY

CURRENT IR/WV SATELLITE VIEWS AND 500MB HEIGHT CONTOURS SHOW
INCREASED MOISTURE CONTENT ALONG A JET STREAK OVER EASTERN CANADA.
ANOTHER MOISTURE-RICH AREA CAN BE FOUND NEAR AND EAST OF TS ODILE
OVER THE FOUR CORNERS REGION. THE WESTERN CONUS IS GENERALLY IN A
RIDGE PATTERN THAT IS EXPECTED TO FLATTEN OUT AND ONLY SLIGHTLY
RAISE PRESSURE HEIGHTS OVER SOUTHEAST MICHIGAN.

EASTERLY FLOW OFF OF LAKE HURON AND A BACKDOOR COLD FRONT IS
EXPECTED TO INCREASE CLOUD COVER ACROSS THE NORTHERN HALF OF THE CWA
THURSDAY. THIS FRONT LOSES ITS PUNCH AS THE DAY WEARS ON WITH H85
THETA E TEMPERATURE DIFFERENTIAL GOING FROM ABOUT 20C IN THE MORNING
TO LESS THAN 10C DURING THE DAY. THIS FRONT MAY HAVE LITTLE AFFECT
ON OUR SOUTHERN 4 COUNTIES...BUT TEMPS WILL BE AROUND 10 DEGREES
COOLER NORTH OF I-69.

THE MAIN EDIT THIS CYCLE WAS TO LOWER MINS ON THURSDAY NIGHT.
SPRAWLING HIGH PRESSURE AND LIKELY LIGHT WINDS WILL ALLOW A GOOD
RADIATIONAL COOLING NIGHT. THERE WILL STILL BE AN EASTERLY COMPONENT
TO THE WIND FIELD THAT WILL ADVECT MOISTURE INLAND. THIS WILL KEEP
COASTAL AREAS AND THE DOMAIN WITHIN 20 MILES SIGNIFICANTLY WARMER.
LOOK FOR INLAND AREAS TO RADIATE INTO THE MID OR UPPER 30S THOUGH.
NEXT CHANCE FOR RAIN REMAINS ON FRIDAY NIGHT AS AN UPPER WAVE AND
CORRESPONDING LOW PRESSURE MOVES TOWARD MICHIGAN. AMERICAN MODEL
SUITE DOES NOT PUSH THE MOISTURE PLUME VERY FAR PAST LAKE
MICHIGAN...SPORTING DRY AIR AND RETREATING HIGH PRESSURE. THE GEM
AND ECMWF DO PLOT HIGHER MOISTURE LEVELS AND QPF AMOUNTS ACROSS THE
CWA. WENT LIKELY JUST FOR AREAS NORTH OF I-69 ON THIS EVENT AND WILL
CONTINUE TO MONITOR WAVE PROGRESSION.

THE NEXT LOW PRESSURE SYSTEM WILL TRACK ACROSS THE NORTHERN PLAINS
AND INTO THE NORTHERN GREAT LAKES REGION BY SATURDAY MORNING. THIS
LOW WILL BRING A CHANCE OF RAIN SHOWERS TO THE ENTIRE CWA. RAIN
SHOULD BEGIN FIRST IN THE THUMB REGION ON SATURDAY MORNING. RAIN
CHANCES WILL BEGIN FOR THE SOUTHERN CWA DURING THE AFTERNOON ON
SATURDAY. THE BEST CHANCES FOR RAIN SHOWERS WILL OCCUR ON SATURDAY
NIGHT AS A COLD FRONT GETS DRAGGED ACROSS LOWER MICHIGAN. SOME LIGHT
RAIN SHOWERS ARE EXPECTED THROUGH THE DAY ON SUNDAY AS MOISTURE
WRAPS AROUND THE DEPARTING LOW. HIGH PRESSURE WILL RETURN ON MONDAY
RESULTING IN DRY CONDITIONS ACROSS THE REGION.

MARINE...

WINDS BECOME MORE SOUTHWESTERLY THIS AFTERNOON AHEAD OF AN
APPROACHING COLD FRONT CURRENTLY DRAPED ACROSS THE NORTHERN GREAT
LAKES. THE FRONT WILL DROP THROUGH THE EASTERN LAKES TONIGHT AND
INTO THURSDAY MORNING VEERING FLOW TO NORTHEASTERLY WHILE INCREASING
THE WINDS WITH GUSTS APPROACHING 25 KNOTS TONIGHT. THE NORTHEAST
WIND DIRECTION WILL BRING INCREASED WAVE HEIGHTS INTO THE NEARSHORE
ZONES AROUND THE THUMB. SMALL CRAFT ADVISORIES HAVE BEEN ISSUED FOR
ALL NEARSHORE AREAS OF LAKE HURON INCLUDING SAGINAW BAY FOR BOTH
WINDS AND WAVES. THE ADVISORIES WILL BE IN EFFECT FROM THIS EVENING
INTO THE LATE MORNING HOURS ON THURSDAY. WINDS WILL EASE THURSDAY
NIGHT INTO FRIDAY BEFORE SOUTHERLY WINDS BEGIN TO RAMP UP AHEAD OF
THE NEXT SYSTEM LATE FRIDAY.

&&

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

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON INCLUDING SAGINAW BAY...UNTIL 10 AM THURSDAY.

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

&&

$$

AVIATION.....SC
SHORT TERM...DRK
LONG TERM....MM/RK
MARINE.......DRK


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





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