Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 281714
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
114 PM EDT THU AUG 28 2014


.AVIATION...

//DISCUSSION...

BKN CU BASED AROUND 3 KFT FORMED LATE THIS MORNING OVER THE THUMB WITH
SOME MOISTURE FLUX OFF LAKE HURON UNDER A LINGERING INVERSION. ITS
SOUTHWARD PROGRESS HAS SLOWED AND DO NOT EXPECT IT TO IMPACT THE
TERMINAL CORRIDOR. STRATOCU DECK NEAR THE OH/MI BORDER ALSO NOT
EXPECTED TO POSE A THREAT AS BOTH AREAS EXPECTED TO MIX OUT LATER
THIS AFTERNOON. OTHERWISE...BENIGN AVIATION CONDITIONS EXPECTED INTO THE
OVERNIGHT. DEEPER MOISTURE WITH HIGH/MIDLEVEL CLOUDS WILL STREAM
INTO THE REGION LATE TONIGHT INTO TOMORROW. BEST MOISTURE/ASCENT
LOOKS TO MOSTLY STAY NORTH/WEST OF TERMINAL CORRIDOR
TOMORROW...AND LINGERING DRIER AIR AT THE SURFACE WILL PRECLUDE
THE MENTION OF ANY PREVAILING CIG/VIS RESTRICTIONS. HAVE INCLUDED
PROB30 GROUP TOMORROW MORNING FOR MBS FOR MVFR CIG/VIS WHERE BEST
CHANCE OF SHOWERS WILL BE LOCATED.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILINGS BRIEFLY APPROACHING 5000 FT TOMORROW AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 331 AM EDT THU AUG 28 2014

SHORT TERM...TODAY AND TONIGHT

A 1023MB SURFACE HIGH CENTERED OVER NW WISCONSIN/WRN UPPER MI WILL
TRACK ACROSS NRN LOWER MI TODAY THEN ADVANCE INTO THE ERN GREAT
LAKES REGION TONIGHT. THIS HIGH WILL BE DRIVEN EAST AHEAD OF A MID
LEVEL SHORT WAVE RIDGE AXIS. THE 00Z DTX SOUNDING SHOWED A FAIRLY
DEEP INVERSION BASED NEAR 840MB. SOME SUBTLE INFLUX OF MOISTURE OFF
LAKE HURON EARLIER IN THE NIGHT PROVED EFFICIENT IN DEVELOPING SOME
STRATUS. ONGOING SHALLOW COLD AIR ADVECTION /925MB TEMPS DROPPING TO
+10 TO +11C BY 12Z/...IS OBVIOUSLY DEVELOPING A MORE SHALLOW
INVERSION AS LOWER BASED STRATUS HAS BEEN EXPANDING OVER PORTIONS OF
THE AREA. SOME OF THESE CLOUDS WILL LINGER DURING THE MORNING. GIVEN
THE MOISTURE IS SHALLOW...LOW LEVEL DRY AIR ADVECTION FROM THE NORTH
TODAY AND DAYTIME HEATING SHOULD MIX ANY MORNING STRATUS OFFERING
PLENTY OF AFTERNOON SUNSHINE. GOOD LARGE SCALE SUBSIDENCE WILL
HOWEVER LIMIT AFTERNOON MIXING DEPTHS. CONSIDERING THE COOL AIRMASS
NOW FILTERING IN FROM THE NORTH...DAYTIME HIGHS WILL BE RELATIVELY
COOL FOR LATE AUGUST /RANGING FROM THE UPPER 60S IN THE THUMB TO MID
70S DETROIT SOUTH/.

MOIST LOW LEVEL INFLOW ACROSS THE UPPER MS VALLEY AND WRN GREAT
LAKES WILL THEN TAKE HOLD OVERNIGHT AHEAD OF AN UPPER TROUGH PUSHING
INTO THE PLAINS STATES. THE BETTER MOISTURE TRANSPORT WILL REMAIN
FOCUSED WELL WEST OF THE FORECAST AREA. HOWEVER AN INCREASE IN MID
AND HIGH LEVEL MOISTURE IS EXPECTED LATE TONIGHT /AFTER 09Z/. THE
LACK OF STEEP MID LEVEL LAPSE RATES AMIDST THE MID LEVEL THETA E
SURGE OVERNIGHT AND VERY DRY AIR IN THE LOW LEVELS WILL SUPPORT A
DRY FORECAST THROUGH DAYBREAK FRI. FURTHER DRYING OF THE BOUNDARY
LAYER THIS AFTERNOON AND CLEAR SKIES WELL INTO THE NIGHT SUGGEST
GOOD NOCTURNAL COOLING TO SUPPORT MIN TEMPS DOWN INTO THE 50S
TONIGHT /WITH A FEW 40S POSSIBLE IN THE THUMB/.

LONG TERM...FRIDAY THROUGH NEXT WEDNESDAY

A FEW CHANGES IN THE EXTENDED FORECAST...MAINLY TO DO WITH COVERAGE
AND TIMING OF PRECIPITATION AS MODELS CONTINUE TO TRY TO RESOLVE
THIS PATTERN. THE OVERALL PATTERN IS MUCH THE SAME AS PREVIOUS FEW
MODELS RUNS WITH LOW AMPLITUDE LONGWAVE PATTERN HOLDING ACROSS THE
NORTHERN CONUS AND SOUTHERN CANADA. THE MAIN PLAYER FOR THE GREAT
LAKES THIS WEEKEND WILL BE AN OPEN WAVE...FORMERLY A CUTOFF
LOW...CURRENTLY DRIFTING INTO THE CENTRAL PLAINS WHICH WILL GET
ABSORBED BY THE MEAN FLOW OVER THE MIDWEST ON FRIDAY. THE RESULTANT
SFC LOW WILL LAY OUT A WARM FRONT ACROSS NORTHERN MI FRIDAY INTO
SATURDAY WITH THE SFC LOW LIFTING THROUGH REGION LATE SATURDAY
NIGHT. MEANWHILE...SEVERAL SMALL SCALE MID LEVEL WAVES WILL TRACK
OVER THE REGION AS WELL. POPS WERE DECREASED QUITE A BIT ON FRIDAY
AS CURRENT MODEL TRENDS ARE SLOWING THE OPEN WAVE A BIT WHICH WILL
KEEP THE MAIN MOISTURE AND INSTABILITY AXIS OFF TO OUR WEST THROUGH
THE DAY. MODELS HAD HINTED AT THIS LAST NIGHT WHICH PUTS A LITTLE
MORE TRUST INTO IT. THIS WILL ALLOW MID LEVEL RIDGING AND SFC HIGH
PRESSURE TO HOLD OVER THE REGION THROUGH MOST OF THE DAY. MODEL
SOUNDING SHOW AN IMPRESSIVE DRY LAYER FROM THE SFC-875MB WITH ABOUT
10C DEWPOINT DEPRESSIONS AS WINDS IN THAT LAYER ARE MORE OUT OF THE
SE. SOUTHWESTERLY FLOW RIDING OVER THE SFC RIDGE WILL WILL BRING
IN PLENTY OF MID LEVEL MOISTURE AS THE ELEVATED WARM FRONT LIFTS
ACROSS SOUTHERN MI. DID LEAVE A SLIGHT CHANCE POP...CHANCE TO THE
FAR NORTHWEST...TO ACCOUNT FOR THE FRONTAL PASSAGE EVEN THOUGH THE
BEST FRONTAL FORCING IS ALSO TO THE WEST ALONG WITH THE STOUT 850MB
JET. QUESTIONS TO WHETHER PRECIP WILL BEGIN AFTER 00Z SAT AS SOME
MODELS INDICATE A SHORTWAVE TRACKING OVER THE AREA WITH THE ELEVATED
ML AND MOISTURE TO WORK WITH. LEFT A CHANCE POP TO ACCOUNT FOR THAT.
ON SATURDAY THE SFC LOW WILL TRACK THOUGH NORTHERN LOWER MI AND WILL
PULL A COLD FRONT THROUGH SE MI OVERNIGHT. FEEL MORE COMFORTABLE
WITH THE HIGH CHANCE/LIKELY POPS AS WE GET INTO THE GOOD SW
FLOW...DEEPER MOISTURE...INSTABILITY AXIS...AND FRONTAL FORCING.
DOES NOT LOOK LIKE SEVERE POTENTIAL IS THAT HIGH BUT WITH PWATS
INCREASING TO AROUND 2 INCHES ON SATURDAY...HEAVY RAINFALL WILL BE A
CONCERN.

THE SYSTEM WILL BEGIN TO LEAVE US ON SUNDAY. A RESIDUAL CHANCE POP
REMAINS AS BOTH GFS AND ECMWF WANT TO BRING ANOTHER COMPACT MID
LEVEL WAVE ACROSS LOWER MI. BUT AFTER THAT...RIDGING WILL BUILD INTO
THE AREA WITH AN ELONGATED SFC HIGH AND SUBSIDENCE IN THE WAKE THUS
WENT DRY SUNDAY NIGHT.

A MUCH STRONGER JET ENTERING THE NW CONUS WILL CARVE A BROADER AND
DEEPER TROUGH OVER THE WESTERN CONUS BY THE END OF THE WEEKEND. THIS
LOOKS TO SEND A SFC LOW THROUGH NORTHERN MI AND COLD FRONT THROUGH
SE MI MONDAY NIGHT INTO TUESDAY. THIS SHOULD BE A QUICK HITTER WITH
A NARROW CORRIDOR OF PRECIP ALONG THE FRONT.

MARINE...

HIGH PRESSURE WILL REMAIN OVER THE GREAT LAKES REGION THROUGH
FRIDAY. SHOWERS AND THUNDERSTORMS WILL RETURN FRIDAY NIGHT AS A WARM
FRONT LIFTS THROUGH SOUTHERN MICHIGAN. THIS WARM FRONT WILL STALL
OVER NORTHERN MICHIGAN ALLOWING RAIN SHOWERS TO CONTINUE THROUGH
SATURDAY. ON SATURDAY NIGHT A LOW PRESSURE SYSTEM WILL TRACK ACROSS
NORTHERN MICHIGAN AND DRAG A COLD FRONT ACROSS THE REGION WHICH WILL
KEEP RAIN CHANCES AROUND THROUGH THE EARLY PART OF SUNDAY.

&&

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

&&

$$

AVIATION.....DT
SHORT TERM...SC
LONG TERM....DRK
MARINE.......DRK


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





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