Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 271658
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1258 PM EDT WED AUG 27 2014


.AVIATION...

//DISCUSSION...

MORNING STRATUS IS UNDERGOING THE EXPECTED TRANSITION TO A PARTIAL
COVERAGE OF DIURNAL CUMULUS. SCT-BKN COVERAGE BETWEEN 2KFT AND 5KFT
IS CURRENTLY BEING OBSERVED ACROSS SE MICHIGAN. ALTHOUGH BRIEF
PERIODS OF SUB 5KFT CEILING WILL BE POSSIBLE, THE EXPECTATION IS FOR
CEILINGS TO BOTH RISE AND BECOME MORE UNIFORM, ULTIMATELY SETTLING
AT SCT COVERAGE AROUND 4KFT DURING THE NEXT COUPLE OF HOURS. HIGH
PRESSURE WILL SETTLE IN TONIGHT ENSURING WIDESPREAD VFR. HOWEVER,
LIGHT NE FLOW OFF OF LAKE HURON MAY RESULT IN SOME STRATUS
FORMATION, THOUGH IT IS NOT EXPECTED TO INFLUENCE THE TAF SITES
ATTM. THE BEST CHANCE FOR A LOW CEILING OVERNIGHT WILL BE AT KDET.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILINGS AOB 5KFT THIS AFTN

&&

.PREV DISCUSSION...ISSUED 339 AM EDT WED AUG 27 2014

SHORT TERM...TODAY AND TONIGHT

THERE HAS BEEN A SLOW YET STEADY PUSH OF DRIER AIR IN THE BOUNDARY
LAYER FOLLOWING THE PASSAGE OF YESTERDAYS COLD FRONT. SHALLOW POST
FRONTAL COLD AIR ADVECTION /925MB TEMPS DROPPING INTO THE LOW TEENS/
IS LEADING TO THE DEVELOPMENT AND SUBSEQUENT DEEPENING OF A LOW
LEVEL INVERSION. THIS COMBINED WITH RESIDUAL POST FRONTAL MOISTURE
HAS BEEN LEADING TO SOME STRATUS WHICH WILL CONTINUE TO EXPAND
ACROSS THE FORECAST AREA EARLY THIS MORNING. THERE IS SOME
UNCERTAINTY AS TO HOW PERSISTENT THESE LOW CLOUDS WILL BE TODAY
/ESPECIALLY ACROSS THE THE SAGINAW VALLEY/ AS THE LOW LEVEL FLOW
TURNS TOWARD THE NW AND BECOMES NOTABLY MORE ANTICYCLONIC. THE
CURRENT SATELLITE LOOP DOES HOWEVER SHOW A REGION OF MID CLOUDS OVER
WISCONSIN...RAPIDLY APPROACHING SRN LOWER MI. THESE CLOUDS ARE
WITHIN A BROAD REGION OF ASCENT PRECEDING A FAST MOVING SHORT WAVE
NOW TRAVERSING NRN MN. THERE HAS EVEN BEEN SOME LIGHT RAIN REPORTS
ACROSS WISCONSIN. THE BULK OF THE LARGER SCALE ASCENT WILL TRACK
ACROSS THE NORTHERN LAKES REGION THIS MORNING. MODEL SOUNDINGS
/SUPPORTED BY THE 00Z GRB RAOB/ SUGGEST A FAIRLY STOUT DRY LAYER
BETWEEN THE LOW STRATUS AND APPROACHING MID CLOUD DECK SETTLING INTO
SE MI THIS MORNING. SO A DRY FORECAST WILL BE MAINTAINED. DESPITE
THE MILD READINGS AS OF 3 AM...CONTINUED LOW LEVEL COLD AIR
ADVECTION THROUGH THE MORNING AND THE EXTENT OF CLOUD COVER WILL
LIMIT THE DIURNAL RESPONSE...HOLDING MAX TEMPS IN THE 70S TODAY.

SFC HIGH PRESSURE WILL BUILD INTO LOWER MI MORE AGGRESSIVELY LATE
THIS AFTERNOON AS CONFLUENT MID LEVEL FLOW OVERSPREADS LOWER MI
FOLLOWING THE PASSAGE OF THE SHORT WAVE ACROSS THE NRN LAKES REGION.
THIS WILL AID IN THE DIMINISHING OF DIURNAL CU AND WITH THE GRADUAL
DEPARTURE OF THE MID CLOUD DECK WILL SUPPORT A LATE
AFTERNOON/EVENING CLEARING TREND. THERE WILL BE A SLIGHT GRADIENT
OVER SE MI TONIGHT AS THE CENTER OF THE SFC HIGH SETTLES INTO NRN
LOWER MI. THERE SHOULD HOWEVER BE ENOUGH DECOUPLING IN THE BOUNDARY
LAYER TO SUPPORT NIGHTTIME MINS IN THE 50S /WITH A FEW 40S POSSIBLE
NORTH OF THE I-69 CORRIDOR/.

LONG TERM...THURSDAY THROUGH TUESDAY

A LOW AMPLITUDE LONGWAVE PATTERN SET UP ACROSS SOUTHERN CANADA WITH
A FLATTENED RIDGE OVER THE SE CONUS WILL RESULT IN A NICE START TO
THE EXTENDED PERIOD. WITH WEAK FLOW OVER MOST OF THE COUNTRY...A CUT
OFF LOW WILL DRIFT EASTWARD OUT OF THE ROCKIES EVENTUALLY BECOMING
REABSORBED IN THE MEAN FLOW OVER THE MIDWEST. THIS WILL PRESENT
SEVERAL GOOD OPPORTUNITIES FOR PRECIPITATION OVER THE COURSE OF THE
WEEKEND. WILL LIKELY SEE A LULL IN THE ACTION SUNDAY NIGHT INTO
MONDAY BEFORE A STRONG JET SURGES INTO THE NW CONUS CARVING OUT A
TROUGH WHICH LOOKS TO TARGET THE GREAT LAKES EARLY NEXT WEEK.

THURSDAY WILL START OFF PLEASANT WITH HIGH PRESSURE CENTERED
OVERHEAD...TEMPERATURES IN THE MID 70S...DEWPOINTS IN THE MID
50S...AND A GOOD DEAL OF SUN EARLY. THIS WILL CHANGE OVERNIGHT
THOUGH AS A STRONG WAVE EJECTS NORTHWARD OUT OF THE CUTOFF AND
TRACKS THROUGH THE WESTERN GREAT LAKES ON THE NOSE OF A 40-50 KNOT
LL JET. THE ASSOCIATED SFC LOW WILL LIFT A WARM FRONT THROUGH LOWER
MI LATE THURSDAY NIGHT WHICH WILL USHER ANOTHER MOIST AIRMASS INTO
THE REGION WITH DEWPOINTS BACK IN THE MID 60S AND PWATS JUST UNDER 2
INCHES. THE FIRST WAVE OF SHOWERS AND THUNDERSTORMS WILL INITIATE ON
THE LEADING EDGE OF THE TIGHT THETA E GRADIENT BEFORE 12Z FRIDAY.
THE MAIN LOW DOES NOT LOOK TO MOVE VERY FAST...RATHER CONTINUE TO
SEND WAVES UP ALONG THE FRONTAL BOUNDARY DRAPED THROUGH CENTRAL MI.
THE SFC LOW WILL EVENTUALLY TRACK THROUGH NORTHERN MI SUNDAY PULLING
A COLD FRONT THROUGH THE AREA...THIS AS THE UPPER LOW GET A GOOD
PUSH EASTWARD AS IT GETS PICKED UP IN THE STRONGER FLOW ALOFT. WITH
THE DEEP MOISTURE PLUME AND STRONG 850MB LL JET JUST OFF TO THE
WEST...WE WILL LIKELY HAVE A GRADIENT OF POPS OVER SE MI WITH
HIGHEST POPS ACROSS THE NW DECREASING AS YOU HEAD TO THE SE. TIMING
OF THE INDIVIDUAL WAVES IS TOUGH 3-5 DAYS OUT...ESPECIALLY WITH
MODELS DIFFERING SO MUCH. WILL CONTINUE CHANCE POPS THROUGH OUT THE
FRI-SUN PERIODS WITH LIKELY POPS INDICATING HIGHER CONFIDENCE OF
SOME STRONGER WAVES/FRONTS.

LOWERED POPS FOR THE START OF NEXT WEEK IN THE WAKE OF THE COLD
FRONT AS IT LOOKS LIKE SHORTWAVE RIDGING WILL PASS OVER SOUTHERN MI
IN ADVANCE OF THE DEEP TROUGH MENTIONED EARLIER. MODELS DO NOT HAVE
A GOOD HANDLE ON THIS WITH NOTABLE DIFFERENCES SO HIGHLIGHTING THE
MOST LIKELY SCENARIO. TEMPERATURES WILL BE FLUCTUATING QUITE A BIT
FROM FRIDAY ON AS THEY WILL BE VERY DEPENDENT ON TIMING OF
CONVECTION. WE SHOULD HOVER AROUND THE 80 MARK THOUGH WITH A COUPLE
OPPORTUNITIES FOR MID 80S WITH INCREASED SW FLOW AHEAD OF THESE COLD
FRONT.

MARINE...

NORTHWESTERLY FLOW IS USHERING COOLER AIR INTO THE EASTERN GREAT
LAKES IN THE WAKE OF TUESDAYS COLD FRONT WHICH IS DECREASING
STABILITY OVER THE WATER. THE LONG FETCH WILL ALLOW WAVE HEIGHTS TO
CLIMB OVER THE OPEN WATERS BUT FORTUNATELY THE FLOW WILL DIRECT THE
ELEVATED WAVES AWAY FROM THE NEARSHORE AREAS. HIGH PRESSURE WILL
BUILD OVER THE AREA TONIGHT THROUGH THURSDAY ALLOWING WINDS AND
WAVES TO SUBSIDE. SHOWERS AND THUNDERSTORMS WILL RETURN ON THURSDAY
NIGHT WITH A WARM FRONT LIFTING NORTHWARD THROUGH THE REGION. THE
FRONTAL BOUNDARY WILL LINGER ACROSS NORTHERN LAKE HURON THROUGH THE
WEEKEND WHICH WILL KEEP THE CHANCES OF STORMS IN THE FORECAST
THROUGH THAT PERIOD.

&&

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

&&

$$

AVIATION.....JVC
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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