Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250740
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
340 AM EDT WED MAR 25 2015

.SHORT TERM...TODAY AND TONIGHT

A BAND OF RAIN HAS BEEN ADVANCING TOWARD THE FORECAST AREA FROM THE
SOUTHWEST DURING THE NIGHT. THIS REGION OF RAIN IS OCCURRING WITHIN
STRONG LOW TO MID LEVEL MOISTURE TRANSPORT ASSOCIATED WITH A COMPACT
MID LEVEL SHORT WAVE AND ASSOCIATED SFC LOW LOCATED OVER CNTRL
ILLINOIS AS OF 06Z. THIS MID LEVEL WAVE WILL QUICKLY LIFT ACROSS
LOWER MI IN THE 12Z TO 18Z TIME FRAME. THE MOISTURE TRANSPORT IS
BEING DRIVEN NORTHWARD BY A 50-60KT LOW LEVEL JET PRECEDING THE SFC
LOW. DESPITE THE WEDGE OF DEEP LAYER DRY AIR WHICH WAS OVER SE MI
LAST EVENING...THE INFLUX OF MOISTURE THIS MORNING WILL RAISE
PRECIPITABLE WATER UP TO 0.9 INCH. THE MOIST LOW LEVEL FLOW FORCED
UP STEEPLY SLOPED ISENTROPIC SURFACES WILL RESULT IN A PERIOD OF
STRONG ASCENT THIS MORNING...AIDED BY MID LEVEL HEIGHT FALLS
ASSOCIATED WITH THE APPROACHING SHORT WAVE. THE FORCING WILL ADVANCE
ACROSS THE REGION BETWEEN 09Z AND 16Z. 00Z MODEL SOLUTIONS SUGGEST
THE FORCING AND THUS RAIN WILL LAST ANYWHERE FROM 3 TO 5 HOURS AT
ANY GIVEN LOCATION. GIVEN THE COLD AND DRY SE FLOW AT THE
SURFACE...THERE STILL REMAINS SOME CONCERN FOR A PERIOD OF FREEZING
RAIN THIS MORNING. UPSTREAM OBSERVATIONS HAVE SHOWN TEMPS TO RISE
ABOVE FREEZING VERY QUICKLY ONCE THE RAIN HAS MOVED IN. THE BOUNDARY
LAYER OVER SE MI IS A LITTLE COLDER AND DRIER COMPARED TO LOCALS
UPSTREAM. THIS STILL SUGGESTS A BRIEF PERIOD /PERHAPS AN HOUR/ OF
FREEZING RAIN BEFORE SURFACE TEMPS RISE ABOVE FREEZING. THE EXPECTED
BRIEF DURATION BELOW FREEZING CONTINUES TO SUPPORT REFRAINING FROM
THE ISSUANCE OF A FREEZING RAIN ADVISORY THIS MORNING.

STRONG MID LEVEL SUBSIDENCE WILL OVERSPREAD SRN MI THIS AFTERNOON AS
THE SHORT WAVE LIFTS ACROSS NRN MI...SUPPORTING DRY CONDITIONS. THE
ASSOCIATED SFC LOW WILL LIFT UP TOWARD THE STRAITS BY 18Z THEN INTO
ONTARIO BY 21Z. THIS SURFACE LOW HAS ALREADY OCCLUDED AS THE MID
LEVEL SHORT WAVE HAS TAKEN ON A NEGATIVE TILT. SO AS THE SFC LOW
TRACKS ACROSS LOWER MI...THE WARM SECTOR WILL BE DEFLECTED INTO
OHIO. AFTERNOON TEMPS WILL THEN DEPEND HEAVILY ON THE DEPTH OF
BOUNDARY LAYER MIXING...WITH THE STRONG MID LEVEL SUBSIDENCE
CERTAINLY A BIG LIMITING FACTOR TO DEEP MIXING. THE EXTENSIVE AMOUNT
OF LOW CLOUDS UPSTREAM SUGGESTS THERE WILL BE A GOOD DEAL OF CLOUDS
TRAPPED UNDER THE INVERSION. THERE WILL NOT BE A REAL PUSH OF COLD
AIR FOLLOWING THE PASSAGE OF THE OCCLUDED FRONT /14-16Z/...SO EVEN
WITH SOME CLOUDS MAX TEMPS SHOULD RISE INTO THE UPPER 40S/LOW 50S
TODAY. AN INCREASING SW GRADIENT TODAY WITH AT LEAST SOME AFTERNOON
GROWTH IN THE BOUNDARY LAYER WILL SUSTAIN BREEZY CONDITIONS. WIND
GUSTS MAY TOP 30 MPH AT TIMES /STRONGER IF SOME LATE DAY BREAKS IN
THE CLOUDS CAN BOOST MIXING DEPTHS/.

PHASING OF SHORT WAVE ENERGY ACROSS THE NRN GREAT LAKES THIS
AFTERNOON AND TONIGHT WITH A SECONDARY SHORT WAVE IMPULSE DROPPING
DOWN FROM CANADA WILL DEEPEN LONG WAVE TROUGHING ACROSS THE UPPER
MIDWEST/WRN GREAT LAKES. A FAIRLY TIGHT BAROCLINIC ZONE WILL BECOME
ESTABLISHED DOWNSTREAM WHICH WILL STRENGTHEN AN UPPER JET MAX ACROSS
THE NRN AND ERN GREAT LAKES. FOR MOST OF TONIGHT...SE MI WILL REMAIN
WITHIN A REGION OF ENHANCED SW FLOW. THIS AND POTENTIAL CLOUD COVER
WILL SUPPRESS THE DEGREE OF RADIATIONAL COOLING /KEEPING MOST LOCALS
ABOVE FREEZING/. THE UPPER JET SUPPORT IS EXPECTED TO ENHANCE
FORCING ALONG THE LOWER TROPOSPHERIC FRONTAL BOUNDARY ACROSS THE
OHIO VALLEY. THE NORTHERN EDGE OF THIS PRECIP MAY MOVE INTO THE
SOUTHERN HALF OF THE FORECAST AREA OVERNIGHT...WARRANTING CHANCE
TYPE POPS ATTM. THE THERMAL PROFILE WILL REMAIN WARM ENOUGH TO
SUPPORT ALL RAIN TONIGHT.

&&

.LONG TERM...THURSDAY THROUGH NEXT TUESDAY

ACTIVE LONGWAVE PATTERN WILL CONTINUE OVER THE GREAT LAKES REGION
FOR THE FORESEEABLE FUTURE. EVEN THOUGH TROUGHING OVER THE EASTERN
CONUS TRYING TO KEEP ITS GRIP ON THE REGION...MORE FREQUENT
FLUCTUATIONS ARE SEEN IN THE MODELS OF LATE. RIDGES SEEM TO BE ABLE
TO PASS THROUGH SOUTHERN MI MORE OFTEN BRINGING BRIEF PERIODS OF
WARM SOUTHERLY FLOW. BUT EVERY TIME IT APPEARS THAT WE ARE HEADING
TOWARD GREENER PASTURES...ANOTHER STRONG CANADIAN SYSTEM BRINGS THE
NEXT SURGE OF COLD AIR INTO THE AREA.

THURSDAY WILL FEATURE THE FIRST OF SEVERAL COLD FRONTS TO PASS
THROUGH THE REGION IN THE COMING WEEK...FIRST OF TWO IN A 24 HOUR
PERIOD AS WELL. AS THE WEDNESDAY LOW LIFTS UP TO THE NORTHEAST IT
WILL PULL A COLD FRONT THROUGH SE MI EARLY THURSDAY MORNING. A
SHORTWAVE ROUNDING THE BASE OF THE DEEP TROUGH EXTENDING DOWN TO
TEXAS WILL THEN QUICKLY TRACK ALONG THE FRONT WITH THE AID OF A
DEVELOPING +130 KNOT JET ORIENTED SW TO NE INTO THE EASTERN GREAT
LAKES. THIS WILL CAUSE THE LOW TO PASS TO OUT SE THROUGH OHIO AND
ALONG THE AXIS OF LAKE ERIE BUT ALLOW THE PRECIP SHIELD TO CLIP
PARTS OF SE MI. MODELS /GEMREG...ECMWF...GFS/ HAVE BEEN PRETTY
CONSISTENT FOR A FEW RUNS WITH KEEPING MOST OF THE PRECIP CONTAINED
SOUTH OF A LINE FROM JACKSON TO PORT HURON.  NOW THE HIRES NMM AND
ARW ARE FOLLOWING SUITE AS WELL.  THE NAM HAS TRENDED MUCH DRIER OF
LATE WHICH WILL BE DISREGARDED FOR NOW BEING THE OUTLIER. AT LEAST
TEMPERATURES WILL ALLOW ANY PRECIP TO FALL AS RAIN FROM THE SYSTEM.

THE TRAILING TROUGH WILL WORK THROUGH THURSDAY NIGHT ALLOWING FOR
THE FIRST SHOT OF COLD AIR INTO THE AREA. THE TROUGH WILL BRING IN
ENOUGH COLD AIR ALOFT TO INCREASE LAPSE RATES COINCIDENT WITH ENOUGH
MOISTURE TO NECESSITATE A SLIGHT CHANCE TO LOW CHANCE MENTION OF
SOME AFTERNOON RAIN SHOWERS...POSSIBLY TURNING TO LIGHT SNOW
OVERNIGHT. THEN AN ARCTIC FRONT WILL DROP SOUTH ON FRIDAY. THIS WILL
OPEN THE DOOR FOR CAA WITH 850MB TEMPS POSSIBLY COLDER THAN -15C
OVER LAKE HURON. THE COLD AIR IS TO THE EXTENT THAT MODELS ARE
ADVERTISING LAKE EFFECT SNOW IN LATE MARCH. LOOKS LIKE A BAND WANT
TO TRY TO SETUP ALONG THE NORTHERN MI SHORELINE OF THE LAKE
TARGETING THE THUMB BRINGING SOME LIGHT SNOW. THE ARCTIC FRONT WILL
DISTURB THE FLOW LEADING TO A LESS FOCUSED BAND AND POSSIBLY PUSHING
WHAT WAS FORMED DOWN THROUGH OUR EASTERN COUNTIES. HARD TO GET TOO
HEAVY HANDED ON LAKE EFFECT THIS FAR OUT...ESPECIALLY CONSIDERING
THE TIME OF YEAR. WILL TAKE A CONSERVATIVE APPROACH AND MENTION UP
TO A HALF INCH POSSIBLE THURSDAY NIGHT INTO FRIDAY.

A COLD CANADIAN HIGH THEN BUILDS BACK ACROSS THE GREAT LAKES FRIDAY
INTO SUNDAY. HIGHS ON FRIDAY LOOK TO STRUGGLE TO REACH 30 AND WILL
ONLY SLOWLY MODERATING THROUGH SUNDAY. ON SUNDAY...A SHORTWAVE RIDGE
WILL SLIDE QUICKLY PASS OVER THE REGION AHEAD OF THE NEXT LOW
PRESSURE SYSTEM. NOT AS MUCH MOISTURE WITH THIS SYSTEM AS PWATS LOOK
TO TOP OFF AROUND A HALF INCH...BUT STILL GOOD ENOUGH FOR A CHANCE
SUNDAY AND SUNDAY NIGHT. THE BAROCLINIC ZONE THEN LOOKS TO HOVER
NEAR SOUTHERN MI TO START NEXT WEEK SO LOWER CONFIDENCE WITH HOW
TEMPERATURES WILL TREND DURING THAT TIME.

&&

.MARINE...

A LOW PRESSURE SYSTEM WILL TRACK THROUGH THE CENTRAL GREAT LAKES
EARLY THIS AFTERNOON. THIS LOW WILL RESULT IN A BAND OF RAIN LIFTING
THROUGH THE EASTERN GREAT LAKES ALONG A WARM FRONT DURING THE EARLY
PART OF THE DAY BEFORE QUICKLY COMING TO AN END AS DRY AIR SURGES IN
BEHIND IT. WINDS WILL INCREASE BEHIND THE FRONT IN THE AFTERNOON AS
WELL AFTER TURNING FROM SOUTHEASTERLY TO SOUTHWESTERLY. FORECAST
WIND SPEEDS HAVE BEEN STEADILY DECREASING OVER THE LAST DAY AS
MODELS CONTINUE TO TREND THAT WAY WITH THE AIRMASS BEING WARM AND
MORE STABLE. WILL STILL SEE A PERIOD OF INCREASED WINDS BEHIND THE
FRONT BUT LOOKS TO TOP OFF AROUND 20-25 KNOTS. WITH THIS IN
CONSIDERATION ALONG WITH THE ICE ANALYSIS IN THE NEARSHORE
ZONES...WILL CANCEL THE SMALL CRAFT ADVISORY WITH THIS ISSUANCE.
WINDS WILL TURN NORTHERN BEHIND AN ARCTIC FRONT THURSDAY NIGHT
RESULTING IN A LONGER DURATION OF INCREASED FLOW WITH WINDS UP TO 20-
25 KNOTS ACROSS MUCH LAKE HURON THURSDAY NIGHT INTO SATURDAY
MORNING. THESE NORTHERLY WINDS MAY ALSO PRODUCE SOME LAKE EFFECT
SNOW SHOWERS THURSDAY NIGHT AND FRIDAY AS TEMPERATURES DROP TO BELOW
FREEZING.

&&

.AVIATION...ISSUED 1156 PM EDT TUE MAR 24 2015

LOW PRESSURE WILL BRING LOWER CIGS AND PRECIPITATION TO THE TAF
SITES LATE TONIGHT INTO EARLY WEDNESDAY. WHILE INITIAL PRECIP MAY
FALL AS -FZRA...TEMPERATURES WILL CLIMB ABOVE FREEZING AND ALLOW A
CHANGE TO ALL -RA INTO WEDNESDAY MORNING. EXPECT MVFR TO OCCASIONAL
IFR CIGS WITH THIS ACTIVITY. DRIER SOUTHWEST FLOW AROUND THE BASE OF
THIS LOW WILL SCOUR THIS MOISTURE OUT BY WEDNESDAY AFTERNOON WITH A
RETURN TO VFR CONDITIONS. WIND GUSTS WILL...HOWEVER...TOP OUT AROUND
25 KNOTS DURING THE AFTERNOON...BEFORE EASING CONSIDERABLY AT THE
FORECAST PERIOD/S END.

FOR DTW...CIGS WILL DROP TO NEAR 5000 FEET BY 09Z-10Z WITH A BRIEF
PERIOD OF -FRZA POSSIBLE AT THAT TIME. PRECIP WILL CHANGE TO -RA AND
PERSIST UNTIL 15Z WITH MVFR TO OCCASIONAL IFR CIGS. VFR CONDITIONS
WILL RETURN AS DRIER SOUTHWEST FLOW ENSUES. THIS FLOW WILL BRING THE
OCCASIONAL GUST OF 25 KNOTS DURING THE AFTERNOON.

//DTW THRESHOLD PROBABILITIES...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET 10Z-18Z WEDNESDAY
  MORNING.

* MEDIUM CONFIDENCE IN BRIEF PERIOD OF -FZRA BEFORE PRECIP CHANGES
  TO RAIN EARLY WEDNESDAY MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 8 PM EDT THIS
     EVENING FOR LHZ421-441.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

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


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


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