Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 162316
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
616 PM EST TUE DEC 16 2014

.AVIATION...

//DISCUSSION...

MOIST LOW LEVEL CONDITIONS CONTAINED WITHIN A MODEST PRE-FRONTAL
SOUTHWEST FLOW WILL MAINTAIN A PERIOD OF IFR CONDITIONS THROUGHOUT
SE MICHIGAN THIS EVENING.  POCKETS OF LIGHT RAIN WILL CONTRIBUTE TO
SOME VISIBILITY REDUCTIONS /3-5 SM/ IN ADDITION TO THE LOW CEILING
HEIGHTS.  THE ENSUING ARRIVAL OF COLDER AIR WITH THE FRONTAL PASSAGE
/03Z-04Z/ WILL LIFT CONDITIONS INTO MVFR FOR THE EARLY MORNING
PERIOD.  THIS PROCESS WILL ALSO RESULT IN AN INCREASE IN WESTERLY
WINDS.  PEAK GUSTS IN THE 25 KNOT RANGE THROUGHOUT THE MORNING
HOURS.

FOR DTW...SUBSTANTIAL AREA OF IFR STRATUS WILL SHIFT THROUGH THE
TERMINAL AIRSPACE THROUGH THE LATTER HALF OF THE EVENING.  CEILINGS
WILL THEN BEGIN TO LIFT AS COLDER AIR ARRIVES AFTER 05Z.  THIS WILL
ALSO REMOVE ANY LINGERING FOG/VISIBILITY RESTRICTIONS.  MVFR LEVEL
CIGS HOLD THROUGH THE MORNING PERIOD.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING BELOW 5000 FEET THROUGH WEDNESDAY
  MORNING.

* HIGH CONFIDENCE IN PRECIPITATION TYPE FALLING AS ALL RAIN.

&&

.PREV DISCUSSION...ISSUED 352 PM EST TUE DEC 16 2014

SHORT TERM... THIS EVENING AND TONIGHT

THE WIDESPREAD RAIN WHICH HAS AFFECTED MUCH OF THE SRN AND ERN
PORTIONS OF SE MI TODAY WILL CONTINUE TO SLOWLY ROTATE EAST OF METRO
DETROIT AND PORT HURON DURING THE REMAINDER OF THE AFTERNOON.
ADDITIONAL SHOWERS NOW ROTATING INTO THE AREA FROM THE WEST ARE
OCCURRING WITHIN ENHANCED LARGE SCALE ASCENT AHEAD OF A SHORT WAVE
SLIDING ACROSS CENTRAL LAKE MI. THERE ALSO APPEARS TO BE SOME
INTERACTION WITH THE UPPER TROUGH OVER THE ERN GREAT LAKES...LEADING
TO INCREASING MID LEVEL DEFORMATION ACROSS SE MI. THE SHORT WAVE IS
FORECAST TO DAMPEN AS IT ROTATES INTO SE MI THIS EVENING...WHILE THE
LONGER WAVELENGTH TROUGH LIFTS NORTH. THE UPPER LOW NOW OVER
MINNESOTA WILL BE THE FEATURE WHICH DRIVES THESE FORCING MECHANISM
NORTH AS IT ADVANCES ACROSS THE WRN GREAT LAKES TONIGHT. THE NET
RESULT WILL BE A SHIFTING OF THE BETTER LARGER SCALE FORCING AND
SHOWER COVERAGE TOWARD THE NORTHERN HALF OF THE FORECAST AREA DURING
THE COURSE OF THE EVENING.

THE SURFACE LOW AND ASSOCIATED OCCLUDED FRONT /LOCATED OVER THE
THUMB REGION AS OF 19Z/ WILL BE FORCED INTO THE SRN BASIN OF LAKE
HURON THIS EVENING...THEN NORTHEAST TO ONTARIO OVERNIGHT. THE 19Z
SURFACE OBSERVATIONS DO SHOW THE COLD AIR LAGGING WELL BEHIND THE
SURFACE LOW...WITH A SECONDARY COLD FRONT STILL ALONG THE WRN SHORE
OF LOWER MI. THIS FRONT WILL NOT PUSH INTO SE MI UNTIL MUCH LATER
THIS EVENING /03Z TO 06Z/. SOME SEMBLANCE OF AN ISSALOBARIC
COMPONENT ALONG THE FRONT AND ARRIVAL OF COLD AIR WILL LEAD TO
INCREASING WINDS. LOW LEVEL COLD AIR ADVECTION THROUGH THE NIGHT
WILL ALSO DEEPEN THE MIXED LAYER AND WILL BE SUPPORTIVE OF SOME
GUSTS UP TO 30 MPH DURING THE OVERNIGHT. AS TEMPS COOL
OVERNIGHT...THE COLUMN WILL BECOME COLD ENOUGH TO SUPPORT ALL SNOW.
A LINGERING THERMAL TROUGH ACROSS THE TRI CITIES AND THUMB SUGGEST
IT WILL TAKE THIS REGION /ALSO THE AREA TO SEE PRECIP PERSIST INTO
THE OVERNIGHT/ BETWEEN 06Z AND 09Z FOR THE COLUMN TO COOL ENOUGH TO
SUPPORT ALL SNOW. THIS WILL BE ALONG THE LEADING EDGE OF DRIER MID
LEVEL AIR AND THUS END OF PRECIP. SO THE CURRENT FORECAST SUGGESTING
A MINIMAL AMOUNT OF SNOW ACCUMS OVERNIGHT ACROSS THE SAGINAW VALLEY
AND THUMB CONTINUES TO LOOK REASONABLE.

LONG TERM...WEDNESDAY THROUGH MONDAY

THE WELL DISCUSSED STACKED LOW PRESSURE SYSTEM WILL BE EXITING TO
THE EAST ON WEDNESDAY BUT A STRONG NORTHERN STREAM PV ANOMALY WILL
BE SHEARING OUT AS IT DIGS DOWN AND THE AROUND THE BACKSIDE OF THE
TROUGH THROUGH SOUTHERN MI. IN ADDITION...LINGERING TROUGH AXIS WILL
BE DRAPED ACROSS CENTRAL/NORTHERN MI BEHIND THE EXITING LOW. A MID
LEVEL COLD POOL...APPROACHING -27C AT 500MB...WILL ACCOMPANY THE VORT
MAX ACROSS SOUTHERN MI DURING THE EVENING HOURS BEHIND AN ARCTIC
FRONT. THE FRONT WILL LOWER FROM ABOUT 500MB OVER MBS TO CLOSER TO
700MB BY THE TIME IT EXITS THE EASTERN CWA...WHILE LOSING SOME
FORCING. THIS SHOULD NOT AMOUNT TO MUCH AT THE SFC BECAUSE MOISTURE
WILL BE LACKING OVER THE AREA WITH DRY AIR BUILDING IN QUICKLY FROM
THE TOP DOWN THROUGH THE PROFILE AS RIDGING BUILDS IN BEHIND THE
UPPER LOW. PWATS WILL BE AROUND 0.4 INCHES WITH SPECIFIC HUMIDITIES
COMING IN MAINLY AROUND 1 G/KG AND ALL BELOW THE INVERSION CENTERED
AROUND 850MB. THIS WILL ALL LEAD TO ANOTHER DAY WITH AMPLE LL CLOUD
COVER AND MUCH COOLER HIGH TEMPS AS WESTERLY WINDS RAMP UP IN THE
WAKE OF THE SFC COLD FRONT. WITH LITTLE MOISTURE TO WORK WITH...DO
NOT EXPECT MUCH IN THE WAY OF ACCUMULATING SNOWFALL ALTHOUGH
FLURRIES OR LIGHT SNOW SHOWERS WILL BE PREVALENT THROUGH THE EVENING
WITH SOME DEGREE OF LAKE EFFECT KICKING IN. THE WILL BE MORE
CONFINED ACROSS THE FAR NORTH ALTHOUGH SOME HIRES MODELS ARE TRYING
TO SHOW A BAND DEVELOPING LATER IN THE DAY BETWEEN M59 AND I94. THIS
REMAINS TO BE SEEN WITH THE POOR CONVERGENT SIGNATURE SO WILL NOT
HIGHLIGHT ANY POTENTIAL FOR ACCUMS ACROSS THE AREA. THE ACTIVITY
WILL SHUT OFF OVERNIGHT WEDNESDAY EXCEPT FOR THE EASTERN THUMB WHERE
THE MAIN LAKE HURON BAND LOOKS TO BRUSH THOSE COUNTIES...WHICH WILL
LINGER INTO THURSDAY. GUSTY W/NW FLOW WILL PERSIST WEDNESDAY INTO
THURSDAY. OVERALL THE SNOW THREAT IS LOW AND TEMPERATURES WILL
RETURN TO NEAR NORMAL FOR MID DECEMBER WITH HIGHS IN THE LOW/MID
30S AND LOWS IN THE MID 20S.

SOUTHERN STREAM JET WILL SPARK LOW PRESSURE IN THE LOWER MISSISSIPPI
VALLEY FRIDAY THAT SHOULD REMAIN WELL SOUTH OF MICHIGAN AS IT MOVES
NORTHEAST THROUGH THE TENNESSEE VALLEY. AN UPPER LEVEL TROUGH WILL
GENERALLY KEEP COOL TEMPS IN THE FORECAST...BUT SURFACE HIGH
PRESSURE WILL ENSURE DRY CONDITIONS. THIS PATTERN WILL REMAIN IN
PLACE THROUGH THE WEEKEND. 170 KT JET AND MOISTURE COMING ONSHORE IN
THE PACIFIC EARLY NEXT WEEK MAY EVENTUALLY REACH MICHIGAN TOWARD DAY
7.

MARINE...

THE CENTER OF THE SFC LOW IS NOW OVER THE EASTERN GREAT LAKES AND
WILL CONTINUE ITS PUSH EAST THROUGH THE OVERNIGHT. THIS WILL OPEN
THE DOOR FOR STRONG WESTERLY FLOW WITH COLD AIR ADVECTION ACROSS THE
LAKES. MIXING DEPTHS UP TO AROUND 900MB WILL TAP INTO THE STRONGEST
FLOW WHICH IS ONLY FORECAST TO BE AROUND 35 KNOTS AT THAT LEVEL. IT
SHOULD NOT TAKE TOO MUCH TO BRING SOME HIGHER GUSTS DOWN THOUGH
WITH SUSTAINED FLOW PUSHING 20 KNOTS. HAVE ISSUED SMALL CRAFT
ADVISORIES FOR ALL NEARSHORE ZONES STARTING WITH LAKE ERIE THIS
EVENING...FOLLOWED BY THE LAKE HURON ZONES AND LAKE ST CLAIR LATE
TONIGHT FOR THESE ELEVATED WINDS. WAVES WILL ALSO REACH CRITERIA IN
SOME OF THE LAKE HURON ZONES BUT OFFSHORE FLOW WILL KEEP WAVE
HEIGHTS DOWN SOMEWHAT ALONG WITH SOME ICE COVER SHOWING UP IN INNER
SAGINAW BAY. WINDS WILL DECREASE BELOW CRITERIA WEDNESDAY AFTERNOON
BUT WILL STAY ELEVATED THROUGH WEDNESDAY NIGHT AS THE VEER TO THE
NORTHWEST.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 4 AM TO 4 PM EST WEDNESDAY FOR LHZ421-422-
     441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 4 AM TO 4 PM EST WEDNESDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 PM EST WEDNESDAY
     FOR LEZ444.

&&

$$

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


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


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