Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 270453
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1153 PM EST WED NOV 26 2014


.AVIATION...

//DISCUSSION...

A DEEP INVERSION BASED AROUND 4K FT AGL IS EXPECTED TO PERSIST
THROUGH THE NIGHT AND INTO EARLY THURS AFTERNOON. THIS WILL SUSTAIN
A 3500-4500 FT STRATUS DECK ACROSS SE MI. THERE HAS ALSO BEEN A
SECOND CLOUD DECK BASED BETWEEN 2500 FT AND 3000 FT WITH SOME
FLURRIES. IN TERMS OF SE MI...THESE LOWER CLOUDS AND FLURRIES HAVE
BEEN MORE PREVALENT IN AND AROUND METRO DETROIT WHERE SOME BETTER
LOW LEVEL MOISTENING FROM THE EAST HAS OCCURRED THIS AFTERNOON. THE
LOW LEVEL FLOW WILL BACK FROM NORTHEAST THIS EVENING TO NORTHWEST
OVERNIGHT. SOME ADDED HEAT FLUX OFF LAKE HURON OVERNIGHT MAY BOOST
THE INVERSION A LITTLE BIT. THE TREND TOWARD NORTHWEST FLOW MAY ALSO
ADD JUST A LITTLE DRYING TO THE LOW LEVELS. THESE FACTORS SUGGEST A
TREND TOWARD PREVAILING LOW END MVFR CLOUD BASES /3500-4500 FT/
OVERNIGHT...ALTHOUGH FLUCTUATING CEILINGS COULD STILL BE POSSIBLY
THROUGH DAYBREAK THURS.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FT THROUGH TONIGHT AND
  THURSDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 924 PM EST WED NOV 26 2014

UPDATE...

AVAILABLE RADAR DATA OVER LAKE HURON SUGGESTS SOME UPTICK IN SNOW
SHOWER ACTIVITY THIS EVENING...AIDED BY LIFT AHEAD OF A WEAK MID
LEVEL SHORT WAVE TRACKING INTO THE THUMB REGION. THE 00Z DTX
SOUNDING DOES SHOW TEMPS OF -13C AT THE BASE OF INVERSION. SUSPECT
CONVECTIVE DEPTHS OVER LAKE HURON TO BE HIGHER. THE NAM AND HRR
SUGGEST BUILDING HIGH PRESSURE ACROSS GEORGIAN BAY OVERNIGHT WILL
BRIEFLY FORCE THIS CONVERGENCE INTO THE THUMB REGION /POSSIBLY
PORT HURON/ PRIOR TO AN OVERALL BACKING OF THE FLOW TO THE
NORTHWEST AFTER 09Z. LATEST OBS INDICATE THAT THIS HIGH IS NOT AS
STRONG AS THESE SOLUTIONS SUGGEST. THESE FACTORS SUPPORT HOLDING
ONTO JUST A CHANCE OF SHSN ACROSS THE LAKE HURON SHORELINE...BUT
INCREASING THE CHANCES A BIT FROM THE CURRENT FORECAST.

THE DEEP INVERSION WILL HOLD CLOUDS IN PLACE THROUGH THE NIGHT.
THIS AND LITTLE TO NO OVERALL THERMAL ADVECTION SUGGESTS NIGHTTIME
TEMPS NOT FALLING MUCH FROM CURRENT READINGS. JUST A MINOR UPWARD
ADJUSTMENT IN OVERNIGHT LOWS WILL BE MADE.

PREV DISCUSSION...ISSUED 351 PM EST WED NOV 26 2014

SHORT TERM...TONIGHT

NORTHEAST GRADIENT WRAPPING AROUND THE EAST COAST CYCLONE WILL
FUNNEL LIGHT NORTHEASTERLY WINDS INTO ONTARIO THROUGH TONIGHT. LAKE
TROUGHING OVER LAKE HURON WILL NUDGE THE FLOW TOWARD A MORE VEERED
EASTERLY FETCH AS IT APPROACHES THE SHORELINE OF THE THUMB TONIGHT.
INCREASED CONVERGENCE WITHIN THE LAKE-INDUCED TROUGH AND ALONG THE
SHORELINE MAY YET SUPPORT A PARTIAL COVERAGE OF SNOW SHOWERS WORKING
INLAND. THERMODYNAMIC PROFILES LEAVE A LOT TO BE DESIRED,
PARTICULARLY WITH REGARD TO A RESPECTABLE DEPTH OF SATURATION WITHIN
THE DENDRITE GROWTH LAYER, SO NOT EXPECTING MORE THAN MINOR
ACCUMULATIONS IN HURON AND SANILAC COUNTIES WITH THE MOIST RESIDENT
AIRMASS SUPPORTING PATCHES OF FLURRIES ELSEWHERE. STOUT INVERSION
EVIDENT ON THIS MORNING`S 12Z DTX SOUNDING AND ONGOING MOIST
EASTERLY FETCH THROUGH TODAY YIELD CONTINUED HIGH CONFIDENCE IN LOW
CLOUD COVER TONIGHT WHICH WILL CONTAIN OVERNIGHT LOWS TO THE
MID/UPPER 20S.

LONG TERM...THURSDAY THROUGH TUESDAY

FAIRLY UNSTABLE/PROGRESSIVE UPPER LEVEL PATTERN LOOKING TO SET UP
ACROSS THE CONUS THIS WEEK AS THE CURRENT TROUGH EXITS EAST BY THE
WEEKEND. WITH THE EXIT OF THE AMPLIFIED TROUGH...A MUCH MORE ZONAL
FLOW SETUP WILL DEVELOP AS AN UPPER LOW STALLS OFF THE COAST OF
CALIFORNIA AND ANOTHER WOBBLES ABOUT ITSELF OVER NORTHERN CANADA.
THIS WILL STEER THE FLOW EASTERLY BY NEXT WEEK WITH THE MAIN
BAROCLINIC ZONE LINING UP VERY NEAR TO THE AREA. THIS RESULTS IN A
LOWER CONFIDENCE FORECAST AS A SLIGHT WOBBLE NORTH OR SOUTH COULD
LEAD TO NOTABLE CHANGES IN THE FORECAST.

THE CURRENT TROUGH WILL BE DRIFTING EASTWARD ON THANKSGIVING WITH
THE UPPER LEVEL TROUGH AXIS TRAVERSING THE AREA IN THE MORNING AND A
MID LEVEL TROUGH PASSING OVERHEAD IN THE AFTERNOON. THIS WILL USHER
IN A VERY COLD AIRMASS WHICH IS BELOW -22C AT 850MB OVER
SOUTH/CENTRAL CANADA BUT WILL BE MODIFIED A BIT TO AROUND -17C BY
THE TIME IT REACHES SE MI THURSDAY NIGHT. DURING THE DAY THURSDAY WE
WILL HAVE A CHANCE OF LIGHT SNOW SHOWERS DUE TO THE COMBINATION OF
THE MID LEVEL TROUGH PASSING AND WESTERLY FLOW AIDING IN A FEW LAKE
EFFECT SHOWERS LATER IN THE DAY. DOES NOT LOOK TO MUCH IN THE WAY OF
ACCUMULATION WITH THIS SCENARIO AS THE TROUGH PUSHES THE BETTER
MOISTURE...A MEAGER 0.25-0.30 PWAT...EARLIER IN THE DAY WITH THE
COLDER AIR ALOFT AND BETTER LL LAPSE RATES COMING LATER IN THE DAY.
MODEL RH FIELDS SHOW A DRAMATIC DROP OFF IN MOISTURE THROUGHOUT THE
COLUMN LATER IN THE DAY AS WELL AS THE SHORTWAVE RIDGE BUILDS INTO
LOWER MI. THIS SHOULD SHUT OFF ANY LINGERING SNOW SHOWERS LATER
THURSDAY EVENING LEADING TO A DRY OVERNIGHT PERIOD. KEPT
ACCUMULATIONS LESS THAN A HALF INCH THROUGH THE DAY.

BETTER CHANCE OF SNOWFALL ON FRIDAY AS RIDGING BUILDS EASTWARD
THROUGH THE CENTRAL CONUS PUSHES THE ACTIVE JET NORTH INTO THE GREAT
LAKES. THIS WILL DIRECT THE LEAD EDGE OF A SHEARING PV ANOMALY INTO
SOUTHERN MI COINCIDENT WITH A BAND OF ISENTROPIC ASCENT ON THE
ELEVATED WARM FRONT ACROSS CENTRAL MI ON THE NOSE OF A MORE THETA
E RICH AIRMASS. MODELS HAVE TRENDED A BIT FURTHER SOUTH WITH THE
BEST FGEN/ISENTROPIC ASCENT BAND THUS SLIGHTLY INCREASED THE
POP/QPF/SNOW AMOUNTS SOUTHWARD AS WELL. START OF THE SNOW IS IN
QUESTION AS MODELS STRUGGLE TO KEEP THE LOW LEVELS
SATURATED...EVEN SEVERAL HOURS AFTER THE COLUMN SATURATES ABOVE
800MB. STILL THINK IT LOOKS LIKE A DECENT SETUP FOR SOME LIGHT
ACCUMULATIONS AS THE FLOW ALIGNS WITH THE AXIS OF THE FORCING
GIVING IT A BETTER RESIDENCE TIME. WITH MODELS IN FAIR AGREEMENT
WITH AROUND 0.10 INCHES OF QPF FRI-FRI NIGHT...THINKING A 1-2 INCH
SNOWFALL FORECAST SEEMS FAIR.

A ZONAL PATTERN WITH MODERATE WARM AIR ADVECTION WILL HOLD
THROUGH THE WEEKEND. THIS WILL BOOST TEMPS TO SLIGHTLY ABOVE NORMAL
FOR SUNDAY. A MID-LEVEL WAVE WILL THEN DYNAMICALLY FORCE A COLD FRONT
ACROSS THE REGION SUNDAY EVENING/NIGHT...WITH MUCH COLDER AIR THEN
FILTERING IN. STRONG 1044 MB HIGH PRESSURE SYSTEM WILL USHER IN COLD
CANADIAN/ARCTIC AIR EARLY NEXT WEEK. THAT PATTERN WILL HOLD THROUGH
THE 7 DAY FORECAST WITH TEMPS TRENDING COLDER THAN NORMAL AND PRECIP
CHANCES QUITE LOW.

MARINE...

WEAK AREA OF HIGH PRESSURE WILL RESULT IN LIGHT EASTERLY WINDS AND
LOW WAVE HEIGHTS THROUGH TONIGHT. ON THURSDAY...AN ARCTIC COLD FRONT
WILL DROP THROUGH THE GREAT LAKES USHERING IN A COLDER AND MORE
UNSTABLE AIRMASS. THIS WILL RESULT IN WINDS INCREASING AS THE BECOME
NORTHWESTERLY DURING THE DAY. CURRENT GUIDANCE OFFERS NO CLEARER
PICTURE FOR THE POTENTIAL GALE FORCE WINDS OVER CENTRAL LAKE HURON
THURSDAY AFTERNOON. WINDS STILL LOOK TO INCREASE RAPIDLY IN THE
AFTERNOON BUT DO NOT LOOK TO STAY ELEVATED FOR VERY LONG BEFORE
SLOWLY DECREASING THROUGH THE NIGHT AS THE COLD AIR CONTINUES TO
ADVECT OVER THE WATERS. WILL HOLD ONTO THE GALE WATCH UNTIL MORE
CONFIDENCE CAN BE RESOLVED. FLOW THEN TURNS TO THE SOUTHWEST ON
FRIDAY AS A WARM FRONT LIFTS NORTH THROUGH THE AREA. THIS WILL AGAIN
INTRODUCE GUSTY WINDS ACROSS THE EASTERN LAKES.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY EVENING FOR
     LHZ362-363.

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

$$

AVIATION.....SC
UPDATE.......SC
SHORT TERM...JVC
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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