Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 251714
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1214 PM EST TUE NOV 25 2014


.AVIATION...

//DISCUSSION...

SNOW SHOWERS WILL CONTINUE ACROSS THE NORTHERN TAF SITES /FNT AND
MBS/ THROUGH THE AFTERNOON HOURS. ISOLATED HEAVY BANDS
WILL RESULT IN VISIBILITIES TO DIMINISH IN ANY SNOW BANDS THAT
IMPACT THE SITES. WINDS WILL ALSO CONTINUE TO GUST UP TO 25 KNOTS
BEFORE WEAK MID LEVEL RIDGING BUILDS INTO THE AREA OVERNIGHT.
SNOW SHOWERS WILL COME TO AN END AFTER SUNSET AS WINDS DIMINISH.
CURRENTLY EXPECTING AT LEAST A FEW CLOUDS TO PERSIST OVERNIGHT WITH
A SCATTERED TO BROKEN CLOUD DECK ACROSS SOUTHEAST MICHIGAN.

FOR DTW...CURRENTLY EXPECTING THE BEST CHANCE FOR SNOW SHOWERS TO
REMAIN NORTH OF DTW. HOWEVER...THERE IS STILL A SMALL CHANCE FOR A
BRIEF SNOW SHOWER TO IMPACT THE TERMINAL OVER THE NEXT FEW HOURS.
TIMING OF ANY SHOWERS WILL BE BETWEEN 18Z AND 21Z. EXPECT REDUCED
VISIBILITIES IN ANY SNOW SHOWER ACTIVITY.

//DTW THRESHOLD THREATS...

* HIGH PROBABILITY THAT CEILINGS WILL REMAIN BELOW 5000 FT THROUGH
  THE TAF PERIOD.

* HIGH CONFIDENCE THAT PRECIPITATION WILL REMAIN ALL SNOW BUT LOW
  CONFIDENCE IN TIMING.

&&

.PREV DISCUSSION...ISSUED 359 AM EST TUE NOV 25 2014

SHORT TERM... TODAY AND TONIGHT

SE MICHIGAN POSITIONED THIS MORNING AT THE EDGE OF THE MAIN HEIGHT
FALL GRADIENT ATTENDANT TO THE UPPER TROUGH AXIS STILL ANCHORED
ACROSS THE UPPER MS VALLEY.  THIS TROUGH WILL STEADILY PROGRESS
EASTWARD TODAY...WORKING ACROSS THE LOCAL AREA DURING THE AFTERNOON
HOURS.  LOW LEVEL FLOW WILL VEER IN RESPONSE TO THIS PROCESS...A
PERIOD OF WEAK CONVERGENCE EMERGING ALONG THE ASSOCIATED LOW LEVEL
THERMAL TROUGH. OVERLAKE THERMODYNAMIC PROCESS REMAINS LIMITED...
WITH CONVECTIVE DEPTH CAPPED BELOW 4000 FT AND 0-1 KM THETA-E LAPSE
RATES BELOW 6 C/KM.  THERE WILL BE SOME DEGREE OF DOWNSTREAM
MOISTURE FLUX OFF LAKE MICHIGAN...LEAVING A MOIST LAYER SUFFICIENTLY
DEEP TO SUPPORT SOME LIGHT SNOW SHOWER/FLURRY DEVELOPMENT THIS
AFTERNOON.  GREATER PROSPECTS WILL EXIST TOWARD THE NORTH...A MORE
FAVORABLE POSITION TO RECEIVE BOTH THE STRONGER CONVERGENCE AND CVA
TIED TO THE PASSING WAVE.  A TIGHTER SOUTH TO NORTH POP GRADIENT
WILL EXIST ACCORDINGLY...ACCUMULATION POTENTIAL RANGING FROM A
DUSTING TO LOCALLY UP TO AN INCH /TRI-CITIES TO I-69 CORRIDOR/.
TEMPERATURES WILL RECOVER LITTLE OFF THE MORNING LOW...HIGHS
ARRIVING IN THE LOWER 30S.

WEAK WARMING BEHIND THE EXITING THERMAL TROUGH WILL CONTINUE TO
DIMINISH THE UPSTREAM LAKE PROCESSES.  WEAK MID LEVEL SUBSIDENCE AND
A GRADUAL BACKING OF THE LOW LEVEL WIND FIELD WILL OCCUR AT THE SAME
TIME. THIS WILL FAVOR SOME DEGREE OF SCATTERING OF THE REMNANT
STRATUS CANOPY TONIGHT. SURFACE RIDGING WILL SETTLE IN
OVERNIGHT...PROVIDING SOME ADDITIONAL REDUCTION TO THE WIND FIELD.
THIS WILL PRESENT A DESCENT RADIATIONAL COOLING SETUP...LOWS
MAKING A RUN TOWARD THE 20 DEGREE MARK IN THE COLDEST LOCALES.

LONG TERM...

SURFACE HIGH IN PLACE OVER LOWER MICHIGAN ON WEDNESDAY WILL PROVIDE
TRANQUIL WEATHER...AS WE ARE SANDWICHED IN BETWEEN THE LOW PRESSURE
SYSTEM OVER THE MIDWEST (IOWA/MISSOURI) AND THE EAST COAST STORM
SYSTEM. THE 00Z NAM IS ADAMANT MOISTURE WILL REMAIN TRAPPED UNDER
THE 3000-4000 FOOT SUBSIDENCE INVERSION...PRODUCING CLOUDY SKIES.
HOWEVER...WITH AN INVERSION THIS LOW...CONFIDENCE IS NOT HIGH IN
CLOUDS HOLDING AS BOUNDARY LAYER EXPANDS DURING THE DAY. WILL CALL
FOR BORDERLINE MOSTLY/PARTLY CLOUDY FORECAST...AS 00Z EURO IS DRIER
AT 925 MB LEVEL. EITHER WAY...WITH 925 MB TEMPS ADVERTISED TO BE
AROUND -5 C...MAX TEMPS CLIMBING IN TO THE LOW TO MID 30S SEEMS
REASONABLE...PER LATEST GUIDANCE.

FOR THURSDAY...BULK OF THE UPPER LEVEL PV ADVECTION WILL
TRANSLATE THROUGH THE OHIO VALLEY DURING THE DAY...WITH JUST A WEAK
EXTENSION COMING DOWN FROM THE NORTHERN GREAT LAKES. THUS...NOT A
WHOLE LOT OF SUPPORT FOR SNOW SHOWERS...BUT THERMAL PROFILES
BECOMING MORE FAVORABLE AS THE DAY WEARS ON...AS 850 MB TEMPS FALL
INTO THE NEGATIVE LOWER TEENS. HOWEVER...THE FLOW IS OUT OF THE
NORTHWEST...AND MEASURABLE SNOW SHOWER ACTIVITY WILL THUS LIKELY
STRUGGLE TO MAKE INROADS THIS FAR EAST.

UPPER LEVEL RIDGING BUILDING IN FOR THURSDAY NIGHT WILL BE SHORT
LIVED AS STRONG UPPER WAVE/PV ANOMALY/JET STREAK WORKS THROUGH
SOUTHERN WISCONSIN/EXTREME SOUTHERN MICHIGAN DURING FRIDAY...PROVING
WHAT LOOKS TO BE GOOD OVERRUNNING SETUP...WITH JUST OVER 3 G/KG OF
SPECIFIC HUMIDITY AT 700 MB TO WORK WITH. STILL PLENTY OF TIME FOR
THE TRACK OF THIS UPPER WAVE TO CHANGE (MUCH LIKE THE WEDNESDAY
SYSTEM)...AND THUS JUST A CHANCE OF SNOW AT THIS POINT.

MARINE...

SOUTHWEST GALES WINDS ARE CONTINUING OVER MUCH OF SOUTHERN LAKE
HURON EARLY THIS MORNING...BUT WINDS WILL CONTINUE TO GRADUALLY
DIMINISH TODAY AS THE PRESSURE GRADIENT SLACKENS AND SURFACE HIGH
PRESSURE BUILDS INTO THE SOUTHERN GREAT LAKES TONIGHT INTO
WEDNESDAY. ANOTHER COLD FRONT WILL SWING THROUGH THE CENTRAL GREAT
LAKES THURSDAY MORNING...WITH STRONG NORTHWEST WINDS TO FOLLOW
OVER THE OPEN WATERS OF LAKE HURON. AT THIS TIME...IT LOOKS LIKE
WIND GUSTS WILL REACH OR SLIGHTLY EXCEED 30 KNOTS...BUT STAY UNDER
GALE FORCE.  SURFACE HIGH RETURNING FOR FRIDAY WILL QUICKLY CAUSE
THE WINDS TO DIMINISH.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING UNTIL 4 PM EST THIS AFTERNOON FOR LHZ462>464.

     SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR LHZ421-422-
     441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR LEZ444.

&&

$$

AVIATION.....RK
SHORT TERM...MR
LONG TERM....SF
MARINE.......SF


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



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