Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 031412
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
912 AM EST TUE MAR 3 2015

.UPDATE...

GOOD OVERRUNNING SETUP AS STRONG MID LEVEL JET (70-80 KTS)
TRANSPORTS SOLID 4-5 G/KG OF SPECIFIC HUMIDITY AT 700 MB THROUGH
SOUTHEAST MICHIGAN. WITH THAT MOISTURE COMES SOME MARGINAL
WARMTH OF ZERO TO 1.5 C AT THE LEVEL. MID LEVEL DRY SLOT WILL BE
TAKING OVER AS THE AFTERNOON WEARS ON...WITH BEST FORCING LIFTING
NORTH. AS PRECIPITATION TAPERS OFF FROM SOUTHWEST TO
NORTHEAST...SURFACE TEMPS SHOULD BE ABLE TO RESPOND...AND RISE
INTO THE 30S LATE IN THE DAY. FORECAST LOOKS TO BE IN DECENT
SHAPE...BUT BETTER RATIOS/INTENSE RATES ON THIS FRONT END PROBABLY
PLACING ACCUMULATIONS UP TO A HALF AN INCH HIGHER.

&&

.PREV DISCUSSION...ISSUED 709 AM EST TUE MAR 3 2015

SHORT TERM...TODAY AND TONIGHT

THE OVERALL FORECAST FOR THE APPROACHING SHORTWAVE DISTURBANCE SEEMS
TO BE IN PRETTY GOOD SHAPE. ONLY MINOR ADJUSTMENTS TO THE GOING
FORECAST WERE NEEDED. FIRST...INITIAL MID LEVEL FGEN BANDING IS
EXPANDING ACROSS THE AREA EARLY THIS MORNING AND EXPECT LOW LEVELS
TO SATURATE WITH THIS FEATURE AS IT LIFTS THROUGH THE NORTHERN HALF
OF THE CWA BEFORE 12Z. SNOW CHANCES WERE EXPANDED IN THE 09Z-12Z
TIME FRAME IN ANTICIPATION OF THIS WITH LIGHT ACCUMULATIONS OF LESS
THAN HALF AN INCH POSSIBLE BEFORE 12Z.

00Z MODEL SUITE IS SLIGHTLY COLDER THAN PREVIOUS RUNS...SO ADJUSTED
SNOWFALL UP SLIGHTLY FROM M-59 NORTH AS SNOW WILL MOST LIKELY BE A
BIT SLOWER TO MIX WITH AND CHANGE TO FREEZING RAIN AND ICE PELLETS.
IN FACT...PARTS OF THE SAGINAW VALLEY AND FAR NORTHERN THUMB MAY
VERY WELL REMAIN ALL SNOW. HERE...TOTAL ACCUMULATIONS WILL MOST
LIKELY BE THE HIGHEST AND APPROACH 4 INCHES BY LATE IN THE DAY.
FURTHER SOUTH...THE I-69 AND M-59 CORRIDOR ARE EXPECTED TO RECEIVE 2
OR 3 INCHES OF SNOW WITH 1 TO 2 INCHES SOUTH NEAR THE I-94 CORRIDOR
AND PERHAPS AN INCH NEAR THE MICHIGAN AND OHIO STATE LINE.

PRECIPITATION IS STILL EXPECTED TO CHANGE TO FREEZING RAIN OR ICE
PELLETS FROM LATE MORNING TO EARLY AFTERNOON FROM SOUTH TO NORTH
ACROSS THE AREA...AGAIN WILL SOME LOCATIONS NORTH OF I-69 QUITE
POSSIBLY REMAINING ALL SNOW OR A SNOW/ICE PELLET MIXTURE AT TIMES.
ICE ACCUMULATIONS WILL BE RATHER LIGHT...PERHAPS A TENTH OF AN INCH
IN SOME AREAS BETWEEN M-59 AND I-69...AND THE LEADING ACCUMULATIONS
OF SNOW WILL ACTUALLY MINIMIZE THE AFFECTS OF THIS ICE TO SOME
DEGREE. STILL...IT WILL BE A RATHER MESSY DAY WITH DIFFICULT TRAVEL
AT TIMES. THE WINTER WEATHER ADVISORY WILL REMAIN UNCHANGED.

DURING THE AFTERNOON INTO EARLY EVENING...TEMPERATURES WILL CLIMB
ABOVE FREEZING AND ALLOW FOR A PERIOD OF RAIN JUST A THE DEEPER
MOISTURE IS BEGINNING TO STRIP AWAY TO THE EAST AND NORTHEAST. THIS
LIQUID PRECIPITATION WILL TRANSITION TO MORE OF A DRIZZLE AS THE
MAIN LAYER OF MOISTURE BECOMES MORE SHALLOW WITH PRECIPITATION THEN
ENDING ALTOGETHER FROM MID TO LATE EVENING.

LONG TERM...WEDNESDAY THROUGH SUNDAY

SOUTHEASTERN MICHIGAN WILL BE INFLUENCED BY A LARGE WAVELENGTH UPPER
LEVEL TROUGH FOR THE MAJORITY OF THE LONG TERM PERIOD. THIS WILL
BRING YET ANOTHER PROLONGED STRETCH OF BELOW NORMAL TEMPERATURES
WITH SUBZERO NIGHTIME READINGS POSSIBLE BOTH WEDNESDAY AND THURSDAY
NIGHTS. THE ITEMS OF NOTE IN THIS FORECAST ARE THE LIKLIHOOD OF WIND
CHILL VALUES FALLING INTO THE 10 TO 20 DEGREE BELOW ZERO RANGE
THURSDAY MORNING AND THE POTENTIAL FOR WINDCHILLS TO RANGE BETWEEN
15 AND 20 DEGREES BELOW ZERO FOR FRIDAY MORNING. THE DRY...STABLE
ARCTIC AIRMASS WILL BRING LITTLE TO NO PROSPECTS FOR MEASURABLE
PRECIPITATION THROUGH FRIDAY. A RESPITE WILL COME IN THE FORM OF
SHORTWAVE RIDGING FRIDAY NIGHT AND ESPECIALLY SATURDAY AHEAD OF A
REINFORCING UPPER LEVEL TROUGH. MODELS AGREE ON A WELL DEVELOPED
THERMAL RIDGE STRUCTURE ALLOWING TEMPERATURES TO REBOUND
SIGNFIICANTLY INTO THE MIDDLE TO UPPER 30S ON SATURDAY. ALL
INDICATIONS POINT TO 1000-500MB HEIGHT FALLS DIGGING INTO THE
CENTRAL GREAT LAKES FOR THE LATTER HALF OF THE WEEKEND. THERE IS
PLENTY TO SORT OUT WITH REGARDS TO PRECIPITATON CHANCES AND TIMING
FOR THE WEEKEND PERIOD AS THE ECMWF/GFS ARE LEAGUES APART WITH THE
PHASING OF NORTHWESTERLY FLOW PV FEATURES.

MARINE...

A SURFACE LOW WILL TRACK ACROSS THE STRAITS TODAY WITH SOUTHERLY
WINDS WILL INCREASING AS THE LOW APPROACHES. WINDS WILL THEN VEER TO
THE WEST TONIGHT IN THE WAKE OF THE LOW PASSAGE. THERE WILL BE AN
INCREASE IN THE WESTERLY WINDS ON WED AS ANOTHER SURGE OF ARCTIC AIR
OVERSPREADS THE LAKES. THERE IS A POTENTIAL FOR GUSTS TO APPROACH
GALE FORCE OVER FAR NORTHERN LAKE HURON ON WEDNESDAY. THE CHANCES
FOR ANY GALE FORCE GUSTS TO EXCEED TWO HOURS IN DURATION DOES NOT
APPEAR HIGH ENOUGH TO JUSTIFY A GALE WATCH ATTM.

&&

.AVIATION...ISSUED 610 AM EST TUE MAR 3 2015

SNOW WILL OVERSPREAD THE TERMINALS BETWEEN 12Z AND 14Z BECOMING
STEADY IN THE 14Z-16Z TIME FRAME. PRECIPITATION WILL THEN BEGIN TO
CHANGE TO FZRA FOR THE I-94 TERMINALS BY 17Z-18Z AND A MIX OF FZRA
AND PL FURTHER NORTH INTO PTK/FNT BY 19Z-20Z. KMBS SHOULD REMAIN
MAINLY SNOW. VFR CONDITIONS WILL BECOME MVFR AND THEN IFR AS THIS
MOISTURE INCREASES TODAY. AS MID LEVEL MOISTURE STRIPS AWAY TO THE
EAST THIS AFTERNOON...A PERIOD OF DZ/FZDZ WILL FOLLOW THE STEADIER
PRECIPITATION WITH THIS THEN ENDING BY 01Z OR SO. BY THAT TIME A
DRIER WEST/NORTHWEST FLOW IN THE WAKE OF THIS SYSTEM WILL BRING A
GRADUAL IMPROVEMENT IN CONDITIONS WITH MVFR/LOWER VFR CIGS EXPECTED
TONIGHT.

FOR DTW...ONSET OF ACCUMULATING SNOWFALL STILL EXPECTED 13Z-15Z.
BURST OF MODERATE SNOW IN IFR INITIALLY MAY RESULT IN A QUICK INCH
OF ACCUMULATION LATE THIS MORNING. A TRANSITION TOWARD A PERIOD OF
FZRA/IP CENTERED ON 17Z-19Z...THEN RA/DZ FROM MID AFTERNOON INTO THE
EARLY EVENING.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS BELOW 5000 FT 06Z TONIGHT...LOWER CONFIDENCE
  THEREAFTER.

* LOW IN VISIBILITY AOB 1/2 MILE IN FOG MID AFTERNOON INTO THE
  EVENING.

* HIGH IN SNOW AS DOMINANT PTYPE THROUGH 17Z...THEN TRANSITIONING TO
  FZRA/IP 17Z-19Z...AND RA/DZ AFTER 19Z-21Z.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ047>049-
     053>055-060>063-068>070.

     WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR MIZ075-
     076-082-083.

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

$$

UPDATE.......SF
AVIATION.....DG
SHORT TERM...DG
LONG TERM....SC
MARINE.......SC


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



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