Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 280457
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1157 PM EST FRI FEB 27 2015

.AVIATION...

A CLEAR SKY AND LIGHT WIND FIELD WILL EXIST OVERNIGHT AND INTO
SATURDAY UNDER THE INFLUENCE OF STRONG HIGH PRESSURE AND A DEEP DRY
LAYER.  AN INCREASING MID/HIGH CLOUD DECK SATURDAY EVENING WILL THEN
LEAD IN THE ARRIVAL OF A DEEPER PLUME OF MOISTURE.  THIS WILL RESULT
IN THE DEVELOPMENT OF ACCUMULATING LIGHT SNOWFALL SUNDAY MORNING.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILING FALLING BELOW 5000 FT EARLY SUNDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 348 PM EST FRI FEB 27 2015

SHORT TERM...TONIGHT

A FEW PATCHES OF CLOUDS ACROSS SOUTHERN LOWER MICHIGAN THIS
AFTERNOON...BUT NOT ENOUGH TO PREVENT TEMPS FROM CLIMBING INTO THE
MID TEENS TO AROUND 20 DEGREES THIS AFTERNOON.

AIRMASS REMAINS VERY DRY (AROUND ZERO/SUB ZERO DEW PTS)...SETTING US
UP FOR ANOTHER COLD NIGHT...WITH ANY REMNANT CLOUDS AND LIGHT
SOUTHWEST FLOW/MODEST WARM ADVECTION THE ONLY HINDRANCES. WITH
STRONG HIGH PRESSURE BUILDING THROUGH THE NORTHERN OHIO
VALLEY...CONFIDENCE IS HIGH LOCATIONS SOUTH OF EIGHT MILE WILL DROP
INTO THE -5 TO -10 F RANGE (SLIGHTLY WARMER CITY OF DETROIT)...WITH
DTW BREAKING THEIR RECORD LOW OF -1 F DEGREES SET IN 1994. FARTHER
NORTH...THE FORECAST BECOMES A BIT MORE CHALLENGING AS GRADIENT IS
BIT STRONGER AND LAKE MICHIGAN INDUCED CLOUDS TRAPPED UNDERNEATH THE
INVERSION COULD LINGER ACROSS TRI-CITIES REGION INTO THE EVENING.
PROBLEM IS THE INVERSION HEIGHTS DO LOWER OVERNIGHT...SO CLOUDS
COULD JUST AS EASILY SCOUR OUT QUICKLY. AS SUCH...EXPECTING MINS IN
THE NEGATIVE LOW TO MID SINGLE NUMBERS.

LONG TERM...

JET MAX NOTED ON WATER VAPOR ALIGNED ALONG THE NORTH SLOPE OF ALASKA
IS PROGGED BY THE 12Z SUITE TO DIG SOUTH ALONG THE EASTERN PERIPHERY
OF THE WESTERN UNITED STATES RIDGE. PV ANOMALY OFF THE WEST COAST
WILL BEGIN TO CLOSE OFF DURING THIS TIME, BUT A MINOR WAVE PHASE IS
PREDICTED AS THE NORTHERN BRANCH AMPLIFIES ON SUNDAY. DEEPENING
SOUTHWEST FLOW WILL ADVECT 2 TO 2.5 G/KG H85-H7 LAYER SPECIFIC
HUMIDITY INTO THE CWA ALONG WITH GRADUALLY MODERATING TEMPERATURES.
AT THE SAME TIME, STRENGTHENING JET OVER THE OHIO VALLEY WILL
GRADUALLY LIFT NORTH TOWARD THE MI/OH BORDER FACILITATING A ZONE OF
STRONG ASCENT PRECEDING THE APPROACHING NORTHERN STREAM SHORTWAVE.
MODEL PREFERENCE LIES WITH THE UKMET, TOWARD WHICH THE ECMWF AND GFS
HAVE BEEN CONVERGING. FGEN WILL INITIALLY SUPPORT A SHARP CUTOFF
ALONG THE NORTHERN EDGE THROUGH MIDDAY BEFORE FORCING INCREASES IN
ADVANCE OF THE PRIMARY WAVE AND SUPPORTS A BROADER NORTHWARD EXTENT
WITHIN MODEST DEFORMATION. EVENT DURATION WILL REACH 18-21 HOURS IN
THE SOUTHERN CWA WHERE QPF IS FORECAST TO REACH A QUARTER TO 0.3".
DEEP ASCENT THROUGH AN INCREASINGLY COLD COLUMN WILL STRONGLY
SUPPORT MIXED CRYSTAL PRODUCTION AND SNOW RATIOS AROUND 14:1 DURING
THE PEAK, AVERAGING 12-13:1 OVER THE COURSE OF THE EVENT. SNOW
TOTALS ARE THEREFORE FORECAST TO RANGE FROM AN INCH IN THE SAGINAW
VALLEY TO 3 ALONG THE M59 CORRIDOR TO 4 NEAR THE OH BORDER WITH THE
BULK FALLING 12-00Z SUNDAY AND PEAK INTENSITY 18-00Z WHEN RATES WILL
AVERAGE A HALF INCH PER HOUR OR LESS.

AS HIGH PRESSURE SLIDES EAST ON MONDAY...GATHERING MOISTURE AND
INSTABILITY WILL GAIN STRENGTH IN THE MMV AND MOVE TOWARDS THE GREAT
LAKES. A LARGE SWATH OF 1.0 INCHES PWAT WILL ENTRENCH SOUTHERN LOWER
MICHIGAN AS LOW PRESSURE AND SOUTHERLY WINDS DEVELOP. HIGH POP RAIN
EVENT SCHEDULED FOR TUESDAY AND TUESDAY NIGHT BEFORE THE CYCLONE
CLEARS THE AREA. THERE WILL BE SNOW MIXING IN AND PTYPE IS NOT FULLY
CERTAIN AT THIS STAGE OF THE FORECAST. A RETURN OF COLDER AIR IS
EXPECTED BEHIND THE LOW PRESSURE WITH MINS AGAIN FLIRTING INTO THE
SINGLE DIGITS. THURS AND FRI MORNING.

MARINE...

HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY ON SATURDAY. MODERATE
SOUTHWEST RETURN FLOW WILL DEVELOP AROUND THIS HIGH OVER THE CENTRAL
GREAT LAKES. CENTRAL SECTIONS OF LAKE HURON WILL MOST LIKELY SEE
WINDS INCREASE INTO THE 15 TO 20 KNOT RANGE. OTHERWISE...WINDS WILL
REMAIN ON THE LIGHT SIDE AS THIS SOUTHWEST PRESSURE GRADIENT WEAKENS
LATE IN THE WEEKEND AS A WEAK LOW PRESSURE SYSTEM LIFTS INTO THE
REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....MR
SHORT TERM...SF
LONG TERM....JVC/MM
MARINE.......JVC


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


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