Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 182003
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
303 PM EST THU DEC 18 2014

LATEST UPDATE...
LONG TERM

.SYNOPSIS...
ISSUED AT 240 PM EST THU DEC 18 2014

LIGHT SNOW AND FREEZING DRIZZLE ARE EXPECTED TO DIMINISH OVERNIGHT.
QUIET WEATHER IS EXPECTED THROUGH THE WEEKEND WITH SOME SUN ON
FRIDAY. HIGHS WILL BE IN THE 30S OVER THE WEEKEND WITH A WARM UP
INTO THE LOWER 40S EARLY NEXT WEEK.

UNSETTLED WEATHER IS EXPECTED NEXT WEEK...WITH MULTIPLE
OPPORTUNITIES FOR BOTH RAIN AND SNOW.  RAIN OR SNOW WILL BE POSSIBLE
BEGINNING SUNDAY AFTERNOON INTO SUNDAY NIGHT. THEN A PERIOD OF RAIN
IS EXPECTED MONDAY AND TUESDAY. COLDER AIR SHOULD ARRIVE ABOUT
TUESDAY NIGHT WHICH SHOULD CHANGE THE PRECIPITATION TO SNOW WHICH
SHOULD CONTINUE INTO CHRISTMAS DAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 240 PM EST THU DEC 18 2014

MAIN CONCERN IS DRIZZLE/FREEZING DRIZZLE THIS AFTERNOON LASTING INTO
THE EVENING. SURFACE BOUNDARY HAS STALLED ROUGHLY ALONG A HOLLAND TO
GRAND RAPIDS TO LANSING LINE. TEMPERATURES SOUTH OF THIS BOUNDARY
HAVE BEEN SLOW TO RISE...BUT EXPECT A SLOW CLIMB ABOVE FREEZING THE
REST OF THIS AFTERNOON. SHORT RANGE GUIDANCE INCLUDING THE HRRR
SHOWS THE BOUNDARY DROPPING SOUTH TO I-94 BY 10 PM. THERE IS A
NARROW WINDOW FOR FREEZING DRIZZLE AGAIN THIS EVENING AS
TEMPERATURES BEGIN TO FALL. PRECIPITATION IS MOST LIKELY TO OCCUR
OVER FAR SOUTHWEST LOWER MICHIGAN WHERE SPEED CONVERGENCE OF WINDS
OFF LAKE MICHIGAN WILL SUPPLEMENT BOUNDARY CONVERGENCE. LIGHT SNOW
WILL ALSO CONTINUE TO BE POSSIBLE EARLY TONIGHT IN THE VICINITY OF
THE BOUNDARY.

OTHERWISE NO SIGNIFICANT WEATHER IS EXPECTED THROUGH SATURDAY NIGHT
WITH HIGH PRESSURE IN CONTROL.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 303 PM EST THU DEC 18 2014

STILL A FAIR AMOUNT OF UNCERTAINTY AS TO THE DETAILS OF THE STORM
SYSTEM EXPECTED TO IMPACT THE REGION JUST PRIOR TO CHRISTMAS AND
INTO CHRISTMAS DAY.

THE MODELS HAVE TRENDED FURTHER NORTH WITH THE SURFACE LOW...NOW
TAKING IT ACROSS NORTHERN LOWER TUESDAY NIGHT.  THEY ARE ALSO
HINTING AT AN EAST COAST LOW WHICH MAY TRANSFER ENERGY FROM THE
GREAT LAKES LOW.  BOTTOM LINE...THIS APPEARS TO BE A SLOW MOVING
STORM AND A FEW WOBBLES EITHER WAY WILL BE MAKE A DIFFERENCE ON
TIMING PCPN TYPE.

THE STORM BECOMES NEGATIVELY TILTED BY TUESDAY NIGHT WHICH SHOULD
FAVOR A QUICKER ARRIVAL TO THE COLDER AIR.  BEST BET RIGHT NOW IS
THAT THIS MOVES IN TUESDAY NIGHT.  SO EXPECTING A WET MONDAY AND
TUESDAY...FOLLOWED BY A COOL DOWN AND A SWITCH TO SNOW TUESDAY
NIGHT.  AND EVEN THOUGH SOME OF THE STORM/S ENERGY MAY SHIFT TO THE
EAST COAST...WE SHOULD REMAIN UNDER A MOIST CYCLONIC FLOW LINGERING
INTO CHRISTMAS DAY.  THIS SHOULD RESULT IN LIGHT SNOW CONTINUING
RIGHT INTO THE THURSDAY.  H8 TEMPS SHOULD BE AROUND -8C BY CHRISTMAS
DAY SO EXPECT LAKE MICHIGAN WILL HELP ENHANCE THE SNOW A BIT.  ALL
IN ALL IT APPEARS A WHITE CHRISTMAS IS A GOOD BET FOR MUCH OF SW MI.

UNTIL THEN...I ADDED POPS TO SUNDAY AFTERNOON AND EVENING...MOSTLY
ALONG AND NORTH OF I-96.  MODELS SHOW A SHARPENING WARM FRONT MOVING
NORTH INTO THE AREA WITH DECENT ISENTROPIC LIFT AHEAD OF IT.  WOULD
EXPECT SOME LIGHT SNOW WITH THIS...ALTHOUGH ACCUMS SHOULD REMAIN
UNDER AN INCH.  THEN WARMER AIR ARRIVES LATE SUNDAY NIGHT/MONDAY
WHEN THE PCPN SHOULD SWITCH TO RAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1255 PM EST THU DEC 18 2014

PILOTS WILL NEED TO BE AWARE OF THE THREAT OF AIRCRAFT ICING TODAY
AND INTO TONIGHT.  SOME REPORTS OF FREEZING DRIZZLE HAVE BEEN
RECEIVED.  AND THE IN CLOUD TEMP WILL BE IN THE -8 TO -11C RANGE
BETWEEN 3000 AND 5000 FT.  THIS IS AN IDEAL RANGE FOR SUPER-COOLED
LIQUID TO EXIST WITHIN THESE CLOUDS. CLOUD TOPS ARE EXPECTED TO BE
AROUND 10,000 FT MUCH OF THE DAY...SO IT MAY BE DIFFICULT TO CLIMB
OUT OF THE ICING. CLOUD TOPS ARE NOT EXPECTED TO LOWER UNTIL
02-04Z WHEN THE ICING THREAT SHOULD DIMINISH.

MUCH OF THE REGION REMAINED UNDER MVFR CONDITIONS EARLY THIS
AFTERNOON...WITH PATCHY IFR IN LOWER CEILINGS AND FREEZING
DRIZZLE. EXPECT LITTLE OVERALL CHANGE IN CONDITIONS...ALTHOUGH THE
FREEZING DRIZZLE THREAT SHOULD END ACROSS THE I-96 TAF SITES BY
21-22Z. THIS THREAT COULD LINGER NEAR THE I-94 TAF SITES UNTIL
ABOUT 01Z.

DRIER AIR SLOWLY MOVES IN FROM THE NORTH TONIGHT AND EXPECT AN
IMPROVEMENT IN CEILINGS PRIOR TO DAYBREAK TO MOSTLY VFR.


&&

.MARINE...
ISSUED AT 240 PM EST THU DEC 18 2014

NO CONCERNS AT THIS TIME. WINDS AND WAVES WILL CONTINUE TO SUBSIDE
THIS EVENING AND STAY LOW INTO THE WEEKEND WITH HIGH PRESSURE IN
CONTROL.


&&

.HYDROLOGY...
ISSUED AT 240 PM EST THU DEC 18 2014

NO SIGNIFICANT HYDRO IMPACTS EXPECTED FOR THE FORESEEABLE FUTURE.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

SYNOPSIS...EBW/JK
SHORT TERM...TJT
LONG TERM...JK
AVIATION...JK
HYDROLOGY...EBW
MARINE...TJT





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