Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 240244
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
944 PM EST TUE DEC 23 2014

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 330 PM EST TUE DEC 23 2014

LOW PRESSURE WILL MOVE NORTH FROM THE GULF COAST TONIGHT AND
WEDNESDAY THEN INTENSIFY AS IT CROSSES SOUTHEAST LOWER MICHIGAN AND
LAKE HURON ON CHRISTMAS EVE.

THIS SYSTEM WILL BRING WIDESPREAD RAINFALL OF AROUND ONE INCH AND
EVEN A RISK OF THUNDERSTORMS AND DAMAGING WIND GUSTS ACROSS
SOUTHEAST LOWER MICHIGAN.

A BAND OF ACCUMULATING WET SLUSHY SNOW THAT MAY IMPACT TRAVEL IS
EXPECTED WEST OF THE LOW TRACK FROM CENTRAL ILLINOIS TO WESTERN AND
NORTHERN LOWER MICHIGAN WEDNESDAY AFTERNOON AND EVENING. DRY WEATHER
WILL FOLLOW FOR CHRISTMAS DAY WITH HIGHS IN THE MID 30S.

TEMPERATURES WILL REMAIN ABOVE NORMAL FRIDAY AND SATURDAY WITH
COLDER AIR ARRIVING ON SUNDAY. AN ARCTIC AIR MASS AND LAKE EFFECT
SNOW APPEARS TO ARRIVE AROUND NEW YEARS.

&&

.UPDATE...
ISSUED AT 935 PM EST TUE DEC 23 2014

00Z NAM GUIDANCE IS ROLLING IN AND CONTINUES TO SUGGEST POTENTIAL
FOR SOME HEAVY WET SNOW PARTICULARLY NEAR TO NW OF A LINE FROM
SOUTH HAVEN TO MT. PLEASANT FROM LATE TOMORROW AFTERNOON THROUGH
TOMORROW EVENING. SNOW WILL POTENTIALLY BECOME HEAVY DUE TO STRONG
MID LEVEL FRONTOGENETICAL FORCING AND THERE IS POTENTIAL FOR
CHRISTMAS EVE TRAVEL TO BE IMPACTED ACROSS PORTIONS OF OUR FCST
AREA.

WE WILL CONTINUE TO REVIEW ALL THE 00Z GUIDANCE AS IT COMES IN
AND THERE IS CERTAINLY POTENTIAL FOR SOME TYPE OF WINTER WX
HEADLINE TO BE ISSUED OVERNIGHT FOR PORTIONS OF OUR FCST AREA.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 330 PM EST TUE DEC 23 2014

THE MAIN CHALLENGE WITH THE FORECAST CONTINUES TO BE THE THREAT OF
ACCUMULATING SNOW ON CHRISTMAS EVE. BELIEVE THAT THE BULK OF THIS
EVENT FOR MOST OF THE AREA WILL BE RAIN AND IT IS TOO WARM FOR TOO
LONG TO RESULT IN SIGNIFICANT SNOWFALL AMOUNTS ACROSS SW MI.

IT REALLY DOES NOT BECOME COLD ENOUGH FOR ALL SNOW UNTIL WEDNESDAY
EVENING AND BY THAT TIME THE HEAVIEST PRECIPITATION SHOULD BE
PULLING AWAY TO THE NORTHEAST. ADD TO THAT THE DIFFICULTY OF
EFFICIENTLY ACCUMULATING SNOW ON EXISTING WARM GROUND FROM ALL THE
RAIN AND RELATIVELY MILD TEMPS AND ANYTHING IN EXCESS OF 4 INCHES
SEEMS UNLIKELY. FOR THESE REASONS THE HIGHER SNOW AMOUNTS SHOWN BY
THE NAM SOLUTION SEEM TOO EXCESSIVE AND WILL NOT ISSUE A WINTER
STORM WATCH.

ALL OF THAT SAID IT IS POSSIBLE THAT A PERIOD OF HEAVIER SNOWFALL
WILL OCCUR LATE WEDNESDAY AFTERNOON AND EVENING NORTH AND WEST OF
GRAND RAPIDS AS DYNAMIC COOLING TAKES PLACE AND PRECIP TYPE
CHANGES TO PREDOMINATELY WET SNOW. BRIEFLY HEAVY SNOWFALL RATES
WITHIN THE TROW AL OF THE DEEPENING SYSTEM COULD LEAD TO QUICK
ACCUMULATIONS ON THE ROADS DESPITE THE WARM GROUND TEMPS. THIS
SCENARIO MAY REQUIRE ADVISORIES FOR TRAVEL.

ALSO OF CONCERN IS A PERIOD OF WINDY CONDITIONS WEDNESDAY EVENING AS
THE DEEPENING LOW GOES BY WHICH COULD REQUIRE WIND ADVISORIES FOR A
TIME... BUT THE STRONGEST WINDS ARE EXPECTED TO BE IN SE LWR MI.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 330 PM EST TUE DEC 23 2014

CHRISTMAS LOOKS FAIRLY QUIET WITH RIDGING IN PLACE OVER THE GREAT
LAKES. HOWEVER...WE`RE STILL IN A QUICK UPPER FLOW AND THE QUIET
WEATHER WON`T LAST LONG. AS THE HIGH MOVE EAST...A COLD FRONT WILL
APPROACH AND MIXED RAIN AND SNOW IS POSSIBLE FRIDAY NIGHT. COLDER
AIR WILL FLOW INTO THE CWA BEHIND THE COLD FRONT AND ANY LINGERING
PCPN WILL TURN TO LIGHT SNOW SATURDAY. APPROACHING UPPER TROUGH WILL
KEEP LIGHT SNOW CHANCES GOING THROUGH SUNDAY. NOTHING OF
SIGNIFICANCE IS EXPECTED THROUGH THE WEEKEND.

A MUCH DEEPER TROUGH WILL APPROACH EARLY NEXT WEEK. H8 TEMPS NEAR
-14C WILL PUT LAKE EFFECT SNOW SHOWERS IN PLAY. THE ECMWF SHOWS A
POTENT STORM MOVING NORTHEAST UP THE WEST SIDE OF THE APPALACHIANS.
THE NW WINDS THAT DEVELOP AS THE LOW MOVES BY WILL AID IN THE LAKE
EFFECT SNOW POTENTIAL. THE PCPN SHIELD FROM THE LOW...IF IT DEVELOPS
MAY BE JUST LARGE ENOUGH TO CLIP THE SOUTHEAST CWA WITH LIGHT SNOW
MONDAY SO THE STORM TRACK WILL HAVE TO BE WATCHED. THE GFS ON THE
OTHER HAND KEEPS A MUCH WEAKER LOW CLOSER TO THE GULF COAST AND
DOESN`T IMPACT THE GREAT LAKES.

HIGHS WILL FALL BACK INTO THE MID TO UPPER 20S BY SUNDAY AND REMAIN
THERE THROUGH THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 654 PM EST TUE DEC 23 2014

CURRENTLY ALL TAF SITES ARE VFR...IN FACT MOST LOCATIONS HAVE ONLY
A FEW CIRRUS CLOUDS AT 2330Z. THIS HOWEVER WILL NOT LAST ALL THAT MUCH
LONGER...A STRONG STORM SYSTEM...DEVELOPING OVER THE DEEP SOUTH
THIS EVENING WILL TRACK NEARLY DUE NORTH OVER LOWER MICHIGAN BY
CHRISTMAS EVENING. THIS WILL SPREAD IFR CIGS/VSBY ACROSS THE AREA
BY 12Z. RAIN WILL BE HEAVY AT TIMES AND THERE AN OUTSIDE CHANCE OF
THUNDERSTORMS DURING THE AFTERNOON (NOT CURRENTLY IN TAFS BUT
POSSIBLE). THE COLD AIR RACES INTO THE SYSTEM LATE IN THE
AFTERNOON AND I EXPECT MKG AND GRR WILL HAVE SOLID MODERATE TO
HEAVY WET SNOW BY 21Z THAT WILL LAST PAST 00Z. LOCATIONS FARTHER
EAST MAY STRUGGLE TO CHANGE TO SNOW BEFORE 00Z. IT WILL BECOME
WINDY LATE IN THE AFTERNOON AS THE COLD AIR MOVES IN.


&&

.MARINE...
ISSUED AT 330 PM EST TUE DEC 23 2014

WINDS AND WAVES WILL RAMP UP CONSIDERABLY ON WEDNESDAY AND WEDNESDAY
NIGHT AS A DEEPENING LOW PRESSURE SYSTEM LIFTS NORTH ACROSS
SOUTHEAST LWR MI AND LK HURON.


&&

.HYDROLOGY...
ISSUED AT 831 PM EST TUE DEC 23 2014

RAINFALL WILL BEGIN TO OVERSPREAD THE AREA TONIGHT AND WILL LAST
THROUGH MUCH OF THE DAY ON WEDNESDAY. SOME RAINFALL COULD
POTENTIALLY BECOME MODERATE TO HEAVY AT TIMES DURING THE LATE MORNING
AND AFTERNOON. TOTAL RAINFALL AMOUNTS ARE EXPECTED TO EXCEED AN
INCH OVER A GOOD PORTION OF THE FORECAST AREA WITH PORTIONS OF
CENTRAL LOWER MICHIGAN POSSIBLY REACHING 1.50 INCHES. A GREAT DEAL
OF THIS COULD FALL IN LESS THAN 12 HOURS. MINOR STREET FLOODING
WILL BE POSSIBLE DURING THE AFTERNOON ON WEDNESDAY. AREA STREAMS
AND RIVERS ARE EXPECTED TO RESPOND WITH A FEW RIVERS REACHING AT OR
ABOVE BANKFULL IN THE NEXT 24 TO 48 HOURS.

&&

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

$$

UPDATE...LAURENS
SYNOPSIS...MEADE
SHORT TERM...MEADE
LONG TERM...93
AVIATION...WDM
HYDROLOGY...JAM
MARINE...MEADE






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