Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 271730
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1230 PM EST SAT DEC 27 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 328 AM EST SAT DEC 27 2014

WE WILL SEE THE LAST OF THE MILD WEATHER TODAY WITH INTERMITTENT
LIGHT RAIN AND DRIZZLE. COLDER AIR MOVES IN TONIGHT WITH A SECOND
WAVE OF ARCTIC AIR MONDAY NIGHT THROUGH WEDNESDAY. HIGHS ONLY IN THE 20S
ARE EXPECTED DURING THE MIDDLE PORTION OF THE WEEK AND MAY
STRUGGLE TO REACH 20 DEGREES ON WEDNESDAY...ESPECIALLY NORTH OF GRAND
RAPIDS. SNOW ACCUMULATIONS ALSO APPEAR POSSIBLE MONDAY NIGHT INTO
WEDNESDAY. TEMPERATURES WILL MODERATE SLIGHTLY TOWARD THE END OF
THE WORK WEEK BEFORE ANOTHER SURGE OF ARCTIC AIR NEXT WEEKEND.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 328 AM EST SAT DEC 27 2014

TEMPERATURES HAD RISEN INTO THE MID 40S MAINLY ALONG AND SOUTH OF
I-96 AS OF THIS WRITING. TEMPS AND DEWPOINTS WILL CONTINUE TO
CREEP UP THIS MORNING. 06Z HRRR CONTINUES TO INDICATE PERIODS OF
LIGHT RAIN AND DRIZZLE TODAY...THE FIRST AFTER 10Z OR SO.

THE WEAK SURFACE LOW IS FORECAST TO DEEPEN TO AROUND 1008 MB OVER
NORTHERN LOWER MI BY 18Z. THE COLD FRONT THEN MOVES THROUGH
FOLLOWED BY A VEERING OF THE WINDS DURING THE AFTERNOON. SURFACE
TEMPS ARE EXPECTED TO REMAIN ABOVE FREEZING AT 00Z THIS
EVENING...AND MOISTURE QUICKLY BAILS AFTER 00Z. THE ONSHORE FLOW
IS ALSO SLIGHTLY DIVERGENT. FORECAST THINKING HAS NOT
CHANGED...LITTLE IF ANY SNOW TONIGHT.

QUIET WEATHER EXPECTED ON SUNDAY. A VERY STRONG 1057 MB HIGH
DEVELOPS OVER WESTERN CANADA AND AN EXTENSION OF THIS HIGH
PRESSURE SYSTEM TURNS LOW LEVEL FLOW NORTHEASTERLY BY MONDAY.
THINKING PARTLY SUNNY FOR NOW WITH HIGHS IN THE LOW TO MID 30S.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 328 AM EST SAT DEC 27 2014

MODELS ARE IN DECENT AGREEMENT IN SHOWING A DEEPENING UPPER LOW OVER
HUDSON BAY AS WE HEAD THROUGH THE EXTENDED PERIOD.  THIS WILL RESULT
IN A COLDER THAN NORMAL PERIOD THROUGH THE LONG TERM PERIOD.

THE ARCTIC AIR WILL ARRIVE IN WAVES.  MONDAY NIGHT THROUGH WEDNESDAY
WILL FEATURE COLD AIR ADVECTION.  THE LOW LEVEL THERMAL TROUGH
PUSHES THROUGH ON WEDNESDAY.  HIGHS ON WEDNESDAY MAY STRUGGLE TO
REACH 20 DEGREES...ESPECIALLY NORTH OF GRAND RAPIDS.  WIND WILL
ACCOMPANY THIS ARCTIC AIRMASS AND SUB ZERO WIND CHILLS WILL OCCUR AT
TIMES.  ALSO MODELS HAVE BEEN TRENDING TOWARD MORE MOISTURE IN THE
DGZ MON NIGHT INTO WED.  THUS WE MAY END UP WITH SOME
ACCUMULATIONS.  I DID TREND POPS UPWARD BASED ON THE TRENDS.

TEMPERATURES ARE LIKELY TO MODERATE SLIGHTLY THURSDAY INTO FRIDAY AS
WARM AIR ADVECTION DEVELOPS ON THE BACKSIDE OF THE DEPARTING
HIGH.    THEY ARE EXPECTED TO STILL AVERAGE OUT BELOW NORMAL.

ANOTHER SURGE OF ARCTIC AIR WILL LIKELY PUSH IN OVER NEXT WEEKEND.
THIS IS WHEN THE SOUTHERN ROCKIES LOW KICKS OUT INTO THE PLAINS AND
TRACKS TO THE CENTRAL APPALACHIANS.  AS THIS WAVE TRACKS EAST...AN
IMPRESSIVE SURGE OF ARCTIC AIR SINKS SOUTH THROUGH THE GREAT LAKES
REGION.  THERE IS A RISK FOR SNOW ASSOCIATED WITH THE ARRIVAL OF
THIS NEXT REINFORCING SHOT OF ARCTIC AIR.  OVERALL MODELS HAVE COME
INTO BETTER AGREEMENT OF THE TIMING AND DURATION OF THIS NEXT ARCTIC
AIRMASS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1230 PM EST SAT DEC 27 2014

IFR AND LOWER CONDITIONS ARE CURRENTLY IN PLACE AT ALL OF THE
TERMINALS ACROSS SW LOWER MICHIGAN EARLY AFTERNOON. THIS IS MAINLY
DUE TO LOW CLOUDS IN PLACE AND DUE TO DRIZZLE/FOG WITH A FEW
SHOWERS AROUND. WE EXPECT THE LOW CONDITIONS TO HOLD ON FOR A FEW
HOURS BEFORE CIGS LIFT AND VSBYS IMPROVE TO MVFR FROM WEST TO EAST LIKE
WHAT IS CURRENTLY HAPPENING UPSTREAM ACROSS WI AND IL. THE BETTER
CONDITIONS APPEAR TO BE OCCURRING AFTER THE PASSAGE OF THE COLD FRONT.

THE AREA WILL REMAIN UNDER MVFR CONDITIONS FOR MOST OF THE NIGHT
WITH CIGS OF AROUND 1500 FT EXPECTED. THESE CLOUDS SHOULD TEND TO
BREAK UP BY MID-LATE SUN MORNING AS HIGH PRESSURE BUILDS IN ACROSS
THE AREA.

&&

.MARINE...
ISSUED AT 328 AM EST SAT DEC 27 2014

A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR 11 AM TODAY THROUGH 11
AM SUNDAY. AS THE SURFACE LOW APPROACHES...SOUTHERLY WINDS WILL
INCREASE TO 15 TO 25 KNOTS TODAY. WINDS WILL VEER WEST TO 30 KNOTS
LATE THIS AFTERNOON AND EVENING. WAVES WILL BUILD TO 4 TO 8 FEET
NORTH OF HOLLAND AND 3 TO 5 FEET SOUTH OF HOLLAND. WEST WINDS WILL
VEER NORTHWESTERLY TONIGHT.


&&

.HYDROLOGY...
ISSUED AT 328 AM EST SAT DEC 27 2014

AROUND A TENTH OF AN INCH OR LESS OF RAINFALL IS EXPECTED
TODAY...WITH SLIGHTLY HIGHER AMOUNTS POSSIBLE TOWARD LUDINGTON.
THIS LIGHT RAINFALL IS NOT EXPECTED TO HAVE A SIGNIFICANT IMPACT
ON RIVERS. ALL RIVER FLOOD ADVISORIES HAVE BEEN CANCELED.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 11 AM EST SUNDAY FOR LMZ844>849.

&&

$$

SYNOPSIS...EBW
SHORT TERM...EBW
LONG TERM...MJS
AVIATION...NJJ
HYDROLOGY...EBW
MARINE...EBW





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