Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 280434
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1134 PM EST SAT DEC 27 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 235 PM EST SAT DEC 27 2014

A COLD FRONT WILL MOVE THROUGH THIS EVENING. COLDER AIR WILL
FOLLOW FOR THE REST OF THE WEEK WITH OCCASIONAL LAKE EFFECT SNOW
SHOWERS. NO BIG STORMS ARE EXPECTED THROUGH NEW YEARS.

&&

.UPDATE...
ISSUED AT 931 PM EST SAT DEC 27 2014

A SECONDARY SURFACE TROUGH WAS NOTED AT 02Z FROM ROUGHLY ALPENA
EXTENDING SW TO HARRISON AND LITTLE SABLE POINT. THIS FEATURE HAS
BEEN THE IMPETUS FOR LIGHT RAIN AND SNOW NORTH AND WEST OF GRAND
RAPIDS THIS EVENING DUE TO ENHANCED SURFACE CONVERGENCE.
CONVERGENCE CAN BE SEEN IN THE 02Z METARS WITH NORTHWEST WINDS AT
MBL AND CAD...WITH MORE WESTERLY FLOW FURTHER SOUTH. COLDER AIR IS
ALSO EVIDENT INLAND AND BEHIND THIS SURFACE TROUGH WITH 32 AT CAD
AND 33 AT HTL.

HAVE SLIGHTLY INCREASED POPS BETWEEN 04-09Z IN WESTERN COUNTIES
DUE TO DECENT LIFT IN THE CLOUD LAYER (MAINLY BELOW 5K FEET).
TEMPERATURES ARE NOT QUITE COLD ENOUGH FOR DENDRITIC GROWTH...BUT
AN ENHANCEMENT OF LIGHT MIXED PRECIP AND EVENTUALLY LIGHT SNOW IS
POSSIBLE OVERNIGHT. STILL THOUGH...NOT MUCH IN THE WAY OF
ACCUMULATIONS DUE TO WARM SURFACES AND AIR TEMPS REMAINING ABOVE
FREEZING AS OF 0230Z.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 235 PM EST SAT DEC 27 2014

SFC LOW AND COLD FRONT MOVE EAST WITH RAIN SHOWERS ENDING. KEPT A
SLIGHT CHANCE OF RAIN/SNOW SHOWERS THIS EVENING ACROSS THE
NORTHWEST FORECAST AREA WHICH COULD BE CLIPPED BY THE SOUTHERN
EDGE OF DEFORMATION ZONE PRECIP. THIS AREA COULD ALSO SEE SOME
LAKE EFFECT SNOW SHOWERS LATER TONIGHT INTO SUNDAY MORNING.

FLOW GOES NORTHWEST THIS EVENING WITH INVERSION HEIGHTS FALLING
BLO 5 KFT...SO SNOW SHOWERS SHOULD BE LIGHT. SNOW SHOWERS SHOULD
TAPER OFF SUNDAY MORNING AS DRYING AND SUBSIDENCE CONTINUE. SNOW
SHOWERS COULD FLARE UP A BIT SUNDAY NIGHT AS AN ARCTIC FRONT SAGS
SOUTH WITH SOME SFC CONVERGENCE HELPING THE CAUSE. THE FLOW GOES
MORE NORTHERLY ON MONDAY BEHIND THE FRONT...SO ANY SNOW SHOWERS
WILL BE CONFINED CLOSE TO THE COAST.

SNOW SHOWERS COULD BE MOVING FURTHER INLAND LATE MONDAY NIGHT AS
FLOW STARTS TO GO MORE NORTHWEST. INVERSION HEIGHTS ARE STILL AOB
5 KFT...SO ACCUMS WILL BE LIMITED.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 218 PM EST SAT DEC 27 2014

WE CONTINUE TO EXPECT A TREND TOWARD COLDER TEMPERATURES WITH CHCS
OF LAKE EFFECT SNOW SHOWERS THROUGH MUCH OF THE LONG TERM. WE WILL
THEN HAVE A CHC OF PCPN NEXT WEEKEND AS A STORM SYSTEM EJECTS FROM
THE SW PORTION OF THE COUNTRY.

NO REAL CHANGE TO THE TUE THROUGH THU TIMEFRAME WITH AN ARCTIC AIR
MASS COMING IN ALONG WITH CHCS OF LIGHT LAKE EFFECT SNOW SHOWERS.
THE RIDGE AXIS IN THE LOWER LEVELS WILL BE SHIFTING SOUTH OF THE
AREA BY TUE. THIS WILL TRANSITION THE MEAN LOW LEVEL FLOW TO THE NW
AND EVENTUALLY WEST. TEMPS AT H850 IN THE NEGATIVE TEENS C WILL BE
SUFFICIENT FOR LAKE EFFECT. THE LAKE EFFECT IS NOT EXPECTED TO BE
SIGNIFICANT AS THE NRN STREAM OF THE JET REMAINS NORTH...LEADING TO
LO INVERSION HEIGHTS AND SHALLOW MOISTURE. A COUPLE OF SHORT WAVES
WILL BE MOVING JUST NORTH OF THE CWFA TRYING TO HELP THE SNOW SHOWER
CHCS OUT.

IT LOOKS LIKE THE BRUNT OF THE SYSTEM THAT HAS BEEN SHOWN TO DEVELOP
IN THE MODELS FOR NEXT WEEKEND WILL MISS MOST OF THE CWFA FOR NOW.
THE TREND OVER THE PAST 24 HOURS IS FOR THE PARALLEL GFS AND EURO TO
SLOW THE EJECTION OF THE SW ENERGY AS EXPECTED. THIS ALLOWS THE NRN
STREAM OF THE JET TO MOVE IN AND SHUNT THE SRN STREAM SYSTEM TO THE
SE. PLENTY OF TIME FOR THE MODELS TO RESOLVE THE INTERACTION OF THE
TWO BRANCHES. FOR NOW WE WILL GO WITH A CHC OF SNOW AND FEATURE
COOLER TEMPS COMPARED TO THE WARMER AND MORE WET SOLUTIONS OF THE
PREVIOUS FEW DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1132 PM EST SAT DEC 27 2014

MVFR CIGS PREVAIL ACROSS THE TAF SITES AT 0430Z. THERE IS A BAND
OF RAIN/SNOW SHOWER MOVING SOUTH NEAR I-96. THIS BAND ON SHOWERS
IS ASSOCIATED THE A SECONDARY COLD FRONT AND THIS FEATURE WILL MOVE
QUICKLY SOUTH AND EAST OUT OF THE AREA. IT IS FOLLOWED NICELY VIA
THE HRRR OVER THE PAST FEW HOURS OF RUNS. I HAVE TEMPO IFR SNOW
SHOWERS AT GRR AND AZO FOR THIS BUT ONLY MVFR AT BTL. AFTER THAT
MVFR CIGS WILL CONTINUE TILL MORNING. DRY AIR SHOULD CLEAR THE
SKIES BY MID TO LATE MORNING. THIS CLEARING IS MOVING INTO EASTERN
WISCONSIN NOW. ANOTHER WEAK COLD FRONT BRINGS MORE CLOUDS AND MAYBE
SNOW SHOWERS MONDAY NIGHT.


&&

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

A SMALL CRAFT ADVISORY REMAINS IN EFFECT THROUGH 11 AM SUNDAY. WINDS
WILL VEER WEST TO 30 KNOTS THIS 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 OVERNIGHT.


&&

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

NO HYDRO ISSUES.

&&

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

&&

$$

UPDATE...EBW
SYNOPSIS...OSTUNO
SHORT TERM...OSTUNO
LONG TERM...NJJ
AVIATION...WDM
HYDROLOGY...EBW
MARINE...EBW





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