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000
FXUS63 KGRR 121140
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
640 AM EST THU DEC 12 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 310 AM EST THU DEC 12 2013

MORE LAKE EFFECT SNOW WILL OCCUR TODAY.  THE HIGHEST SNOW TOTALS
SHOULD BE IN THE 1 TO 3 INCH RANGE...IMPACTING AREAS ALONG AND WEST
OF U.S. 131 FROM SOUTH HAVEN NORTHWARD.  ELSEWHERE AN INCH OR LESS
CAN BE EXPECTED.

A BIT OF A LULL IN THE SNOW WILL OCCUR TONIGHT AND FRIDAY...ALTHOUGH
SOME VERY LIGHT SNOW IS POSSIBLE OVER CENTRAL LOWER MICHIGAN.  THEN
BY FRIDAY NIGHT LOW PRESSURE WILL MOVE OUT OF THE SOUTHERN PLAINS
AND MOVE INTO THE OHIO VALLY ON SATURDAY.  THIS SYSTEM WILL SPREAD
MORE SNOW ACROSS ALL OF SOUTHERN LOWER.  AT THIS POINT THE HEAVIEST
SNOWS SHOULD OCCUR OVER THE SOUTHEAST PORTION OF MICHIGAN...POSSIBLY
INCLUDING LANSING...JACKSON AND BATTLE CREEK.  BUT IF THE TRACK OF
THE STORM CHANGES...HEAVIER SNOW COULD COVER MORE OF SOUTHWEST
MICHIGAN.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 310 AM EST THU DEC 12 2013

THE FORECAST LOOKS TO BE IN GOOD SHAPE FOR TODAY.  ANOTHER SHORT
WAVE WAS MOVING ACROSS WISCONSIN EARLY THIS MORNING AND WAS ALREADY
PERKING UP THE LAKE EFFECT SNOW.  THE SNOW SHOULD PEAK MID/LATE
MORNING.  BUT THE QUICK MOVING WAVE WILL BE PASSING THE LAKE BY
18Z...AND THE SNOW WILL DIMINISH THEREAFTER.  SO ABOUT A SIX HOUR
PERIOD OF ENHANCED SNOW SHOULD PUT DOWN ANOTHER 1 TO 3 INCHES.  THE
FLOW WILL BE 250-270 THROUGH THE DAY...FAVORING AREAS ALONG AND WEST
OF U.S. 131 AND POINTS NORTH OF SOUTH HAVEN.

BY TONIGHT THE LAKE EFFECT WILL CONTINUE TO DWINDLE AS TEMPS ALOFT
WARM.  HOWEVER WE WILL ALSO HAVE AN ARCTIC FRONT THAT SAGS INTO
NORTHERN LOWER TONIGHT AND THROUGH THE GRR CWA ON FRIDAY.  THE
MOISTURE LOOKS FAIRLY LIMITED WITH THIS FRONT...BUT AREAS ALONG
HIGHWAY 10 MAY PICK UP AROUND AN INCH OF SNOW.

THEN WE WILL BE WATCHING HOW WELL NORTHERN AND SOUTHERN STREAM
ENERGY COME TOGETHER FRIDAY NIGHT AND SATURDAY.  THE MODELS HAVE
TRENDED WITH A BETTER MERGER AND SHOW SURFACE LOW PRESSURE COMING
OUT OF OK/TX AND RIDING NE ACROSS OH.  THIS TRACK WOULD FAVOR AREAS
TO OUR SE FOR THE HEAVIEST SNOW...BUT THE MODELS ARE CONSISTENT
SHOWING A SURFACE TROUGH EXTENDING FROM THE LOW ACROSS LOWER MI.
THIS WOULD INDICATE A FAIRLY WIDESPREAD AREA OF LIFT WHICH SHOULD
SUPPORT SNOW ACROSS ALL OF GRR CWA.  AT THIS POINT 2 TO 5 INCHES
SEEMS REASONABLE...HEAVIEST OVER THE SE CWA.  BUT THE MODELS HAVE
BEEN WOBBLING ON A SOLUTION...SO THE FORECAST IS SUBJECT TO CHANGE.
HOWEVER...AT THIS POINT THE STEADIEST SNOWS LOOK TO OCCUR LATE
FRIDAY NIGHT INTO THE FIRST HALF OF SATURDAY.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 310 AM EST THU DEC 12 2013

LOW PRESSURE MOVES EAST SATURDAY NIGHT...BUT LOWER MICHIGAN REMAINS
IN THE TROWAL SO THE SNOW WILL LESSEN IN INTENSITY BUT NOT END.
THERE COULD BE SOME ENHANCED PERIODS OF SNOW SUNDAY AND SUNDAY NIGHT
AS A NORTHERN STREAM VORT MAX MOVES THROUGH AND AN ARCTIC FRONT
PROVIDES SFC CONVERGENCE.

SFC RIDGING BUILDS IN LATE SUNDAY NIGHT AND RETURN FLOW FOLLOWS FOR
MONDAY IN ADVANCE OF NEXT CLIPPER. WARM ADVECTION SNOWS BREAK OUT
LATE MONDAY FOLLOWED BY LAKE ENHANCED SNOW SHOWERS FOR TUESDAY.
THERMAL TROUGH AXIS MOVES EAST BY WEDNESDAY WITH SNOW SHOWERS ENDING
AS INVERSION HEIGHTS LOWER AND FLOW GOES ANTICYCLONIC.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 640 AM EST THU DEC 12 2013

LIGHT LAKE EFFECT SNOW SHOWERS WILL BRING PERIODS OF MVFR AND IFR
THIS MORNING BUT CONDITIONS SHOULD IMPROVE TO MOSTLY VFR THIS
AFTERNOON. WEST WINDS WILL GUST TO NEAR 20 KNOTS THIS AFTERNOON.

&&

.MARINE...
ISSUED AT 310 AM EST THU DEC 12 2013

WILL EXTEND THE SMALL CRAFT ADVISORY THROUGH TONIGHT.  WEST
SOUTHWEST FLOW WILL ONLY BEGIN TO LIGHTEN UP AFTER MIDNIGHT.
THEREAFTER THE WINDS BECOME OFFSHORE FOR FRI/SAT...RESULTING IN
LOWER WAVES.


&&

.HYDROLOGY...
ISSUED AT 310 AM EST THU DEC 12 2013

WITH THE ARCTIC AIR FIRMLY IN PLACE MUCH OF THE ICE ON THE RIVERS
HAS BEEN LOCKED UP.  THE ICE JAM THREAT SEEMS TO BE LESSENING
NOW...BUT IT WILL CONTINUE TO BE MONITORED.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 9 AM EST FRIDAY FOR LMZ844>849.

&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...OSTUNO
AVIATION...OSTUNO
HYDROLOGY...JK
MARINE...JK