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000
FXUS63 KGRR 090456
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1156 PM EST SUN DEC 8 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 321 PM EST SUN DEC 8 2013

IT HAS FELT LIKE WINTER THE LAST FEW DAYS GIVEN THE AIR
TEMPERATURES...BUT NOW WE WILL ADD SOME SNOW AS WELL. A BURST OF
SNOW ACROSS THE AREA THIS EVENING INTO TONIGHT WILL PROVIDE A
GENERAL 1 TO 3 INCH SNOWFALL. THE HIGHEST AMOUNTS SHOULD BE FOUND
ACROSS CENTRAL LOWER MICHIGAN...WITH THE 1 INCH TOTALS OCCURRING
TOWARDS INTERSTATE 94. COLD AIR WILL PERSIST THROUGH THE WORK WEEK
WITH BOUTS OF LAKE EFFECT SNOW TOWARDS LAKE MICHIGAN. THE PERSISTENT
LAKE EFFECT WILL GET A BOOST MONDAY NIGHT INTO TUESDAY WITH
ACCUMULATIONS LIKELY DOWNWIND OF LAKE MICHIGAN. TEMPERATURES SHOULD
NOT RISE ABOVE FREEZING ALL WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 321 PM EST SUN DEC 8 2013

FIRST ORDER OF BUSINESS IS THE BURST OF SNOW MOVING THROUGH THE
FORECAST AREA THIS EVENING. VISIBILITIES IN A HEAVIER BURST MOVING
UP THE LAKESHORE HAVE BEEN AROUND 1 MILE. THE SNOW MOVING INTO LOWER
MICHIGAN IS ASSOCIATED WITH A PUSH OF WARM AIR ADVECTION ALOFT. IT
SHOULD CONTINUE RIGHT THROUGH THE EVENING...ENDING FROM SOUTH TO
NORTH AFTER MIDNIGHT. THE MOST PROLONGED SNOW SHOULD OCCUR ACROSS
CENTRAL LOWER MICHIGAN WHERE SHEARED SHORTWAVES IN THE
WEST-SOUTHWEST UPPER FLOW WILL KEEP IT GOING THROUGH THE NIGHT.
AGAIN...FORECAST TOTALS UP AROUND 3 INCHES TO THE NORTH AND AROUND
AN INCH IN THE FAR SOUTH. GIVEN THE TIMING...SUNDAY EVENING INTO
SUNDAY NIGHT AND TOTALS THAT ARE NOT IMPRESSIVE NO HEADLINE NEEDED.
THERE MAY BE SOME FREEZING DRIZZLE THAT OCCURS OVERNIGHT AS THE MID
LEVEL DRY WEDGE SWINGS IN. PUSHED THE MENTION OF FZDZ FURTHER NORTH
INTO THE CWA AS IT APPEARS ONLY THE FAR NORTH MAY BE OUT OF THE
THREAT FOR A CHANCE OF FZDZ. NOT EXPECTING THE FZDZ TO BE MUCH OF AN
ISSUE THOUGH AS ROAD CREWS WILL ALREADY BE OUT DEALING WITH THE SNOW
AND IT WILL BE FALLING ON TOP OF FRESH SNOW.

LAKE EFFECT CONCERNS RAMP UP MONDAY AND WILL CONTINUE THROUGH
TUESDAY NIGHT. LIFT IS NOTED IN THE DGZ ALMOST THE ENTIRE TIME FROM
MONDAY THROUGH TUESDAY NIGHT...BUT IT IS TUESDAY INTO TUESDAY NIGHT
THAT MAY CONTAIN THE HEAVIEST LAKE EFFECT SNOW. THIS IS THE TIME
FRAME WHERE THE DEEPEST MOISTURE AND LIFT OCCUR...ASSOCIATED WITH A
SHORTWAVE DRIVING THROUGH THE REGION. TUESDAY NIGHT MAY FEATURE A
CONVERGENCE BAND BETWEEN I94 AND I96 AS COLD AIR WRAPS AROUND THE
BOTTOM OF LAKE MICHIGAN. THESE CAN BE SOME OF THE STRONGEST LAKE
BANDS TO EFFECT THE AREA OUTSIDE OF THE BIG NORTH-NORTHWEST FLOW
DOMINANT BANDS THAT OCCUR IN A LONG FETCH. CONVERGENCE IS MAXIMIZED
NEAR THESE I94-I96 BANDS AS LARGE THERMAL GRADIENTS EXIST ACROSS
THEM. HAVE BUMPED UP POPS AND AMOUNTS...BUT WE WILL NEED TO FINE
TUNE THINGS AS WE MOVE CLOSER TO THE EVENT.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 321 PM EST SUN DEC 8 2013

THE COLD WEATHER WILL CONTINUE THROUGH THE EXTENDED PERIOD. HIGHS
WILL REMAIN IN THE 20S...SEVERAL DEGREES BELOW NORMAL. THE BEST
CHANCE FOR SNOW WILL COME WEDNESDAY. UPPER TROUGH SWINGING THROUGH
COUPLED WITH A WEAK SFC WAVE MOVING BY TO THE SOUTH WILL ENHANCE
LAKE EFFECT SNOW POTENTIAL WEDNESDAY. H8 TEMPS IN THE -20S WILL
RESULT IN A VERY LOW SNOW GROWTH REGION WHICH WILL LIMIT FLAKE SIZE.
SO ACCUMS WILL BE HELD DOWN SOMEWHAT...BUT A COUPLE OF INCHES OF
SNOW SEEM PLAUSIBLE.

THE NEXT CHANCE OF SNOW WILL COME AT THE BEGINNING OF THE WEEKEND
WHEN A WEAK COLD FRONT DROPS SOUTH. DECENT CONVERGENCE ALONG THIS
BOUNDARY MAY LEAD TO ACCUMULATING SNOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1151 PM EST SUN DEC 8 2013

I EXPANDED THE MENTION OF FZDZ IN THE TAFS. KGRR AND KMKG ARE NOW
INCLUDED MAINLY FOR A PERIOD AFTER 08Z. THE DEEPER CLOUDS AND
ASSOCIATED SNOW ARE MOVING OUT OF SW LOWER MI AT THIS TIME.
UPSTREAM IN ILLINOIS THERE WAS SOME FZDZ...WHICH SHOULD MOVE INTO
THE TAFS SITES LEADING TO SOME IMPACT. CONDITIONS WILL TREND
TOWARD MVFR...BUT STILL SOME IFR AROUND THROUGH DAYBREAK.

WINDS SHIFT TO THE WEST ON MONDAY AND THAT WILL HELP TO CREATE
LAKE EFFECT SNOW SHOWERS. MVFR WEATHER TO PREVAIL.

&&

.MARINE...
ISSUED AT 321 PM EST SUN DEC 8 2013

HAVE ISSUED A SMALL CRAFT ADVISORY FOR THE ENTIRE NEARSHORE FROM
100AM TONIGHT THROUGH 700AM ON TUESDAY MORNING. WINDS WILL INCREASE
OUT OF THE SOUTHWEST TONIGHT AND RAMP FURTHER TO AROUND 30 KNOTS ON
MONDAY PERSISTING INTO MONDAY NIGHT. MONDAY AFTERNOON AND EVENING
ESPECIALLY WE MAY APPROACH GALES...BUT AT THIS POINT THINKING WE
WILL STAY JUST BELOW GIVEN THAT 35 KNOTS IN THE PROFILE IS AT 5000FT
AT ABOVE. IT APPEARS WINDS MAY STRENGTHEN FURTHER ON TUESDAY WHEN A
GALE WARNING MAY IN FACT BE NEEDED. WAVES WILL BUILD TO 6 TO 10 FEET
IN MOST AREAS ON MONDAY. GIVEN THE AIR TEMPERATURES...PIERS AND
BREAKWALLS WILL BECOME ICE COVERED.


&&

.HYDROLOGY...
ISSUED AT 321 PM EST SUN DEC 8 2013

HYDRO THREATS CONTINUE TO BE RELATED TO ICE JAM FORMATION. THE
COMBINATION OF COLD AIR TEMPERATURES...SLIGHTLY ABOVE FREEZING WATER
TEMPERATURES AND FALLING SNOW WILL CREATE A SITUATION FOR ICE JAM
POTENTIAL ACROSS THE AREA. MOST AREA RIVERS REMAIN LEVEL WITH THE
EXCEPTION OF EAGLE ON THE LOOKING GLASS RIVER. IT SHOWED A SLIGHT
INCREASE IN STAGE TODAY AND WILL BE MONITORED. NO INFORMATION HAS
BEEN RECEIVED AT THIS POINT IN TERMS OF ANY ICE JAM FORMATION. SOME
PANCAKE ICE WAS SEEN IN THE GRAND RIVER DOWNTOWN THIS MORNING WHILE
ROBINSON TOWNSHIP REMAINS WIDE OPEN WITH NO ICE SEEN. THE
COMBINATION OF SNOW AND COLD WILL KEEP ICE JAMS THE MAIN HYDRO
THREAT RIGHT THROUGH THE WEEK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST TUESDAY FOR LMZ844>849.

&&

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...93
AVIATION...MJS
HYDROLOGY...DUKE
MARINE...DUKE