Small Craft Advisory 93, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
245 PM EST TUE DEC 30 2008

LATEST UPDATE...SYNOPSIS...SHORT TERM...LONG TERM...MARINE...

.SYNOPSIS...(245 PM EST TUE DEC 30 2008)
SNOW OVER CENTRAL LOWER MICHIGAN WILL SPREAD SOUTH INTO SOUTHERN
LOWER MICHIGAN BY EARLY THIS EVENING. SNOW ACCUMULATIONS OF 2 TO 4
INCHES ARE EXPECTED...GENERALLY NORTH OF INTERSTATE 94...WITH
LOCALLY HIGHER AMOUNTS POSSIBLE. EAST WINDS THIS EVENING WILL SHIFT
TO THE NORTHWEST AND STRENGTHEN OVERNIGHT. QUIETER WEATHER RETURNS
BY WEDNESDAY NIGHT. HOWEVER ANOTHER SNOW PRODUCING SYSTEM IS
EXPECTED TO APPROACH THE AREA IN THE EVENING ON NEW YEARS DAY.

&&

.SHORT TERM...(245 PM EST TUE DEC 30 2008)
(TONIGHT THROUGH WEDNESDAY)
HAVE KEPT THE WINTER WEATHER ADVISORY INTACT TO ACCOUNT MAINLY FOR
IMPACTS WITH BLOWING SNOW AFTER MIDNIGHT. HEAVIEST SNOWFALL RATES
SHOULD OCCUR BETWEEN 7 PM AND MIDNIGHT...WHILE LOWER VISIBILITIES
SHOULD COMMENCE SHORTLY AFTER MIDNIGHT AS WINDS INCREASE AT THE END
OF THE HEAVIEST SNOWFALL. WE HAVE LOWERED TOTAL SNOWFALL TO THE 2 TO
4 INCH RANGE BASED ON LATEST GUIDANCE. THE TIMING OF THIS EVENT
SUGGESTS A MINIMAL IMPACT...AS THE BULK OF IT WILL BE FELT BETWEEN
COMMUTE TIMES THIS EVENING AND WEDNESDAY MORNING.

LAKE EFFECT CONTRIBUTION TO SNOW TOTALS WEDNESDAY MORNING SHOULD BE
NEGLIGIBLE DUE TO MARGINAL LAPSE RATES. STILL WOULD EXPECT SOMEWHAT
STRONGER WINDS AND REDUCED VISIBILTIES IN BLOWING SNOW NEAR THE
LAKESHORE WEDNESDAY MORNING.

GRADIENT QUICKLY RELAXES DURING THE DAY WEDNESDAY...SUGGESTING
NORTHWEST WINDS SHOULD SUBSIDE DURING THE AFTERNOON. LAKE EFFECT
EFFECT CLOUDS AND TEMPERATURES AROUND TEN DEGREES BELOW NORMAL WILL
STILL MAKE IT A BLUSTERY DAY.

&&

.LONG TERM...(245 PM EST TUE DEC 30 2008)
(WEDNESDAY NIGHT THROUGH TUESDAY)
MID RANGE MODELS CONTINUE IN DECENT AGREEMENT. LEANING TOWARD THE
ECMWF FOR CONSISTENCY. DID NOT MOVE MUCH FROM THE GOING FORECAST OR
GRIDS AS THE MODELS HAVE BEEN SOMEWHAT CONSISTENT OF LATE.

AN AREA OF HIGH PRESSURE WILL BE MOVING INTO THE REGION WEDNESDAY
NIGHT AND LAKE EFFECT SHOULD END BY THURSDAY FROM A DEPARTING
SYSTEM. ANOTHER LOW PRESSURE SYSTEM WILL APPROACH AND PASS THROUGH
THE REGION THURSDAY EVENING INTO FRIDAY NIGHT. THIS SYSTEM LOOKS
CAPABLE OF PRODUCING OVER 2 INCHES OF SNOW INCLUDING THE LAKE EFFECT
SNOW ON THE BACK SIDE. HIGH PRESSURE WILL THEN BUILD INTO THE REGION
SATURDAY. ANOTHER WEAK LOW WILL APPROACH AND PASS NORTH OF THE AREA
SATURDAY NIGHT THROUGH SUNDAY NIGHT... BRINGING MORE SNOW. HIGH
PRESSURE WILL THEN BUILD BACK IN SUNDAY NIGHT AND MONDAY. A SOUTHERN
STREAM LOW MAY THEN PASS TO THE SOUTH AND EAST TUESDAY. HAVE
INTRODUCED SNOW AT THIS TIME... BUT HAVE LOW CONFIDENCE WITH THE
PRECIPITATION AMOUNTS AND DURATION THROUGHOUT THIS FORECAST PACKAGE.
STILL BELIEVE PRECIPITATION IS OVERDONE.

TEMPERATURES THROUGH THE PERIOD WILL BE CLOSE TO OR A LITTLE BELOW
NORMAL.

&&

.MARINE...(245 PM EST TUE DEC 30 2008)
HAVE UPGRADED THE GALE WATCH TONIGHT FOR A WARNING TO BE CONSISTENT
WITH LOT AND IWX. EXPECTATIONS ARE THAT THIS WILL BE A VERY
BORDERLINE EVENT...WITH A WINDOW OF RELATIVELY FREQUENT GUSTS IN THE
35 KNOT RANGE TOWARDS DAYBREAK. WITH WAVEHEIGHTS EXPECTED TO
INCREASE SIGNIFICANTLY AFTER 06Z...THIS STILL WILL BE A HAZARDOUS
TIME TO VENTURE OFFSHORE.

&&

.AVIATION...(1230 PM EST TUE DEC 30 2008)
PUSHED THE ONSET OF SNOW AND REDUCED VISIBILITIES TO A SLIGHLY LATER
TIME BASED ON OBSERVATIONS AND MODEL GUIDANCE. MVFR VSBYS IN SNOW
SHOULD SPREAD SOUTH BEGINNING AROUND 21Z AT MKG AND 01Z AT JXN. IFR
VSBYS ARE EXPECTED TO COMMENCE ABOUT 3 HOURS AFTER THE SNOW BEGINS
AT ANY GIVEN SITE. THERE IS A DECENT CHANCE THAT IFR VSBYS COULD
PERSIST AFTER 12Z AT MKG DUE TO LAKE EFFECT SNOW. VSBYS IN BLSN FOR
INLAND TAF SITES REMAINS SOMEWHAT UNCERTAIN AFTER 06Z. HAVE LEANED
TOWARDS SLIGHTLY MORE OPTIMISTIC CONDITIONS DURING THIS PERIOD.

&&

.HYDROLOGY...(440 AM EST TUE DEC 30 2008)
MANY RIVER LEVELS ARE STILL AT OR ABOVE FLOOD STAGE WITH CRESTS
EXPECTED OVER THE NEXT COUPLE OF DAYS. SNOW IS EXPECTED THIS
AFTERNOON AND TONIGHT WITH MUCH COLDER AIR RETURNING FOR WEDNESDAY
AND THURSDAY. THIS PATTERN SHOULD ALLOW FOR LOWERING WATER LEVELS
INTO LATE WEEK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 11 AM EST
     WEDNESDAY FOR MIZ050>052-056>059-064>067-073-074.

     WINTER WEATHER ADVISORY UNTIL 11 AM EST WEDNESDAY FOR
     MIZ037>040-043>046.

LM...GALE WARNING FROM 11 PM THIS EVENING TO 11 AM EST WEDNESDAY FOR
     LMZ844>849.

&&

SYNOPSIS:     TJT
SHORT TERM:   TJT
LONG TERM:    IOD
MARINE:       TJT
AVIATION:     TJT
HYDROLOGY:    JK