Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 210416
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1116 PM EST SAT DEC 20 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 329 PM EST SAT DEC 20 2014

A DEEP LOW PRESSURE SYSTEM IS FORECAST TO MOVE THROUGH THE GREAT
LAKES REGION AS WE HEAD FROM CHRISTMAS EVE INTO CHRISTMAS DAY. THE
MAIN ITEMS OF NOTE WILL BE A SOAKING RAIN FROM MONDAY NIGHT
INTO CHRISTMAS EVE ALONG WITH WINDY CONDITIONS. THE RAIN WILL TRY TO
CHANGE OVER TO SOME SNOW CHRISTMAS EVE NIGHT WITH SOME LIGHT
ACCUMULATIONS POSSIBLE. HIGH TEMPERATURES WILL MODERATE FROM THE 30S
ON SUNDAY TO THE 40S ON TUESDAY AND CHRISTMAS EVE AS WARMER AIR
MOVES IN WITH THE LOW.

&&

.UPDATE...
ISSUED AT 636 PM EST SAT DEC 20 2014

UPDATED THE GRIDS TO REFLECT PATCHY FREEZING DRIZZLE. A FEW SLICK
SPOTS BEGINNING TO DEVELOP ACROSS MUSKEGON AND ALLEGAN COUNTIES.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 329 PM EST SAT DEC 20 2014

SHORT TERM CONCERNS PERTAIN TO CLOUD COVER INITIALLY...THE CHANCE OF
SOME LIGHT WARM FRONTAL SNOW SUNDAY EVENING AND RAIN MOVING IN
MONDAY AFTERNOON AND NIGHT.

AS FOR THE CLOUDS...FEEL THE LOWER CLOUDS WILL CONTINUE TO ADVECT
ACROSS THE FORECAST AREA FROM THE WEST AS WE MOVE THROUGH THE NIGHT.
BY MORNING ALL AREAS SHOULD BE MOSTLY CLOUDY. HAVE THE MENTION IN
LATE THIS AFTERNOON AND EARLY EVENING FOR SOME FLURRIES AS THE DGZ
BRIEFLY MOISTENS ASSOCIATED WITH A WEAK SHORTWAVE MOVING THROUGH THE
FLOW. THIS ACTIVITY SHOULD END THIS EVENING. SOME PATCHY FREEZING
DRIZZLE NOT OUT OF THE QUESTION IN AREAS WHERE THE DGZ BECOMES
UNSATURATED...BUT TOO SMALL OF A CHANCE TO INCLUDE IN THE FORECAST.

SUNDAY LOOKS MAINLY DRY...BUT AS WE APPROACH EVENING...THERE IS SOME
ISENTROPIC ASCENT NOTED IN THE FAR NORTHWEST CWA TOWARDS LUDINGTON.
PEELED BACK ON THE POPS AND AREA OF LIGHT SNOW...BUT THINK WE MAY
SEE A LITTLE IN THE FAR NORTHWEST IN THE EVENING. TRACE AMOUNTS OF
SNOW AT BEST.

THE RAIN LOOKS TO MOVE IN MONDAY AFTERNOON LATE...WITH MOST OF IT
HOLDING OFF UNTIL AFTER 21Z. THE RAIN SHOULD INCREASE IN COVERAGE
AND INTENSITY SUBSTANTIALLY OVERNIGHT AS A 30-35KT LLJ WORKS THROUGH
THE AREA. MOISTURE TRANSPORT VECTORS AT 850MB/S ARE NOT OVERLY
IMPRESSIVE BUT ENOUGH FOR SOME STEADY RAINS.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 329 PM EST SAT DEC 20 2014

FORECAST CONCERNS DEAL WITH THE EVOLUTION OF A STORM IN THE MIDWEST
DURING THE MIDDLE OF THE WEEK.

THE MEDIUM RANGE MODELS ARE CONVERGING ON A SOLUTION MIDWEEK IN
WHICH A SOUTHERN STREAM STORM MOVES PHASES WITH A CLIPPER AND FORMS
A DEEP LOW OVER THE NORTHERN GREAT LAKES WEDNESDAY. LIKE MOST
SOUTHERN STREAM STORMS...THERE WILL BE A STRONG FEED OF GULF
MOISTURE INTO THE SYSTEM MOST OF WHICH WILL FALL AS RAIN. THE MODELS
KEEP THE TRACK OF THE LOW MAINLY NORTH FROM MISSISSIPPI INTO LOWER
MICHIGAN. THE COLD AIR WITH THIS SYSTEM WILL BE WELL WEST OF THE CWA
SO WE/LL INITIALLY SEE RAIN TUESDAY AND WEDNESDAY. AN INCH OR MORE
OF RAIN IS POSSIBLE FROM THIS SYSTEM WITH HIGHS IN THE MID 40S. AS
THE LOW APPROACHES...A MODEL SIGNAL IS BEGINNING TO DEVELOP WHERE
THERE MAY BE A LOW DEVELOPING OFF THE EAST COAST. THIS IS NOT
UNCOMMON AND MAY OCCUR THIS TIME. IF IT DOES...IT WILL LIKELY LIMIT
THE DEEPENING OF THE GREAT LAKES LOW WHICH IN TURN WILL LIMIT THE
WIND POTENTIAL. AS IT STANDS NOW BREEZY CONDITIONS CAN BE EXPECTED
CHRISTMAS DAY AS THE COLD AIR WRAPS IN BEHIND THE SYSTEM. IS SEEMS
POSSIBLE THAT AN INCH OR TWO OF SNOW MAY FALL CHRISTMAS EVE INTO
CHRISTMAS DAY.

ANOTHER LOW WILL HEAD TOWARD LOWER MICHIGAN FRIDAY. MIXED RAIN AND
SNOW WILL DEVELOP AHEAD OF THE SYSTEM BECOMING ALL SNOW BEHIND IT
WITH SMALL ACCUMS POSSIBLE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1109 PM EST SAT DEC 20 2014

FLURRIES WILL CONTINUE TO DIMINISH FOR THE REMAINDER OF THE NIGHT.
PATCHY FZDZ POSSIBLE...BUT REPORTS HAVE BEEN VERY LIMITED. ICING A
POSSIBILITY IN THE LOW CLOUDS THROUGH THE NIGHT. MVFR CONDITIONS
GENERALLY PREVAILING...BUT EASTERN TAF SITES LIKE KLAN HAVE BEEN
VFR. MODELS SHOW THE LOW LEVEL MOISTURE INCREASING THROUGH THE
NIGHT. HOWEVER...WIDESPREAD IFR IS NOT AS LIKELY TO OCCUR AS
PREVIOUSLY FORECASTED. STILL WILL NEED TO MONITOR THIS THREAT
THROUGH THE NIGHT.

OVERALL CONDITIONS LOOK LIKE THEY WILL TREND TOWARD VFR SUNDAY
AFTERNOON FOR MOST LOCATIONS.

&&

.MARINE...
ISSUED AT 329 PM EST SAT DEC 20 2014

SOUTHERLY WINDS RAMP UP ON SUNDAY AND MAY CONTINUE THROUGH THE DAY
ON MONDAY AS LOW PRESSURE MOVES TOWARD OUR DIRECTION FROM THE
NORTHERN PLAINS. EXPECT THAT WAVES WILL REACH SMALL CRAFT ADVISORY
CONDITIONS NORTH OF HOLLAND AFTER MIDDAY AND REMAIN THAT WAY THROUGH
SUNDAY NIGHT AT LEAST. COULD SEE NEEDING TO STRETCH THE SCA INTO
MONDAY AS WELL...BUT OPTED TO LET LATER SHIFTS MAKE THAT CALL.

THE MOST SIGNIFICANT WIND WITH THE UPCOMING SYSTEM FOR MID WEEK WILL
PASS OVER LAKE MICHIGAN FROM CHRISTMAS EVE INTO CHRISTMAS DAY. THE
STRONGEST CORE WILL LIKELY BE OVER THE LAKE EARLY CHRISTMAS MORNING.
WILL LET THE MODEL DETAILS SHAKE OUT...BUT GALES APPEAR LIKELY WITH
STORM FORCE WINDS A POTENTIAL. MODEL SOLUTIONS AT THIS POINT ARE
VARIED SO WE HAVE SOME TIME TO MAKE THAT CALL.


&&

.HYDROLOGY...
ISSUED AT 329 PM EST SAT DEC 20 2014

LIMITED HYDRO ISSUES INTO MONDAY WITH MAINLY DRY WEATHER EXPECTED
THROUGH THAT TIME. RIVER LEVELS ARE NEAR NORMAL VALUES.

A SOAKING RAIN LOOKS TO BE SETTING UP FOR MONDAY NIGHT INTO
CHRISTMAS EVE WITH A DEEP SOUTHERLY FLOW OF MOISTURE WRAPPING INTO
THE SYSTEM FOR MID WEEK. PWAT VALUES RISE TO ABOVE ONE INCH (1.15
INCHES) WHICH IS APPROACHING THE 99TH PERCENTILE FOR THIS TIME OF
YEAR. BOTTOM LINE...A VERY MOIST SYSTEM BY DECEMBER STANDARDS. EVEN
WITH FORECAST RAINFALL AMOUNTS IN THE 1 TO 1.5 INCH RANGE THOUGH WE
SHOULD NOT GET INTO TOO MANY HYDRO ISSUES GIVEN THE LOW FLOWS ON
AREA RIVERS. THERE COULD BE SOME PONDING OF WATER IN THE HEAVIER
BOUTS OF PRECIP.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 1 PM SUNDAY TO 7 AM EST MONDAY FOR
     LMZ846>849.

&&

$$

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





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