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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