FXUS63 KGRR 022359
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
759 PM EST WED DEC 2 2009
LATEST UPDATE...AVIATION...
.SYNOPSIS...(348 PM EST WED DEC 2 2009)
LOW PRESSURE ENTERING KENTUCKY THIS EVENING WILL RACE NORTHEAST
TONIGHT AND BE CENTERED NEAR LAKE ONTARIO BY THURSDAY MORNING. THE
LOW PRESSURE SYSTEM WILL SPREAD RAIN INTO SOUTHERN LOWER MICHIGAN
THIS EVENING PUSHING NORTHWARD OVERNIGHT. COLDER AIR WILL GRADUALLY
FILTER INTO SOUTHWEST LOWER MICHIGAN AFTER MIDNIGHT AS NORTHERLY
WINDS INCREASE. RAIN WILL TRY TO MIX WITH AND CHANGE OVER TO SNOW
LATE. ANY ACCUMULATION SHOULD BE AN INCH OR LESS.
COLDER AIR WILL INVADE THE STATE ON THURSDAY...PERSISTING INTO THE
WEEKEND. LAKE EFFECT SNOW WILL OCCUR MUCH OF THIS TIME. ACCUMULATING
SNOW WILL BE POSSIBLE THURSDAY NIGHT AS A LAKE EFFECT BAND SETS UP.
LOCATIONS ALONG AND WEST OF U.S. HIGHWAY 131 WILL SEE SOME
ACCUMULATION OF SNOW BY THE WEEKEND.
&&
.SHORT TERM...(348 PM EST WED DEC 2 2009)
(TONIGHT THROUGH FRIDAY NIGHT)
MAIN CONCERNS OBVIOUSLY PERTAIN TO SNOW...SPECIFICALLY WHEN DOES IT
CHANGE OVER FROM RAIN TONIGHT AND HOW MUCH FALLS EACH FORECAST
PERIOD AFTER TONIGHT.
TRACK OF THE LOW IS SIMILAR IN THE MODELS...WELL EAST OF THE
FORECAST AREA. ALL OF THE SHORT TERM MODELS HAVE A LOW CENTERED NEAR
LAKE ONTARIO AT 700AM THURSDAY MORNING. RAIN WILL SPREAD INTO THE
SOUTHERN HALF OF THE FORECAST AREA THIS EVENING AS THE LOW MOVES
INTO KENTUCKY. THE BOUNDARY LAYER AT THIS POINT IS WARM...WITH TEMPS
IN THE MIDDLE TO UPPER 40S. DEW POINTS ARE IN THE LOWER TO MIDDLE
30S...SO WE WILL WET BULB DOWN AS THE PRECIP STARTS...BUT IT MAY
TAKE A GOOD PORTION OF THE NIGHT BEFORE WE CAN MIX/CHANGE TO SNOW.
THINK THE WARMER NAM IS THE BETTER OPTION TONIGHT...SO NOT THINKING
MUCH IN THE WAY OF ACCUMULATIONS. HALF INCH OR LESS IN MOST
LOCATIONS ON GRASSY AREAS.
THE COLD AIR MAKES ITS MOVE IN EARNEST ON THURSDAY AS 850MB TEMPS
DROP TO AROUND -9C BY EVENING. THIS WILL PUSH DELTA T/S INTO THE
UPPER TEENS C WITH A LAKE AROUND +8C. DEEP MOISTURE IS LACKING ON
THURSDAY THOUGH AS LOWER MICHIGAN WILL BE IN BETWEEN THE UPPER WAVE
THAT WILL PUSH EAST OF THE AREA AND THE UPPER TROUGH TO THE WEST.
ANY ACCUMULATIONS ON THURSDAY SHOULD BE ON THE LIGHT SIDE...AN INCH
OR LESS.
FIRST TIME FRAME OF CONCERN IS THURSDAY NIGHT. BOTH THE GFS AND THE
NAM ARE INDICATING A CONVERGENT DOMINANT LAKE BAND SETTING UP IN
VICINITY OF INTERSTATE 96. IT APPEARS SOMEWHAT TRANSIENT THOUGH...AS
RIDGING TRIES TO BUILD NORTH OUT OF THE PLAINS. THE AREA FROM SOUTH
HAVEN TO GRAND RAPIDS TO MUSKEGON WILL BE THE MAIN SNOWBAND
LOCATION...FUNNELING TOWARD LANSING. AT THIS POINT THINKING 2-4
INCHES WILL BE POSSIBLE IN THE ABOVE MENTIONED AREA...WITH LOWER
AMOUNTS AWAY FROM THIS ZONE. WE WILL BE WATCHING THIS TIME FRAME
CLOSELY...AS WE MAY NEED AN ADVISORY WITH TIME. WE STILL HAVE SOME
TIME TO WATCH THIS THOUGH.
LAKE EFFECT SNOW WILL CONTINUE FRIDAY AND FRIDAY NIGHT AS THE FLOW
GRADUALLY SWINGS TOWARD THE SOUTHWEST. LOCATIONS FROM SOUTH HAVEN TO
GRAND RAPIDS AND NORTH UP THE LAKESHORE WILL BE THE AREAS THAT ARE
FAVORED. MOISTURE LOOKS TO BE A BIT ON THE SHALLOW SIDE...BUT MORE
THAN SUFFICIENT FOR SNOW...UP THROUGH ABOUT 5000FT. WILL HAVE
CATEGORICAL/LIKELY POPS DURING THIS TIME FRAME TOWARD THE COAST WITH
LIGHT ACCUMS. IT APPEARS 1-3 INCHES WILL BE POSSIBLE NORTH AND WEST
OF GRAND RAPIDS ON FRIDAY FROM FREMONT TOWARD SCOTTVILLE AND BALDWIN.
&&
.LONG TERM...(430 PM EST WED DEC 2 2009)
(SATURDAY THROUGH WEDNESDAY)
THE PRIMARY FORECAST CHALLENGE IS DEALING WITH THE TIMING...
LOCATION AND OCCURRENCE OF SNOW FALL. THE MID RANGE MODELS HAVE
LARGE DIFFERENCES AND CONFIDENCE IS LOW. WENT CLOSER TO THE ECMWF
12Z SOLUTION... THOUGH THE GRIDS RESEMBLE NO MODEL SOLUTION.
WINDS WILL BE OUT OF THE SOUTHWEST WITH CYCLONIC FLOW SATURDAY INTO
SATURDAY NIGHT... AS A LOW PRESSURE SYSTEM MOVES AWAY FROM THE AREA.
LAKE EFFECTS WILL BE WINDING DOWN... WITH THE FOCUS MAINLY ON WEST
CENTRAL LOWER MICHIGAN. ACCUMULATIONS WILL BE POSSIBLE NEAR AND
INLAND FROM BIG AND LITTLE SABLE POINTS. THE NEXT LOW MAY APPROACH
THE AREA EARLY MONDAY MORNING. HAVE BROAD BRUSHED 30 POPS MONDAY
THROUGH WEDNESDAY FOR SYSTEM AND LAKE EFFECT SNOWS. WILL VERY LIKELY
HAVE TIMES WITH NO SNOW... BUT NOT CONFIDENT ENOUGH TO LIMIT
PRECIPITATION.
TEMPERATURES WILL BE AROUND TO A LITTLE BELOW AVERAGE FOR THIS TIME
OF YEAR... WITH HIGHS IN THE LOWER TO MID 30S AND LOWS IN THE 20S.
&&
.AVIATION...(759 PM EST WED DEC 2 2009)
RAIN ALONG WITH LOWER CIGS AND VSBYS ARE OCCURRING THIS
EVENING...BUT NO IFR CONDITIONS EXPECTED WITH THE EXCEPTION OF
PERHAPS JXN CLOSER TO MIDNIGHT. HOWEVER...IT MAY BE A CLOSE CALL FOR
THE SOUTHEASTERN TAF SITES WITH RESPECT TO IFR DURING THE LATE NIGHT
HOURS. WILL NEED TO BE MONITORED. OTHERWISE...ANTICIPATING CIGS AND
VSBYS TO TREND OR REMAIN MVFR. WINDS MAY HOVER AROUND 10 KTS AND
COULD GUST INTO THE TEENS...BUT DIDN'T GET CARRIED AWAY WITH THAT IN
THE TAFS. WILL STILL MONITOR TRENDS.
WINDS WILL BACK TOWARD THE NW BY THE MID MORNING HOURS THURSDAY AND
RAIN WILL MIX WITH SNOW. DON'T SEE ANY IFR CONDITIONS TOMORROW
AFTERNOON AT THIS POINT...BUT EXPECT LAKE EFFECT SNOW SHOWERS TO GET
GOING TOMORROW EVENING THAT MAY IMPACT THE WESTERN TAFS WITH REDUCED
VSBYS. TOO EARLY TO DETERMINE HOW INTENSE THE BANDS WILL BE SO DID
NOT ADD DETAILS BEYOND THURSDAY MORNING.
&&
.MARINE...(348 PM EST WED DEC 2 2009)
SURFACE LOW PRESSURE TRACKING FROM THE OHIO VALLEY INTO THE EASTERN
GREAT LAKES WILL TIGHTEN A PRESSURE GRADIENT OVER LAKE MICHIGAN.
WINDS WILL INCREASE TO AROUND 30 KNOTS TONIGHT...BUILDING WAVES INTO
THE 5 TO 8 FOOT RANGE. WAVES WILL GRADUALLY SUBSIDE INTO THE 3 TO 5
FOOT RANGE BY THURSDAY AT SUNSET...BUT WINDS WILL INCREASE ONCE
AGAIN THURSDAY NIGHT. WAVES WILL LIKELY BE A HAZARD TO SMALLER CRAFT
ALL THE WAY INTO SATURDAY.
&&
.HYDROLOGY...(348 PM EST WED DEC 2 2009)
ALL RIVER SITES ARE REPORTING VALUES WELL WITHIN BANK. PRECIPITATION
TONIGHT WILL RANGE FROM POSSIBLY A TENTH OF AN INCH IN THE FAR
NORTHWEST NEAR LUDINGTON TO BETWEEN A QUARTER AND A HALF INCH CLOSER
TO THE TRACK OF THE LOW AT JACKSON. THESE VALUES WILL NOT AFFECT
RIVER LEVELS MUCH AT ALL. THURSDAY INTO SATURDAY LAKE EFFECT SNOW
WILL BE THE DOMINANT MODE AND WILL NOT AFFECT RIVER LEVELS EITHER.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY ST. JOSEPH TO MANISTEE THROUGH THURSDAY.
&&
$$
SYNOPSIS: DUKE
SHORT TERM: DUKE
LONG TERM: IOD
AVIATION: HOVING
MARINE: DUKE
HYDROLOGY: DUKE
