000
FXUS63 KGRR 200933
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
433 AM EST THU NOV 20 2008
LATEST UPDATE...ALL SECTIONS EXCEPT AVIATION...
.SYNOPSIS...(433 AM EST THU NOV 20 2008)
COLD AIR WILL MOVE IN ACROSS THE AREA THROUGH THE DAY ON FRIDAY.
THIS COLDER AIR MOVING OVER THE RELATIVELY WARMER WATERS OF LAKE
MICHIGAN WILL BRING LAKE EFFECT SNOW SHOWERS TO THE AREA. THESE SNOW
SHOWERS WILL BE LOCALLY HEAVY AT TIMES ALONG THE LAKESHORE...
ESPECIALLY NORTH OF MUSKEGON AND SOUTH OF HOLLAND. SNOW SHOWERS WILL
BE MUCH WEAKER INLAND. THE SNOW SHOWERS ARE EXPECTED TO DIMINISH
FRIDAY AND FRIDAY EVENING AS THE AIR MASS MODERATES A BIT. THE NEXT
CHANCE OF PRECIPITATION WILL COME SUNDAY THROUGH TUESDAY AS ANOTHER
SHOT OF COOLER AIR MOVES IN. QUIET WEATHER IS EXPECTED FOR THE
THANKSGIVING HOLIDAY.
&&
.SHORT TERM...(433 AM EST THU NOV 20 2008)
(TODAY THROUGH SATURDAY)
WE HAVE UPGRADED ALL OF THE COUNTIES UNDER A WATCH UP TO A LAKE
EFFECT SNOW WARNING THROUGH 18Z FRI. WE HAVE ISSUED LAKE EFFECT SNOW
ADVISORIES FOR LAKE...OTTAWA...AND MUSKEGON COUNTIES VALID THROUGH
18Z FRI.
LATEST RADAR IMAGERY SHOWS LAKE EFFECT LIGHTING UP FAIRLY STEADILY
ACROSS THE STATE EARLY THIS MORNING. COLD AIR IS MOVING IN ON
NORTH/NORTHWEST WINDS AND FLOW ALOFT IS NOW BECOMING CYCLONIC AS ONE
SHORT WAVE PASSES EAST OF THE STATE...AND THE NEXT SHORT WAVE IS NOW
DIVING SOUTHEAST ACROSS THE DAKOTAS AND MN.
MODELS HAVE NOT CHANGED MUCH AS COMPARED TO 24 HOURS AGO. THEY
CONTINUE TO SHOW H850 TEMPS FALLING INTO THE NEGATIVE MID TEENS AND
INVERSION HEIGHTS INCREASING TO AROUND 15K FEET BY LATER THIS
EVENING. IN ADDITION...THE BEST FORCING IS EXPECTED TO COINCIDE WITH
THE DGZ. THE FLOW IS EXPECTED TO BECOME NNW THIS MORNING /WHICH IS
OCCURRING/ AND THEN LIKELY BECOMING MORE NW AND EVENTUALLY WNW ON
FRI.
DIFFERENCES BETWEEN THE VARIOUS MODELS ARE FAIRLY SMALL...MAINLY
HAVING TO DO WITH THE EXACT PLACEMENT OF THE BEST CONVERGENCE BAND.
HOWEVER THE SMALL DIFFERENCES WILL MAKE A BIG DEAL AS TO WHETHER THE
HEAVIEST BANDS REMAIN JUST OFFSHORE OR WILL CLIP PORTIONS OF THE
CWFA. THE GFS AND THE LOCAL WRF INITIALIZED FROM THE GFS ARE THE
MAIN MODELS HOLDING THE BAND OFFSHORE FROM LATER THIS EVENING INTO
EARLY FRI. ALL OF THE OTHER MODELS /NAM...RGEM...AND SREF/ SHOW THE
BAND CLIPPING FAR WRN ALLEGAN AND VAN BUREN COUNTY TODAY THROUGH
FRI. LOCAL HISTORY/GUIDELINES SHOW WITH A 325-350 TRAJECTORY...THESE
TWO COUNTIES WILL BE FAVORED FOR HEAVY SNOW. WE ALSO BELIEVE THE
HIGHER RESOLUTION MODELS HAVE A BETTER HANDLE ON THE MESOSCALE
FEATURES. THIS BAND WHERE EVER IT GOES WILL BE ROBUST AS IT WILL BE
PRE-CONDITIONED FROM LAKE SUPERIOR.
AS FOR MASON AND OCEANA COUNTIES...MODELS SHOW GOOD CONVERGENCE HERE
ALSO FROM TODAY INTO THE OVERNIGHT PERIOD TONIGHT. CONVERGENCE
DIMINISHES A BIT LATE TONIGHT AND ON FRI WITH THE FLOW BECOMING MORE
WNW. WE BELIEVE HERE THAT THE TRAJECTORY WILL COME IN JUST NORTH OF
THE POINTS AND SNOW PRETTY GOOD AT TIMES OVER THE WRN PORTIONS OF
THE COUNTIES INTO THE OVERNIGHT HOURS. WITH THE BIGGER POPULATIONS
OF THESE COUNTIES ON THE WEST...WE FELT IT WAS BETTER TO HIT THE
EVENT A LITTLE HARDER.
CYCLONIC FLOW IS EXPECTED TO HOLD ON THROUGH ABOUT 18Z FRI...BEFORE
THE JET AXIS SHIFTS EAST OF THE AREA. IT WILL BE AT THAT TIME THAT
THE SNOW ACCUMULATING POTENTIAL WILL SIGNIFICANTLY DIMINISH. SOME
RESIDUAL SNOW SHOWERS WILL MOVE INLAND AS THE FLOW BECOMES
WRLY...HOWEVER ACCUMS SHOULD REMAIN UNDER AN INCH AFTER 18Z FRI.
CLOUDS WILL HOLD IN THROUGH THE FIRST HALF OF FRI NIGHT...RIDGING
SHOULD ALLOW FOR SOME BREAKS TO DEVELOP. TEMPS WILL WARM ENOUGH ON
SAT THAT DELTA T/S WILL BE TOO SMALL FOR EVEN A LOT OF CLOUDS.
&&
.LONG TERM...(400 AM EST THU NOV 20 2008)
(SATURDAY NIGHT THROUGH WEDNESDAY)
EXTENDED PERIOD LOOKS TO BE A CONTINUATION OF THE REPEATING PATTERN
OF THE LAST FEW DAYS. THIS CONSISTS OF BRIEF PERIODS OF SFC
RIDGING/FAIR WEATHER ALTERNATING WITH LIGHT SYNOPTIC PRECIP EVENTS
FOLLOWED BY NW FLOW LAKE EFFECT SNOW EVENTS. TEMPERATURES REMAIN
MOSTLY BELOW NORMAL THROUGHOUT.
SFC RIDGING TO BRING FAIR WEATHER SATURDAY NIGHT. ON SUNDAY...THERE
IS A CHANCE OF SOME OVERRUNNING LIGHT SNOW OR MIXED PRECIP BREAKING
OUT ACROSS THE NORTHERN FORECAST AREA AS WARM AIR ADVECTION PATTERN
PRECEDES THE PASSAGE OF THE NEXT SHORTWAVE TROUGH. CHANCE OF LIGHT
SNOW SUNDAY NIGHT AS THE SFC LOW MOVES THROUGH AND COLD AIR FILTERS
IN WITH A LAKE EFFECT SNOW EVENT FOR MONDAY INTO TUESDAY. BUMPED
POPS UP MONDAY AND TUESDAY ACROSS THE WESTERN HALF OF THE FORECAST
AREA. LAKE EFFECT ENDING TUESDAY NIGHT AS SFC RIDGING BUILDS IN.
FAIR WEATHER ON WEDNESDAY WHICH MAY LAST INTO THANKSGIVING.
&&
.MARINE...(433 AM EST THU NOV 20 2008)
SOLID GALES UP TO 40 KNOTS WERE EXPERIENCED AT THE MKG GLERL SITE
AND AT THE BIG SABLE OBSERVATION LAST EVENING AND INTO THE EARLY
MORNING HOURS THIS MORNING. A TEMPORARY LULL HAVE DEVELOPED AT
MKG...HOWEVER THE WINDS ARE STILL ROARING AT BIG SABLE. GALES ARE
EXPECTED TO HOLD ON THROUGH A GOOD PORTION OF THE DAY TODAY BEFORE
THE STRONGEST WINDS MOVE OUT OF THE AREA SLOWLY AND GRADUALLY LATER
TODAY. THE GALE WARNING THROUGH 00Z LOOKS GOOD FOR NOW...AND A SMALL
CRAFT ADVISORY WILL BE NEED ONCE THE WINDS COME DOWN SLIGHTLY THIS
EVENING.
&&
.AVIATION...(1155 PM EST WED NOV 19 2008)
THE SNOW BAND WILL LIKELY SAY CLOSE OR EAST OF US-31. QUESTIONABLE
IF MKG WILL BE IN THE BAND OR NOT. IT IS CLOSE ENOUGH THAT I HAVE
THEM WITH LIGHT SNOW ALL DAY THURSDAY AFTER THE POLAR JET GETS SOUTH
OF THEM AROUND 7 AM. OTHERWISE MOSTLY VFR CIGS THROUGH THURSDAY
EVENING. FLURRIES ARE POSSIBLE DURING THE DAY BUT VCSH SEEMS THE
BEST WAY TO SHOW THIS.
&&
.HYDROLOGY...(433 AM EST THU NOV 20 2008)
NO HYDRO ISSUES ARE EXPECTED THROUGH THE PERIOD. MOST ALL
PRECIPITATION THROUGH THE UPCOMING WEEKEND WILL BE OF THE
FROZEN VARIETY. THIS COMBINED WITH THE COLD TEMPERATURES WILL
SIGNIFICANTLY LIMIT ANY RUNOFF INTO THE LOCAL RIVERS AND STREAMS.
SOME RUNOFF WILL BE POSSIBLE THIS WEEKEND AS TEMPERATURES WARM SOME.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...LAKE EFFECT SNOW WARNING IN EFFECT THROUGH 18Z FRI FOR MASON...
OCEANA...ALLEGAN...AND VAN BUREN COUNTIES.
LAKE EFFECT SNOW ADVISORY IN EFFECT THROUGH 18Z FRI FOR LAKE...
MUSKEGON...AND OTTAWA COUNTIES.
LM...GALE WARNING IN EFFECT FROM 00Z THU THROUGH 00Z FRI.
&&
$$
SYNOPSIS: NJJ
SHORT TERM: NJJ
LONG TERM: OSTUNO
MARINE: NJJ
AVIATION: WDM
HYDROLOGY: NJJ
