000
FXUS63 KGRR 032039
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
340 PM EST WED DEC 3 2008
LATEST UPDATE...ALL BUT AVIATION AND LONG TERM...
.SYNOPSIS...(340 PM EST WED DEC 3 2008)
A COLD FRONT WILL CROSS LOWER MICHIGAN THIS EVENING BRINGING THE
COLDEST AIR OF THE SEASON. SNOW WILL FOLLOW THE COLD FRONT THIS
EVENING ACROSS THE AREA WITH THE HEAVIEST SNOWFALL NEAR ROUTE 10
EARLY TONIGHT. BEHIND THE FRONT A HIGH PRESSURE SYSTEM FROM THE
ARCTIC WILL BRING LAKE EFFECT SNOW SHOWERS TO THE REGION INTO FRIDAY
NIGHT. AN ALBERTA CLIPPER TYPE SYSTEM WILL CROSS LOWER MICHIGAN OVER
THE WEEKEND BRINGING ANOTHER WINTER STORM THROUGH THE AREA.
&&
.SHORT TERM...(340 PM EST WED DEC 3 2008)
(TONIGHT THROUGH FRIDAY NIGHT)
I SEE NO REASON TO CHANGE OUR WINTER WEATHER ADVISORY FOR SNOWFALL
FOR MASON...OCEANA...LAKE...NEWAYGO...OSCEOLA...MECOSTA...AND CLARE
COUNTIES THROUGH 06Z TONIGHT... SO IT REMAINS AS IS.
THE WAVE ON THE FRONT IS NOW NEAR HOUGHTON LAKE (3 PM) AND WILL
CONTINUE TO MOVE NORTHEAST INTO ONTARIO BY EARLY TONIGHT. THAT WILL
SWEEP THE COLD FRONT ACROSS THE GRR CWA BETWEEN 5 PM SOUTH OF
MUSKEGON TO NEAR 8 PM BY JACKSON. MOST OF THE PRECIPITATION IS STILL
BEHIND THE FRONT AND IN THE FORM OF SNOW. STILL SOME MIXED RAIN AND
SNOW IS POSSIBLE AT THE START OF THE PRECIPITATION LATE THIS
AFTERNOON BEFORE THE AIR GETS COLD ENOUGH FOR IT TO BE ALL SNOW.
MOST OF THE CWA WILL SEE BETWEEN ONE AN TWO INCHES OF SNOW THIS
EVENING AS SOME MID LEVEL FGEN DUE TO JET COUPING BETWEEN THE
DEPARTING 135 KNOT JET CORE ON THE PRIMARY POLAR JET OVER MICHIGAN
AND THE INCOMING SPEED MAX ON THE POLAR JET OVER IOWA. ONCE THAT IS
EAST OF THE CWA (10 PM OR SO) THE DEEP MOISTURE WILL BE GONE AND THE
SNOW WILL COME TO AN END.
DIRECTLY BEHIND THAT (AFTER MIDNIGHT)AFTER THE SYNOPTIC SNOW MOVES
OUT...IS WHEN THE SURFACE TEMPERATURES WILL REALLY START TO FALL.
THE POLAR JET CORE WILL NOT YET BE SOUTH AND EAST OF SOUTHERN LOWER
MICHIGAN SO THAT WILL LIMIT THE DEPTH OF THE LOW LEVEL MOISTURE DUE
TO THE SUBSIDENCE INVERSION. THE CLOUD TOPS WILL ONLY BE TO NEAR THE
-10C ISOTHERM SO SNOW GRAIN OR GRAUPEL WOULD BE THE MOST LIKELY
PRECIPITATION TYPE. THAT BEING SO... ACCUMULATIONS WOULD BE RATHER
LIMITED. EVEN SO THE LOW LEVEL THICKNESS PLUNGE TONIGHT. ENOUGH THAT
EVEN WITH THE CLOUDS...LOWS SHOULD BE IN THE LOWER 20S BY SUNRISE
MOST AREA. TEMPERATURES IN CENTRAL WISCONSIN AT 1 PM WERE IN THE
LOWER 20S...EVEN WITH IT CROSSING THE LAKE... JUST THE ADVECTION OF
THAT AIR WOULD BRING OUR TEMPS (CONSIDERING THE LAKE TEMPS THAT AIR
HAS TO CROSS) WOULD BE IN THE MID 20S.
DURING THURSDAY THE REALLY COLD AIR CONTINUES TO COME IN THAT THE
LOW LEVEL THICKNESS FALL DURING THE DAY. THAT WILL ALLOW THE
SURFACE TEMPERATURES TO DO THE SAME THING. THUS THE HIGHS THURSDAY
WILL BE THE MIDNIGHT TEMP. THE DAY TIME HIGH WILL BE DURING THE MID
MORNING. BY 7 AM THE DGZ GETS SATURATED AND THE BOUNDARY LAYER WIND
WILL BE 280 AT 20 KNOTS SO WE WILL SEE A WEST WIND LAKE EFFECT
EVENT. SNOWFALL SHOULD NOT BE TO HEAVY DURING THE DAY TIME HOWEVER
SINCE INVERSION HEIGHTS ARE BELOW 5000 FT.
THURSDAY NIGHT INTO FRIDAY MORNING ANOTHER WAVE ON THE POLAR JET
MOVES THROUGH AND THE INVERSION HEIGHT INCREASES TO NEAR 8000 FT BY
06Z. THE BEST OMEGA IS IN THE DGZ THEN AND BOUNDARY LAYER WINDS WILL
STILL BE FROM THE WEST. THUS I EXPECT A BETTER SNOWFALL EVENT AT
THAT TIME. WE MAY NEED AN ADVISORY FOR THIS EVENT. LATER SHIFTS WILL
HAVE TO LOOK AT THIS.
AHEAD OF THE NEXT CLIPPER SYSTEM WINDS WILL BECOME SOUTHWEST FRIDAY
NIGHT BUT THE AIR IS STILL COLD ENOUGH FOR LAKE EFFECT SO WE
CONTINUED THE SNOW SHOWERS IN THE GRIDS.
&&
.LONG TERM...(340 PM EST WED DEC 3 2008)
(SATURDAY THROUGH WEDNESDAY)
A CLIPPER SYSTEM WILL PASS ACROSS THE STATE ON SATURDAY GIVING US
ANOTHER BURST OF SNOWFALL. ARCTIC AIR WILL SURGE INTO THE REGION
BEHIND THE CLIPPER. THIS WILL PROBABLY BE THE COLDEST AIR OF THE
SEASON SO FAR AS LOWS DROP INTO THE TEENS SATURDAY NIGHT WITH TEMPS
ONLY RISING INTO THE LOW AND MID 20S ON SUNDAY. ON TOP OF THIS
THERE WILL BE A BRISK NW WIND DRIVING WIND CHILL READINGS INTO THE
SINGLE DIGITS.
FORTUNATELY THIS APPEARS TO BE A BRIEF COLD PERIOD. BY MONDAY WE
WILL SEE WARMING TEMPS WITH RETURN FLOW AROUND HIGH PRESSURE IN THE
MID ATLANTIC. HOWEVER THE WARMER AIR WILL COME WITH A COST...MORE
SNOW. WE WILL MOST LIKELY SEE WARM ADVECTION SNOW BREAKING OUT ON
MONDAY. WE WILL NEED TO WATCH THE POSSIBILITY OF MAJOR SNOWFALL
MONDAY NIGHT INTO TUESDAY. THE MODELS BEGIN TO DRAW UP GULF
MOISTURE AND DEVELOP LOW PRESSURE TO OUR SOUTH. THE GFS ENSEMBLE
MEMBERS SUGGEST THIS SYSTEM COMES CLOSE TO THE GREAT LAKES...WHILE
THE OPERATIONAL GFS AND ECMWF KEEPS THE HEAVIER PCPN SOUTH OF MI.
COOLER AIR AND MORE LAKE EFFECT IS ANTICIPATED INTO MID WEEK.
&&
.MARINE...(340 PM EST WED DEC 3 2008)
WINDS WILL REMAIN OVER 15 KNOTS THROUGH FRIDAY AND WITH THE AIR TEMP
WELL BELOW THE LAKE TEMP THE MOMENT TRANSFER WILL KEEP WAVE HEIGHTS
AT 4 FEET OR HIGHER THROUGH FRIDAY. I CONTINUED THE SCA THROUGH
FRIDAY AT 12Z.
OUTLOOK: GALES ACCOMPANIED BY SIGNIFICANT FREEZING SPRAY ARE
POSSIBLE ON SATURDAY NIGHT INTO SUNDAY MORNING WITH ARCTIC AIR
SPILLING SOUTH ON THE HEELS OF NEXT STORM SYSTEM.
&&
.AVIATION...(1247 PM EST WED DEC 3 2008)
SNOW WILL ARRIVE AT ALL THE TAF SITES FROM WEST TO EAST THIS
AFTERNOON INTO THE EVENING. THERE WILL BE BURSTS OF HEAVIER
SNOW...ESPECIALLY ACROSS THE NORTHERN TAF SITE...WHICH WILL REDUCE
CEILINGS AND VSBYS INTO THE LIFR RANGE AT TIMES. THE SNOW WILL ONLY
LAST 4 TO 7 HOURS AT ANY ONE LOCATION...WITH CONDITIONS IMPROVING TO
MVFR AROUND 05Z. SNOW ACCUMULATIONS ARE EXPECTED TO BE 1-3
INCHES...WITH THE HIGHER END OCCURRING AROUND THE NORTHERN TAF
SITES.
THERE WILL BE SCATTERED LAKE EFFECT SNOW SHOWERS DEVELOP ONCE THE
FRONT HAS PAST AFTER 05Z...HOWEVER THIS DOES NOT LOOK TO BECOME VERY
WELL ORGANIZED. FLOW BEHIND THE FRONT WILL BE NW...TAKING THE BULK
OF THE LAKE EFFECT SNOW SHOWERS INTO MKG AND AZO. AT THIS POINT CAN
ONLY ENVISION THESE TAF SITES OCCASIONALLY GOING DOWN TO MVFR OR
BRIEF IFR VSBYS IN THE SNOW SHOWERS. ALTHOUGH THEY ARE NOT EXPECTED
TO BECOME WELL ORGANIZED THE SNOW SHOWERS WILL LAST THROUGH THE
OVERNIGHT AND AT LEAST TO MID DAY THURSDAY.
&&
.HYDROLOGY...(340 PM EST WED DEC 3 2008)
NO SIGNIFICANT HYDRO PROBLEMS ARE EXPECTED THROUGH THE WEEKEND. IF
THE COLD AIR REMAINS IN PLACE WITH TIME WE COULD HAVE ICE JAM ISSUES
BUT THAT IS SOME TIME DOWN THE ROAD YET.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY FOR SNOW IN EFFECT THROUGH 06Z TONIGHT
FOR NRN TWO ROWS OF COUNTIES EXCEPT ISABELLA.
LM...SMALL CRAFT ADVISORY IN EFFECT THROUGH 12Z FRIDAY MORNING.
&&
$$
SYNOPSIS: WDM
SHORT TERM: WDM
LONG TERM: JK
MARINE: WDM
AVIATION: JK
HYDROLOGY: WDM
