FXUS63 KGRR 041750
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1250 PM EST FRI DEC 4 2009

LATEST UPDATE...SYNOPSIS/SHORT TERM...

.SYNOPSIS...(1250 PM EST FRI DEC 4 2009)
SNOW SHOWERS WILL SLOWLY TAPER OFF THIS AFTERNOON AND EVENING BUT AN 
INCH OR TWO OF SNOW IS POSSIBLE FROM LUDINGTON TO SOUTH HAVEN AND 
INLAND TO GRAND RAPIDS AND KALAMAZOO. WINTER LOOKS LIKE IT IS HERE 
TO STAY AS A CLIPPER STORM COULD BRING SOME LIGHT SNOW ON MONDAY.

THEN OUR ATTENTION TURNS TO THE POSSIBLE BIG STORM COMING FOR LATE 
TUESDAY INTO WEDNESDAY...WHICH COULD BRING HIGH WINDS AND LOTS OF 
SNOW OR MIXED PRECIPITATION.

&&

.SHORT TERM...(1250 PM EST FRI DEC 4 2009)
(THIS AFTERNOON THROUGH SUNDAY)
FORECAST UPDATE IS OUT. ONLY SIGNIFICANT CHANGES WERE TO BUMP UP 
SNOW AMOUNTS TO AN INCH OR TWO FOR THIS AFTERNOON ACROSS THE 
NORTHWEST FORECAST AREA WHERE RADAR SHOWS SOME LIGHT LAKE EFFECT 
DEVELOPING IN SW FLOW. INVERSION HEIGHTS ARE RELATIVELY LOW ALTHOUGH 
MOISTURE REMAINS DEEP FOR NOW...BUT SHOULD BE DECREASING LATER THIS 
AFTERNOON.

ELSEWHERE...THINGS ARE QUIETING DOWN AS VORT CENTER MOVES EAST AND 
OUT OF THE FORECAST AREA. CONVECTIVE BANDING LAST NIGHT RESULTED IN 
NARROW BUT INTENSE SNOWFALL AREA ACROSS OTTAWA AND KENT COUNTIES. 
ROAD CONDITIONS SHOULD BE IMPROVING THERE THIS AFTERNOON AS HEAVY 
SNOW HAS NOW ENDED AND SOME SUN HAS HELPED MELT OFF SNOW ON TREATED 
ROADS. WILL LEAVE THE WARNING HEADLINES GOING THOUGH AS SNOW WILL 
CONTINUE TO FALL ON AND OFF THROUGH 4 PM. REST OF PREVIOUS FORECAST 
DISCUSSION FOLLOWS.

THE PERIOD FROM TONIGHT THROUGH THE DAY ON SUNDAY WILL NOT SEE A 
SIGNIFICANT AMOUNT OF CHANGE DURING THE PERIOD. SW 1000-850MB FLOW 
WILL DOMINATE THE PERIOD WITH DELTA T/S GENERALLY AROUND THE MID TO 
UPPER TEENS. INVERSION HEIGHTS WILL GENERALLY RANGE FROM 4-6K FT. IT 
APPEARS AT LEAST SOME SNOW SHOWERS WILL BE AROUND FOR A GOOD PORTION 
OF THE WEEKEND FOR THE NW HALF OF THE CWFA. THE SNOW SHOWERS DO NOT 
LOOK TO BE ALL THAT INTENSE WITH A LIMITED DGZ DEPTH AND WITH A LACK 
OF SHORT WAVE ACTIVITY. THE SW FLOW AREAS COULD SEE AN INCH OR TWO 
EACH PERIOD FROM FRI NIGHT INTO SAT NIGHT. THE MODELS DRY OUT THE 
LOWER LEVELS ON SUN...SO THE CHC DOES NOT LOOK ALL THAT EXCITING 
THEN.    

&&

.LONG TERM...(423 AM EST FRI DEC 4 2009)
(SUNDAY NIGHT THROUGH THURSDAY)
THE TWO SYSTEMS TO WATCH IN DAYS 4-7 ARE IN THE SUNDAY NIGHT AND 
MONDAY TIME FRAME...THEN THE TUESDAY NIGHT THROUGH THURSDAY PERIOD. 

THE FIRST SYSTEM IS A SHORTWAVE WHICH APPEARS TO WEAKEN/SHEAR AS IT 
HEADS NORTHEAST FROM THE CENTRAL PLAINS SUNDAY NIGHT AND MONDAY. THE 
SURFACE REFLECTION IS RATHER WEAK... BUT AT LEAST SOME TYPE OF WEAK 
SFC LOW/INVERTED TROUGH SHOULD IMPACT THE REGION. AM THINKING A 1-3 
INCH SNOWFALL CAN BE EXPECTED OVER PORTIONS OF THE CWFA AS AN EARLY 
ESTIMATE. 

THE 00Z ECWMF/GFS/GEM ARE ALL IN GOOD AGREEMENT IN TRACKING A 
DEEPENING SFC LOW ACROSS THE REGION ON WEDNESDAY... WITH A TRACK 
FROM ROUGHLY NRN IL TO NRN LK HURON. THE CENTRAL PRESSURE IS PROGGED 
TO DROP TO AROUND 970 MB BY THE TIME IT REACHES NRN LK HURON AROUND 
00Z THU. IT/S MUCH TOO EARLY TO BANK ON THAT SPECIFIC SFC LOW TRACK 
AND TIMING... BUT IT CERTAINLY APPEARS A SIGNIFICANT CYCLONE IS 
GOING TO IMPACT THE REGION MID WEEK. 

WE COULD SEE A BAND OF STRONG TSTMS SOUTH OF THE SFC LOW TRACK AND 
HEAVY SNOW NORTH OF THE LOW... WITH VERY WINDY CONDITIONS AND SNOW 
SHOWERS ON THE BACK SIDE OF THE SYSTEM WED NIGHT INTO THURS. IN THE 
GRR CWFA... IT MAY BE A SNOW TO RAIN THEN BACK TO SNOW SHOWERS 
SCENARIO.  

&&

.AVIATION...(1150 AM EST FRI DEC 4 2009)
MVFR TO IFR CONDITIONS WILL CONTINUE THIS AFTERNOON DUE TO A LOW 
STRATOCU DECK AND INTERMITTENT SNOW SHOWERS. BRIEF REDUCTIONS INTO 
THE LIFR FLIGHT CATEGORY ARE STILL POSSIBLE DURING THE EARLY TO MID 
AFTERNOON HOURS... MAINLY AT THE GRR AND MKG TERMINALS DUE TO WSW TO 
SW FLOW LAKE ENHANCED SNOW. 

CONDITIONS SHOULD IMPROVE INTO THE VFR FLIGHT CATEGORY AT MOST OF 
THE TERMINALS TONIGHT THROUGH 18Z SATURDAY WITH SOME LINGERING 
FLURRIES. THE ONLY EXCEPTION TO THAT COULD BE THE MKG TERMINAL WHERE 
SOME LINGERING SNOW SHOWERS MAY STILL RESULT IN A FEW REDUCTIONS 
INTO THE MVFR TO IFR FLIGHT CATEGORY OVERNIGHT. 

&&

.MARINE...(423 AM EST FRI DEC 4 2009)
WE WILL BE MAINTAINING THE SMALL CRAFT ADVISORY THROUGH EARLY 
SATURDAY MORNING. GOOD COLD AIR ADVECTION COMBINED WITH GOOD OVER 
LAKE INSTABILITY AND 20-25 KNOTS 2-3K FT ABOVE THE GROUND WILL 
CONTINUE TO PRODUCE WINDS AND WAVES EXCEEDING SMALL CRAFT ADVISORY 
THRESHOLDS. 

IT DOES APPEAR WINDS WILL DROP BELOW 20 KNOTS TONIGHT AND REMAIN 
BELOW 20 KNOTS THEN THROUGH EARLY SATURDAY NIGHT. GRADIENT WILL THEN 
TIGHTEN UP A BIT AS HIGH PRESSURE MOVES EAST OF THE AREA.

&&

.HYDROLOGY...(423 AM EST FRI DEC 4 2009)
NO HYDROLOGY ISSUES EXPECTED THROUGH THE WEEKEND. ALL PRECIPITATION 
THROUGH THE WEEKEND WILL BE SNOW...AND VERY LITTLE...IF ANY RUNOFF 
IS EXPECTED WITH HIGHS EXPECTED ONLY TO BE AROUND OR SLIGHTLY ABOVE 
FREEZING.

WE COULD SEE SOME DECENT RIVER RISES NEXT WEEK IF THE STRONG STORM 
SYSTEM TAKES SHAPE AS MOST MODELS ARE INDICATING. PRECIPITATION TYPE 
WITH THIS STORM IS STILL IN QUESTION...BUT IT COULD VERY WELL BE A 
DECENT AMOUNT OF RAIN WITH A NICE SURGE OF MOISTURE FROM THE GULF. 
THAT COMBINED WITH MELTING SNOW WOULD PRODUCE QUITE A BIT OF RUNOFF.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING FOR KENT AND OTTAWA COUNTIES THROUGH 
THIS AFTERNOON.
WINTER WEATHER ADVISORY FOR MUSKEGON... MONTCALM... GRATIOT... 
IONIA... CLINTON... ALLEGAN... BARRY... EATON... VAN BUREN AND 
KALAMAZOO COUNTIES THROUGH THIS AFTERNOON. 
LM...SMALL CRAFT ADVISORY ST. JOSEPH TO MANISTEE THROUGH FRIDAY 
NIGHT.

&&

$$

SYNOPSIS:     OSTUNO
SHORT TERM:   OSTUNO
LONG TERM:    MEADE
AVIATION:     LAURENS
MARINE:       NJJ
HYDROLOGY:    NJJ