FXUS63 KGRR 291726
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1230 PM EST SUN NOV 29 2009

LATEST UPDATE...AVIATION...

.SYNOPSIS...(338 AM EST SUN NOV 29 2009)
A COLD FRONT WILL MOVE THROUGH LOWER MICHIGAN TODAY. SCATTERED 
SHOWERS WILL DEVELOP ALONG THE FRONT AND MAY BECOME MIXED WITH WET 
SNOW NORTH OF US-10. COLDER WEATHER ALONG WITH SCATTERED SNOW 
SHOWERS WILL FOLLOW FOR MONDAY AND EARLY TUESDAY. ANOTHER SHOT OF 
COLDER AIR IS POSSIBLE LATE IN THE WEEK.  

&&

.SHORT TERM...(1127 AM EST SUN NOV 29 2009)
(TODAY THROUGH TUESDAY)
MID LEVEL INSTABILITY PRODUCING ISOLATED TSTORMS UPSTREAM.  WILL ADD 
THUNDER FOR THE SOUTHERN TWO ROWS OF COUNTIES.  

FOR IS MOST DENSE NEAR FRONTAL BOUNDARY.  AS IT SLIPS SOUTH AND 
MIXING INCREASES...THE FOG SHOULD SLOWLY IMPROVE AFTER 18Z.

FORECAST CONCERNS DEAL WITH PCPN TRENDS THROUGH THE PERIOD. LATEST 
SFC ANALYSIS SHOWS A LOW IN SE IOWA MOVING TOWARD LOWER MICHIGAN. 
THE LOW AND THE TRAILING COLD FRONT WILL MOVE THROUGH TODAY. WE/LL 
SEE SCT SHRA DEVELOP ALONG THE FRONTAL BOUNDARY TODAY BUT NOT 
EXPECTING ANYTHING SUBSTANTIAL. ADDED SOME PATCHY DENSE FOG TO THE 
GRIDS THIS MORNING TO REFLECT CURRENT TRENDS ACROSS THE CWA. COLDER 
AIR WILL MOVE IN LATE IN THE DAY/EVENING ALONG WITH A MODERATELY 
STRONG SHORT WAVE. H8 TEMPS NEAR -7C BY MONDAY MORNING WILL CREATE 
SUFFICIENT INSTABILITY OVER THE LAKE TO GENERATE SHSN. BUT GIVEN 
THAT THE DGZ REMAINS UNSATURATED ANY SHSN ACTIVITY SHOULD BE LIGHT. 
THE NAM SHOWS WARMER AIR MOVING INTO THE CWA LATE MONDAY NIGHT 
EFFECTIVELY ENDING THE SHSN. HOWEVER THE GFS IS A BIT SLOWER MOVING 
THE COLD AIR OUT. DUE TO THE UNCERTAINTY WE KEPT CHC POPS IN THE 
GRIDS MONDAY NIGHT. TUESDAY SHOULD BE A BIT BRIGHTER AS SHORT WAVE 
RIDGING MOVES IN AHEAD OF THE NEXT COLD FRONT. 

&&

.LONG TERM...(338 AM EST SUN NOV 29 2009)
(TUESDAY NIGHT THROUGH SATURDAY)
THE MAIN CHALLENGE IN THE LONG TERM DEALS WITH THE POTENTIAL FOR 
ACCUMULATING SNOW.  

THE 00Z RUN OF THE ECMWF BUILDS ON THE IDEA OF MUCH COLDER AIR 
ARRIVING FOR THU INTO FRI TIMEFRAME.  THE GFS SUPPORTS THIS SCENARIO 
AS WELL.  THE LOW LEVEL FLOW IS NOTICEABLY MORE VEERED AND THAT WILL 
RAISE THE POTENTIAL FOR ACCUMULATIONS.  GIVEN THE ADDED 
CONFIDENCE...I BUMPED UP POPS TO LIKELY ALONG THE LAKESHORE FOR SNOW 
SHOWERS PRIMARILY IN THE THU TO THU NIGHT TIMEFRAME.  MAY NEED TO GO 
LIKELY FOR FRI AS WELL.

I KEPT TUE NIGHT INTO WED DRY WITH THE MAJORITY OF THE MODELS 
SHOWING NO PRECIPITATION.  STILL MONITORING THE WAVE LIFTING UP FROM 
THE GULF.  CURRENT RUNS SHOW A MORE EASTERLY TRACK OF THE LOW AND 
THAT LOWERS THE RISK FOR PRECIPITATION HERE IN SOUTHWEST LOWER MI 
FOR WED. 

&&

.AVIATION...(1230 PM EST SUN NOV 29 2009)
MAINLY IFR CONDITIONS ARE ANTICIPATED THIS AFTERNOON AT ALL THE 
TERMINALS DUE TO LOW CLOUDS AND LINGERING LIGHT RAIN SHOWERS. 
CONDITIONS WILL GRADUALLY IMPROVE INTO THE MVFR FLIGHT CATEGORY 
OVERNIGHT AS CEILINGS BEGIN TO IMPROVE. 

A FEW VERY LIGHT LAKE EFFECT SNOW SHOWERS OR FLURRIES MAY CLIP THE 
MUSKEGON TERMINAL OVERNIGHT. HOWEVER WE DID NOT FEEL CONFIDENT 
ENOUGH IN THE PCPN POTENTIAL TO INCLUDE MENTION OF IT IN THE FCST 
FOR THE MUSKEGON TERMINAL. IT SEEMS THE BETTER CHANCE FOR LAKE 
EFFECT PCPN WILL BE NORTH OF MKG. 

PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED MONDAY AS CIGS IMPROVE 
TO GREATER THAN 3000 FEET AGL. THERE MAY BE SOME ICING IN THE LAYER 
FROM 1000 FT TO 8000 FT DURING THE DAY MONDAY.

&&

.MARINE...(338 AM EST SUN NOV 29 2009)
WINDS AND WAVES WILL INCREASE TOWARD EVENING AS COLDER AIR FLOWS 
INTO THE REGION BEHIND THE FRONT. ISSUED A SCA THROUGH TUESDAY DUE 
TO THE EXPECTED INCREASE IN WAVES. 

&&

.HYDROLOGY...(338 AM EST SUN NOV 29 2009)
NO HYDRO ISSUES.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY LATE THIS AFTERNOON THROUGH TUESDAY FROM 
ST JOSEPH TO MANISTEE.

&&

$$

SYNOPSIS:     93
SHORT TERM:   93 JK
LONG TERM:    MJS
AVIATION:     LAURENS
MARINE:       93
HYDROLOGY:    93