Issued by NWS Grand Rapids, MI
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000 FXUS63 KGRR 210857 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 400 AM EST SAT NOV 21 2009 LATEST UPDATE...ALL EXCEPT AVIATION... .SYNOPSIS...(400 AM EST SAT NOV 21 2009) HIGH PRESSURE WILL PRODUCE DRY WEATHER AND PARTLY CLOUDY SKIES THROUGH THE WEEKEND. PATCHY FOG IS ANTICIPATED DURING THE EARLY TO MID MORNING HOURS OF SATURDAY... SUNDAY AND MONDAY. TEMPERATURES WILL REMAIN ABOVE NORMAL INTO MID WEEK BEFORE IT TURNS A LITTLE COOLER LATE IN THE WEEK. && .SHORT TERM...(400 AM EST SAT NOV 21 2009) (TODAY THROUGH MONDAY AFTERNOON) SHORT TERM FCST CONCERNS REMAIN FAIRLY MINIMAL. HIGH PRESSURE WILL PRODUCE DRY WX THROUGH THE WEEKEND. SFC OBS EARLY THIS MORNING SHOW PATCHY FOG CONTINUES TO DEVELOP WHICH WILL LINGER THROUGH THE EARLY TO MID MORNING HOURS BEFORE DISSIPATING. LINGERING MORNING CLOUD COVER WILL GIVE WAY TO PARTIAL SUNSHINE THAT WILL HELP TO BOOST MAX TEMPS INTO THE LOW TO MID 50S. 00Z MODEL RH PROGS AND NUMERICAL GUIDANCE SUGGESTS MORE CLEARING WILL OCCUR TONIGHT AS COMPARED TO EARLY THIS MORNING. THIS IN CONJUNCTION WITH LIGHT AND VARIABLE WINDS WILL ONCE AGAIN SET THE STAGE FOR PATCHY FOG DEVELOPMENT DURING THE EARLY MORNING HOURS SUNDAY AND THEN AGAIN ON MONDAY. HIGH TEMPS SUNDAY AND MONDAY WILL REACH THE LOW TO MID 50S WITH MIN TEMPS MAINLY IN THE UPPER 30S TO LOWER 40S. && .LONG TERM...(400 AM EST SAT NOV 21 2009) (MONDAY NIGHT THROUGH FRIDAY) THE 00Z/21 RUNS OF THE GFS AND ECMWF ARE STILL NOT IN VERY GOOD AGREEMENT REGARDING THE MID WEEK SYSTEM AND HAVE TRIED TO INCORPORATE BOTH SOLUTIONS INTO THE FCST GRIDS. A LOW PRESSURE SYSTEM WILL BE TRACKING FROM THE CNTRL/NRN PLAINS ON TUESDAY... EAST NORTHEAST THROUGH THE GREAT LAKES REGION ON WED AND THU. THE FASTER GFS SOLUTION SUPPORTS WAA RAIN MOVING INTO THE REGION ON TUESDAY WHILE SLOWER ECMWF KEEPS IT DRY AND HOLDS THE RAIN OFF UNTIL WEDNESDAY. THE COMPROMISE IS TO CARRY CHANCE POPS BOTH DAYS... ALTHOUGH BELIEVE WEDNESDAY OFFERS THE BETTER PCPN POTENTIAL AND WILL CARRY SCTD VS CHANCE WORDING ON THAT DAY. PCPN TYPE BECOMES QUITE PROBLEMATIC BY THANKSGIVING DAY AS THE SFC LOW MOVES BY AND COOLER AIR IS DRAWN DOWN ON THE BACK SIDE OF THE SYSTEM. GFS SOLUTION IS STILL COLDER THAN THE ECMWF... ALTHOUGH IT IS A COMMON BIAS OF THE GFS TO BE COLDER BEYOND DAY 4. EVEN IF ONE WERE TO RUN WITH THE COOLER GFS SOLUTION... THE 00Z FCST SOUNDINGS LOOK JUST A TAD TOO WARM IN THE BOUNDARY LAYER TO SUPPORT SNOW. WILL THEREFORE GO WITH WITH RAIN OR SNOW SHOWER WORDING. THE CURRENT FCST FOR THURSDAY NIGHT AND FRIDAY CURRENTLY HAS ALL SNOW FOR PCPN TYPE AND LEFT THAT UNCHANGED... ALTHOUGH THE SPEED OF THE SYSTEM DEPARTURE WILL DICTATE PCPN CHANCES AND THE DEGREE OF COLD AIR ON THE BACK SIDE WILL DICTATE PCPN TYPE. THAT/S STILL A BIG UNCERTAINTY ATTM. && .AVIATION...(400 AM EST SAT NOV 21 2009) UPDATE... THE LATEST RUC IS HOLDING THE DECK OF MID LEVEL CLOUDS OVER MOST OF THE AREA FOR THE REMAINDER OF THE NIGHT... WHICH WILL LIMIT RADIATIONAL FOG FORMATION. WILL UPDATE TAFS TO BE LESS PESSIMISTIC WITH THE FOG. HOWEVER... SHOULD ANY RANDOM BREAKS IN THE MID DECK DEVELOP LONG ENOUGH BEFORE DAYBREAK... VSBYS COULD LOWER ABRUPTLY TO LIFR. && .MARINE...(400 AM EST SAT NOV 21 2009) HIGH PRESSURE AND LIGHT WINDS WILL RESULT IN MINIMAL WIND/WAVE ACTION THROUGH THE WEEKEND. SOME PATCHY EARLY TO MID MORNING FOG THROUGH THE WEEKEND COULD POSE A HAZARD TO MARINERS. && .HYDROLOGY...(400 AM EST SAT NOV 21 2009) DRY WEATHER IS EXPECTED THROUGH MONDAY. NO HYDRO ISSUES. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. && $$ SYNOPSIS: LAURENS SHORT TERM: LAURENS LONG TERM: MEADE AVIATION: MEADE MARINE: LAURENS HYDROLOGY: LAURENS