Issued by NWS Grand Rapids, MI
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000 FXUS63 KGRR 292225 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 624 PM EDT WED OCT 29 2008 LATEST UPDATE...AVIATION .SYNOPSIS...(240 PM EDT WED OCT 29 2008) CLOUDS WILL PERSIST THROUGH MUCH OF THE AFTERNOON WITH HIGH TEMPERATURES IN THE 40S. AS HIGH PRESSURE BUILDS IN OVER THE NEXT FEW DAYS...TEMPERATURES WILL WARM UP. A WEAK COLD FRONT WILL PASS THROUGH ON HALLOWEEN NIGHT...BUT FAIR WEATHER SHOULD PREVAIL WITH TEMPERATURES IN THE 50S FOR THE TRICK OR TREATERS. && .SHORT TERM...(240 PM EDT WED OCT 29 2008) (TONIGHT THROUGH FRIDAY NIGHT) FAIR WEATHER THROUGH THE NEAR TERM WITH THE ONLY FORECAST ISSUE BEING THE POTENTIAL FOR SOME LOW CHANCE OR ISOLATED POPS FRIDAY NIGHT AS A COLD FRONT PUSHES DOWN FROM THE NORTH. WENT WITH MAXES CLOSE TO GUIDANCE THROUGH THE PERIOD AS THE GUIDANCE TEMPS SEEM TO ACCOUNT FOR ADVECTION PATTERNS. LEFT FRIDAY NIGHT DRY SINCE MOISTURE APPEARS VERY LIMITED...ALTHOUGH THE GFS IS ABLE TO PRODUCE SOME LIGHT QPF ACROSS THE FAR EASTERN FORECAST AREA. WILL HAVE TO WATCH THIS...AND MAY NEED TO ADD LOW CHANCE POPS AT SOME POINT DEPENDING ON FUTURE MODEL TRENDS. ANY PRECIP SHOULD BE SCATTERED AND FAIRLY LIGHT GIVEN THE SHALLOW NATURE OF THE RH SEEN IN MODEL CROSS SECTIONS AND LACK OF DEEP LIFT ASSOCIATED WITH THE FROPA. FRIDAY NIGHT TEMPS ARE TRICKY SINCE IT DEPENDS ON THE TIMING OF THE FRONT AND WHETHER CLOUDS CLEAR OUT BEFORE SUNRISE. WENT WITH MIN TEMPS A BIT BELOW GUIDANCE ON THE ASSUMPTION THAT MOISTURE IS LIMITED RESULTING IN LESS CLOUDS AND GREATER RADIATIONAL COOLING. && .LONG TERM...(115 PM EDT WED OCT 29 2008) HIGH PRESSURE WILL PRODUCE FAIR WEATHER WITH SEASONABLE TEMPS SATURDAY THROUGH SUNDAY AFTERNOON. THERE IS A CHC OF SHOWERS SUNDAY EVENING AS A WARM FRONT LIFTS THROUGH THE REGION. ABOVE NORMAL TEMPS ARE ANTICIPATED MONDAY AND TUESDAY AS WE GET INTO STRONG SSW FLOW WARM AIR ADVECTION AND AN UPPER LEVEL RIDGE BUILDS OVERHEAD. A COLD FRONT WILL BRING OUR NEXT CHC FOR RAIN FOR THE MIDDLE PORTION OF NEXT WEEK. && .MARINE...(240 PM EDT WED OCT 29 2008) WINDS AND WAVES WILL DIMINISH THIS EVENING AS NIGH PRESSURE BUILDS IN. THE SMALL CRAFT ADVISORY WILL BE EXPIRING THIS EVENING BUT THE BREAK IN LOWER WAVES WILL ONLY LAST ABOUT 12 HOURS AS SOUTHERLY WINDS ON THE BACKSIDE OF THE HIGH BEGIN TO STIR UP THE LAKE ONCE AGAIN BY THURSDAY AFTERNOON. IN FACT IT APPEARS THAT WINDS MAY APPROACH GALE FORCE ACROSS CENTRAL LAKE MICHIGAN BY MID AFTERNOON INTO EARLY THURSDAY NIGHT. && .AVIATION...(624 PM EDT WED OCT 29 2008) THE THE CORE OF THE POLAR JET NOW WELL EAST OF THE CWA...SURFACE WINDS HAVE BECOME ANTICYCLONIC AND CLOUDS HAVE CLEARED NICELY (AS OF 6 PM). THE SHORTWAVE RIDGE MOVES THROUGH THE AREA THURSDAY WHILE THE CYCLONIC FLOW AROUND A STRONG STORM IN CENTRAL CANADA CREATES QUIET THE PRESSURE GRADIENT OVER LOWER MICHIGAN THURSDAY. THAT WILL RESULT IN STRONG AND GUSTY SOUTHWEST WINDS BY THURSDAY AFTERNOON OVER THE NORTHERN AND WESTERN SECTIONS OF THE CWA. SOUTHEAST SECTIONS... BEING CLOSER TO THE SURFACE HIGH WILL HAVE LESS WIND. SO WITH SURFACE RIDGE OVERHEAD AT MIDNIGHT... WINDS WILL BE LIGHT AND SKIES WILL BE CLEAR. ON THURSDAY WINDS WILL INCREASE FROM NW TO SE ACROSS THE CWA IN RESPONSE TO THE CANADIAN STORM SYSTEM. I PUT GUSTY WINDS IN THE WESTERN AND NORTHERN TAF SITES. LOCATIONS LIKE LAN AND JXN MAY BE JUST FAR ENOUGH TO THE SOUTHEAST TO LIMIT JUST HOW GUSTY IT WILL GET. I USED NAM 29TH/18Z RUN IN BUFKIT WITH THE MIXING HEIGHT TO DECIDE WHICH TAF SITE TO PUT GUSTY WINDS THURSDAY. && .HYDROLOGY...(240 PM EDT WED OCT 29 2008) RIVERS SHOULD CONTINUE TO REMAIN STEADY OR SLOWLY FALL AS NO SIGNIFICANT PRECIPITATION IS EXPECTED OVER THE NEXT FEW DAYS. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY IN EFFECT THROUGH THIS EVENING FROM ST. JOSEPH TO MANISTEE. && $$ SYNOPSIS: OSTUNO SHORT TERM: OSTUNO LONG TERM: LAURENS MARINE: OSTUNO AVIATION: WDM HYDROLOGY: OSTUNO
