Issued by NWS Grand Rapids, MI
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000 FXUS63 KGRR 271144 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 745 AM EDT THU AUG 27 2009 LATEST UPDATE...AVIATION... .SYNOPSIS...(428 AM EDT THU AUG 27 2009) THE REST OF THE WEEK THROUGH THE WEEKEND WILL BE RATHER UNSETTLED. SHOWERS WILL DEVELOP LATER TODAY AND MOVE FROM SOUTHWEST TO NORTHEAST AS A COLD FRONT MOVE ACROSS THE REGION. AN UPPER LOW WILL FOLLOW OVER THE WEEKEND BRINGING MORE SHOWERS AND MUCH COOLER WEATHER. && .SHORT TERM...(428 AM EDT THU AUG 27 2009) (TODAY THROUGH SATURDAY) FORECAST CONCERNS DEAL WITH PCPN TRENDS. MODELS ARE NOT ON THE SAME PAGE WITH RESPECT TO PCPN. THE LATEST ECMWF HITS THE PCPN MUCH HARDER AND FARTHER NORTH THAN IT/S PREVIOUS RUNS. THE NAM DOESN/T REALLY BRING PCPN INTO THE CWA UNTIL TONIGHT. GIVEN CURRENT RADAR TRENDS SHOWING ABUNDANT PCPN JUST TO THE SW...IT/S CLEARLY TOO SLOW. THE GFS BRINGS IN PCPN TO THE SOUTHWEST THIS MORNING AND DECREASES IT A BIT THIS AFTERNOON. THIS IS IN LINE WITH THE SREF AND LOOKS LIKE THE BEST SOLUTION. THE FRONTAL BOUNDARY TO THE SOUTH WILL CONTINUE TO ACT AS A FOCUS FOR PCPN DEVELOPMENT. THE SHORT RANGE MODELS SHOW A WAVE ON THE FRONT PHASING WITH THE LOW CURRENTLY IN MANITOBA OVER LOWER MICHIGAN ON FRIDAY AS IT MOVES THROUGH. THE MANITOBA LOW WILL ALSO DRAG A COLD FRONT THROUGH THE STATE USHERING COOLER WX IN FOR THE WEEKEND. WE/LL SEE PCPN...MOSTLY SHOWERS ALTHOUGH A STORM OR TWO IS POSSIBLE TOO...INCREASE IN COVERAGE TONIGHT INTO FRIDAY. THE UPPER LOW WILL FOLLOW THE COLD FRONT FRIDAY NIGHT INTO SATURDAY AND SUNDAY. INSTABILITY WILL INCREASE A BIT AS LAPSE RATES STEEPEN IN RESPONSE TO THE COOLER AIR ALOFT ADVECTING INTO THE GREAT LAKES. TEMPERATURES WILL HOLD MOSTLY IN THE 60S SATURDAY. && .LONG TERM...(428 AM EDT THU AUG 27 2009) (SATURDAY NIGHT THROUGH WEDNESDAY) DEEP CYCLONIC FLOW AND H8 AIR OF ONLY 2-4C IS PROGGED TO BE OVER THE REGION SATURDAY NIGHT AND SUNDAY...RESULTING IN UNSEASONABLY COLD TEMPERATURES AND SCATTERED RAIN SHOWERS. AS THE TROUGH SHIFTS EAST SUNDAY NIGHT AND MONDAY... SURFACE RIDGING BUILDS INTO THE REGION FROM THE WEST AND THE RAIN SHOWER THREAT IS EXPECTED TO END. SURFACE HIGH PRESSURE WILL DOMINATE THROUGH MUCH OF NEXT WEEK WHICH WILL LEAD TO AN EXTENDED PERIOD OF DRY WEATHER...ALTHOUGH TEMPERATURES WILL BE SLOW TO MODERATE. && .AVIATION...(745 AM EDT THU AUG 27 2009) DESPITE THICK CLOUDINESS... VFR CONDITIONS ARE EXPECTED TODAY. RAIN WILL LIKELY IMPACT THE I-94 TAF SITES MUCH OF THE DAY... BUT THE LOWER LEVELS ARE DRY WHICH SHOULD KEEP CIGS ABOVE 5K FEET AND VSBYS AOA 6SM. THE I-96 TAF SITES MAY SEE SOME SPRINKLES FROM TIME TO TIME WITH CIGS MOSTLY AOA 12K FT. AFTER 06Z TONIGHT IT APPEARS CIGS MAY BEGIN TO LOWER AS SRN STREAM LOW MOVES ALONG THE FRONT. MVFR CONDITIONS SHOULD DEVELOP ALONG AND SOUTH OF THE I-94 CORRIDOR... POSSIBLY REACHING UP TO I-96 TOWARD 12Z. && .MARINE...(428 AM EDT THU AUG 27 2009) RELATIVELY LIGHT WINDS WILL RESULT IN WAVES AOB 3 FEET TODAY. AS MUCH COLDER AIR ALOFT MOVES OVER THE LAKES SATURDAY AND SUNDAY...INSTABILITY WILL INCREASE AND A LOW CHANCE EXISTS FOR WATERSPOUTS. && .HYDROLOGY...(428 AM EDT THU AUG 27 2009) RISES ARE EXPECTED ON AREAS STREAMS AND RIVERS OVER THE NEXT COUPLE OF DAYS...ESPECIALLY OVER THE SRN CWA. ANOTHER INCH OR TWO OF RAIN IS POSSIBLE OVER THE NEXT FEW DAYS WHICH COULD RESULT IN LOCALIZED FLOODING. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. && $$ SYNOPSIS: 93 SHORT TERM: 93 LONG TERM: MEADE AVIATION: MEADE MARINE: 93 HYDROLOGY: 93
