FXUS63 KGRR 071934 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 240 PM EST SAT JAN 7 2012 LATEST UPDATE...ALL BUT AVIATION... .SYNOPSIS...(240 PM EST SAT JAN 7 2012) LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO TRACK EASTWARD AWAY FROM THE GREAT LAKES REGION. MEANWHILE A LARGE AREA OF HIGH PRESSURE ACROSS THE CANADIAN PRAIRIES AND THE UPPER PLAINS STATES WILL BUILD INTO MICHIGAN. THIS FAIR WEATHER SYSTEM WILL ACT TO KEEP THE TEMPERATURES ABOVE NORMAL INTO EARLY NEXT WEEK. A WEAK COLD FRONT WILL SLIP THROUGH THE AREA ON MONDAY...BUT IT WILL BE FOLLOWED BY ANOTHER HIGH PRESSURE SYSTEM. && .SHORT TERM...(240 PM EST SAT JAN 7 2012) (TONIGHT THROUGH MONDAY NIGHT) HIGH PRESSURE WILL BE BUILDING INTO LOWER MI THROUGH SUNDAY. THIS SYSTEM WILL KEEP THE WEATHER RELATIVELY DRY. LOWER CLOUDS COVERING SOUTHWEST LOWER MI WILL GRADUALLY DIMINISH AS WE LOSE THE DAYTIME HEATING. THERE STILL COULD BE A FEW FLURRIES MAINLY UP AROUND TUSTIN AS THE DGZ WAS CLIPPING THE TOPS OF THE LOWER CLOUDS. LATEST IR IMAGERY SHOWS CLOUD TOP TEMPS OF AROUND -15 DEG C NORTH OF RQB. 16Z POES SOUNDING NEAR RQB SHOWS MOISTURE ALMOST UP TO THE 700 MB LEVEL. WHILE IT IS SHOWN THAT WE LOSE THE LOWER CLOUDS...HIGHER CLOUDS UP AROUND 300 MB MOVE OVERNIGHT. THEN FOR SUNDAY WEAK WARM AIR ADVECTION DEVELOPS. THIS SHOULD LIMIT THE RISK FOR ANY LOWER CLOUD FORMATION ACROSS AT LEAST SOUTHERN LOWER MI. WITH LIGHT WINDS AND SOME SUN ALONG WITH 925 MB TEMPS ONLY -4 DEG C...HIGH TEMPERATURES WILL CLIMB BACK TO ABOVE NORMAL LEVELS...GENERALLY IN THE MID TO UPPER 30S. A WEAKENING COLD FRONT PUSHES EASTWARD THROUGH LOWER MI ON MONDAY. THIS FEATURE SHOULD NOT LEAD TO ANY PRECIPITATION AS THERE IS ROUGHLY 5K TO 10K FT OF DRY AIR BELOW THE CLOUD BASES UP AROUND 10K FT. && .LONG TERM...(240 PM EST SAT JAN 7 2012) (TUESDAY THROUGH SATURDAY) MAIN WX STORY IN THE LONG TERM CONTINUES TO BE THE RETURN OF MUCH COLDER AIR TO LWR MI AND POTENTIAL FOR SIGNIFICANT LAKE EFFECT SNOW LATE IN THE WEEK. H8 TEMPS WILL BE DOWN TO -14 TO -16 C BY THURSDAY EVENING... IN A WEST TO WNW FLOW PATTERN FAVORABLE FOR POTENTIALLY SIGNIFICANT LAKE EFFECT SNOW. THE FCST IS BECOMING A LITTLE MORE UNCERTAIN BEGINNING FRIDAY. 00Z ECMWF KEPT COLD AIR LOCKED IN THROUGH FRIDAY... WHEREAS 12Z GFS GUIDANCE SHOWS A SFC RIDGE BUILDING IN WITH H8 TEMPS ALREADY BACK UP TO -10 TO -12C BY FRIDAY EVENING. THIS HAS IMPLICATIONS ON WHETHER LAKE EFFECT SNOW WILL CONTINUE TO GO RATHER STRONG THROUGH THE DAY FRIDAY OR WHETHER SNOW SHOWERS MAY ALREADY BEGIN TO TAPER OFF LATE FRIDAY AS GFS GUIDANCE WOULD SUGGEST. AT THIS TIME WE WILL KEEP SNOW SHOWERS IN THE FCST THURSDAY THROUGH FRIDAY... WITH HIGHEST POPS MAINLY WEST OF US-131. REGARDING THE WEATHER TUESDAY AND WEDNESDAY... UNSEASONABLY MILD/DRY DRY WX TO CONTINUE TUESDAY. THE OVERALL MEDIUM RANGE GUIDANCE CONSENSUS CONTINUES TO SUGGEST THAT LOW PRESSURE OVER THE TN VALLEY REGION WEDNESDAY WILL TRACK NE TO THE MID ATLANTIC REGION WEDNESDAY NIGHT... KEEPING SYNOPTIC PCPN SE OF LWR MI. HOWEVER THE SAME FCST CONCERNS ELUDED TO BY THE PREVIOUS SHIFT ARE STILL THERE FOR MIDWEEK... THAT IF THE SOUTHERN STREAM SYSTEM WERE TO TRACK FURTHER NORTH AND IF THE NORTHERN STREAM WAVE IS FASTER AND MERGES WITH THE SOUTHERN STREAM... THAT THIS WOULD YIELD A FURTHER NNW TRACK OF THE SFC LOW. THE MOST LIKELY OUTCOME FAVORS A TRACK FAR ENOUGH SE THAT SYNOPTIC PCPN WOULD MISS LWR MI WEDNESDAY... BUT IT IS NOTED THAT 12Z GFS GUIDANCE DOES CLIP OUR SE FCST AREA WITH SOME LIGHT PCPN WEDNESDAY WHICH WOULD PROBABLY BE IN THE FORM OF RAIN. && .AVIATION...(1240 PM EST SAT JAN 7 2012) MVFR TO NEAR MVFR CONDITIONS ANTICIPATED THIS AFTERNOON WITH CIGS OF 2500-3500 FT AGL. NW SFC WINDS WILL GUST TO NEAR 20 KTS AT TIMES THROUGH LATE AFTERNOON. SHOULD START TO SEE SOME GRADUAL CLEARING OVERNIGHT AS SFC RIDGING BUILDS IN... RESULTING IN MAINLY VFR CONDITIONS OVERNIGHT THRU 18Z SUN. && .MARINE...(240 PM EST SAT JAN 7 2012) GUSTY NORTHWEST WINDS AND COLD AIR ADVECTION WARRANT THE SMALL CRAFT ADVISORY. AS WE GO THROUGH THE OVERNIGHT PERIOD WINDS AND WAVES WILL BE DIMINISHING. THE PRESSURE GRADIENT REMAINS LOW THROUGH SUNDAY. HOWEVER ON MONDAY A WESTERLY WIND WILL INCREASE AND HEADLINES WILL LIKELY BE NEEDED. && .HYDROLOGY...(240 PM EST SAT JAN 7 2012) BELOW NORMAL PRECIPITATION AMOUNTS THROUGH THE PERIOD COMBINED WITH ABOVE NORMAL TEMPERATURES WILL MEAN LITTLE OR NO IMPACTS ON THE AREA RIVERS THROUGH THE PERIOD. THE WARMER THAN NORMAL TEMPERATURES WILL LESSEN THE RISK FOR ICE RELATED ISSUES. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY ENTIRE NEARSHORE INTO TONIGHT. && $$ SYNOPSIS: MJS SHORT TERM: MJS LONG TERM: LAURENS AVIATION: LAURENS MARINE: MJS HYDROLOGY: MJS