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000 FXUS63 KGRR 241722 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1222 PM EST TUE NOV 24 2009 LATEST UPDATE...AVIATION... .SYNOPSIS...(436 AM EST TUE NOV 24 2009) WE WILL SEE ONE MORE DRY AND MILD DAY. THEN RAIN WILL MOVE IN TONIGHT AS LOW PRESSURE APPROACHES THE STATE. SINCE THIS LOW WILL BE A SLOW MOVER...THE PRECIPITATION WILL CONTINUE THROUGH WEDNESDAY NIGHT. COOLER AIR WILL BE PUSHED INTO THE REGION BY LATE WEDNESDAY NIGHT WHEN THE RAIN COULD BECOME MIXED WITH OR CHANGE TO SNOW. THE MIXTURE SHOULD CONTINUE INTO THANKSGIVING DAY...HOWEVER ANY ACCUMULATION OF SNOW IS EXPECTED TO BE MINIMAL. && .SHORT TERM...(436 AM EST TUE NOV 24 2009) (TODAY THROUGH THANKSGIVING DAY) THE MAIN FORECAST ISSUES CONTINUED TO CENTERED ON THE LOW PRESSURE THAT WAS NEAR KANSAS CITY THIS MORNING. THIS SYSTEM WILL BE TEAMED UP WITH AN UPPER LOW THAT WILL DIVE ACROSS THE NORTHERN PLAINS BY EARLY WEDNESDAY. IT WILL BE THIS UPPER LOW THAT BRINGS IN COOLER AIR AND THE CHANCE OF RAIN MIXING WITH SNOW LATE IN THE SHORT TERM PERIOD. PCPN FROM THE KANSAS CITY LOW WAS ALREADY SPREADING EAST TOWARD THE MISSISSIPPI RIVER EARLY THIS MORNING. IT SHOULD TAKE UNTIL EVENING BEFORE THE DEEPER MOISTURE ARRIVES OVER SW MI. WILL KEEP THE FORECAST DRY FOR MUCH OF THE DAY WITH ONLY A SLGT CHANCE OF MOVING INTO THE LAKESHORE COUNTIES AROUND SUNSET. THE STACKED LOW HEADS FOR SOUTHERN LAKE MICHIGAN BY LATE TONIGHT AND WILL SPREAD RAIN FROM WEST TO EAST ACROSS THE CWA. THE LEFT EXIT REGION OF THE UPPER JET PUSHES NORTHWARD ACROSS LAKE MICHIGAN/WESTERN MI WHICH MAY ASSIST IN POCKETS OF HEAVIER RAIN. HAVE INCREASED POPS TO CATEGORICAL ACROSS THE CWA. BY WEDNESDAY THE UPPER LOW BEGINS TO SHEAR AND WEAKEN AS IT HEADS TOWARD THE TIP OF THE MITT. THE RAIN SHOULD BECOME MORE SCATTERED...ESPECIALLY AROUND MID DAY...WITH THIS WEAKENING TREND. BY WEDNESDAY NIGHT THE NORTHERN STREAM UPPER LOW FROM THE NORTHERN PLAINS BECOMES THE MAIN PLAYER. IT SHOULD MOVE FROM EASTERN IA TO NORTHERN IN OVERNIGHT. IT WILL BRING ANOTHER WAVE OF RAIN ACROSS THE CWA ALONG WITH COOLER AIR MOVING IN FROM THE SW. THE MODELS CONTINUE TO BE CONSISTENT SHOWING IT COOL ENOUGH FOR A RAIN/SNOW MIX AFTER 06Z ACROSS MUCH OF THE CWA. AS THE UPPER LOW GOES BY THURSDAY MORNING WE MAY GET DRY SLOTTED WITH THE MOISTURE BECOMING SHALLOW...SO HAVE LOWER POPS EARLY IN THE DAY. HOWEVER SOME LAKE EFFECT SHOULD BE GETTING STARTED IN A SW FLOW...SO WILL KEEP HIGHER POPS FOR THE NW CWA. THEN INTO THE AFTERNOON AS THE LOW HEADS FOR WESTERN LAKE ERIE DEEPER MOISTURE WILL RETURN. LIKELY POPS FOR THE LAKESHORE DUE TO LAKE ENHANCEMENT...AND HIGH CHANCE POPS WILL BE CONTINUED INLAND FOR A RAIN/SNOW MIX. THERE COULD BE A FEW AREAS THAT SEE A DUSTING OF SNOW ON GRASSY AREAS BY THURSDAY EVENING. BUT WITH TEMPS REACHING AROUND 40 AND WITH A WARM GROUND...ROADS SHOULD REMAIN WET. && .LONG TERM...(436 AM EST TUE NOV 24 2009) (THURSDAY NIGHT THROUGH MONDAY) DEEP MOISTURE AND LIFT IS PROGGED TO BE SWINGING THROUGH THE REGION THURSDAY NIGHT ON THE WEST SIDE OF THE UPPER LOW. GFS BUFKIT OVERVIEW INDICATES THAT THE -12C TO -16C DENDRITIC SNOW GROWTH REGION WILL BE ACTIVATED MUCH OF THE NIGHT. THE FCST SOUNDINGS ALSO SHOW NO INVERSION PRESENT ALOFT WITH H8 TEMPS AROUND -5C AND DELTA T/S AROUND 14C... SO WOULD EXPECT THERE TO BE SOME FAIRLY DECENT LAKE EFFECT/ENHANCED CONVECTION TAKING PLACE. NORTHWEST FLOW IS PROGGED TO BECOME RATHER STRONG WITH 30 KTS SEEN AT 925 MB AND THAT SHOULD BE CARRYING THE CONVECTION BUT ALSO THE WARMER MARINE AIR QUITE A DISTANCE INLAND FROM LAKE MICHIGAN. AS SUCH IT WOULD SEEM THAT THE PCPN THURSDAY NIGHT WILL STILL REMAIN PREDOMINATELY MIXED... ALTHOUGH WHERE THE MORE INTENSE BANDS PERSIST THERE COULD CERTAINLY BE A COATING OF WET SNOW ACCUMULATION. H5 LONGWAVE TROUGH AND COLD AIR SHOULD BE DEPARTING EITHER FRIDAY OR FRIDAY NIGHT... THEN A PERIOD OF QUIET WX WITH ABOVE NORMAL TEMPS IS EXPECTED AS UPPER RIDGING IMPACTS THE REGION. A DIGGING LONGWAVE TROUGH IN THE CENTER OF THE NATION INDUCES DEEP SOUTHWEST FLOW INTO MICHIGAN... WHICH LEADS TO A CHANCE OF RAIN SUNDAY INTO MONDAY. && .AVIATION...(1222 PM EST TUE NOV 24 2009) MAIN CONCERNS TO AVIATION INTERESTS WILL BE RESIDUAL LOWER CONDITIONS AT THE BEGINNING OF THE PERIOD...AND POTENTIAL LOWER CONDITIONS WITH THE FRONT MOVING IN TONIGHT. 17Z OBS SHOW THAT MOST OF ALL THE IFR HAS DISSIPATED ACROSS TERMINALS. A COUPLE OF POCKETS OF IFR REMAIN...HOWEVER WE EXPECT THESE LOCATIONS TO IMPROVE BY THE VALID TIME OF THE TERMINALS. WE EXPECT THAT MVFR-VFR CONDITIONS WILL HOLD IN THROUGH 00Z BEFORE CONDITIONS START DETERIORATING ONCE AGAIN AS THE SUN SETS AND THE FRONT APPROACHES. IFR WILL BE LIKELY AS RAINFALL BEGINS AND THE FRONT MOVES ACROSS THE AREA. CORE TIME OF THIS IFR LOOKS TO BE FROM AROUND 02-12Z. AS THE FRONT MOVES THROUGH...CONDITIONS WILL IMPROVE SLIGHTLY TO MVFR BETWEEN 10-12Z AND WINDS WILL BE SW. && .MARINE...(436 AM EST TUE NOV 24 2009) IT WILL REMAIN FAIRLY CALM ON THE LAKE UNTIL THE FIRST SURFACE LOW ON WEDNESDAY PASSES BY AROUND MID DAY. ONCE THE COLD ADVECTION BEGINS WINDS AND WAVES WILL BE ON THE INCREASE WEDNESDAY AFTERNOON INTO THE EVENING. A SMALL CRAFT ADVISORY MAY BE NEEDED. && .HYDROLOGY...(436 AM EST TUE NOV 24 2009) AN EXTENDED PERIOD OF PCPN IS EXPECTED FROM TONIGHT THROUGH THANKSGIVING DAY. HOWEVER...THIS PCPN IS EXPECTED TO BE FAIRLY LIGHT WITH MOST AREAS SEEING AROUND A HALF INCH OF RAIN. THE PCPN SHOULD BE A BIT HEAVIER WEST AND LIGHTER EAST DUE TO LAKE ENHANCEMENT INTO WED NIGHT/THURSDAY. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. && $$ SYNOPSIS: JK SHORT TERM: JK LONG TERM: MEADE AVIATION: MEADE MARINE: JK HYDROLOGY: JK
