Issued by NWS Grand Rapids, MI
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000 FXUS63 KGRR 262356 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 755 PM EDT SUN OCT 26 2008 LATEST UPDATE...SHORT TERM... .SYNOPSIS...(415 PM EDT SUN OCT 26 2008) THE GREAT LAKES REGION WILL EXPERIENCE THE FIRST TASTE OF WINTER EARLY THIS WEEK AS A SERIES OF COLD FRONTS PASS THROUGH AND BRING PROGRESSIVELY COLDER AIR DOWN FROM CANADA. SCATTERED LAKE EFFECT RAIN SHOWERS WILL BE MIXED WITH SNOW SHOWERS TONIGHT AND MONDAY THEN CHANGE TO MOSTLY SNOW ON MONDAY NIGHT INTO TUESDAY. SOME LIGHT ACCUMULATIONS WILL BE POSSIBLE WEST OF HIGHWAY 131 MONDAY NIGHT. A WARMING TREND WILL BEGIN ON WEDNESDAY. && .SHORT TERM...(755 PM EDT SUN OCT 26 2008) (TODAY THROUGH TUESDAY) WILL EXTEND THE WIND ADVISORY OVER THE SW PORTION OF THE CWA THROUGH 11 PM. HIGHEST CORE OF BOUNDARY LAYER WINDS WILL BE SWEEPING ACROSS THIS REGION THROUGH THE EVENING. AFTER 11 PM THIS CORE OF WIND WILL BE WELL SOUTH OF THE REGION. THE CORE OF THE STRONGEST WINDS ALOFT /50-55KT AT H8/... AS WELL AS THE STRONGEST COLD ADVECTION /-8C AT H8/... IS PASSING SOUTHWEST OF MICHIGAN THIS AFTERNOON AND EVENING. THUS WIND GUSTS ARE STRUGGLING TO REACH ADVISORY CRITERIA OF 45 MPH (39KTS). HOWEVER HAVE OPTED TO RIDE THE ADVISORY THROUGH IT/S EXPIRATION TIME OF 8 PM SINCE THERE IS CURRENTLY SOME CONVECTION AROUND THAT COULD HELP PRODUCE SOME BRIEF/ISOLATED 45 MPH GUSTS. WILL ALSO CARRY A MENTION OF THUNDER AND POSSIBLE SMALL HAIL IN THE GRIDS THROUGH 00Z AS LIFTED INDICES HOLD AROUND -2 OR SO UNTIL AROUND SUNSET. THE CORE OF THE COLDEST AIR GOES SOUTH OF MI TONIGHT AND A TROUGH OF WARMER H8 AIR /-3C/ PIVOTS DOWN FROM THE NW WITH THE NEXT SHORTWAVE. THIS WILL MAKE IT VERY TOUGH TO TRANSITION THE LAKE EFFECT PCPN TO ALL SNOW TONIGHT WHICH WILL MAKE ACCUMULATIONS UNLIKELY. NAM LOW LEVEL THICKNESS SCHEMES AND SFC TEMP PROGS LOOK A TAD TOO WARM. THIS IS A TREND WHICH BEGAN WITH THE 00Z GUIDANCE AND HAS CONTINUED IN THE 12Z GUIDANCE. THERE IS STILL A STRONG CONCERN HOWEVER THAT OCCASIONAL CHANGEOVERS TO ALL SNOW COULD OCCUR WITHIN THE MORE INTENSE LAKE EFFECT BANDS LATE TONIGHT. SOME OF THOSE BANDS CERTAINLY COULD BE INTENSE SINCE DEEP MOISTURE WILL BE PRESENT WITH VIRTUALLY NO INVERSION ALOFT INDICATED IN THE FCST SOUNDINGS. THUS QUICK COATINGS OF AN INCH OR SO CANNOT BE COMPLETELY RULED OUT TONIGHT AND MONDAY MORNING. LAKE EFFECT BANDS WILL PROBABLY BECOME MORE OPEN CELLULAR BY MONDAY AFTERNOON DUE TO DISRUPTION FROM DIURNAL EFFECTS. THE BEST CHANCE OF ACCUMULATING LAKE EFFECT SNOW WILL BE MONDAY NIGHT AND TUESDAY MORNING. THIS IS WHEN THE COLDEST H8 AIR OF -8C WILL BE IN PLACE BEHIND THE DEPARTING SECONDARY TROUGH. FLOW IS NNW... WHICH WOULD SUPPORT SOME POTENTIAL 1-3 ACCUMULATIONS WEST OF HIGHWAY 131. EXCEPTION WOULD BE THE IMMEDIATE LAKE MI COASTLINE WHERE A MIX WILL LIKELY CONTINUE SINCE THE LK MI WATER TEMP IS 55F. MEANWHILE AREAS ALONG/EAST OF HWY 131 WILL LIKELY CLR OUT MONDAY NIGHT AND HAVE A HARD FREEZE. && .LONG TERM...(415 PM EDT SUN OCT 26 2008) (TUESDAY NIGHT THROUGH SATURDAY) UPPER CYCLONIC FLOW WILL BE EXITING THE CWFA AS THE UPPER JET MIGRATES TO THE EAST AT THE BEGINNING OF THE LONG TERM ON WED MORNING. UPPER RIDGING IS EXPECTED TO BUILD...AND DRY OUT THE AREA FOR A COUPLE OF DAYS ALONG WITH SOME ABOVE NORMAL TEMPERATURES. STRONG UPPER ENERGY DIVING SOUTHEAST OUT OF CANADA WILL SQUEEZE THE UPPER RIDGING TO THE EAST. MODELS ARE COMING INTO AGREEMENT ON THIS HAPPENING IN THE FRI TIME FRAME. MODELS ARE INDICATING THAT LITTLE IF ANY PCPN IS GOING TO BE ASSOCIATED WITH THE FRONT. MOISTURE IS NOT ALL THAT DEEP WITH DIFFERENT LAYERS OF MOISTURE NOT OVERLAPPING WELL. WE WILL MAINTAIN THE DRY FCST FOR NOW WITH NO GOOD JUSTIFICATION ATTM TO INTRODUCE POPS INTO THE FCST. H850 TEMPS ARE EXPECTED TO DROP FROM AROUND +10C OR SO AHEAD OF THE FRONT...TO -6C OR SO BEHIND THE FRONT. THREAT OF LAKE EFFECT SEEMS RATHER LOW EVEN WITH THE COLD AIR DROPPING INTO THE CWFA. THIS IS BECAUSE THE FLOW IS EXPECTED TO BE NORTHEAST AS A RESULT OF THE ORIENTATION OF THE SFC HIGH COMING IN FROM THE NW. THIS RIDGE WILL THEN MOVE OVERHEAD NEXT WEEKEND. && .MARINE...(415 PM EDT SUN OCT 26 2008) MAY BE ABLE TO CANCEL THE GALE WARNING EARLY BUT EVEN SO VERY ROUGH CONDITIONS WILL PERSIST IN LAKE MI INTO TUESDAY AS UNSEASONABLY COLD AIR AND CYCLONIC FLOW AFFECTS THE REGION. WAVE HEIGHTS NEAR 10 FEET SHOULD BEGIN TRENDING DOWN MONDAY NIGHT... BUT REMAIN ABOVE SMALL CRAFT ADVISORY CRITERIA INTO TUESDAY. && .AVIATION...(205 PM EDT SUN OCT 26 2008) AFTER A BRIEF BREAK IN THE SHOWER ACTIVITY THIS MORNING FOLLOWING THE COLD FRONT...SHOWERS HAVE POPPED UP ONCE AGAIN MAINLY NORTH OF THE TERMINALS. A SHORT WAVE MOVING ACROSS NRN LOWER MI IS LIKELY RESPONSIBLE FOR THESE SHOWERS. THESE SHOWERS WILL TEND TO DIMINISH IN COVERAGE OVER THE NEXT COUPLE OF HOURS...AND SHOULD NOT BE MUCH OF AN IMPACT TO THE TERMINALS. WIND GUSTS OF AROUND 30 KNOTS WILL CONTINUE TO BE POSSIBLE UNTIL AROUND 00Z. A FEW LAKE EFFECT RAIN SHOWERS WILL BECOME POSSIBLE ACROSS THE ENTIRE AREA LATER THIS AFTERNOON AS THE COLDER AIR MOVES IN ACROSS THE LAKE. THE MAIN BATCH OF RAIN IS EXPECTED BETWEEN 00Z AND 08Z AS DEEPER MOISTURE MOVES IN...AND AS AN AREA OF MID LEVEL FORCING MOVES ACROSS FROM NW TO SE. THIS WILL LIKELY BRING CIGS DOWN TO MVFR AT ALL TERMINALS AND VSBYS HAVE THE POSSIBILITY OF DROPPING DOWN TO MVFR LEVELS ALSO. WIND GUSTS OF AROUND 25 KNOTS WILL CONTINUE. IN THE WAKE OF THE BAND OF RAIN EXPECTED THIS EVENING AND EARLY OVERNIGHT...THE FLOW WILL BECOME MORE NW AND MORE PURE LAKE EFFECT. THE NW FLOW WILL SHIFT THE GOOD MAJORITY OF SHOWER ACTIVITY OVER THE KAZO AND KBTL TERMINALS. THIS SETUP IS EXPECTED TO REMAIN NEARLY STEADY THROUGH 18Z MON. PCPN TYPE IS EXPECTED TO REMAIN MOSTLY RAIN AT ALL OF THE TERMINALS THROUGH 18Z MON AS FREEZING LEVELS ARE EXPECTED TO REMAIN ABOUT 2K FEET AND WET BULB ZERO LEVELS WILL BE 1-2K FEET. && .HYDROLOGY...(415 PM EDT SUN OCT 26 2008) NO HYDRO CONCERNS AS PCPN NEXT 72 HOURS WILL BE GENERALLY SCATTERED IN NATURE WITH QPF AMOUNTS BELOW HALF INCH. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...WIND ADVISORY THROUGH 11 PM...SOUTHWEST OF A MUSKEGON TO CALHOUN COUNTY LINE. LM...GALE WARNING IN EFFECT ST. JOE TO MANISTEE TODAY THROUGH MONDAY AFTERNOON. && $$ SYNOPSIS: MEADE SHORT TERM: MEADE JK LONG TERM: NJJ MARINE: MEADE AVIATION: NJJ HYDROLOGY: MEADE
