Issued by NWS Grand Rapids, MI
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000 FXUS63 KGRR 272353 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 753 PM EDT MON OCT 27 2008 LATEST UPDATE...AVIATION... .SYNOPSIS...(415 PM EDT MON OCT 27 2008) UNSEASONABLY COLD AIR AND SCATTERED LAKE EFFECT RAIN AND SNOW SHOWERS WILL LINGER ACROSS THE REGION THROUGH TUESDAY NIGHT. DRY WEATHER AND A WARMING TREND WILL BEGIN ON WEDNESDAY. && .SHORT TERM...(415 PM EDT MON OCT 27 2008) (TODAY THROUGH WEDNESDAY) LAKE ENHANCED OPEN CELL CONVECTION IS GETTING A DIURNAL BOOST THIS AFTERNOON... AND THERE HAVE BEEN SOME REPORTS OF HEAVIER SHOWERS MIXED WITH GRAUPEL. LATER TONIGHT AS THE DIURNAL EFFECTS ARE LOST AND THE FLOW BECOMES MORE NORTHERLY... THE LAKE EFFECT SHOWERS SHOULD BECOME RESTRICTED TO THE LAKE MICHIGAN SHORELINE COUNTIES. ONE DOMINATE BAND MAY EVOLVE... ESPECIALLY IF IT CLEARS INLAND AND AND BOUNDARY LAYER DECOUPLES. THIS SCENARIO APPEARS LIKELY. AS FAR AS PCPN TYPE TONIGHT... BELIEVE IT WILL PROBABLY REMAIN RAIN OR A MIX OF RAIN AND SNOW ALONG THE LAKESHORE SOUTH OF MKG DUE TO THE LENGTHY FETCH DOWN LK MI WHICH STILL HAS WATER TEMPS IN THE LOWER TO MID 50S. STILL CAN/T RULE OUT SOME LOCAL 1-2 INCH ACCUMULATIONS IN HEAVIER BANDS THAT ARE INLAND JUST ENOUGH FROM THE LK MI WARMING EFFECTS. PAW PAW FOR EXAMPLE WOULD BE A SPOT THAT COULD POTENTIALLY SEE THIS OCCUR. BACKING FLOW AND DIURNAL COMPONENT SHOULD ALLOW LAKE EFFECT SHOWERS TO SPREAD/DEVELOP INLAND AGAIN BY MID/LATE MORNING TUESDAY. PCPN SHOULD BE MIXY AGAIN BY AFTERNOON AS SFC TEMPS WARM TO AROUND 40... EXCEPT IN HIGHER ELEVATION AREAS IN THE FAR NRN CWFA. LITTLE OR NO SNOW ACCUMULATION EXPECTED. CYCLONIC FLOW WILL REMAIN ENTRENCHED OVER THE REGION TUESDAY NIGHT AND NW WINDS MAY ACTUALLY INCREASE AS DEEPENING LOW PRESSURE SYSTEM LIFTS NNW ACROSS NEW ENGLAND. WE SHOULD SEE A CONTINUATION OF LAKE EFFECT SNOW (OR MIXED RAIN AND SNOW SHOWERS)... AND THE STRONGER FLOW MAY KEEP THEM GOING INLAND MOST OF THE NIGHT. NO ACCUMS EXPECTED ATTM. DRIER AIR ARRIVES WEDNESDAY AND THE H8 THERMAL TROUGH BEGINS TO LIFT OUT. THUS A DECREASING CLOUD PATTERN IS EXPECTED ALONG WITH SLIGHTLY WARMER HIGH TEMPS. && .LONG TERM...(247 PM EDT MON OCT 27 2008) (THURSDAY THROUGH MONDAY) LONG WAVE RIDGING WILL BE IN CONTROL OF THE WX FOR THE STATE AT THE BEGINNING OF THE LONG TERM ON THU MORNING. STRONG RETURN FLOW WILL DEVELOP ACROSS THE AREA AS SFC RIDGE MOVES SE AND AS THE NEXT LOW BEGINS TO APPROACH THE AREA FROM THE NW. THIS RETURN FLOW WILL SEND H850 TEMPS UP INTO THE LOW TO MID TEENS C. THIS WILL ALLOW TEMPS TO MAKE A RUN AND POTENTIALLY EXCEED 60F ON THU. THIS FRONT WILL DROP SOUTH THROUGH THE AREA DURING THE AFTERNOON TO EVENING HOURS ON FRI. DEPENDING ON HOW FAST THE FRONT MOVES THROUGH...WE COULD SEE ONE MORE MILD DAY. THE FRONT CONTINUES TO LOOK LIKE IT WILL BE MOISTURE STARVED AND THE SUPPORTING UPPER WAVE IS EXPECTED TO REMAIN NORTH OF THE AREA. TEMPS WILL PLUMMET FOR SAT AS COLD AIR ADVECTS IN FROM THE NNE WITH THE HIGH REMAINING TO OUR NW. MODELS ARE INDICATING THAT IT MAY NOT BE AS COLD AS PREVIOUS RUNS HAVE SHOWN. THE RIDGE WILL MOVE ACROSS THE AREA SAT NIGHT...AND RETURN FLOW WILL SET UP FOR SUN. THIS WILL OCCUR AS AN UPPER TROUGH DIGS OVER THE WRN U.S. AND UPPER HEIGHTS WILL BUILD A BIT OVER THE EAST. MILDER AIR WILL RETURN FOR SUN...AND ESPECIALLY ON MON WITH A LOW THREAT OF PCPN. && .MARINE...(415 PM EDT MON OCT 27 2008) GALE WARNING AS BEEN ALLOWED TO EXPIRE BUT THE NW FLOW REMAIN AS HIGH AS 30 KNOTS THROUGH AT LEAST WEDNESDAY MORNING. THUS WAVES GREATER THAN 4 FEET...HAZARDOUS TO SMALL CRAFT...WILL CONTINUE. && .AVIATION...(753 PM EDT MON OCT 27 2008) AS EXPECTED THE CONVECTION HAS DISSIPATED INLAND AND CONTINUES OVER LAKE MICHIGAN AND WEST OF US-31. THE PASSAGE OF ANOTHER STRONG MID LEVEL SHORTWAVE AIDED THE CONVECTION DURING THE DAY TIME TODAY... HOWEVER AS OF 23Z STRONG DIFFERENTIAL NEGATIVE VORTICITY ADVECTION IS HEADING INTO SOUTHWEST LOWER MICHIGAN BEHIND THE DEVELOPING MID LEVEL LOW. THIS CAN BE SEEN ON THE WATER VAPOR LOOPS HEADING SOUTH ACROSS THE SOUTHERN UPPER PENINSULA AT 23Z. THE COMBINATION OF ALL OF THESE THINGS WILL RESULT IN NORTH WINDS THROUGH A DEEP LAYER. TYPICALLY THAT MEANS CLEAR SKIES INLAND OF LAKE MICHIGAN. THE ONLY PROBLEM WITH THAT IS THE LAKE EFFECT BAND OFF LAKE SUPERIOR CURRENTLY COMING ACROSS GRAND TRAVERSE BAY. AS WINDS BECOME MORE NORTHERLY OVERNIGHT CLOUDS FROM THIS BAND COULD MOVE SOUTH INTO THE US-131 AREA. I BELIEVE THE DOWN SLOPE EFFECTS WILL BE MORE THAN ENOUGH TO MITIGATE THESE CLOUDS MOVING IN (IF THEY DO IT WOULD BE AFTER MIDNIGHT). THUS I HAVE FORECAST MOSTLY CLEAR SKIES TONIGHT AT ALL BUT THE MKG TAF SITE. FOR TUESDAY...DAY TIME HEATING COMBINED WITH THE AID OF A 7000 FT INVERSION WILL STILL ALLOW FOR SHOWERS AND MOSTLY CLOUDY SKIES. IT WILL BE COLD ENOUGH FOR MOSTLY SNOW SHOWERS IN THE MID TO LATE MORNING BUT IF ANY HAPPEN THEY WOULD BE BRIEF AND LIGHT (SO I DID NOT PUT THEM IN THE TAFS). DAY TIME HEATING WOULD CHANGE THE SNOW SHOWERS TO MIXED RAIN AND SNOW BY EARLY AFTERNOON. && .HYDROLOGY...(415 PM EDT MON OCT 27 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...NONE. LM...SMALL CRAFT ADVISORY IN EFFECT THROUGH 15Z WED FROM ST. JOSEPH TO MANISTEE. && $$ SYNOPSIS: MEADE SHORT TERM: MEADE LONG TERM: NJJ MARINE: MEADE AVIATION: WDM HYDROLOGY: MEADE