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000 FXUS63 KGRR 250506 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1155 PM EST TUE NOV 24 2009 LATEST UPDATE...AVIATION... .SYNOPSIS...(421 PM EST TUE NOV 24 2009) AN AREA OF LOW PRESSURE WILL SWING THROUGH THE GREAT LAKES REGION OVER THE NEXT COUPLE DAYS...PUSHING A BAND OF RAIN INTO THE AREA THIS EVENING. THE RAIN WILL PERSIST INTO WEDNESDAY MORNING...TAPERING OFF SOME THOUGH INTO THE AFTERNOON. RAIN SHOWERS WILL CONTINUE INTO WEDNESDAY NIGHT AS SOME LAKE ENHANCEMENT OFF OF LAKE MICHIGAN OCCURS. THE AIR WILL BE COLD ENOUGH FROM LATE WEDNESDAY NIGHT INTO FRIDAY WHERE SOME SNOW MAY MIX IN AT TIMES. WE ARE NOT EXPECTING ANY SIGNIFICANT ACCUMULATION OF SNOW WITH THIS SYSTEM. TRAVEL CONCERNS OVER THE WEEKEND SHOULD BE MINIMAL AS SATURDAY IS EXPECTED TO BE DRY AND ONLY A CHANCE OF RAIN ON SUNDAY. && .SHORT TERM...(421 PM EST TUE NOV 24 2009) (TONIGHT THROUGH THURSDAY NIGHT) CONCERNS IN THE SHORT TERM REVOLVE AROUND THE SYSTEM LIFTING TOWARD THE FORECAST AREA FROM IOWA. PRECIPITATION CHANCES AND TYPE ARE THE MAIN ISSUES. THE MOST CONCENTRATED AREA OF PRECIPITATION WITH THE SYSTEM WILL COME TONIGHT WITH A BAND OF RAIN THAT WILL PUSH THROUGH THE ENTIRE FORECAST AREA. A RUMBLE OF THUNDER IS NOT OUT OF THE REALM OF POSSIBILITIES...BUT NOT EXPECTING A WIDESPREAD BAND OF STORMS MOVING THROUGH THE FORECAST AREA. AT THIS POINT LEFT THUNDER OUT OF THE FORECAST. LIGHTNING DATA SHOWS STORMS DWINDLING ACROSS ILLINOIS. ONLY A FEW STRIKES REMAIN OUT IN IOWA RIGHT NEAR THE LOW. SHOWERS WILL CONTINUE INTO WEDNESDAY...AS THE UPPER TROUGH WILL BE OVERHEAD AND A LAKE ENHANCEMENT BEGINS TO TAKE SHAPE AS DELTA T/S INCREASE TO AROUND 10 DEGREES C. WEDNESDAY NIGHT DELTA T/S INCREASE INTO THE LOWER TEENS C...WHICH WILL MAKE THE PRECIPITATION A COMBINATION OF LAKE EFFECT AND SYSTEM RELATED SHOWERS. THE RAIN DURING THE EVENING WILL TRY TO MIX WITH SOME SNOW LATE...ESPECIALLY IN THE SOUTHWEST WHERE THE COLD AIR WRAPS IN FIRST. A MIX OF RAIN AND SNOW SHOWERS LOOK REASONABLE THANKSGIVING AND THANKSGIVING NIGHT. MAIN ISSUE WITH SNOW IS THE FACT THAT THE DGZ IS UNSATURATED AT TIMES. SO...ENVISION SOME LAKE EFFECT RAIN SHOWERS AND DRIZZLE...WHICH WILL MIX WITH SNOW AT TIMES IN THE MORE CONVECTIVE SHOWERS AND BANDS. MOST CONCERNED ABOUT THANKSGIVING EVENING AS THE FLOW GOES NORTHWEST PRODUCING A LONG FETCH DOWN THE LAKE. THIS BAND WILL HAVE THE POTENTIAL TO PRODUCE SOME LIGHT ACCUMULATING SNOW AWAY FROM THE LAKE IN ALLEGAN AND VAN BUREN COUNTIES. && .LONG TERM...(421 PM EST TUE NOV 24 2009) (FRIDAY THROUGH TUESDAY) BIGGEST CONCERN IN THE LONG TERM IS DETERMINING PCPN CHANCES FROM SUN THROUGH TUE AS A COLD FRONT MOVES TOWARD THE AREA AND A UPPER SYSTEM WINDS UP OVER THE SW PORTION OF THE COUNTRY. MODELS HAVE PRETTY MUCH SETTLED ON DRIVING THE THANKSGIVING UPPER LOW OUT OF THE AREA FRI NIGHT. THIS WILL BRING DRY CONDITIONS BACK OVER THE AREA...AND TEMPS ALOFT WILL BEGIN THE PROCESS OF MODERATING. CAN NOT RULE OUT MOISTURE GETTING TRAPPED UNDER DEVELOPING SUBSIDENCE INVERSION...BUT WE SHOULD NOT SEE ANY LAKE EFFECT WITH LIMITED DELTA T/S. NEXT COLD FRONT IS POISED TO MOVE IN ON SUN AS A NORTHERN STREAM TROUGH MOVES ALONG THE U.S./CANADIAN BORDER. THIS COLD FRONT WILL NOT HAVE A LOT OF MOISTURE TO WORK WITH INITIALLY...BUT ENOUGH WILL BE THERE TO JUSTIFY THE GOING CHC FOR SUN. THE CONFIDENCE LEVEL DIMINISHES THEN FOR THE MON...AND ESPECIALLY TUE PERIOD. STRONG PV ANOMALY WILL DEVELOP ACROSS THE DESERT SW THIS WEEKEND. AS USUAL...MODELS ARE ALL OVER THE PLACE WITH THE STRENGTH AND TIMING OF THIS FEATURE. WE BELIEVE THE 00Z/24 EURO HAS THE RIGHT IDEA IN CLOSING THE LOW OFF OVER THE SW PORTION OF THE COUNTRY...AND EVENTUALLY EJECTING NE TOWARD THE AREA. UPPER TROUGHING WILL LINGER ON MON ALONG WITH SOME COOLER AIR...AND WILL KEEP A THREAT OF A FEW SHOWERS IN. AS THE LOW TAKES SHAPE ACROSS THE SW...RIDGING WILL BUILD OVER THE AREA AND SHOULD DRY CONDITIONS OUT FOR A DAY OR TWO TUE AND MAYBE WED. WE BELIEVE THE NEW EURO AND GFS ARE TOO QUICK IN EJECTING THIS SYSTEM OUT. && .AVIATION...(1159 PM EST TUE NOV 24 2009) THE MAIN CONCERNS WITH THE AVIATION FORECAST DEAL WITH THE POTENTIAL FOR IFR OR LOWER CONDITIONS FOR THE REST OF TONIGHT AND WEDNESDAY. ALSO ANOTHER CONCERN IS THE POSSIBILITY FOR ICING. CONDITIONS ARE LARGELY EXPECTED TO BE IFR OR LOWER THROUGH THE NIGHT INTO WED AM AS A WARM FRONT LIFTS NORTH THROUGH THE REGION. SOUTHWEST WINDS WILL DRAW IN ABUNDANT LOW LEVEL MOISTURE...LEADING TO THE LOW CLOUDS AND RAIN. WILL NEED TO MONITOR THE POTENTIAL FOR LIFR TOWARD DAYBREAK...BUT LITTLE OR NO SUCH CONDITIONS UPSTREAM IN IL TO SUPPORT THAT SCENARIO. WEDNESDAY...WINDS WILL BE SOUTHWEST AND THAT WILL DRAW ABUNDANT LOW LEVEL MOISTURE IN THROUGHOUT THE DAY. I DID FEATURE MORE IFR CONDITIONS WITH THIS SET OF TAFS. MOISTURE AND LIFT LOOK MORE IMPRESSIVE...THUS I TRENDED CONDITIONS DOWNWARD. SUSPECT A BRIEF LIFR EVENT WILL BE POSSIBLE WED AFTERNOON AS THE COLD FRONT COMES THROUGH GIVEN ALL THE LOW LEVEL MOISTURE AROUND. BETWEEN 06Z AND 10Z THE DEEPER MOISTURE WILL BE LIFTING NORTHEAST OF THE TAF SITES. HOWEVER WITH ABUNDANT LOW LEVEL MOISTURE HANGING AROUND AFTER THAT...A LAYER OF ICING IS POSSIBLE. CURRENT PROJECTIONS HAVE THE FREEZING LEVEL FALLING FROM AROUND 5K FEET AT 06Z TO AROUND 4K FEET BY 12Z. IT THEN REMAINS SATURATED UP TO AROUND 12K FEET THROUGH 03Z THU. THIS IS THE LAYER WHERE SOME ICING MAY DEVELOP. && .MARINE...(421 PM EST TUE NOV 24 2009) WINDS AND WAVES WILL RAMP UP LATE TONIGHT AND INTO WEDNESDAY AS LOW PRESSURE TRAVERSES CENTRAL PORTIONS OF LAKE MICHIGAN. A SOUTHWEST WIND WILL RISE INTO THE 15 TO 25 KNOT RANGE WHICH WILL BUILD WAVES INTO THE 3 TO 5 FOOT RANGE ON WEDNESDAY MORNING. WINDS WILL SHIFT A BIT MORE WESTERLY WEDNESDAY NIGHT WHICH WILL KEEP WAVES AT SMALL CRAFT HEIGHTS. THE SMALL CRAFT ADVISORY WILL LIKELY NEED TO BE EXTENDED INTO THANKSGIVING AS NORTHWEST FLOW COLD AIR ADVECTION WILL LIKELY BUILD WAVE HEIGHTS FURTHER. && .HYDROLOGY...(421 PM EST TUE NOV 24 2009) STILL EXPECTING RAINFALL AMOUNTS BETWEEN 0.25 AND 0.75 OF AN INCH ACROSS THE FORECAST AREA INTO THANKSGIVING. NOT OUT OF THE REALM OF POSSIBILITIES OF SEEING A FEW HIGHER AMOUNTS ACROSS THE NORTHWEST CWA UP TOWARD LUDINGTON. RIVER LEVELS ARE WELL WITHIN BANK...SO THESE RAINFALL AMOUNTS SHOULD NOT AFFECT STAGES TOO MUCH. THE PERE MARQUETTE RIVER AT SCOTTVILLE FOR EXAMPLE IS CURRENTLY AT ABOUT 2.3 FEET. BANKFULL IS 4.0 FEET...SO WE HAVE QUITE A BIT OF BUFFER YET. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY ST. JOE TO WHITEHALL WEDNESDAY AND WEDNESDAY NIGHT. && $$ SYNOPSIS: DUKE SHORT TERM: DUKE LONG TERM: NJJ AVIATION: MJS MARINE: DUKE HYDROLOGY: DUKE
