Issued by NWS Gaylord, MI
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000 FXUS63 KAPX 212301 AFDAPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 600 PM EST SAT NOV 21 2009 .SYNOPSIS.../ISSUED AT 401 PM/ HIGH PRESSURE...WILL MAINTAIN ITS INFLUENCE OVER THE REGIONS WEATHER THROUGH MONDAY...AS IT MOVES FROM THE OHIO VALLEY...ACROSS NEW ENGLAND...AND INTO THE CANADIAN MARITIME PROVINCES. PATCHY FOG WILL DEVELOP AGAIN TONIGHT...AND COULD BE BRIEFLY DENSE IN A COUPLE SPOTS. SUNDAY AND MONDAY WILL BE SIMILAR...WITH PATCHY MORNING FOG GRADUALLY GIVING WAY TO SUNSHINE. THE NEXT CHANCE OF RAIN WILL BE TUESDAY...AS A STORM SYSTEM LIFTS INTO THE UPPER MIDWEST. TEMPERATURES WILL TURN COLDER BEHIND THIS SYSTEM. SOME PRECIPITATION WILL LINGER INTO WEDNESDAY AND THURSDAY...AND IT COULD TURN WINTRY THANKSGIVING DAY. ADAM && .SHORT TERM.../ISSUED AT 401 PM/...TONIGHT LARGE AREA OF HIGH PRESSURE CURRENTLY PARKED ACROSS THE EASTERN CONUS/GREAT LAKES THIS AFTERNOON. WAS A SLOW PROCESS...BUT MID NOVEMBER SUNSHINE WAS ABLE TO MIX OUT SHALLOW LOW STRATUS ACROSS NRN LOWER MICHIGAN...ALLOWING TEMPS TO REACH THE 50S. EASTERN UPPER MICHIGAN NOT SO LUCKY AS SHALLOW STRATUS (LIKELY HELPED BY WEAK FLOW OFF LAKE MICHIGAN) STILL LINGERS THERE...WITH TEMPS ONLY IN THE MIDDLE 40S. TONIGHT...HIGH PRESSURE/LIGHT WINDS WILL CONTINUE TO DOMINATE. MAIN FORECAST ISSUES REVOLVE AROUND THE REDEVELOPMENT OF FOG/STRATUS. FAIR AMOUNT OF DRY AIR MIXING FROM ALOFT HAS KNOCKED SFC DEWPOINTS DOWN INTO THE MIDDLE 30S TO LOWER 40S THIS AFTERNOON ACROSS NRN LOWER MICHIGAN. GIVEN THAT...DON/T THINK WE WILL SEE QUITE THE WIDESPREAD STRATUS/FOG DEVELOPMENT THAT WE HAD LAST NIGHT...ALTHOUGH NOT BRAVE ENOUGH TO YANK IT COMPLETELY. SO...HAVE GONE A BIT MORE OPTIMISTIC WITH SKY COVER THIS EVENING BEFORE BRINGING SOME STRATUS BACK INTO THE PICTURE LATER OVERNIGHT TOWARD MORNING. EASTERN UPPER MICHIGAN IS A BIT MORE PROBLEMATIC AS STRATUS HAS YET TO LEAVE. BUT...MODEL RH PROGS AND LATE AFTERNOON SATELLITE IMAGERY DOES SUGGEST THAT STRATUS WILL THIN OUT TO SOME DEGREE BY THIS EVENING. WILL PLAY IT THAT WAY FOR NOW AND SEE HOW IT GOES. ADAM && .LONG TERM.../ISSUED AT 401 PM/...SUNDAY AND BEYOND OUTSIDE OF SOME FOG/STRATUS ISSUES SUNDAY/MONDAY MORNINGS...THE MAIN FORECAST ISSUES FOR THE UPCOMING WEEK WILL REVOLVE AROUND THE UPPER LEVEL ENERGY MOVING OUT OF THE CENTRAL ROCKIES AND TOWARD THE GREAT LAKES. MULTITUDE OF MODEL DIFFERENCES IN TIMING/STRENGTH OF FEATURES...WITH ABOUT A 12 HOUR SPREAD BETWEEN THE FASTER/COLDER GFS AND THE SLOWER/WARMER ECMWF. THINK THE ECMWF IS TOO SLOW GIVEN THE LACK OF BACKSIDE JET ENERGY ON THE WESTERN EDGE OF UPPER FEATURE TUE/WED AND WILL TAKE A BLENDED GFS/ECMWF SOLUTION. SUNDAY-MONDAY...VERY SIMILAR ISSUES AS FRIDAY NIGHT W/ SHALLOW /SUB-950MB/ MOISTURE...RELATIVELY WEAK LOW LEVEL FLOW AND ABUNDANT DRY AIR ALOFT. A BIT MORE RIDGING ALOFT AND MOISTURE NOT QUITE AS WIDESPREAD...SO FOG/STRATUS MAY BE A BIT PATCHIER THAN FRIDAY NIGHT. OVERALL...EXPECT AREAS OF STRATUS IN NE LOWER AND EASTERN UPPER DURING THE OVERNIGHT/EARLY MORNING HOURS. THE STRATUS WILL THIN AND BREAK UP EACH DAY...LEADING TO AT LAST PARTLY SUNNY SKIES BY MIDDAY. UPPER SYSTEM MOVES INTO THE CENTRAL PLAINS ON TUESDAY...THEN TOWARD THE WESTERN LAKES ON WEDNESDAY. EVEN WITH THE MODEL DIFFERENCES MENTIONED PREVIOUSLY...THEY ALL AGREE ON NORTHERN MICHIGAN SITTING IN THE WARM SECTOR OF THIS STORM THROUGH WEDNESDAY...RESULTING IN JUST RAIN /NO SNOW/. WILL RAISE POPS TO LIKELY FOR SOME AREAS WED/WED NIGHT GIVEN PLUME OF DEEPER 850MB THETA-E AIR SURGING NORTHWARD INTO THE AREA ALONG WITH FAVORABLE FORCING. THE RAIN MAY BEGIN TO CHANGE TO SNOW LATE WEDNESDAY NIGHT OVER WESTERN AREAS/HIGHER TERRAIN AS COLDER AIR IS DRAWN SOUTHWARD ON THE BACKSIDE OF UPPER LOW. SURFACE BASED MELT LAYERS DECREASE TOWARD 1.5K BY THANKSGIVING MORNING...WHICH IS SQUARELY ON THE RAIN/SNOW LINE. THANKSGIVING...COLD AIR ADVECTION CONTINUES AND THE RAIN WILL CHANGE TO SNOW ACROSS MUCH OF THE AREA DURING THE DAY /LAKESHORE AREAS MAY REMAIN MAINLY LIQUID/ AS UPSTREAM UPPER LEVEL ENERGY DROPS INTO THE SOUTHERN GREAT LAKES. COMBO OF IMPRESSIVE H8-H7 OMEGA AND DEEP MOISTURE FROM GAYLORD WEST TOWARD LAKE MICHIGAN...AND WILL GO WITH LIKELY POPS IN THOSE AREAS. WILL HAVE TO KEEP AN EYE ON THIS SYSTEM...AS IT HAS THE POTENTIAL TO PRODUCE A SNEAKY WINTER EVENT FOR PARTS OF THE AREA /ACCUMULATING SNOW?/. RISING UPPER HEIGHTS AND DRIER AIR ADVECTING INTO THE AREA FOR FRIDAY/SATURDAY...RESULTING IN QUIET WEATHER ONCE AGAIN AS A LOW AMPLITUDE RIDGE MOVES INTO THE GREAT LAKES. JK && .MARINE.../ISSUED AT 401 PM/ STRONG HIGH PRESSURE OVER THE GREAT LAKES/EASTERN CONUS WILL RESULT IN FAIRLY LIGHT WINDS/MINIMAL WAVES TONIGHT. AS THE HIGH NUDGES EASTWARD ON SUNDAY...STRONGER S/SW RETURN FLOW WILL DEVELOP THROUGH THE DAY. BUT WINDS/WAVES EXPECTED TO REMAIN BELOW SMALL CRAFT CRITERIA. ADAM && .AVIATION.../ISSUED AT 600 PM/...VALID FOR 00Z TAFS LOW STRATUS/IFR/LIFR CIGS EXPECTED TO REDEVELOP TONIGHT... PARTICULARLY AT APN. HOWEVER...FORECAST SOUNDINGS/SLIGHTLY DRIER AIR OVERSPREADING THE REGION SHOULD PRECLUDE WIDESPREAD DENSE FOG DEVELOPMENT. WHATEVER STRATUS/FOG DEVELOPS WILL MIX OUT AGAIN ON SUNDAY...LEAVING VFR CONDITIONS FOR MUCH OF THE DAY. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$
