Issued by NWS Duluth, MN
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000 FXUS63 KDLH 222346 AFDDLH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 546 PM CST SUN NOV 22 2009 .AVIATION...00Z TAFS. COMPLEX WEATHER CIGS/VSBYS ACROSS THE FA THIS EVENING. VFR AT KINL AND KHYR...WHICH WILL CONTINUE UNTIL 04-06Z WHEN -DZ/BR REDUCE VSBYS AND CIGS TO MVFR WITH ISOLD IFR. BOTH LOCATIONS BECOME IFR/LIFR AS LOW CLOUDS/-DZ/BR PERSIST AFTER 06Z. KDLH/KHIB/KBRD WILL BE IFR THROUGH THE TAF PERIOD WITH INSTANCES OF LIFR IN -DZ/BR/FG. && .PREV DISCUSSION... /ISSUED 246 PM CST SUN NOV 22 2009/ DISCUSSION...TONIGHT THROUGH WEDNESDAY MODELS IN AGREEMENT WITH SHARPENING THE LOW LEVEL TROUGH OVER OUR CWA TONIGHT. UPPER WAVE IS FORECAST TO MOVE FROM THE NORTHERN ROCKIES...SOUTHEAST INTO NE/KS BY 00Z TUE...THEN EAST INTO IL BY 12Z WED. THE MODELS HAVE MADE SOME RUN TO RUN CHANGES...BUT OVERALL THE FORECAST IS SIMILAR TO WHAT YESTERDAYS RUNS SHOWED. RAIN WAS MOVING OVER PINE/BURNETT COUNTIES THIS AFTERNOON...NORTHEAST INTO THE TWIN PORTS. THIS WAS OCCURRING IN AN AREA OF LOW LEVEL FGEN AND ISENTROPIC LIFT. WE HAVE HIGHEST POPS OVER THAT AREA TONIGHT. WE ISSUED A DENSE FOG ADVISORY EARLIER THIS AFTERNOON...AND VSBYS HAVE COME UP IN SPOTS...BUT KCKC WAS REPORTING LESS THAN A QUARTER MILE. WEAK ONSHORE FLOW...AND PLENTY OF LOW LEVEL MOISTURE WILL BE SUPPORTIVE OF FOG TONIGHT...AND WE`LL KEEP THE ADVISORY GOING. FOG WILL BE MOST DENSE IN THE HIGHER TERRAIN JUST INLAND FROM LAKE SUPERIOR. CLOUDS WILL REMAIN OVER CENTRAL AND EASTERN CWA...BUT A PORTION OF THE WEST-NORTHWEST WILL BE CLEAR TO PARTLY CLOUDY FOR A PORTION OF THE NIGHT. TEMPERATURES WILL NOT FALL MUCH...EXCEPT IN THE W-NW. AS THE UPPER WAVE MOVES INTO KS/NE ON MONDAY...THE INVERTED TROUGH WILL ROTATE BACK TO THE WEST...AND WE SHIFTED HIGHER POPS OVER OUR WESTERN ZONES. CLOUDS MAY DIMINISH OVER A PORTION OF NORTHWEST WISCONSIN...BUT WE KEPT THEM MOSTLY CLOUDY AT THIS TIME. AS THE UPPER LOW DEEPENS MONDAY NIGHT INTO TUESDAY...SURFACE LOW PRESSURE WILL DEVELOP/DEEPEN IN SOUTHERN IA. THERE WILL BE A CONTINUED CHANCE FOR RAIN...WITH RAIN LIKELY OVER OUR WEST NEAR THE WEAKENING TROUGH. A STRONG NORTHERN STREAM WAVE WILL DIVE INTO THE AREA TUESDAY NIGHT/WEDNESDAY. LOW PRESSURE AT THE SURFACE WILL TRACK INTO THE LAKE MICHIGAN AREA. WE KEPT A MENTION OF JUST RAIN TUESDAY EVENING...THEN MIXED IN SNOW FROM WEST TO EAST LATE TUESDAY NIGHT INTO WEDNESDAY. WE HAVE CHANCE POPS ON WEDNESDAY AT THIS TIME...BUT THEY MAY HAVE TO BE INCREASED WITH LATER FORECASTS. SNOW ACCUMULATIONS LOOK LIGHT TUESDAY NIGHT INTO WEDNESDAY. EXTENDED...THURSDAY THROUGH SUNDAY ADJUSTED POPS FURTHER WEST AND INCREASED FOR MOST AREAS WED NIGHT/THURS AS MDLS CONTINUE TO SUPPORT A SLOWER TREND IN EJECTING THE MID LVL LOW OVER THE ERN GRT LKS FRI. UPR LVL RIDING WILL PUSH E OVER THE UPR MIDWEST OVER THE WEEKEND AS ANOTHER TROUGH CROSSES THE ROCKIES AND MOVES INTO THE NORTHLAND LATE IN THE WEEKEND/EARLY NEXT WEEK. MAIN FCST CHALLENGE IN EXTENDED IS PTYPE AND CHANGE OVER TIMING WED/THURS AS THE LOW TRACKS TO THE SE OF THE FA AND CANADIAN AIR FILTERS INTO THE REGION. THE 12Z GFS/ECM IN GOOD AGREEMENT THAT CORE OF COLDEST 850 MB TEMPS /-8C/ FUNNEL SWRD OVER THE DAKOTAS/SW MN ALONG THE MAIN VORT/JET MAX WED WHILE 850 TEMPS IN THE NEGATIVE 2-5 C RANGE SPREAD OVER THE DLH FA BY THURS. HOWEVER...CROSS SECTIONS FROM THE GFS/ECM AT KIWD/KHYR/KPBH DEPICT A SHALLOW LAYER SFC-900 MB THAT REMAINS A FEW DEGREES ABV FZING THROUGH 12Z THURS. IN ADDITION...THE GFS BUFKIT AT KIWD/HYR SHOWS RAIN FOR MOST OF THE NIGHT AND HOLD OFF CHANGING TO SN UNTIL 08Z-12Z THURS WITH A BRIEF PERIOD OF IP POSSIBLE. ATTM...LEFT PTYPE AS ALL SN WED NIGHT DUE TO THE UNCERTAINTY IN TIMING THE PHASE CHANGE. HOWEVER...THERE REMAINS A POSSIBILITY FOR THE RA/SN MIX TO CONTINUE THROUGH WED EVENING. LATER SHIFTS MAY NEED TO CARRY THE RA/SN MIX INTO WED NIGHT FOR THE S SHORE AND NRN WIS ZONES. AVIATION...18Z TAF ISSUANCE WDSPRD IFR/LIFR CONDITIONS WITH FG/DZ WILL PERSIST THROUGH TAF PERIOD. THE EXCEPTION WILL BE ALONG AND WEST OF TROUGH SITUATED FROM KINL TO KSAZ/KBRD. THE KINL AREA WILL REMAIN VFR THROUGH THE NIGHT...FALLING IFR MON MORNING. THE KBRD AREA MAY HAVE A FEW HR PERIOD THIS EVENING WITH MVFR CIGS AND SCT LOW CLOUDS...BUT IFR RESTRICTIONS AND BR/FG WILL AGAIN PREVAIL AFT 06Z. && .POINT TEMPS/POPS... DLH 44 47 39 41 / 60 60 40 40 INL 24 43 35 42 / 10 60 60 40 BRD 40 49 40 46 / 30 50 70 40 HYR 43 50 40 46 / 50 20 10 30 ASX 45 49 40 46 / 50 20 10 30 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...DENSE FOG ADVISORY UNTIL 3 PM CST MONDAY FOR MNZ012-020-021-037. WI...DENSE FOG ADVISORY UNTIL 3 PM CST MONDAY FOR WIZ001. LS...NONE. && $$ GSF/GSF/GSF
