Issued by NWS Duluth, MN
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000 FXUS63 KDLH 202143 CCA AFDDLH AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE DULUTH MN 316 PM CST FRI NOV 20 2009 ..CORRECTED FOR TYPO ERRORS... .DISCUSSION...A PROGRESSIVE PATTERN WITHIN THE MID LVL FLOW WILL BRING CHANGEABLE WEATHER TO THE REGION OVER THE NEXT SEVERAL DAYS. HIGH PRESSURE AT THE SFC WILL MOVE ACROSS THE CWA OVERNIGHT. SHOULD SEE FOG TONIGHT WITH HIGHEST POTENTIAL FOR WIDESPREAD AREAL COVERAGE/DURATION ACROSS NW WISC WHERE LONGER DECOUPLED BDRY LYR WILL EXIST. USED AREAS OF FOG TERMINOLOGY IN ERN CWA AND PATCHY ELSEWHERE. LATEST FCST OF 925 WINDS SUGGEST WARM ADVECTION REGIME WILL BEGIN WEST OF A CDD-DLH- HINCKLEY LINE AFTER 6Z. HOPEFULLY THIS MAY MITIGATE EXTENT OF FOG OVER WRN CWA. AS IS THE CASE WITH MOST FOG POTENTIAL FORECASTS...LATER UPDATES MAY BE NEEDED. PLEASANT DAY ACROSS THE REGION SATURDAY WITH WARM ADVECTION PATTERN AND ABOVE NORM TEMPS. 85H MSTR TRANSPORT AXIS LOCATED WEST OF CWA SATURDAY...WILL TRANSLATE EAST INTO REGION SATURDAY NIGHT/SUNDAY. EXISTING FCST HAD GOOD SOLUTION REGARDING TIMING OF LOW STRATUS CLOUD DEVELOPMENT AND POPS. DID NOT CHANGE ALIGNMENT OF POP GRADIENT SUNDAY ALTHOUGH TREND IS FOR HIGHER POPS TO BE OVER NW WISC SUNDAY AFTERNOON IN ZONE OF BEST LOW LEVEL THETAE AXIS. SFC BDRY MOVING INTO THE REGION SUNDAY GETS SOMEWHAT WASHED OUT IN THE LOW LVL WIND FIELD BUT MAINTAINS WELL DEFINED SIGNAL IN LOW LVL THERMAL FIELDS. ALTHOUGH SOME WEAK FRONTOGENESIS MAY DEVELOP LATE SUNDAY INTO MONDAY...OVERALL SYNOPTIC SCALE FORCING WILL BE LIMITED. AS A RESULT...EXPECT ABUNDANT CLOUDS BUT NOT A LOT OF PRECIPITATION MONDAY. NAM/EC/GEM FAVOR NWRN PART OF CWA FOR HIGHER POPS. .EXTENDED...MONDAY NIGHT THROUGH FRIDAY GFS AND ECMWF ARE STILL IN SIGNIFICANT DISAGREEMENT WITH THE LOW PRESSURE SYSTEM THAT WILL BE AFFECTING THE REGION THROUGH THURSDAY. WE FOLLOWED CLOSE TO THE ECMWF SOLUTION...WHICH HAS BEEN CONSISTENT...AND HAS SUPPORT FROM THE CANADIAN. THE UPPER LOW IS FORECAST TO TRACK FROM KS...NORTHEAST TOWARD IA ON WEDNESDAY...WITH A NORTHERN STREAM WAVE ALSO STRENGTHENING AS IT NEARS MB/OT. THESE UPPER WAVES WILL THEN CONTINUE EAST THURSDAY. AT THE SURFACE...LOW PRESSURE WILL ACCOMPANY THE UPPER WAVE IS IT MOVES THROUGH. THE ECMWF IS WARMER THAN THE GFS. PRECIP TYPE WILL BE AN ISSUE WITH THIS SYSTEM...ESPECIALLY DURING THE OVERNIGHT PERIODS WHEN BOUNDARY LAYER TEMPS COOL. WE WENT WITH A RAIN/SNOW MIX FOR SEVERAL OF THE PERIODS BETWEEN MONDAY NIGHT AND WEDNESDAY NIGHT. MAINLY RAIN COULD VERY WELL OCCUR IF BOUNDARY LAYER TEMPS REMAIN A BIT WARMER THAN CURRENTLY FORECAST...AND THOSE DETAILS WILL BE WORKED OUT AS THE SYSTEM NEARS. AT THIS TIME...THIS SYSTEM DOES NOT LOOK LIKE A HEAVY PRECIP MAKER. .AVIATION...18Z TAFS HIGH PRESSURE WILL CONTINUE TO DOMINATE THE WEATHER THROUGH THE PERIOD. FOG AND SOME STRATUS WILL BE POSSIBLE AGAIN OVERNIGHT...BUT INCREASING WINDS JUST ABOVE THE SURFACE MAY KEEP THE FOG FROM BECOMING TOO WIDESPREAD AND DENSE TONIGHT. WE DID INCLUDE FOG AND STRATUS IN ALL THE TAF SITES...EITHER AS A PREDOMINATE ELEMENT...OR AS A TEMPORARY CONDITION. A STRONGER PRESSURE GRADIENT WILL EXIST ON SATURDAY...SO THE FOG WILL BURN OFF QUICKER THAN IT DID TODAY. && .POINT TEMPS/POPS... DLH 27 49 36 48 / 0 0 20 40 INL 23 48 33 45 / 0 0 20 20 BRD 26 52 36 47 / 0 0 20 30 HYR 23 51 40 48 / 0 0 20 30 ASX 26 52 39 49 / 0 0 20 30 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. && $$ CANNON/MELDE