000 FXUS63 KDLH 231928 AAB AFDDLH AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DULUTH MN 128 PM CST MON NOV 23 2009 .AVIATION...18Z TAF ISSUANCE... KINL/KHIB/KDLH UNDER IFR CEILINGS AS MOIST SOUTHERLY FLOW OF AIR CONTINUES INTO REGION AHEAD OF SLOW MOVING FRONTAL BDRY/INVERTED SFC PRESSURE TROUGH. COND PRESS DEFICITS FCST SUGGESTS WHATEVER LIFTING OF CEILING OCCURS THIS AFTERNOON WILL BE TEMPORARY AS STRATUS LAYER BUILDS DOWNWARD AGAIN THIS EVENING. KDLH TRICKY AS VLIFR HAS JUST IMPROVED TO LIFR AND MAY EVEN REACH IFR FOR A FEW HOURS THIS AFTERNOON BEFORE CEILINGS LOWER AGAIN. BR/FG EXPECTED TO REDEVELOP TONIGHT AT MOST TERMINALS AS MOIST BDRY LYR COOLS OVERNIGHT. ELONGATED SFC PRESS TROUGH WITH WINDSHIFT TO W/NW WILL ENTER INL/BRD TERMINALS BY 18Z WITH SOME IMPROVEMENT && .PREV DISCUSSION... /ISSUED 1055 AM CST MON NOV 23 2009/ UPDATE...HAVE UPDATED TO EXTEND THE DURATION OF THE DENSE FOG ADVISORY THROUGH 10 AM TUESDAY. WHILE RAIN AND DAYTIME HEATING IS EXPECTED TO BRING AN IMPROVEMENT IN THE DENSE FOG FOR THE AFTERNOON...WE EXPECT THE DENSE FOG TO QUICKLY RE-ESTABLISH ITSELF DURING THE EARLY PART OF THE EVENING. CONDITIONS SHOULD THEN IMPROVE ON TUESDAY. RATHER THAN CANCEL THE ADVISORY AND THEN REISSUE...WE DECIDED TO NOT AN IMPROVING TREND FOR A TIME...BEFORE CONDITIONS DETERIORATE ONCE AGAIN EARLY THIS EVENING. FEEL FAIRLY STRONGLY THAT DENSE FOG WILL AGAIN BE A PROBLEM TONIGHT...AND THE DENSE FOG REPORTED LAST NIGHT WAS VERY HAZARDOUS...WITH VIRTUALLY NO DRIVING VISIBILITY. AS A RESULT...WE WILL EXTEND THE ADVISORY THROUGH 10 AM TUESDAY. ELSEWHERE...WE SHOULD SEE A DECREASE IN RAIN FROM SE TO NW ACROSS NW WI. MUCH OF NE MN SHOULD SEE RAIN CONTINUING...IF NOT DECREASING IN AREAL COVERAGE TO SOME EXTENT. PREV DISCUSSION... /ISSUED 642 AM CST MON NOV 23 2009/ AVIATION.../12Z TAF ISSUANCE/ AREAS OF LIGHT RAIN WILL AFFECT MUCH OF THE FORECAST AREA THROUGH TONIGHT. SOME OF THE FOG THIS MORNING AND AGAIN TONIGHT MAY BE DENSE...ALTHOUGH GUIDANCE HAS HAD A DIFFICULT TIME IN FORECASTING THE ONSET AND END OF THE DENSE FOG. THEREFORE CONFIDENCE IS LOW WRT TO LIFR VSBYS. CIGS WILL ALSO VARY FROM LIFR TO VFR TODAY THROUGH TONIGHT. PREV DISCUSSION... /ISSUED 358 AM CST MON NOV 23 2009/ DISCUSSION... EAST-WEST BANDS OF LOW LEVEL WARM ADVECTION...ASSOCIATED WITH A DISSIPATED SURFACE TROUGH...ARE SPREADING NORTH ACROSS OUR AREA. AT THIS TIME...BANDS ARE ASSOCIATED WITH LIGHT RAIN AND FOG FORMATION MORE RAPID THAN RAIN CAN RINSE OUT. BETWEEN BANDS... COMPENSATORY LOW LEVEL DOWNWARD MOTION BRIEFLY EXPOSES A MID DECK AND CAUSES TEMPORARY IMPROVEMENT. A BAND NOW ALONG OUR SOUTHERN EDGE IS INCREASING IN WIDTH AND MOISTURE AS IT SPREADS NORTH. LOW PRESSURE OVER THE CENTRAL/SOUTHERN PLAINS WILL ESTABLISH AN INVERTED TROUGH NORTHWARD ALONG OR IMMEDIATELY EAST OF THE RED RIVER VALLEY BY NOON TODAY. A WEAK BUT DIGGING TROUGH ALOFT WILL ANCHOR THE INVERTED TROUGH ALONG OUR WESTERN EDGE THROUGH TONIGHT AND TUESDAY. WE ANTICIPATE FOG AND LIGHT RAIN TO CONTINUE...WITH THE BACK EDGE NOT APT TO REACH OUR WESTERN AREAS EITHER TONIGHT OR TUESDAY. AGAIN...CONTINUED WARM ADVECTION ALONG AND EAST OF THE INVERTED TROUGH WILL KEEP THE COLUMN UNSEASONABLY WARM. EXTENDED...TUESDAY NIGHT THRU SUNDAY. THE MEDIUM RANGE MODELS SHOW A COMPLEX SCENARIO SETTING UP FOR THE BEGINNING OF THE EXTENDED FORECAST PERIOD...WITH TWO DISTINCT SHORTWAVE TROUGHS AFFECTING OUR CWA. A SRN WAVE LOCATED OVER THE CENTRAL MIDWEST WILL BRING RAIN TO OUR SRN ZONES TUESDAY NIGHT AND WEDNESDAY...WHILE A STRONGER SYSTEM DIGS SEWD OUT OF CANADA...BRINGING A CHANCE OF RAIN AND SNOW TO OUR NRN ZONES. THE MODELS SHOW THAT THESE TWO WAVES WILL EVENTUALLY MERGE OVER THE GREAT LAKES REGION ON WEDNESDAY AND WEDNESDAY NIGHT. LIFT ASSOCIATED WITH THESE SYSTEMS WILL PROVIDE LIFT WHICH WILL TAP AMPLE MOISTURE...CONTINUING THE CHANCE OF PRECIP ACROSS OUR ENTIRE CWA...WITH THE BEST CHANCE FOR PRECIP ACROSS OUR ERN ZONES. DURING THIS TIME FRAME...THE RAIN WILL MIX WITH SNOW...AND EVENTUALLY CHANGE TO ALL SNOW WEDNESDAY NIGHT AS COLDER AIR ADVECTS SOUTH FROM CANADA ON THE WEST SIDE OF THE NOW DEPARTING LOW. A WEAKER ELONGATED VORTMAX WILL FOLLOW AND AFFECT THE NORTHLAND ON THURSDAY...CONTINUING THE CHANCE OF SNOW SHOWERS ACROSS THE ERN HALF OF OUR CWA. THE SNOW WILL END FOR MOST LOCATIONS THURSDAY NIGHT...EXCEPT ACROSS THE SNOWBELT OF NWRN WI WHERE LAKE EFFECT SNOW SHOWERS MAY LINGER. HIGH PRESSURE WILL MOVE OVER THE WRN GREAT LAKES BY FRIDAY...RESULTING IN DRIER CONDITIONS. ATTM...NEXT WEEKEND APPEARS DRY...ALTHOUGH THE ECMWF DOES SHOW ANOTHER SHORTWAVE DIGGING SEWD OUT OF CANADA AND OVER THE UPPER MIDWEST. HOWEVER MOST OF THE PRECIP ASSOCIATED WITH THIS DISTURBANCE SHOULDNT AFFECT THE FCST AREA UNTIL SUNDAY AND SUNDAY NIGHT. && .POINT TEMPS/POPS... DLH 41 46 33 38 / 50 50 40 70 INL 38 43 31 35 / 70 50 40 60 BRD 39 46 32 36 / 70 40 40 60 HYR 41 48 35 39 / 20 50 50 70 ASX 41 47 38 41 / 20 40 50 70 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...DENSE FOG ADVISORY UNTIL 10 AM CST TUESDAY FOR MNZ012-019>021- 026-037. WI...DENSE FOG ADVISORY UNTIL 10 AM CST TUESDAY FOR WIZ001. LS...NONE. && $$ 06/CANNON/CANNON