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000 FXUS63 KDMX 210534 AFDDMX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 1135 PM CST FRI NOV 20 2009 .UPDATE... VISIBILITIES DROPPING FAIRLY QUICKLY THROUGHOUT THE EVENING HOURS WITH MANY SITES IN THE 1 TO 3 MILE RANGE AND A FEW ALREADY BELOW A MILE. THEREFORE WITH LINGERING MOISTURE IN THE BOUNDARY LAYER...LIGHT WINDS AND CLEAR SKIES EXPECT ANOTHER NIGHT WITH DENSE FOG DEVELOPMENT. THEREFORE HAVE ISSUED A DENSE FOG ADVISORY FOR AREA WHERE SFC DEWPOINTS REMAIN HIGHER AND VSBYS HAVE BEEN DROPPING THE MOST SO FAR. .SHORT TERM /TONIGHT/... LOW LEVEL MOISTURE HAS REMAINED IN A NARROW AXIS ACROSS THE EASTERN TWO-THIRDS OF THE CWA TODAY. THIS HAS PRODUCED SCATTERED TO BROKEN CU AND AREAS OF HAZE AS WELL. AS WE HEAD INTO TONIGHT...WL SEE WEAK RIDGING PERSIST ACRS THE AREAS...ALTHOUGH THE HIGH WL BE PUSHING TO THE EAST OF THE STATE BY MORNING. WITH LOW LEVEL MOISTURE REMAINING AND RELATIVELY CLEAR SKIES...IT APPEARS FOG IS LIKELY TO DEVELOP ACRS THE CWA ONCE AGAIN...ESPECIALLY IN THOSE LOCATIONS WHERE HAZE IS CURRENTLY ONGOING. HAVE INCLUDED FOG AFTER MIDNIGHT FOR THE SOUTHEAST TWO-THIRDS OR SO OF THE CWA WHERE MOST FAVORABLE CONDITIONS WILL EXIST. IT IS LIKELY THAT SOME AREAS OF DENSE FOG WILL FORM AND WOULD NOT BE SURPRISED TO SEE SOME SORT OF ADVISORY ISSUED OVERNIGHT AS LOCATIONS DROP. .LONG TERM /SATURDAY THROUGH FRIDAY/...EXTENDED MODELS STARTING TO SHOW SIGNS OF COMING TOGETHER FOR NEXT WEEK FROM MONDAY INTO THURSDAY. GFS IS STILL A BIT FASTER THAN THE ECMWF...BUT BOTH HAVE A VERY ACTIVE AND COLDER PATTERN THROUGH THE MIDDLE OF THE WEEK NEXT WEEK. THE MAIN TROUGH OF LOW PRESSURE IS PROGGED TO MOVE INTO THE REGION BY MONDAY NIGHT...WITH A WEAK SHORTWAVE QUICKLY MOVING ACROSS THE CWA OUT AHEAD THIS SYSTEM DURING THE DAY SUNDAY. 12Z ECMWF HAS SLOWED THE TROUGH DOWN EVEN FURTHER FROM PREVIOUS RUNS...PUTTING THE BEST CHANCES TUESDAY NIGHT INTO WEDNESDAY...WITH 12Z GFS HINTING ON TWO SEPARATE SYSTEMS MONDAY INTO WEDNESDAY. THE LATEST ECMWF SEEMS MORE REALISTIC AND LEANED MORE TOWARDS THAT SOLUTION DURING THE EXTENDED. SATURDAY AND SUNDAY...WEAK RIDGE MOVES IN OVER THE AREA ON SATURDAY AND SHOULD PROVIDE A SLIGHT WARM UP WITH SOME WEAK WAA AT THE SURFACE. TWEAK TEMPS UP A BIT ACROSS THE SOUTH FOR HIGHS TOMORROW. INCREASING CLOUDS BY 00Z SUNDAY WITH BUFR SOUNDINGS BECOMING SATURATED AHEAD OF WEAK SHORTWAVE EXPECTED BY SUNDAY. KEPT WITH MENTION OF DRIZZLE OVERNIGHT SATURDAY INTO SUNDAY AND WITH CHANCE POPS DURING THE DAY SUNDAY. WENT DRY SUNDAY NIGHT FOR THE MAJORITY OF THE CWA. MONDAY THROUGH WEDNESDAY....TIMING AND PRECIP TYPE WILL BE MAIN FORECAST ISSUES WITH THE TROUGH OF LOW PRESSURE ENTERING THE REGION MONDAY INTO TUESDAY. GFS BUFR AND ECMWF SOUNDINGS HAVE TEMPS ABOVE FREEZING BELOW 850MB DURING THE TIME FRAME...AND WENT WITH RAIN THROUGH TUESDAY. HAVE MENTIONED OF SNOW/RAIN TUESDAY NIGHT WITH COLDER TEMPERATURES BEGINNING TO FILTER INTO THE CWA. THURSDAY AND FRIDAY...GFS/ECMWF DEPICTING A DECENT RIDGE BUILDING INTO THE REGION BY THANKSGIVING AND DOMINATING INTO NEXT WEEKEND. SO...AS OF RIGHT NOW...LOOKING A DRY AND COOL HOLIDAY PERIOD. && .AVIATION... VSBYS CONTINUE TO DROP ACROSS THE EASTERN HALF OF THE CWA WHERE NEAR SURFACE LAYER MOISTURE REMAINS HIGHER. THEREFORE STILL ANTICIPATE FOG DEVELOPMENT...WITH WIDESPREAD IFR/LIFR VSBYS/CIGS TONIGHT INTO SATURDAY MORNING. AS WINDS PICK UP OUT OF THE SOUTH AHEAD OF THE NEXT SYSTEM...INCREASING MOISTURE WILL LEAD TO LOW STRATUS/DRIZZLE DEVELOPMENT ACROSS THE AREA FOR SATURDAY NIGHT. && .DMX WATCHES/WARNINGS/ADVISORIES... DENSE FOG ADVISORY UNTIL 10 AM CST SATURDAY FOR ADAIR-ADAMS- APPANOOSE-BLACK HAWK-BOONE-BREMER-BUTLER-CERRO GORDO-CLARKE- DALLAS-DAVIS-DECATUR-FRANKLIN-GRUNDY-HAMILTON-HANCOCK-HARDIN- JASPER-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK- POWESHIEK-RINGGOLD-STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN- WAYNE-WINNEBAGO-WORTH-WRIGHT. && $$ UPDATE...BEERENDS SHORT TERM...COGIL LONG TERM...PODRAZIK AVIATION...BEERENDS
