Issued by NWS Goodland, KS
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000 FXUS63 KGLD 211056 AFDGLD AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 356 AM MST SAT NOV 21 2009 .DISCUSSION... 221 AM MST SAT NOV 21 2009 0430Z WATER VAPOR IMAGERY INDICATES SHORTWAVE RIDGING ACROSS THE CWA WITH LARGE TROUGH ACROSS THE WESTERN CONUS. AT THE SFC TROUGH AXIS WAS PRESENT ACROSS EASTERN WYOMING WITH SFC RIDGE AXIS DRAPED ACROSS SOUTHERN KANSAS. 00Z RAOBS INDICATED SOME WARMING OVER THE LAST 24 HOURS. OF SOME INTEREST IS DEEPENING MOISTURE PROFILE OBSERVED AT DDC. WITH THIS LOCATION CURRENTLY DIRECTLY UNDER SFC RIDGE COULD SEE A FAVORABLE SET UP FOR FOG EARLY THIS MORNING ACROSS EASTERN ZONES. MAIN CONCERN FOR SHORT TERM PERIOD WILL BE APPROACHING STORM SYSTEM DURING THE BEGINNING OF THE WEEK. TODAY-TONIGHT...SOME FOG/STRATUS MAY SNEAK INTO EASTERN/SOUTHEASTERN CWA AS DOWNSTREAM SOUNDINGS INDICATE AIRMASS MORE FAVORABLE FOR RADIATION FOG THAN PREVIOUS NIGHTS. WINDS WILL GENERALLY BECOME MORE SOUTHERLY ADVECTING THIS AIRMASS TOWARDS THE REGION...BUT WINDS MAY OFFSET ANY RADIATIONAL COOLING COMPONENT. FOR NOW PLAN TO WAIT UNTIL FORECAST ISSUANCE AND USE OBSERVATIONAL TRENDS TO DETERMINE FOG THREAT. OTHERWISE LARGE SCALE FORCING FOR ASCENT WILL OVERSPREAD THE AREA LATE THIS AFTERNOON AND INTO THE EVENING. AS HAS BEEN THE CASE WITH THE PAST SEVERAL MODEL RUNS...FAIRLY STRONG FORCING OVERSPREADS THE AREA OVERNIGHT WITH LARGE SCALE AND FRONTOGENETIC FORCING PEAKING OVERNIGHT...BUT THERE DOES NOT APPEAR TO BE ANY QUALITY MOISTURE RETURN AHEAD OF THIS SYSTEM...WHICH BASED ON CURRENT WV IMAGERY LOOKS LIKELY. WITH LARGE T-TD SPREADS IT WOULD BE UNLIKELY THAT ANY LEVEL COULD BE SATURATED AND ANY INSTABILITY BE REALIZED...SO KEEPING CURRENT DRY FORECAST LOOKS LIKE THE WAY TO GO. OTHERWISE EXPECT A LARGE GRADIENT IN WINDS TODAY WITH RELATIVELY LIGHT WINDS IN THE WEST...AND SUSTAINED WINDS 15-20KTS IN EASTERN CWA BEFORE COLD FRONT MOVES ACROSS THE AREA OVERNIGHT. SUNDAY-SUNDAY NIGHT...FIRST OF A SERIES OF SHORT WAVE TROUGHS WILL DEPART THE AREA DURING THE MORNING HOURS BRINGING A BRIEF BREAK TO THE CLOUDS. SHORT RANGE MODELS SEEM TO STALL FRONTAL ZONE ALONG/JUST EAST OF THE CWA DURING THE MORNING HOURS BRINGING STRATUS...AND POINT SOUNDINGS SUGGEST FG/-DZ POSSIBLE ALONG AND IMMEDIATELY BEHIND FRONTAL ZONES. IS GOING TO TAKE A LOT OF MOISTURE ADVECTION FOR THIS TO DEVELOP...BUT LOWER 40 TDS NOT TO FAR FROM THE CWA SO THIS SCENARIO NOT TOTALLY UNREASONABLE. OTHERWISE EXPECT HIGH CLOUDS TO ONCE AGAIN OVERSPREAD THE AREA BY THE AFTERNOON AS NEXT STRONG SHORT WAVE TROUGH APPROACHES. INCREASED MOISTURE ADVECTION WILL ALSO LIMIT HOW COLD THINGS WILL GET IN EASTERN CWA WHICH IS HANDLED WELL BY GOING FORECAST. MONDAY-TUESDAY...MOST IMPORTANT AND UNFORTUNATELY MOST UNCERTAIN FORECAST PERIOD WILL BRING THE POTENTIAL FOR YET ANOTHER WINTER STORM TO IMPACT THE AREA. MODELS STILL SPREAD OUT IN TO NUMEROUS DIFFERENT CAMPS WITH THIS STORM. 12Z ECMWF CONTINUES TO SUGGEST H5/SFC LOW STRENGTHENING AND OCCLUDING OVER KANSAS...WHILE GFS CONTINUES TO HOLD ONTO MORE NORTHERLY AND PROGRESSIVE SOLUTION. THE 00Z ECMWF HAS CONTINUED TO HOLD ONTO THE STRENGTH AND SPEED OF THE SYSTEM...BUT HAS TRANSITIONED CONSIDERABLY FARTHER NORTH. LOOKING AT OTHER AVAILABLE MODELS...THE UKMET APPEARS TO BE A MUCH SLOWER VERSION OF THE GFS...WHILE THE NAM AND CANADIAN APPEAR TO BE DEEPER AND SOMEWHAT SLOWER VERSIONS OF THE GFS. THIS SPREAD IN SOLUTIONS MAKE THE FORECAST VERY DIFFICULT AS DIFFERENCES ARE NOT SIMPLY THINGS LIKE TIMING AND TRACK...BUT OVERALL EVOLUTION OF THE SYSTEM. FURTHER COMPLICATING THINGS ARE SREF AND GFS ENSEMBLES. WHILE THE GEFS HAS 3 MEMBERS (OUT OF 20) THAT SUGGEST A MUCH MORE SOUTHERLY AND SLOWER SYSTEM...21Z SREF DATA FIRMLY IN MORE PROGRESSIVE/WEAKER CAMP WITH MEAN ACTUALLY SHOWING LITTLE SPREAD IN H5 SOLUTION UNTIL SYSTEM GETS OVER MISSOURI. 12Z/00Z CANADIAN MEAN KIND OF LEANING THIS DIRECTION AS WELL. THE ECMWF AND UKMET HAVE BEEN THE MOST STABLE WITH THERE SOLUTION...BUT IT IS HARD TO ARGUE WITH THE AVAILABLE ENSEMBLE DATA WHICH PERFORMED FAIRLY WELL THE LAST TWO SNOWSTORMS. FOR ALL THE REASONS LISTED ABOVE...CONFIDENCE IN ANY PARTICULAR SET OF MODEL SOLUTIONS REMAINS LOW ALTHOUGH SOME SORT OF COMPROMISE BETWEEN AN ECMWF AND NAM SOLUTION WOULD BE A REASONABLE STARTING POINT AS IT WOULD INCORPORATE MORE OF A WORST CASE SCENARIO WHILE STILL PUTTING A BIT MORE WEIGHT ON RECENT ENSEMBLE DATA. CANNOT GET TOO EXCITED TO MUCH ABOUT THINGS LIKE TROWALS AND POTENTIAL INSTABILITY WHEN THE CONFIDENCE OF A CLOSED LOW EVEN BEING THERE IS LOW. DESPITE THE UNCERTAINTY...THERE DOES LOOK TO BE A WINDOW WHERE ACCUMULATING SNOW IS POSSIBLE LATE MONDAY AFTERNOON AND OVERNIGHT TUESDAY. WHILE AMOUNTS MAY DIFFER BETWEEN THE MODELS...ALL AGREE THAT STRONG NORTHWESTERLY WINDS WILL DEVELOP BEHIND THE LOW CREATING A BLOWING SNOW PROBLEM IF ANYTHING FALLS. WHILE ENSEMBLE DATA WOULD SUPPORT A MUCH DRIER FORECAST AM GOING TO TRY TO MAINTAIN PREVIOUS FORECAST AS SYSTEM NOT EVEN ON SHORE AT THIS TIME. WILL UP POPS SLIGHTLY WHERE MODELS GENERALLY AGREE CHANCES ARE BEST ON MONDAY AND MONDAY NIGHT. JRM && .AVIATION... 356 AM MST SAT NOV 21 2009 FOR THE 12Z TAFS...A RIDGE OF HIGH PRESSURE AND SUBSIDENCE WILL KEEP KGLD AND KMCK IN VFR CONDITIONS DURING THIS TAF PERIOD. FOG PRODUCT SATELLITE INDICATING SOME STRATUS AND FOG ADVECTING NORTH OVER CENTRAL AND EASTERN KANSAS BUT LATEST TRENDS INDICATE IT SHOULD STAY EAST OF THE TAF SITES. THERE IS SOME POTENTIAL AGAIN SUNDAY MORNING IN THE EAST BUT TIME HEIGHT CROSS SECTIONS INDICATE A LACK OF LOW LEVEL RH. SOUTH WINDS INCREASE TO BREEZY CATEGORY TODAY IN RESPONSE TO A SURFACE TROUGH IN EASTERN COLORADO. EXPECT WIND TO SUBSIDE DUE TO DECOUPLING AROUND SUNSET. A WEAK COLD FRONT IS PROGGED TO SHIFT WIND TO THE NORTH EARLY SUNDAY MORNING. FS && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$
