RSS FeedsIssued by NWS Cheyenne, WY
000 FXUS65 KCYS 220350 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 850 PM MST SAT NOV 21 2009 .UPDATE...MINOR GRIDDED FORECAST CHANGES FOR THE REST OF THE NIGHT FOR SOME MODIFICATIONS TO TEMPERATURES...DEWPOINTS... WINDS...CLOUD COVER AND SNOWFALL COVERAGE. RUBIN && .PREV DISCUSSION... /ISSUED 346 PM MST SAT NOV 21 2009/ SHORT TERM...TONIGHT THROUGH MONDAY...UPPER TROUGH MOVING OUT OF UT AND EASTERN ID CURRENTLY. MODELS SEEM TO BE HANDLING IT WELL AND PROGRESS IT ACROSS WY TONIGHT TO NEAR EASTERN WY BORDER JUST AFTER 12Z SUNDAY EXITING OUR EASTERN CWA BEFORE 18Z. PACIFIC COLD FRONT HAS ADVANCED OUT OF SE WY NOW AND WILL PASS THROUGH NEBRASKA PANHANDLE NEXT COUPLE HOURS. GUSTY WINDS THAT ACCOMPANIED THE FRONT EARLIER HAVE DECREASED THROUGH AFTERNOON. THERE WILL BE LOTS OF CLOUDS OVER THE CWA TONIGHT WITH SOME SNOW SHOWERS OVER THE MOUNTAINS ACCUMULATING TO PERHAPS AN INCH OR SO. A FEW SNOW SHOWERS ARE ALSO POSSIBLE KLAR-KCYS PER GFS SO INCLUDED A LOW POP THERE AS WELL TONIGHT. IMPROVEMENT FROM WEST TO EAST BEHIND UPPER TROUGH LATE TONIGHT THEN SHORTWAVE RIDGE WILL PREVAIL OVER THE CWA SUNDAY BRINGING DRY CONDITIONS. NEXT UPPER TROUGH IN THE PROGRESSIVE UPPER AIR PATTERN WILL MOVE IN SUNDAY NIGHT... WITH A TIMING NOT ALL THAT UNLIKE THE ONE TONIGHT. DIFFERENCE IS THE LATTER UPPER TROUGH IS MUCH STRONGER WITH VEERING UPPER FLOW AND AN UPPER LOW DEVELOPS WITH IT TO OUR EAST. IT ALSO IS SLOWER TO MOVE OUT. MODELS ARE GETTING CLOSER TO A CONVERGENT SOLUTION ON THIS LATTER TROUGH BUT STILL SHOW SOME DIFFERENCES...UPPER LOW DOES NOT REALLY GET CRANKED UP UNTIL IT GETS TOO FAR EAST OF US. GFS HAS SLOWED DOWN AND ECMWF IS NOT QUITE AS DEEP AS FAST AS IT WAS ON THE 12Z FRIDAY RUN. STILL...THERE WILL BE WIND AND SNOW FOR MOST AREAS WITH THIS FEATURE AND ITS ASSOCIATED COLD FRONT...WITH A FEW INCHES FALLING IN THE MOUNTAINS. AN ADVISORY MAY END UP BEING NECESSARY FOR THE SOUTH CENTRAL WY MOUNTAINS SUNDAY NIGHT AND MONDAY MORNING WHILE A WIND ADVISORY IS LIKELY FOR THE NEBRASKA PANHANDLE MONDAY. BOTH ARE TOO EARLY FOR NOW. TEMPS WILL BE COLDER BOTH DAYS. LONG TERM...MONDAY NIGHT THROUGH SATURDAY...MODELS IN GOOD AGREEMENT EARLIER IN THE WEEK...AND THEN SHOW DIVERGING SOLUTIONS LATE IN THE WEEK AND EARLY NEXT WEEK. GFS...GEM...AND ECMWF SHOW MAINLY NORTHERLY FLOW ACROSS THE FRONT RANGE THROUGH THURSDAY AS AN UPPER LEVEL TROUGH EXITS EAST OF THE REGION ON TUESDAY...AND A BACKDOOR POLAR FRONT MOVES INTO THE HIGH PLAINS ON WEDNESDAY. THIS WILL KEEP TEMPS ON THE COLD SIDE THROUGH THE MIDDLE OF NEXT WEEK WITH MODELS HINTING AT HIGHS IN THE 30S ACROSS MOST OF THE AREA AND LOWS IN THE TEENS AND TWENTIES. DID NOT GO QUITE THAT LOW IN THE FORECAST WITH THE ECMWF SHOWING THE BULK OF THE COLDER AIR FURTHER TO THE EAST. DO NOT EXPECT MUCH PRECIP AS THE MAIN JET ENERGY WILL BE EAST OF THE AREA AND MODELS SHOW LITTLE MOISTURE WITH THE FRONT. KEPT LOW POP ACROSS THE AREA THROUGH THE WEEK WITH 20 PCT POP ACROSS THE NRN RIDGES OF THE NEBRASKA PANHANDLE AND ERN WYOMING. BY LATE IN THE WEEK...00Z GFS AND GFS ENSEMBLE SHOW AN UPPER LEVEL RIDGE DRIFTING EAST OVER THE AREA RESULTING IN WARMER TEMPS AND CLEARING SKIES. IN CONTRAST...THE ECMWF SHOWS AN UPPER LEVEL TROUGH FROM THE NRN PACIFIC PUSHING ACROSS THE NORTHWEST COAST ON FRIDAY AND INTO THE ROCKY MOUNTAIN REGION FOR NEXT SATURDAY...WITH SOME SNOW OVER THE AREA AND A CONTINUATION OF COLD TEMPS. WITH POOR MODEL AGREEMENT...LIMITED CONFIDENCE IN THE FORECAST AFTER THANKSGIVING DAY. INCREASED POP TOWARDS CLIMO FOR FRIDAY NIGHT AND NEXT SATURDAY AND KEPT TEMPS NEAR OR SLIGHTLY BELOW NORMAL NORMAL. AVIATION...MAINLY VFR CONDITIONS EXPECTED THROUGH TONIGHT WITH WESTERLY WINDS BETWEEN 15 TO 25 KTS AND GUSTS UP TO 35 KTS EARLY THIS EVENING...DIMINISHING TO 10 TO 15 KTS AFTER SUNSET. THERE IS A 10 PCT CHANCE OF MVFR CONDITIONS AND BRIEF LIGHT SNOW THIS EVENING AT KRWL...KCYS AND KLAR AS A WEAK COLD FRONT PUSHES ACROSS THE AREA TONIGHT...OTHERWISE...EXPECT CIGS TO REMAIN ABOVE 3K FEET AGL TONIGHT THROUGH TOMORROW WITH ANY SNOW MAINLY CONFINED TO THE MOUNTAINS. FIRE WEATHER...NO CONCERNS THROUGH MONDAY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ SHORT TERM/FIRE WEATHER...JLH LONG TERM/AVIATION...TJT
