Issued by NWS Grand Junction, CO
000 FXUS65 KGJT 211100 AFDGJT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 400 AM MST SAT NOV 21 2009 .SHORT TERM...TODAY THROUGH SUNDAY NIGHT... THE FIRST IN A SERIES OF WAVES HAS MOVED OVER THE FORECAST AREA EARLY THIS MORNING...AND WILL CONTINUE TO BRING NOTHING MORE THAN AN INCREASE IN CLOUDS THROUGH TODAY. ENERGY/MOISTURE ASSOCIATED WITH THIS IMPULSE WILL MAINLY STAY TO OUR NORTH. THE NEXT WAVE WILL BE JUST A LITTLE STRONGER AND AGAIN STAY MAINLY TO OUR NORTH. HOWEVER... THIS IMPULSE IS JUST A LITTLE STRONGER AND COLDER. ALONG WITH THE INCREASED CLOUDS...THE CHANCE OF SNOW WILL DEVELOP OVER THE NORTHERN MOUNTAINS THIS EVENING...MAINLY NEAR THE CONTINENTAL DIVIDE. THE PATTERN WILL REMAIN PROGRESSIVE THROUGH THE SHORT TERM PERIOD WITH A FAST MOVING RIDGE SWEEPING BY ON SUNDAY. THEN LATE SUNDAY THE LAST AND STRONGEST SHORTWAVE OF THE SERIES WILL MOVE INTO THE AREA. AGAIN THE MAIN FOCUS OF THIS SYSTEM WILL STAY TO OUR NORTH. BUT ENOUGH ENERGY WILL DIP INTO OUR FORECAST AREA FOR THE CHANCE OF SNOW TO SPREAD ACROSS ALL THE COLORADO MOUNTAINS AND INTO THE NORTHERN VALLEYS. THE BEST TIMING IS FOR SUNDAY EVENING AS AN ASSOCIATED SURFACE COLD FRONT SWEEPS ACROSS THE FORECAST AREA. THE PREVIOUS FORECAST ON THE RIGHT TRACK SO MADE ONLY MINOR CHANGES FOR THIS PACKAGE. TEMPS WILL REMAIN QUITE SEASONABLE FOR THIS TIME OF YEAR. DAYTIME TEMPS WILL DROP A FEW DEGREES AS CLOUDS INHIBIT MUCH OF A WARM UP... THOUGH NIGHTS WILL BE SLIGHTLY WARMER ALSO BECAUSE OF BETTER CLOUD COVER. .LONG TERM...MONDAY THROUGH FRIDAY... MONDAY...NORTHWEST FLOW BEHIND DEPARTING TROUGH SHOULD BRING SOME OROGRAPHIC SNOW TO THE NORTHERN DIVIDE MOUNTAINS. COLD ADVECTION APPEARS WEAK WITH THE COLD POCKET STAYING NORTH OF COLORADO... THEREFORE THE AIR MASS MAY STAY SOMEWHAT STABLE DESPITE NW FLOW. THIS WOULD LIMIT SNOW PRODUCTION AND THE MODELS SEEM TO AGREE AS QPF OVER THE NRN DIVIDE MOUNTAINS IS LOW AND ENDS BY BY EVENING. HIGH PRESSURE BUILDS INTO THE GREAT BASIN WITH RIDGE AXIS EXTENDING TO THE CANADIAN PLAINS. THIS WILL KEEP THE FORECAST AREA DRY THROUGH THE LONG TERM PERIOD WITH A SLOW WARMING TREND. BY FRIDAY THE GFS AND EC DIVERGE SIGNIFICANTLY WITH THE EC SHOWING A DIGGING TROUGH INTO NEVADA AND UTAH. THE GFS SOLUTION SHOWS A SHORT WAVE FLATTENING THE RIDGE BUT KEEPS THE FORECAST AREA DRY. NO CHANGES TO THE DRY FORECAST UNTIL MODELS SHOW BETTER AGREEMENT. && .AVIATION... VFR CONDITIONS WILL CONTINUE FOR THE REMAINDER OF TODAY AND INTO TONIGHT. RIDGETOP WINDS WILL INCREASE SOMEWHAT DURING THE AFTERNOON AND EVENING ESPECIALLY OVER NE UTAH AND NORTHWEST COLORADO. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...NONE. UT...NONE. && $$ SHORT TERM.....EH LONG TERM......PF AVIATION.......TGJT
