FXUS65 KGJT 142026 AFDGJT WESTERN COLORADO & EASTERN UTAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 226 PM MDT MON APR 14 2003 ...WINTER WEATHER TO RETURN TO THE MOUNTAINS ON TUESDAY... CIRRUS SHIELD HAS FILLED IN ACROSS MUCH OF THE CWFA EARLY THIS AFTERNOON AHEAD OF 115+ KT JET MOVING INTO THE SOUTHWEST US. AS A RESULT...WINDS HAVE BEEN SLOW TO DEVELOP AND TEMPERATURES WERE RUNNING 3 TO 5 DEGREES COOLER THAN YESTERDAY. TONIGHT: MODELS IN VERY GOOD AGREEMENT WITH APPROACHING PACIFIC SYSTEM DRIFTING ACROSS THE WESTERN GREAT BASIN DURING THE NIGHT. BOTH MODELS SHOW DRY SLOT THIS EVENING ACROSS SOUTHEAST UTAH AND EXTREME WESTERN COLORADO AND THEREFORE...LEFT DRY FORECAST IN PLACE FOR THE EVENING PERIOD. LATER TONIGHT RIDGE AXIS TILTS TO THE NEGATIVE OVER SOUTHWEST UTAH ALLOWING SOME MID-LEVEL MOISTURE TO MOVE NORTH INTO THE SAN JUAN MOUNTAINS AND POINTS WEST. GIVEN DRYNESS OF THE LOWEST LEVELS OF THE ATMOSPHERE...BELIEVE IT WILL TAKE SOME TIME TO MOISTEN THE COLUMN SUFFICIENTLY FOR GREATER THAN CHANCE POPS. AS SUCH...LEFT POP FORECAST PRETTY MUCH ALONE FOR LATE TONIGHT. TUESDAY: TOMORROW LOOKS VERY ACTIVE AS UPPER LEVEL TROF AXIS SHIFTS INTO EASTERN UTAH DURING THE MORNING THEN PUSHES EAST OF THE DIVIDE BY EARLY EVENING. THE COLD FRONT ASSOCIATED WITH THIS SYSTEM MAKES RAPID PROGRESS ACROSS THE CWFA DURING THE DAY MOVING FROM EASTERN UTAH AT 12Z THEN FROM A DRO-RIL-CAG LINE BY MIDDAY...THEN EAST OF THE AREA BY 00Z. CAA BEHIND THE FRONT WILL LOWER SNOW LEVELS RAPIDLY TO NEAR 7500'. SOUTHWEST MOUNTAINS LOOK TO BE THE FOCUS OF SIGNIFICANT SNOWFALL DURING THE DAY WITH CYCLONICALLY CURVED 100+ KT JET MOVING JUST SOUTH OF THE AREA. DYNAMICS WILL BE WORKING ON AN AIRMASS SUBJECTED TO STRONG SOUTHWEST FLOW (25-35 KTS) AND LI'S AT OR BELOW ZERO. CONSEQUENTLY...DECIDED TO ISSUE THE WINTER WEATHER ADVISORY FOR THE SOUTHERN MOUNTAINS OF THE CWFA ABOVE 8000 FEET WITH UP TO 12 INCHES OF NEW SNOW POSSIBLE IN THE SAN JUANS BY DAYS END. MEANWHILE...NORTHERN ZONES LIKELY TO SEE LESS SNOW AS DYNAMICS NOT AS IMPRESSIVE. HOWEVER...AS COLD CORE MOVES OVERHEAD INSTABILITY SHOWERS WILL INCREASE BECOMING NUMEROUS DURING THE AFTERNOON WITH ACCUMULATIONS IN THE MOUNTAINS. LOWER ELEVATIONS CAN EXPECT SCATTERED TO NUMEROUS RAIN SHOWERS...MIXED WITH OR CHANGING OVER TO SNOW IN THE HIGH VALLEYS. GOING TEMPERATURE FORECAST SEEMED TO SPLIT THE DIFFERENCE BETWEEN THE MAV AND MET MOS PRODUCTS. TIMING OF THE FRONT WILL BE CRUCIAL TO HIGHS SO DIDN'T ADJUST FORECAST MUCH. TUESDAY NIGHT: MOIST UNSTABLE AIRMASS REMAINS DURING THE EVENING... THOUGH FLOW BEGINS TO FAVOR THE NORTHERN MOUNTAINS. ETA INDICATES SOME DECENT ACCUMULATIONS OVERNIGHT DESPITE DECREASING LAPSE RATES. THIS WILL PROBABLY WORK OUT OK SO WENT WITH NEAR ADVISORY SNOW AMOUNTS FROM THE AFTERNOON THROUGH THE NIGHT FOR THOSE AREAS. LATER SHIFTS WILL NEED TO MONITOR THESE AREAS CLOSELY FOR POSSIBLE EXPANSION OF THE WINTER WEATHER ADVISORY. ELSEWHERE...CONTINUED WITH LOW POPS IN THE EVENING FOR THE WESTERN ZONES...ENDING OVERNIGHT AS STABILIZATION OCCURS OVER THOSE AREAS. TEMPERATURE FORECAST IN SAME BALLPARK AS MOS SO LEFT THEM ALONE. NL WEDNESDAY...DRIER CONDITIONS FOR WED DUE TO SHORTWAVE RIDGING. WARMING TREND BEGINS ON WED WITH HIGHS REACHING AROUND NORMAL READINGS. THURSDAY-SATURDAY...12Z SIMILAR TO 06Z GFS AND QUITE A BIT FASTER THAN 00Z RUN WITH NEXT TROUGH ON THU NIGHT/FRI. HOWEVER WILL NOT SPEED UP THE FORECAST YET AS EC/NOGAPS SLOWER STILL. IN ANY CASE LOOKS LIKE INCREASING WINDS/CLOUDS THU AFTERNOON WITH A SLIGHT CHANCE OVER THE NORTHEAST. THEN ACTIVITY SPREADING AREA-WIDE THU NIGHT WITH BEST FORCING/INSTABILITY FRI AFTERNOON. STRONGER WINDS PRECEDE THE MOISTURE LATE THU...THEN DIMINISH AS IT DEEPENS. SO OROGRAPHIC COMPONENT NOT GREAT. IF THE SLOWER SOLUTIONS VERIFY CHANCE POPS REMAIN THROUGH SAT. WILL BACK OFF POPS ON SAT NIGHT...HOWEVER WILL WAIT FOR BETTER AGREEMENT ON TIMING TO DO OTHER CHANGES. SUNDAY-MONDAY: SHORTWAVE RIDGE MOVES OVER THE AREA LATE SUN FOR DRIER/WARMER CONDITIONS SUN AND MON. NEXT PACIFIC TROUGH DIGS ALONG THE WEST COAST ON MON. HEFFERNAN GJT...WINTER WEATHER ADVISORY IN EFFECT TUESDAY FOR THE SOUTHERN MOUNTAINS INCLUDING COZ017...018...019 AND UTZ028.