Issued by NWS Grand Junction, CO
000 FXUS65 KGJT 212138 AFDGJT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 338 PM MDT TUE OCT 21 2008 .SHORT TERM...TONIGHT THROUGH THURSDAY... AN UPPER LEVEL TROUGH IS MOVING ACROSS THE NORTHERN ROCKIES THIS AFTERNOON WHILE AN ASSOCIATED COLD FRONT PUSHES SOUTHEAST ACROSS THE FORECAST AREA. THE FRONT HAS PROGRESSED TO ABOUT CRAIG AND THEN DRAPES WEST INTO NORTHEAST AND EAST CENTRAL UTAH AS OF 3 PM. A PERIOD OF STRONG GUSTY WINDS CAN BE EXPECTED WITH FRONTAL PASSAGE... ESPECIALLY PRIOR TO SUNSET. A STRONG UPPER LEVEL JET BEHIND THE FRONT WILL DRIVE IT TO THE FOUR CORNERS AREA EARLY THIS EVENING WITH STRONG COLD AIR ADVECTION BEHIND IT. LINES OF CONVECTIVE SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ALONG AND AHEAD OF THE FRONT OVER NORTHWEST COLORADO AND THE CENTRAL MOUNTAINS. PRECIPITATION WILL CONTINUE TO BE CONCENTRATED OVER THESE AREAS LATE THIS AFTERNOON AND TONIGHT...ESPECIALLY OVER THE MOUNTAINS AS COLD AIR ADVECTION IN NORTHWEST FLOW SQUEEZES OUT AVAILABLE MOISTURE. EXPECTING 1 TO 4 INCH SNOW ACCUMULATIONS BY WEDNESDAY MORNING WITH SOME LOCAL AMOUNTS OF 5 TO 6 POSSIBLE ACROSS THE HIGHER PEAKS AND NORTHWEST ASPECTS OF THE MOUNTAINS TOWARD THE CONTINENTAL DIVIDE. CROSS SECTIONS SHOW POST FRONTAL LOW LEVEL MOISTURE IN PLACE OVER NORTHWEST COLORADO THROUGH MUCH OF TONIGHT SO BOOSTED CLOUD COVER AND RAISED MIN TEMPERATURES A FEW NOTCHES FOR SOME OF THE CENTRAL AND NORTH OF WESTERN COLORADO FOR LACK OF A RADIATIONAL COOLING COMPONENT. THE TROUGH WILL MOVE OVER THE PLAINS WEDNESDAY WITH ISOLATED SNOW SHOWERS LINGERING NEAR THE CONTINENTAL DIVIDE IN NORTH NORTHWEST FLOW. MUCH COOLER WEDNESDAY WITH MINUS 8 TO MINUS 11 CELSIUS 700MB TEMPERATURES PROGGED ACROSS THE CENTRAL AND NORTH IN THE MORNING. HIGH PRESSURE WILL BUILD INTO THE AREA WEDNESDAY AND THURSDAY WITH DRY CONDITIONS PREVAILING. COLD OVERNIGHT MIN TEMPERATURES WEDNESDAY NIGHT AND COOL DAYTIME TEMPERATURES THURSDAY. .LONG TERM...THURSDAY NIGHT THROUGH TUESDAY... UPPER LOW SPINNING OVER KS SLOWLY STARTS TO MOVE EAST THURSDAY NIGHT AND FRIDAY. UPPER LEVEL WINDS REMAIN NORTH OVERNIGHT AND THEN TRANSITION TO NORTHWEST FRIDAY INTO SATURDAY. THE DRY NORTHWESTERLY FLOW CONTINUES THROUGH THE BEGINNING OF NEXT WEEK. NIGHTTIME TEMPERATURES WILL BE SLOW TO INCREASE WITH DAYTIME TEMPS SLOWLY INCREASING TO NEAR AND SLIGHTLY ABOVE NORMAL THIS WEEKEND. RIDGE BUILDS OVER THE WESTERN USA WITH OUR CWA ON THE EASTERN SIDE OF THE RIDGE. GFS IS HINTING IN A WEAK DISTURBANCE MOVING UNDER THE RIDGE AND NEAR THE FOUR CORNERS REGION EARLY NEXT WEEK ALTHOUGH THERE IS LITTLE MOISTURE TO WORK WITH. KEPT THE DRY CURRENT FORECAST TREND. && .AVIATION... MVFR TO IFR CIGS AND VIS WILL OCCUR IN SCATTERED SHOWERS EAST OF A LINE FROM ASPEN TO GLENWOOD SPRINGS TO CRAIG LATE THIS AFTERNOON WITH AREAS OF MVFR TO IFR CONDITIONS OVER THE HIGHER MOUNTAINS NEAR THE CONTINENTAL DIVIDE. ISOLATED THUNDERSTORMS UNTIL ABOUT 00Z THIS EVENING. AREAS OF MVFR TO IFR CIGS AND VIS IN SNOW AND SNOW SHOWERS WILL CONTINUE OVER THE MOUNTAINS THROUGH TONIGHT GENERALLY EAST OF A LINE FROM GUNNISON TO RIFLE TO CRAIG. IMPROVING CONDITIONS AFTER DAYBREAK WEDNESDAY BUT STILL A FEW SHOWERS AND LOCALIZED MVFR CIGS NEAR THE CONTINENTAL DIVIDE. OUTSIDE OF THESE AREAS VFR WILL PREVAIL TONIGHT AND WEDNESDAY. SEE SHORT TERM DISCUSSION FOR PROGRESSION OF COLD FRONT ACROSS THE AREA. && .GJT WATCHES...WARNINGS...ADVISORIES... .CO...NONE. .UT...NONE. $$ SHORT TERM.....TAL LONG TERM......AS AVIATION.......TGJT
