RSS FeedsIssued by NWS Cheyenne, WY
000 FXUS65 KCYS 242039 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 139 PM MST TUE NOV 24 2009 .SHORT TERM...TONIGHT THROUGH THANKSGIVING DAY... MID AND HIGH CLOUDS WILL SPREAD SE ACROSS MUCH OF THE CWA THIS EVENING AS CLIPPER TYPE SYSTEM DROPS QUICKLY OUT OF SOUTHERN CANADA ACROSS THE NORTHERN PLAINS TONIGHT. THIS SYSTEM WILL PUSH A COOL FRONT ACROSS THE EASTERN PLAINS OF WY AND THE NEB PANHANDLE TONIGHT BEFORE THE FRONT RETREATS BACK EAST WEDS AFTERNOON. SHALLOW LOW LEVEL MOISTURE EXPECTED BEHIND THIS FRONT ALONG WITH SOME WEAK LIFT WILL GENERATE LOW CLOUDINESS. SOME SNOW SHOWERS AND FLURRIES ALSO EXPECTED FOR A SHORT TIME LATER TONIGHT FROM EAST CENTRAL WY INTO THE NORTHEAST HALF OF THE PANHANDLE. CLEARING CONDITIONS EXPECTED WEDS AFTERNOON AS UPPER SYSTEM MOVES AWAY AND DRIER AIR SPREADS BACK OVER THE CWA. WARMER AND DRY WEATHER THEN SET UP FOR THANKSGIVING DAY AS UPPER RIDGE MOVES OVER THE REGION. .LONG TERM...THURSDAY NIGHT THROUGH MONDAY NIGHT...MAINTAINED CONTINUITY WITH PREVIOUS FORECAST AND TRENDED THE LONG TERM FORECAST TOWARD THE 12Z ECMWF SOLUTION. 12Z GFS AND GEM ARE NOT TOO FAR OFF THOUGH. UPPER LEVEL RIDGE WILL BE OVERHEAD THURSDAY NIGHT AND WILL SHIFT EAST DURING THE DAY FRIDAY AS AN UPPER TROUGH MOVES INTO THE WESTERN US. AT THE SFC...A LEE TROUGH WILL DEEPEN IN RESPONSE TO THE APPROACHING UPPER TROUGH THUS WILL SEE THE SFC PRESSURE GRADIENT STRENGTHEN AND WESTERLY WINDS INCREASE IN THE TYPICAL WINDY LOCALES. ATMOSPHERE LOOKS QUITE DRY SO WILL KEEP DRY CONDITIONS IN THE FORECAST. EXPECT FRIDAY TO BE A FEW DEGREES WARMER THAN THURSDAY WITH UPPER 30S AND 40S OVER THE WEST...WITH LOW 50S TO LOW 60S IN THE EAST. BROAD SURFACE CYCLOGENESIS WILL OCCUR ACROSS THE NORTHERN PLAINS LATE FRIDAY INTO SATURDAY AS THE TROUGH MOVES ACROSS THE ROCKIES. A COLD FRONT ASSOCIATED WITH THE LOW WILL MOVE THROUGH THE EASTERN ZONES BY EARLY SATURDAY MORNING. SFC HIGH PRESSURE WILL QUICKLY BUILD OVER THE AREA BRINGING COOLER TEMPS AND GUSTY NORTHWEST WINDS ACROSS MUCH OF THE CWA FOR SATURDAY. MODELS DURING THIS TIME ARE BEGINNING TO SHOW SIGNS OF AGREEMENT WITH THE TIMING AND INTENSITY OF THE TROUGH ALTHOUGH NOT COMPLETELY. ECMWF STILL MAINTAINS A CLOSED CIRCULATION AT 500 MB OVER THE SOUTHWEST CONNECTED TO ANOTHER CLOSED LOW OVER SOUTHERN CANADA ALTHOUGH IS WEAKER THAN ITS PREVIOUS RUN. GFS SHOWS A DEEP TROUGH EXTENDING ACROSS THE CENTRAL US AND IS MORE PROGRESSIVE THAN THE ECMWF...WITH THE CANADIAN A COMBINATION OF THE TWO. SO WITH THESE TIMING DIFFERENCES IN MIND...WILL SEE THE POTENTIAL FOR LIGHT PRECIPITATION SATURDAY AND SATURDAY NIGHT BEHIND THE FRONT IN UPSLOPE FLOW. WITH THE SLOWER MOVEMENT OF THE ECMWF...COULD SEE SHOWERS LINGER THROUGH THE EARLY PART OF SUNDAY. IN GENERAL...PRECIP TYPE WILL BE SNOW EXCEPT FOR AREAS BELOW 5000 FT WHICH WILL BEGIN AS RAIN OR A MIX OF RAIN AND SNOW ON SATURDAY BEFORE TURNING TO SNOW. THE UPPER TROUGH WILL MOVE OFF TO THE EAST SUNDAY NIGHT AND HIGH PRESSURE WILL BUILD ALOFT. FAST NORTHWEST FLOW WILL MOVE OVERHEAD MONDAY SO WILL BE A RETURN TO DRY AND WINDY WEATHER FOR THE BEGINNING OF NEXT WEEK. && .AVIATION...VFR CONDITIONS EXPECTED THROUGH THIS EVENING. SFC COLD FRONT WILL PASS OVER EARN WY AND THE NEB PANHANDLE TONIGHT WITH MVFR/LOCAL IFR CONDITIONS DEVELOPING OVER THAT AREA MAINLY DUE TO LOW CIGS. SCTD SNOW SHOWERS EXPECTED MAINLY OVER THE EAST CENTRAL WYOMING AND THE NORTHERN PANHANDLE LATER TONIGHT INTO EARLY WEDNESDAY MORNING. CONDITIONS IMPVG WEDS LATE MORNING AND AFTERNOON WITH VFR BY WEDS EVENING. && .FIRE WEATHER...NO CONCERNS EXPECTED THROUGH THURSDAY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ SHORT TERM/AVIATION...RE LONG TERM...RJM
