377 FXUS65 KCYS 051104 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 404 AM MST TUE MAR 5 2013 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT... NORTHERN PLAINS STORM SYSTEM CONTINUES TO PRODUCE GUSTY WINDS OVER THE PANHANDLE EARLY THIS MORNING. WINDS WERE STILL GUSTING AS HIGH AS 35 MPH IN THAT AREA. THOSE WINDS WILL CONTINUE TO DIMINISH THROUGH THE MORNING HOURS. WARMING AND DRY WEATHER WILL THEN AFFECT THE CWA THROUGH 12Z THURSDAY. THE RIDGE ALOFT WILL MOVE OVER THE CWA BETWEEN 06Z AND 12Z WEDNESDAY AND THEN CONTINUE TO MOVE EAST AND OVER THE PLAINS. A SURFACE TROUGH WILL DEVELOP OVER EASTERN WYOMING TONIGHT AND THEN PROGRESS SLOWLY EAST THROUGH 12Z THURSDAY. MID AND HIGH LEVEL CLOUDS WILL INCREASE OVER THE CWA WEDNESDAY AND THURSDAY IN THE SOUTHWEST FLOW ALOFT BEHIND THE RIDGE AXIS. WILL KEEP LOW POPS OVER AND NEAR THE SNOWY AND SIERRA MADRE RANGES WEDNESDAY NIGHT...OTHERWISE THE CWA SHOULD REMAIN DRY. THE WINDIER AREA FOR THIS AFTERNOON THROUGH 12Z THURSDAY WILL SHIFT TO AREAS ALONG AND WEST OF THE LARAMIE RANGE. MOST OF THAT TIME THE GUSTS WILL BE BETWEEN 25 AND 35 MPH. THE SURFACE PRESSURE GRADIENT TIGHTENS OVER THE CWA ON WEDNESDAY AND WILL PRODUCE GUSTS AS HIGH AS 45 MPH IN SOME AREAS ALONG AND WEST OF THE LARAMIE RANGE. TEMPERATURES WARM QUITE A BIT TODAY FROM THOSE OF MONDAY AND WILL BE JUST BELOW NORMAL. THEN THE 700 MB THERMAL RIDGE AXIS WILL BE OVER THE CWA ON WEDNESDAY AND WILL HELP TO RETURN TEMPERATURES TO ABOVE NORMAL WITH HIGHS IN THE 50S EAST OF THE LARAMIE RANGE. .LONG TERM...THURSDAY THROUGH MONDAY. THURSDAY...SOUTHWEST FLOW ALOFT PREVAILS WITH OUR COUNTIES IN THE WARM SECTOR AS RESULTANT SURFACE LEE TROUGHING DEVELOPS FROM EASTERN WYOMING SOUTHWARD THROUGH EASTERN COLORADO. MAXIMUM TEMPERATURES SOARING WELL INTO THE 50S AND LOWER 60S EAST OF I-25...SOME 10 TO 15 DEGREES ABOVE NORMAL. FRIDAY...FLOW ALOFT BACKS TO SOUTH SOUTHWEST...INDUCING SURFACE LOW PRESSURE TO DEVELOP OVER EAST CENTRAL COLORADO AND PRODUCING NORTH NORTHEAST UPSLOPE OVER OUR COUNTIES...THUS COOLER. LOW AND MID LEVEL MOISTURE INCREASES ON THE GFS AND ECMWF OVER OUR WESTERN COUNTIES...THUS INCREASING CHANCES FOR RAIN AND SNOW IN THE AFTERNOON MAINLY WEST OF INTERSTATE 25. SATURDAY...COLDER AIR POURS SOUTHWARD ACROSS OUR COUNTIES EARLY IN THE DAY. 05/06Z GFS NOW IN BETTER AGREEMENT WITH THE CONSISTENT ECMWF DEPICTION AND THE 05/00Z ECMWF AND 05/06Z GFS SHOWING CLOSING OFF UPPER LOW OVER NORTHERN ARIZONA WITH SURFACE CYCLOGENESIS OVER SOUTHEAST COLORADO BY SATURDAY MORNING. OUR INHERITED SNOW CHANCES LOOK GOOD AND HAVE RAISED THEM SLIGHTLY FROM LARAMIE TO SIDNEY AS CONFIDENCE INCREASES IN THE ECMWF SOLUTION WHICH HAS BEEN QUITE CONSISTENT THE PAST FEW DAYS...AND SINCE THE ECMWF SOLUTION HAS TENDED TO DO BETTER THAN THE GFS THE PAST FEW WINTERS AND DURING PROGRESSIVE PATTERNS. BY LATE SATURDAY AFTERNOON...THE 05/00Z ECMWF TRACKS THE DEEP UPPER LOW OVER CENTRAL COLORADO AND THE 05/06Z GFS IS SIMILAR THOUGH MORE DISORGANIZED WITH THE TROUGH. WE STILL LEAN TOWARDS THE MORE CONSISTENT ECMWF SOLUTION...AS DOES THE LONG RANGE DISCUSSION FROM HPC...THUS HAVE CONTINUED OUR TRENDS AND BOOSTED SNOW CHANCES TO THE 60 TO 80 PERCENT RANGE OVER MOST OF OUR SOUTHEAST HALF OF OUR COUNTIES. IF THE ECMWF SOLUTION VERIFIES...OR EVEN CLOSE...WE WILL SEE A WIDESPREAD HEAVY SNOWFALL EVENT OVER MOST OF OUR AREA. SUNDAY...THE ECMWF CONTINUES TO STALL THE DEEP CLOSED UPPER LOW OVER NORTHEAST COLORADO WHILE THE 05/06Z GFS OPENS UP THE TROUGH TRACKING IT OVER THE SOUTHERN PLAINS STATES. FROM YEARS OF EXPERIENCE...TIME OF YEAR CONSIDERATIONS WITH MARCH AND APRIL BEING OUR SNOWIEST MONTHS AND SINCE THE ECMWF HAS ALMOST ALWAYS OUTPERFORMED THE GFS IN THE WINTER AND SPRING MONTHS...CONTINUE TO LEAN TOWARDS THE ECMWF. THUS...HAVE CONTINUED OUR RELATIVE HIGH POPS FOR SNOW AND BOOSTED EVEN SLIGHTLY MORE BASED ON THE LATEST ECMWF TRENDS. MONDAY...SLOW MOVING CLOSED LOW ALOFT FINALLY TRACKS OVER CENTRAL KANSAS ACCORDING TO THE ECMWF...THUS DRYING TREND ACROSS OUR COUNTIES. CURRENT FORECASTED HIGH TEMPERATURES WILL NEED TO BE LOWERED IF INDEED THE ECMWF VERIFIES WITH A DEEP SNOWPACK AND HIGH ALBEDO. && .AVIATION...12Z TAF ISSUANCE... VFR CONDITIONS WILL CONTINUE OVER THE CWA THROUGH AT LEAST WEDNESDAY AND LIKELY THROUGH THURSDAY NIGHT. CLOUDS WILL INCREASE OVER THE REGION STARTING ON WEDNESDAY WITH CLOUD BASES GRADUALLY LOWERING THROUGH THE WEEKEND. CLOUDS WILL BE MID AND HIGH LEVEL THROUGH THURSDAY OVER THE CWA. MVFR CEILINGS AND VISIBILITIES IN SNOW WILL AFFECT THE CWA FRIDAY NIGHT...WITH IFR CONDITIONS QUITE POSSIBLE OVER THE WEEKEND. NORTHWEST SURFACE WINDS WILL GUST AS HIGH AS 30 KNOTS OVER THE NEBRASKA PANHANDLE THROUGH 15Z. THEN WESTERLY SURFACE WINDS WILL GUST AS 30 KNOTS THIS AFTERNOON AND TONIGHT IN AREAS ALONG AND WEST OF THE LARAMIE RANGE. STRONGER WINDS...WITH GUSTS TO 40 KNOTS WILL BE POSSIBLE ON WEDNESDAY OVER THAT SAME AREA. && .FIRE WEATHER...WARMING AND DRY WEATHER WILL AFFECT THE CWA THROUGH THURSDAY. NORTHWEST WINDS WILL GUST AS HIGH AS 35 MPH OVER THE NEBRASKA PANHANDLE THROUGH MID MORNING. THEN THE AREA OF THE STRONGER WINDS WILL SHIFT TO THE AREAS ALONG AND WEST OF THE LARAMIE RANGE THROUGH THURSDAY. IN MOST TIMES...THE WINDS WILL GUST AS HIGH AS 35 MPH IN THAT AREA. HOWEVER...STRONGER WINDS ARE EXPECTED FOR WEDNESDAY WITH GUSTS TO 45 MPH. THE MINIMUM RELATIVE HUMIDITY VALUES WILL BE BETWEEN 20 AND 30 PERCENT OVER THE LOWER ELEVATIONS TODAY THROUGH THURSDAY. A STORM SYSTEM WILL BRING COOLER TEMPERATURES AND SNOW TO THE REGION FRIDAY NIGHT THROUGH SUNDAY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ SHORT TERM/AVIATION/FIRE WEATHER...WEILAND LONG TERM...RUBIN