Issued by NWS Cheyenne, WY
000 FXUS65 KCYS 140924 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 324 AM MDT THU MAY 14 2009 .SHORT TERM...TODAY THROUGH FRIDAY NIGHT... ZONAL FLOW WILL BE ALOFT OVER THE AREA TODAY WITH SOUTHERLY WINDS AT THE SURFACE. BOTH NAM AND GFS ARE VERY SIMILAR WITH THE FEATURES IN THE SHORT TERM. DRY CONDITIONS AND WARMER TEMPERATURES WILL OCCUR ACROSS THE ENTIRE FORECAST AREA TODAY. AN UPPER TROUGH AXIS WILL MOVE ACROSS THE CWA THIS EVENING...BUT WITH ONLY LIMITED MID LEVEL MOISTURE...EXPECT THAT IT WILL BE BENIGN. NW FLOW WILL DEVELOP ALOFT ON FRI AS AN UPPER RIDGE BUILDS ALONG THE WEST COAST AND THE UPPER TROUGH MOVES EAST. A COLD FRONT WILL ALSO MOVE ACROSS THE CWA LATE TONIGHT/EARLY FRI MORNING...WITH SURFACE WINDS BECOMING NORTH ON FRI...THEN NE TO E FRI NIGHT. LOW AND MID LEVEL MOISTURE WILL INCREASE DURING THIS TIME...ESPECIALLY EAST OF THE LARAMIE RANGE. WILL GO WITH A SLIGHT CHANCE OF SHOWERS AND AFTERNOON THUNDERSTORMS FRIDAY ACROSS THE NORTHERN ZONES. SHOWERS WILL OCCUR IN THE LARAMIE RANGE BY EVENING...THEN RAIN AND SNOW SHOWERS WILL DEVELOP OVER THE SOUTHERN ZONES LATE FRIDAY NIGHT. HIGH TEMPERATURES WILL BE FROM 3 TO 6 DEGREES ABOVE NORMAL TODAY...AND AROUND NORMAL ON FRIDAY. .LONG TERM...SATURDAY THROUGH WEDNESDAY... NORTHWEST FLOW ALOFT WILL BE OVER THE AREA WITH SLIGHTLY COOLER THAN NORMAL TEMPERATURES SATURDAY. THIS WILL BE THE RESULT OF A COLD FRONT WHICH SHOULD MOVE THROUGH LATE FRIDAY AND CREATE LIMITED MIXING CONDITIONS FOR SATURDAY. TEMPERATURES WILL NOT BE ABLE TO COOL MUCH SATURDAY DUE TO THE APPROACHING UPPER LEVEL RIDGE AND THE RESULTING WARMING THROUGH SUBSIDENCE ACROSS THE ROCKIES. THE EUROPEAN...NORTH AMERICAN AND GFS MODELS ARE IN GENERAL AGREEMENT INTO EARLY NEXT WEEK WITH REGARD TO THE EXPECTED WARMING TREND TO TEMPERATURES AROUND 15 DEGREES ABOVE NORMAL. WITH THE UPPER LEVEL RIDGE OVERHEAD...THE MODELS ARE ALSO IN AGREEMENT ON THE ABSENCE OF PRECIPITATION DURING THESE PERIODS. TUESDAY AND WEDNESDAY...THE MEDIUM RANGE FORECAST MODELS ARE SHOWING VERY LITTLE SIMILARITY WITH THE UPPER LEVEL FLOW PATTERN. THE SOLUTIONS RANGE FROM A SLIGHTLY FLATTENED UPPER LEVEL RIDGE IN THE EUROPEAN MODEL TO A DEEP AMPLIFIED TROUGH EXTENDING SOUTH ALONG THE PACIFIC COAST INTO CENTRAL CALIFORNIA BY TUESDAY. THE CANADIAN MODEL IS INDICATING SOMEWHAT OF A COMPROMISE BETWEEN THE OTHER TWO SOLUTIONS...SIMILAR TO THE LATEST GFS ENSEMBLE MEAN...WITH A WEAKER UPPER TROUGH MOVING INTO THE WESTERN UNITED STATES. GIVEN THE UNCERTAINTY... HAVE INTRODUCED NEAR CLIMATOLOGICAL SLIGHT CHANCES FOR PRECIPITATION AT THE END OF THE FORECAST PERIOD. DEPENDING ON THE SOLUTION WHICH VERIFIES AND HOW THE UPPER LEVEL TROUGH DEVELOPS AND MOVES ACROSS THE AREA...THERE WILL PROBABLY BE A COOLING TREND BACK TO NEAR NORMAL TEMPERATURES DURING THE LATTER PART OF NEXT WEEK. && .AVIATION... VFR CONDITIONS WILL PREVAIL ACROSS THE AREA THROUGH FRIDAY NIGHT. && .FIRE WEATHER... BREEZY TO WINDY CONDITIONS WILL OCCUR ACROSS THE DISTRICT TODAY...BUT WITH GREEN UP WELL UNDERWAY...DO NOT EXPECT ANY FIRE WEATHER CONCERNS. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ SHORT TERM/AVIATION/FIRE...KMD LONG TERM...CARPENTER
