Issued by NWS Cheyenne, WY
000 FXUS65 KCYS 130847 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 247 AM MDT MON OCT 13 2008 .SHORT TERM...COLUMBUS DAY THROUGH TUESDAY NIGHT. SATELLITE IMAGERY THIS MORNING SHOWS THE EXTREMELY AMPLIFIED UPPER LEVEL TROUGH CONTINUING TO BE LOCATED FROM EASTERN MONTANA SOUTHWEST TO SOUTHERN CALIFORNIA. THE STRONGEST JET ENERGY IS ON THE EAST SIDE OF THE TROUGH NOW AND WILL CAUSE THE TROUGH TO BEGIN MOVING NORTHEAST OF THE FORECAST AREA TODAY. A SLIGHTLY WEAKER JET STREAK ON THE WESTERN SIDE OF THE TROUGH WILL CREATE SUFFICIENT VORTICITY IN THE BASE OF THE TROUGH OVER ARIZONA AND SOUTHERN UTAH TO SHEAR OFF A CLOSED LOW FEATURE THAT WILL MUCH MORE SLOWLY EJECT EAST-NORTHEAST ACROSS COLORADO BY LATE TUESDAY. THIS WEAK FEATURE IS NOT EXPECTED TO CREATE PRECIPITATION FOR SOUTHEAST WYOMING AS IT MOVES EAST OF THE AREA TUESDAY NIGHT. SURFACE HIGH PRESSURE WILL REMAIN IN PLACE TODAY ALONG WITH FAIRLY LIGHT NORTHWEST FLOW. CLOUD COVER WILL GRADUALLY DECREASE THROUGH THE DAY...AND TEMPERATURES WILL WARM SLIGHTLY WHILE REMAINING AROUND 12 TO 20 DEGREES BELOW NORMAL ACROSS SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE. TEMPERATURES TUESDAY WILL WARM SLIGHTLY AGAIN...BUT WILL STILL BE AROUND 10 DEGREES BELOW NORMAL. THE SOUTHERN END OF A WEAK COLD FRONT WILL MOVE SOUTHEAST ACROSS THE AREA EARLY TUESDAY NIGHT...BUT NO PRECIPITATION IS EXPECTED WITH THIS FRONTAL PASSAGE. .LONG TERM...WEDNESDAY THROUGH SUNDAY DRY CONDITIONS WILL PREVAIL THROUGHOUT THE EXTENDED PERIOD. A WEAK SHORT WAVE WILL MOVE ACROSS THE CWA LATE WED MORNING INTO EARLY AFTERNOON...WITH ANOTHER WAVE MOVING ACROSS THE FORECAST AREA THUR MORNING. BOTH THESE WAVES WILL ONLY PRODUCE SOME CLOUDS OVER THE AREA. BRISK WINDS WILL OCCUR AT THE SURFACE THURSDAY MORNING IN THE VICINITY OF THE SHORT WAVE. AN UPPER RIDGE WILL MOVE ACROSS THE CWA FRIDAY...WHILE THE AIRMASS REMAINS DRY. ON SAT...SW FLOW WILL DEVELOP ALOFT SAT...BUT THE UPPER FLOW WILL BECOME ZONAL ON SUN AS A HIGH AMPLITUDE RIDGE DEVELOPS OVER THE WESTERN U.S. HIGH TEMPERATURES WILL BE AROUND NORMAL FOR WED...THEN 4 TO 7 DEGREES ABOVE NORMAL FOR THUR THROUGH SUNDAY. && .AVIATION... LOCALIZED MVFR CONDITIONS DUE TO LOW STRATUS CLOUD WILL OCCUR THROUGH AROUND 14Z THIS MORNING...FOLLOWED BY VFR CONDITIONS THROUGH THE REST OF THE PERIOD AS DRY LOW LEVELS OF THE ATMOSPHERE WILL BE EXPECTED WITH THE SURFACE HIGH PRESSURE. PATCHY FOG WILL BE POSSIBLE ACROSS CARBON AND ALBANY COUNTIES TONIGHT...ALTHOUGH CONFIDENCE IS LIMITED AS TO HOW MUCH ADDITIONAL MOISTURE WILL ENTER THE BOUNDARY LAYER FROM SNOW-MELT TODAY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ SHORT TERM/AVIATION...CARPENTER LONG TERM...KMD
