Issued by NWS Cheyenne, WY
000 FXUS65 KCYS 070130 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 729 PM MDT WED MAY 6 2009 .DISCUSSION...SHOWERS AND A FEW THUNDERSTORMS WERE LOCATED OVER THE NORTH AND EAST PARTS OF THE CWA EARLY THIS EVENING. THE ACTIVITY WAS BEING AIDESD BY A WEAK SHORTWAVE TROUGH CURRENTLY MOVING ACROSS EASTERN WYOMING AS WELL AS THE PROXIMITY OF THE 300 MB JET. CAPE VALUES ARE LOW AT THIS TIME AND SO ANY STORM THAT FORMS WILL BE WEAK AND GENERALLY HIGH BASED. TIMING OF THE SHORTWAVE TROUGH WILL MOVE IT EAST OF THE CWA BY 05Z...WITH THE ACTIVITY WEAKENING AND MOVING EAST OF THE CWA AFTER THAT TIME. THE FORECAST CONCERN FOR EARLY TONIGHT ARE STRONG WINDS CURRENTLY OBSERVED IN SOME AREAS ALONG AND WEST OF THE LARAMIE RANGE. GUSTS HAVE BEEN OVER 50 MPH AT TIMES AT KRWL AND KCLM EARLY THIS EVENING. THE MODEL WINDS AT 700 MB REMAIN STRONG THROUGH 06Z AS WELL AS A FAIRLY TIGHT SURFACE PRESSURE GRADIENT OVER THE REGION. BELIVE THAT THE STRONGER WINDS WILL PERSIST THROUGH LATE EVENING. IN A RECENT FORECAST UPDATE HAVE INCREASE WINDS IN THE WESTERN CWA AND POPS IN THE EAST PART OF THE CWA EARLY TONIGHT. && .PREVIOUS DISCISSION.../ISSUED AT 208 PM MDT WED MAY 6 2009/... SHORT TERM...TONIGHT THROUGH FRIDAY... UPPER FLOW WILL BE FAST AND FLAT TONIGHT THROUGH THURSDAY NIGHT. FLOW ALOFT WILL VEER AND BECOME SOMEWHAT CONFLUENT LATE FRI IN RESPONSE TO A SHORTWAVE MOVING OVER THE CENTRAL PLAINS AND EXTENDING WESTWARD OVER THE CENTRAL ROCKIES. A WEAK COLD FRONT WILL WARRANT A SMALL CHANCE OF THUNDERSTORMS THIS EVENING OVER NORTHERN AND EASTERN PORTIONS OF THE FORECAST AREA...WITH A FEW SHOWERS POSSIBLE LATE TONIGHT OVER THE SAME AREAS. OVERNIGHT LOW TEMPERATURES TONIGHT WILL BE SOMEWHAT ABOVE NORMAL DUE TO PERSISTENT DOWNSLOPE SURFACE WINDS. THU WILL BE JUST A FEW DEGREES COOLER. ANOTHER COLD FRONT WILL ENTER NORTHERN PORTIONS OF THE FORECAST AREA THU AFTERNOON WITH A FEW STORMS POSSIBLE ALONG AND BEHIND THE FRONT. AREAS OF BRISK WINDS WILL EXIST THU IN SOUTHEAST AND SOUTH CENTRAL WY. THE COLD FRONT WILL PUSH THROUGH THE REGION THU NIGHT WITH EVENING THUNDERSTORMS AND LATE NIGHT SHOWERS POSSIBLE OVER THE NORTHERN TWO THIRDS OF THE FORECAST AREA. FRI WILL BE COOLER WITH AREAS OF BRISK WINDS. SHOWERS AND AFTERNOON THUNDERSTORMS WILL BE POSSIBLE FRI OVER NORTHERN AND EASTERN PORTIONS OF THE FORECAST AREA. LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY ZONAL FLOW WILL BE ALOFT OVER THE CWA FRI NIGHT AND SATURDAY. A DISTURBANCE IN THE FLOW WILL RESULT IN A CHANCE OF SHOWERS NEAR THE COLORADO BORDER FRIDAY NIGHT. ANOTHER DISTURBANCE WILL MOVE ACROSS THE AREA SAT EVENING WHICH WILL RESULT IN A CHANCE OF SHOWERS AND LATE DAY THUNDERSTORMS...MAINLY EAST OF THE LARAMIE RANGE. ON SUN...ANOTHER SHORT WAVE WILL MOVE ACROSS THE FORECAST AREA ALONG WITH AN INCREASE IN MID LEVEL MOISTURE. THIS WILL RESULT IN A CHANCE OF SHOWERS AND AFTERNOON AND EVENING THUNDERSTORMS ACROSS MUCH OF THE AREA. ZONAL FLOW WILL RETURN TO THE AREA MONDAY AND WITH SURFACE BASED INSTABILITY AND MID LEVEL MOISTURE...WILL KEEP A SLIGHT CHANCE OF SHOWERS AND LATE DAY THUNDERSTORMS IN THE FORECAST. MORE OF THE SAME FOR TUES AND WED AS NW FLOW SETS UP ALOFT AND A FEW DISTURBANCE CONTINUE TO TRACK ACROSS THE CWA. THIS WILL CONTINUE THE CHANCE OF SHOWERS AND LATE DAY THUNDERSTORMS OVER THE FORECAST AREA. HIGH TEMPERATURES WILL BE FROM 5 TO 10 DEGREES ABOVE NORMAL THROUGH THE PERIOD. && .AVIATION...VFR CONDITIONS EXPECTED TONIGHT AND THU. SOUTHEAST WY WILL HAVE AREAS OF STRONG AND GUSTY SURFACE WINDS THROUGH EARLY TONIGHT AND THEN AGAIN THU. STRONG MID AND UPPER LEVEL FLOW WILL RESULT IN MOUNTAIN WAVE TURBULENCE AND LEE EDDY EFFECTS AROUND THE MOUNTAINS OF SOUTHEAST WY. && .FIRE WEATHER...BRISK WINDS AND FAIRLY LOW MINIMUM RELATIVE HUMIDITY VALUES WILL WARRANT MARGINAL FIRE WEATHER CONCERNS AGAIN THURSDAY AFTERNOON. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ WEILAND
