828 FXUS65 KCYS 242208 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 408 PM MDT SUN MAY 24 2015 .SHORT TERM...(THIS EVENING THROUGH TUESDAY) ISSUED AT 408 PM MDT SUN MAY 24 2015 SHOWERS AND THUNDERSTORMS HAVE EXPANDED IN COVERAGE SINCE THE EARLIER FORECAST UPDATE...WITH MODERATE RAINFALL OBSERVED AT TIMES ALONG WITH SMALL HAIL NEAR CHEYENNE. ACTIVITY IS INCREASING OVER THE NORTHERN LARAMIE RANGE AND CENTRAL CONVERSE COUNTY AS WELL...WITH SLOW MOVING THUNDERSTORMS OBSERVED ON RADAR. COULD STILL SEE SOME HEAVIER RAINFALL TOTALS OUT OF THIS ACTIVITY SO WILL MAINTAIN THE FLASH FLOOD WATCH. THE STRONGEST STORM SO FAR THOUGH IS OVER NORTHERN SIOUX COUNTY WITHIN THE SLIGHTLY MORE UNSTABLE ENVIRONMENT. IT CONTINUES TO TREK EAST TOWARD DAWES COUNTY WITH FURTHER DEVELOPMENT TO THE SOUTH. EXPECT THESE TRENDS TO CONTINUE THROUGH THE EVENING. FOR TONIGHT...THE UPPER LOW WILL FINALLY MOVE NORTHEAST OVER THE CWA AND WILL WEAKEN. SIMILARLY...THE SFC LOW WILL STEADILY TREK NORTHEAST WITH WINDS SHIFTING TO THE NNW BEHIND THE LOW. OVERALL FLOW SHOULD REMAIN ON THE WEAKER SIDE TONIGHT...WITH AREAS OF FOG REDEVELOPING OVERNIGHT ACROSS MUCH OF THE AREA. WITH THE NW FLOW IN PLACE...DRIER AIR SHOULD BEGIN TO FILTER INTO THE CWA WHICH WILL REDUCE OVERALL COVERAGE OF SHOWERS AND THUNDERSTORMS FOR MONDAY. HOWEVER...COOLER AIR WITHIN THE UPPER TROUGH WILL REMAIN OVERHEAD SO EXPECT AT LEAST SCATTERED COVERAGE OF SHOWERS WITH ISO-T LATE MORNING THROUGH THE EVENING...ESPECIALLY OVER HIGHER TERRAIN FEATURES. A WEAK TRANSITORY RIDGE LOOKS TO MOVE OVERHEAD FOR TUESDAY BRINGING WARMER TEMPS TO THE FORECAST AREA ALONG WITH SUBSIDENCE ALOFT. SFC HIGH PRESSURE IS FORECAST TO SLIDE SOUTHEAST INTO THE CENTRAL PLAINS THROUGH THE DAY...WITH SFC WINDS VEERING BACK TO THE SOUTHEAST AND INCREASING LLVL UPSLOPE FLOW OVER THE CWA THROUGH THE AFTERNOON. THE COMBINATION OF UPSLOPE AND HIGHER TEMPS SHOULD MAINTAIN AT LEAST A CHANCE FOR AFTERNOON SHOWERS AND THUNDERSTORMS...AGAIN ESPECIALLY NEAR TERRAIN FEATURES. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 408 PM MDT SUN MAY 24 2015 AN ACTIVE PATTERN IS EXPECTED TO CONTINUE THROUGH THE WEEK AS LARGE SCALE TROUGHING REMAINS INTACT ACROSS THE WESTERN US. A FEW EMBEDDED DISTURBANCES WITHIN MOIST SOUTHWEST FLOW ALOFT COMBINED WITH PERIODS OF LLVL UPSLOPE WILL PROMOTE DAILY CHANCES FOR CONVECTION THROUGH AT LEAST THE END OF THE WORK WEEK. GENERALLY WEAK MID LEVEL FLOW / LESS THAN 25 KTS AT H5 / WILL KEEP CHANCES FOR STRONG TO SEVERE STORMS ON THE LOW SIDE...BUT THE GFS SUGGESTS SBCAPE AROUND 1500 J/KG ACROSS A LARGE PART OF THE EASTERN PLAINS ON WED-THU. CANNOT RULE OUT A STRAY SEVERE STORM...BUT ANYTHING ORGANIZED APPEARS UNLIKELY. EXPECT DAILY HIGHS TO HOLD FAIRLY STEADY THROUGH THE EXTENDED GIVEN A PERSISTENT UPPER LEVEL PATTERN IN PLACE. H7 TEMPS AVERAGING AROUND 5 C SUGGEST HIGHS IN THE 65 TO 75 DEGREE RANGE FOR MOST AREAS. RIDGING ALOFT AND A PUSH OF DRIER AIR ASSOCIATED WITH A CANADIAN SURFACE HIGH DIPPING INTO THE UPPER MIDWEST MAY GIVE US A BREAK FROM PRECIPITATION AS WE HEAD INTO THE WEEKEND. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED AT 1213 PM MDT SUN MAY 24 2015 SCT-TO-BKN COVERAGE OF LOW-LEVEL CUMULUS CAN BE EXPECTED THIS AFTN ALONG WITH INCREASING SHOWERS AND THUNDERSTORMS. VFR TO MVFR CIGS SHOULD PREVAIL TODAY...WITH THE WORST CONDITIONS OCCURRING BENEATH ANY HEAVIER STORMS. SHOWERS MAY CONTINUE THROUGH THE NIGHT ACROSS MUCH OF THE AREA. IFR/LIFR CONDITIONS ARE POSSIBLE AT KRWL AND MUCH OF THE WESTERN PANHANDLE AFTER 06Z...CONTINUING THROUGH MID AM MON. && .FIRE WEATHER... ISSUED AT 408 PM MDT SUN MAY 24 2015 SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH MUCH OF THE WEEK AND WILL BRING MODERATE TO HEAVY RAINFALL AT TIMES ACROSS THE DISTRICT. WITH PLENTIFUL MOISTURE ANTICIPATED...NO FIRE WEATHER CONCERNS ARE EXPECTED. && .HYDROLOGY... ISSUED AT 408 PM MDT SUN MAY 24 2015 FORECAST RAINFALL FROM SHOWERS DURING THE NEXT 24 HOURS WILL AVERAGE BETWEEN 0.25 AND 0.50 INCHES...WITH LOCALLY HEAVIER AMOUNTS POSSIBLE WITH THUNDERSTORMS. RUNOFF FROM THIS RAINFALL WILL MAINTAIN HIGH WATER LEVELS ALONG THE LARAMIE RIVER AT LARAMIE AND NEAR FORT LARAMIE THROUGH EARLY NEXT WEEK. REFER TO THE LATEST RIVER AND FLOOD STATEMENTS FOR SPECIFIC INFORMATION. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...FLASH FLOOD WATCH UNTIL 6 PM MDT THIS EVENING FOR WYZ101-103>105- 109. NE...NONE. && $$ SHORT TERM...RJM LONG TERM...CLH AVIATION...CLH FIRE WEATHER...RJM HYDROLOGY...MJ/RJM