106 FXUS63 KUNR 042327 AFDUNR AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 527 PM MDT WED SEP 4 2013 .SHORT TERM...THIS EVENING THROUGH THURSDAY NIGHT ISSUED AT 146 PM MDT WED SEP 4 2013 UPPER LEVEL ANALYSIS HAS HIGH CENTER OVER EASTERN COLORADO WITH RIDGE EXTENDING NORTH INTO SOUTHWESTERN CANADA. MONSOONAL MOISTURE CONTINUES TO PIVOT INTO THE CENTRAL ROCKIES AND NORTHERN PLAINS. SKIES ARE MOSTLY CLEAR ACROSS THE AREA...WITH WEAK CONVECTION FIRING ACROSS THE BLACK HILLS. AT THE SURFACE...A WEAK STATIONARY BOUNDARY IS DRAPED ACROSS WESTERN SOUTH DAKOTA WITH CANADIAN HIGH PRESSURE SLIDING IN FROM THE NORTHEAST. TEMPERATURES ARE IN THE 80S TO AROUND 90 DEGREES...WITH LIGHT EAST TO SOUTHEAST WINDS. WEAK BOUNDARY ACROSS THE HILLS WILL BE THE FOCUS FOR SHOWERS AND STORMS THIS AFTERNOON AND EVENING. CAP HAS BEEN SLOWLY ERODING THIS AFTERNOON...AND BEST INSTABILITY AXIS PER MODEL SOUNDINGS RUNS FROM SOUTHEAST MONTANA THROUGH THE BLACK HILLS INTO THE NEBRASKA PANHANDLE. ROUGHLY 1000-1500 J/KG CAPE AND SUFFICIENT SHEAR WILL SUPPORT A FEW STRONGER STORMS ACROSS THE AREA. THE MAIN CONCERN WILL BE HAIL AND DAMAGING WINDS. STORM THREAT WILL DIMINISH LATER TONIGHT AS ATMOSPHERE STABILIZES AND BEST UPPER DYNAMICS SHIFT INTO NORTH DAKOTA. TEMPERATURES WILL BE MILD OVERNIGHT...WITH READINGS FALLING INTO 50S AND 60S. UPPER RIDGE REMAINS OVER THE NORTHERN PLAINS FOR THURSDAY...AS WEAK SURFACE BOUNDARY REMAINS OVER WESTERN SOUTH DAKOTA. ANOTHER WEAK UPPER LEVEL SHORTWAVE WILL BRING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO PARTS OF NORTHEAST WYOMING AND THE BLACK HILLS AREA. TEMPERATURES WILL REMAIN ABOVE AVERAGE...WITH HIGHS CLIMBING INTO THE MID 80S TO UPPER 90S. OVERNIGHT LOWS WILL BE WELL ABOVE AVERAGE...IN THE 60S TO AROUND 70 DEGREES. && .LONG TERM...FRIDAY THROUGH WEDNESDAY ISSUED AT 146 PM MDT WED SEP 4 2013 LONG WAVE RIDGE REMAINS IN PLACE JUST WEST OF OUR CWA WITH LONG WAVE TROFS OVER EACH COAST OF THE US. STRONG SHORT WAVE TROF IS FCST BY GFS TO MOVE OUT OF THE WEST COAST LONG WAVE TROF TO ERN MT BY 12Z MON...THOUGH A BIT WEAKER THAN YESTERDAYS RUN. AS THIS TROF CONTINUES E WARD...THE LONG WAVE RIDGE UNDERGOES DISCONTINUOUS RETROGRESSION AND THEN AMPLIFIES WHILE MOVING SLOWLY E WARD. GFS FCST HAS IT NEAR 135W BY 12Z WED. THE ECMWF IS SLOWER AND SOMEWHAT STRONGER WITH THE SHORT WAVE TROF AND A LITTLE FARTHER WEST WITH THE LONG WAVE RIDGE BY MID WEEK. WEAK SFC CYCLOGENESIS OVER WRN SD AND ERN WY RESULTS FROM THE APPROACH OF THE SHORT WAVE TROF...ACCOMPANIED BY A SOUTHWARD SURGE OF COOLER AIR OVER OUR CWA AND HIGHER PRECIP CHANCES. TIMING OF BOTH MAY BE LATER THAN IN PRESENT FCSTS IF ECMWF IS CLOSER THAN GFS. TEMPERATURES WILL REMAIN ON THE VERY WARM SIDE UNTIL THE COLD FRONT APPROACHES AND PASSES MONDAY AND TUESDAY. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING) ISSUED AT 526 PM MDT WED SEP 4 2013 OVER NORTHEAST WY/FAR WESTERN SD...ISOLATED/SCATTERED TSRA ARE EXPECTED THIS EVENING WITH LOCAL MVFR CIGS/VSBYS ALONG WITH GUSTY WINDS. OTHERWISE VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. && $$ SHORT TERM...15 LONG TERM...BARBER AVIATION...HELGESON