Area forecast discussion for western South Dakota and northeastern Wyoming National Weather Service Rapid City South Dakota 259 am MDT Thursday may 23 2013 Short term...today through Friday night issued at 208 am MDT Thursday may 23 2013 Current surface map places high pressure ridge across the eastern Dakotas...with Lee side trough across Montana/Wyoming. Large upper low spinning across the Pacific northwest. Tight pressure gradient across the forecast area along with 3-4mb/3hr pressure falls across Montana will result in windy conditions...especially across northeast Wyoming and northwest South Dakota. Wind gusts of 45-50 miles per hour likely. With upper level subsidence and strong inversion...will be dry today. For tonight...40-50kt low level jet is located across western South Dakota while strong shortwave lifts through western Wyoming into southern Montana. 2-3c/hour 850-700mb Theta-E advection develops across central South Dakota. With MUCAPE around 250j/kg...a few thunderstorms possible across south central South Dakota late tonight. As upper shortwave lifts into eastern Montana early Friday morning...moderate q-g forcing passes through western South Dakota. Best chance of precipitation on Friday shifts east of the forecast early in the day. Have trimmed back on probability of precipitation across western South Dakota due to lack of instability. Long term...Saturday through Wednesday issued at 208 am MDT Thursday may 23 2013 Upper low over the Pacific northwest will generally remain in place over the weekend...with southwesterly flow aloft over our region. A series of disturbances in this flow will move across the northern plains over the Holiday weekend...bringing daily chances for showers and thunderstorms. Lee trough/dry line will generally remain in place across far eastern Montana and northeastern Wyoming during the period...with moist southeasterly flow and increasing instability to the east of the trough across the Dakotas. The threat for strong to severe thunderstorms will begin to increase on Saturday over most of the forecast area...with the better chances still looking to be on Sunday and Monday. The extent of the severe risk will depend on the timing of these disturbances...which is still uncertain at this point. Chances for thunderstorms will likely continue into the middle of next week as general pattern continues. Temperatures will remain above average...with highs in the 70s and lower 80s across the area through early next week. && Aviation...for the 06z tafs through 06z Thursday night issued at 208 am MDT Thursday may 23 2013 MVFR/IFR conditions will persist across much of northeastern Wyoming and southwestern South Dakota this morning. Patchy fog is also possible... especially over the higher terrain. Gusty southeasterly winds will develop across northeastern Wyoming and western South Dakota this morning and persist through the day and into the evening. The strongest winds will be across northeastern Wyoming and far northwestern South Dakota...where gusts to near 45 heights are expected later this morning and afternoon. && Unr watches/warnings/advisories... South Dakota...Wind Advisory from 9 am this morning to 9 PM MDT this evening for sdz001-002-012>014-025-026-031-072-073. Wyoming...none. && $$ Short term...7 long term...26 aviation...26