Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/11/18

Area Forecast Discussion
National Weather Service Bismarck ND
1102 PM CDT Sun Jun 10 2018 .UPDATE... Issued at 1036 PM CDT Sun Jun 10 2018 Line of convection from Bottineau to Linton continues to move east across central ND. Current watch expires at 11 PM. After coordination with SPC and surrounding offices, will not extend the watch east. CAMS suggest that the convection will continue to hold together as it tracks into eastern ND. However current low level lapse rates are minimal and upper flow is parallel to the line with no strong forcing for line segements to bow out. We could still see some isolate severe reports, especially along the South Dakota border, but the probability of widepsread severe activity requiring a watch is low and will not be extending the watch area to the east. Will be sending out a cancellation for the watch at the top of the hour. UPDATE Issued at 642 PM CDT Sun Jun 10 2018 Quick update to cancel the Severe Thunderstorm Watch for Divide, Williams, McKenzie, Billings, and Slope counties where dry post cold front air has overtaken. Will maintain the watch across Bowman county for convection propagating north out of Harding county in South Dakota. && .SHORT TERM...(This evening through Monday) Issued at 317 PM CDT Sun Jun 10 2018 Severe thunderstorm potential through tonight is the main focus of this forecast. As of 20 UTC, visible satellite imagery shows a well-defined cold front from just east of Williston to near Medora and Bowman. There are signs of an agitated and deepening cumulus field in proximity to that frontal zone as height falls are beginning to impinge on that region of low-level mesoscale ascent, which is aiding with the erosion of the stout capping layer seen on regional 12 UTC and the 19 UTC Rapid City RAOBs at the base of a formidable elevated mixed layer which has 700-500 mb lapse rates as large as 9 C/km. Given surface dewpoints in the mid 60s F just ahead of the frontal zone and its associated wind shift, significant MLCAPE on the order of 2500 to 4000 J/kg has developed. As capping continues to erode, we expect convective initiation to occur along the length of the cold front from the Canadian border south to the SD state line before 22 UTC, which is an expectation long-heralded by nearly every CAM simulation available. The strongest wind fields aloft associated with the shortwave trough approaching the region from the northern Rockies are still expected to lag the primary frontal interface, and that will likely serve as a limiting factor to the overall strength and longevity of individual convective elements during the afternoon and early evening. Models call for effective bulk wind differences mainly on the order of 30 to 40 kt. Moreover, the orientation of the deep-layer shear and anvil- level storm-relative flow vectors relative to the cold frontal boundary all support upscale growth into a linear complex with time following initial multicellular or transient supercell modes. This falls in line with CAMs through the 18 UTC HRRR. Initially, large bouyancy including through the hail growth zone will favor risks for large hail within a few hours of initiation until a full-scale linear mode is established, though the lack of stronger deep-layer shear in favor of somewhat tempered mesocyclones will likely subdue high-end hail sizes. Both the large hail and significant hail parameters favor peak hailstone sizes generally less than 2 inches in diameter. Damaging winds will also be a concern, especially as upscale growth occurs by evening, and very heavy rainfall will be a concern too given slow storm motions and precipitable water values as high as 1.50 inches. However, we have held off from issuing a Flash Flood Watch at this time given some uncertainty in the magnitude of the threat. Mesobeta-element (Corfidi) vectors suggest that the orientation of mean cloud-layer winds and related mean outflows and the southerly low-level jet will not favor gust-front-induced convergence and that will temper the longevity and downshear propagation of the cold-pool-related MCS. Therefore, the eastward progression of the convection will be slow, and that may limit the magnitude of wind gusts, as well. However, the density of wind reports could still be significant, and is the primary motivation for the Enhanced Risk from SPC. Moreover, some CAM guidance has suggested storms will form over the higher terrain of northeast WY into western SD and propagate into far southwest and south central ND after about 01 UTC. This convection could be slightly post-frontal in nature and would have access to stronger deep-layer wind fields with effective bulk wind differences potentially in excess of 40 kt. That is reflected in HREF updraft helicity output which has peak values from any member in the 2-5 km layer up to 200 m/2s across north central SD, and which some iterations of the operational HRRR have brought as far north as Bismarck. Either way, after about 00 UTC the severe threat will be greatest in south central ND even with the initial line, within the axis of largest CAPE. Otherwise, Monday will be cooler and breezy in the post-frontal regime, but the 12 UTC global model suite suggests that maximum winds in the well-mixed boundary layer will be insufficient for Wind-Advisory-type conditions. That`s further supported by the consensus of 12 UTC MOS guidance. .LONG TERM...(Monday night through Sunday) Issued at 317 PM CDT Sun Jun 10 2018 Global models suggest a cooler and mainly dry period will be in place through midweek as weak and transitory ridging crosses the region. However, the 00 and 12 UTC models also suggest a stronger upper-level shortwave trough will cross the region by Thursday night. Taken at face value both the GFS and ECMWF support strong instability driven by boundary layer dewpoints potentially in the middle to upper 60s F along with strengthening wind fields aloft, which would support potential severe storms once again from Thursday into Thursday night. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1036 PM CDT Sun Jun 10 2018 A line severe thunderstorms associated with a slow moving cold front from near Bott. Strong southeast winds with gusts to 35kts will continue ahead of the cold front this evening. Widespread rain showers and embedded thunderstorms will fill in behind the cold front across most of western and central North Dakota overnight with MVFR conditions expected. Rain showers will end across central North Dakota Monday morning. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...TWH SHORT TERM...CJS LONG TERM...CJS AVIATION...TWH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
833 PM MDT Sun Jun 10 2018 .UPDATE... Issued at 824 PM MDT Sun Jun 10 2018 Cool front was moving across nwrn CO and should affect nern CO by midnight. A brief period of gusty northwest winds will occur behind the front. Otherwise with a dry airmass in place no precip is expected with the front. Meanwhile smoke from the fires over swrn CO should stay to the south and southeast of Denver based on hrrr smoke model. It has best concentration of smoke affecting portions of Elbert and Lincoln counties overnight. && .SHORT TERM...(This evening through Monday) Issued at 244 PM MDT Sun Jun 10 2018 A positively-tilted upper trough is swinging into the northern Rockies this afternoon, the hot, dry and breezy conditions continue with southwesterly flow aloft. Temperature readings are in the 90s across the plains, with a few in the upper 90s. With some daylight left, wouldn`t be surprised to see a few 100 degree readings over the lower elevations of the plains. Gusty southwest winds across the area will continue into the late afternoon. Fire activity over southwestern Colorado has increased significantly, s