889 FXUS65 KBOU 221637 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1037 AM MDT Sat Jun 22 2019 .UPDATE... Issued at 1036 AM MDT Sat Jun 22 2019 No significant change expected to the big picture outlook heading into this afternoon thru Sunday as the current cold and moist trough dominates the region. Precipitation currently remains mainly jet driven as the back edge of upper level 70-80 kt winds pull northeastward over the northern Great Plains states. The 12z NAM12 capes have come in a bit richer then previous runs while again placing the Palmer Ridge region in the favored area for any storm initiation and activity. Visible satellite shows plenty of clear to partly cloudy skies over the San Luis Valley, central mountains and even along the southern Urban Corridor area and this may be enough to initiate surface based convection for this afternoon. If these can get established near midday, the southwest flow aloft may take these showers and storms onto the 400-100 J/kg ML capes along the Palmer. Therefore, can't rule out a few strong to potentially severe storms for this afternoon for the ridge and points east and south. Across the northeast plains this afternoon, scenario looks similar to yesterday, however cooler with near zero capes under mostly cloudy skies. For tonight and Sunday, the upper trough gradually works eastward with the coldest air aloft still to come for Sunday morning. Short range models indicate a series of widespread and mostly light shower episodes for this evening and overnight period similar to what occurred this morning, however less banded. && .SHORT TERM...(Today and tonight) Issued at 456 AM MDT Sat Jun 22 2019 Welcome to Colorado's Summer 2019. A late season upper level storm system will be moving across the state today and tonight with temperatures aloft cold enough to produce accumulating snowfall in the mountains. On the plains, a moist airmass is in place, being held over northeast Colorado by easterly and northeast winds circulating around a surface low over southeast Colorado and northern New Mexico. The approaching upper level trough is providing abundant dynamic forcing for ascent which will result in periods of rain showers, especially through the afternoon and evening. High temperatures on the plains will only be in the 60s, and that will be while it is not raining. Temperatures may remain in the 50s if rainfall is widespread and persistent enough. Mountains temperatures will only be in the 30s to 40s, allowing for snow to accumulate above 10,000 feet. A Winter Weather Advisory will remain in effect for most of the north central Colorado mountains through tonight. Over Rabbit Ears Pass and in the Park and Gore ranges, it appears that drier air will begin moving in later today, so the Advisory for that zone will be allowed to expire at 6 AM this morning. Back on the plains this afternoon, as the rainfall is expected to become widespread, elevated instability above the low levels could lead to some embedded thunderstorm activity. This will enhance rainfall amounts locally and produce gusty winds in the vicinity of the embedded heavier showers. The HRRR has been indicating that one or two of the embedded thunderstorms could become quite strong as they progress across the plains in the late afternoon. These could produce hail up to one-half or three-quarters of an inch, despite temperatures being so cool. The HRRR models do not show much precipitation over the plains after midnight, but other short range models do not bring any drying to the region until later tomorrow. For the time being, will not be too anxious to clear precipitation out of the forecast area. .LONG TERM...(Sunday through Friday) Issued at 456 AM MDT Sat Jun 22 2019 Highlights include one more cool and showery day on Sunday followed by a significant warming and drying trend through the rest of the week. The upper level trof will move across Colorado on Sunday and then into the central plains on Sunday night and Monday. There is still moderate upward ascent as noted on layered QG fields on Sunday morning, then significant subsidence moves in during the late afternoon and extending through Sunday night. 700mb temperatures only around +2c, so again temperatures will only be in the upper 50s and 60s across lower elevations. Showers will diminish Sunday evening followed by clearing skies and a chilly night with readings in the 40s plains. For Monday, Colorado will be under a mainly dry moderate northwest flow pattern. Mid level warming expected to cap thunderstorm development with 700mb temperatures soar to +11c but could see some isolated high based showers over higher terrain. This will bring temperatures back to around 80 degrees. On Tuesday, the high pressure ridge will be over Colorado with the flow becoming more westerly. From Wednesday through Friday, a strong low pressure system will be over the Pacific Northwest which will increase the southwest flow aloft over Colorado and building high pressure back into the desert southwest. Afternoon high temperatures will be approaching 90 degrees on Thursday and Friday with summer in full swing. Moisture will be limited, with mainly isolated, high based showers and storms expected during the late afternoon/evening hours. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1036 AM MDT Sat Jun 22 2019 Lower clouds have mostly broken up across the Denver area airports. However, convective clouds were quickly developing over the mountains and will grow into numerous showers and thunderstorms this afternoon. The most likely time for thunderstorms will be from 21Z-01Z, with stronger storms capable of producing brief heavy rain with 1-2SM visibility, IFR ceilings, small hail, and variable wind gusts to 30-35 knots. After the main batch of showers and storms move through, we may see patchy IFR/MVFR ceilings develop due to low level moisture and light surface winds, but confidence is low on occurrence and timing at this point. Could see the lower stuff hang around through Sunday morning, and expect a few more showers as well with the upper low moving overhead. && .HYDROLOGY... Issued at 1036 AM MDT Sat Jun 22 2019 Stream gauges have come up to near action stage near Northgate and have issued a Flood Advisory for rain and snowmelt along the North Platte and Michigan River. As for potential hydro issue over the urban areas and plains, not seeing any at this time. The atmos will remain near saturated with PWs in the .50-.70 range, but storms are moving fairly quick and current hydro gages are showing plenty of capacity with no significant spikes indicated from the overnight showers. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 AM MDT Sunday for COZ033-034. && $$ UPDATE...Fredin SHORT TERM...Dankers LONG TERM...Entrekin AVIATION...Barjenbruch HYDROLOGY...Fredin/Barjenbruch