891 FXUS65 KBOU 120108 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 708 PM MDT Sat May 11 2019 .UPDATE... Issued at 706 PM MDT Sat May 11 2019 Scattered showers and couple of thunderstorms tracked across northeast Colorado today. By mid evening when the airmass stabilizes, the showers will end and most of the cloud cover will dissipate. This is expected to lead to another cool night across northeast Colorado with lows in the 30s. Issued a Frost Advisory for most of northeast Colorado. Temperatures should be slightly warmer than last night. && .SHORT TERM...(This evening through Sunday) Issued at 311 PM MDT Sat May 11 2019 Skies have become "Mostly Cloudy" across the CWA this afternoon. There is a bit of shower activity over the CWA with a little of lightning over the eastern plains. The low level winds are all northerly now across the plains with some gusts as high as 30 knots. Models show the upper closed low, now centered over central South Dakota, to move into the northwest corner of Missouri by 18Z on Sunday. The CWA will stay in northerly flow aloft through Sunday. The QG Omega fields keep weak downward synoptic scale energy of the CWA tonight and Sunday. The northerly low level winds this evening should transition to their normal diurnal patterns late this evening and continue that way through Sunday. Moisture is progged to decrease by 06Z tonight, with very limited amounts for the CWA through Sunday. There is a bit of CAPE lingering around this evening over the foothills. On Sunday, there is limited CAPE over the mountains and foothills in the afternoon. The QPF fields show a bit of measurable precipitation, mainly over the southern half of the CWA this evening. On Sunday, there is only a tiny bit of measurable precipitation in the mountains only. For temperatures, Sunday's look to be 4-9 C warmer than this afternoon's highs. .LONG TERM...(Sunday night through Saturday) Issued at 311 PM MDT Sat May 11 2019 Sunday night an upper level trough of low pressure will cover the central and eastern U.S. with a secondary upper level low pressure system moving across northern Mexico. In addition, an upper level ridge of high pressure will stretch from the coast of California into the Great Basin. Colorado will lie between these systems under the influence of a light northwesterly flow aloft. This pattern will bring dry weather to all of north central and northeastern Colorado. Much warmer weather is expected Monday through Thursday as the upper level ridge of high pressure builds and moves over the Rocky Mountain Region. Temperatures across the plains are expected to be above normal with highs ranging from the upper 70s to lower 80s. Mainly dry conditions are expected through this period. However, there could be enough mid level level moisture, combined with daytime, heating to produce a few high based gusty afternoon and evening showers and storms mainly over the higher terrain. The GFS suggests a boundary sagging into the far northeastern plains Tuesday night with increased surface moisture behind it. The GFS sounding has capes over 1000 J/KG and enough shear to produce one or two strong to severe storms late Wednesday afternoon and evening. However, the ECMWF and GEM solutions are lacking in moisture and have no QPF across the far northeastern plains. Thursday and Friday, the upper ridge shifts eastward into the Central Plains States as a large upper trough pushes into the western U.S. Ahead of the trough, Colorado will be under the influence of a southwesterly flow aloft which should translate to mostly dry and continued warm weather across the plains with isolated to scattered showers and storms in the mountains. Cooler unsettled weather is expected on Saturday as the upper trough moves across the region. There is some uncertainty in how active the weather will be due to the model differences. The GFS shows a broad upper trough moving over Colorado with a west- southwesterly flow aloft and a relatively dry airmass at the surface. This solution would result in isolated to scattered light showers across the CWA. The GEM and ECMWF models are deeper with the upper trough which would result in a better chance for precipitation across the area. If the timing of these models is correct, we could see the potential for strong to severe storms. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 706 PM MDT Sat May 11 2019 Showers will come to an end and clouds will decrease by 03Z as the airmass stabilizes. Northeast winds will become light by 03Z and turn south-southwest by 06Z. For Sunday, mostly sunny skies are expected. Winds will turn northerly by late morning. Gusts to 20 knots will be possible after 18Z. && .BOU WATCHES/WARNINGS/ADVISORIES... Frost Advisory from midnight tonight to 8 AM MDT Sunday for COZ038-042>051. && $$ UPDATE...Meier SHORT TERM...RJK LONG TERM.....JK AVIATION...Meier