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212 FXUS65 KBOU 170534 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1134 PM MDT Fri May 16 2025 .KEY MESSAGES... - Scattered thunderstorms over the mountains Saturday afternoon, with just a slight chance of storms on the plains. - Threat of severe storms on Sunday afternoon, mainly in the northeast corner of Colorado. There is uncertainty due to the track of the low pressure system and timing. - Near critical fire weather possible south of I-70 Sunday. - Cooler and windy with more showers/storms Monday and possibly Tuesday, but a lower severe threat. && .DISCUSSION /Through Friday/... Issued at 330 PM MDT Fri May 16 2025 It`s looking like a pretty quiet late afternoon/evening as we`ve still got stable air over the mountains, evidenced by the trapped waves in the mid level cloud deck. Winds have finally started to ease a bit and that will continue into the evening. We did update the forecast for more cloud cover through Saturday as we`ll have a weak shortwave trough passing and then the edge of the moisture stalling over us ahead of the developing western trough. This will keep temperatures from rising too much on Saturday despite a warming air mass. With the moistening, we`ll return to scattered afternoon thunderstorms over the mountains, but the clouds will limit the eastward progression. The combination of lift from the trough and increasing low level moisture could produce a cluster of stronger storms over the northeast corner Saturday evening. There`s been a little model convergence for the Sunday through Tuesday time frame, though we`ll need a better handle on details before we know what it means. There`s clearer agreement on the two jet streaks rotating around the trough, bringing a lead wave kicking out of the trough on Sunday and then the second part of the trough sliding east Monday night or Tuesday. Unfortunately, there`s still a lot of disagreement on the relative strength of the jet streaks and their associated troughs. In general, there`s a trend towards a bit weaker trough for Sunday, but we don`t have a lot of confidence in that. This could result in a northward shift in the position of the QG lift, but it could also mean that there`s less southwest flow to push the developing dryline eastward out of Colorado. The main threat for severe weather is with convergence along the developing dryline which may start in northeastern Colorado Sunday afternoon, or it may focus a bit further east or north and be a few hours later. There should be enough ingredients for all kinds of severe weather somewhere in this area. The severe threat is probably greatest in bordering areas of Kansas and Nebraska in the evening, but there may be a better threat of strong isolated storms in our northeast corner at the beginning. There may be critical fire weather conditions on our southern flank, but with green grass for the moment, the threat is diminished. Monday is in between the two pieces of the trough, and while details about any possible lift or the mid level flow have some uncertainty, we will be in a moist and cooler air mass, probably with decent north or northeast winds. If there`s not much cooling, this could be a showery/stormy day, though it may be too cool for much of a severe threat. That will depend on how much cooling there is. The current trends towards a more sheared large scale trough point towards either a faster departure or more westerly flow on Tuesday, but again there`s not a lot of confidence in that. NBM gradual decrease in PoPs without warming seems fine for now. Then pretty solid warming and drying in westerly flow with weak ridging for Wednesday into the later part of the week. There may be a shortwave passing north of us in the Thursday/Friday time frame, but this would probably just generate a bit of wind. && .AVIATION /06Z TAFS through 06Z Sunday/... Issued at 1126 PM MDT Fri May 16 2025 VFR conditions will prevail for all terminals through the TAF period. Light drainage flow will prevail through Sat AM before a transition to more easterly flow for the afternoon. High-based -SHRA will develop across the region 19-01Z, and may produce periods of enhanced gusts to ~25 kts. Wind direction during this period is likely to be highly variable, with low confidence in any prevailing direction. In the evening, there`s a possibility of more organized convection over the eastern plains which could drive more persistent easterly outflow towards the Denver metro before a return to drainage flow overnight. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Gimmestad AVIATION...Rodriguez