Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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168 FXUS65 KBOU 160950 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 350 AM MDT Mon Sep 16 2024 .KEY MESSAGES... - Scattered showers and thunderstorms for the high county late today, with little to no chances over the plains. - The windy conditions become widespread on Tuesday. - Scattered thunderstorms Tuesday afternoon. Some storms may be strong to severe over the plains. - Cooler temperatures Friday and next weekend with good chances (30-60%) for rain and high mountain snow. && .SHORT TERM /Through Tonight/... Issued at 350 AM MDT Mon Sep 16 2024 There a still a few showers over the eastern border at this time. They were moving east-northeastward out of the CWA. Normal drainage wind patterns were in place for much of the CWA. Models show a pretty strong upper low over northern California to move into the western Great Basin by 00Z this afternoon, then to be centered over northeastern Nevada by 12Z Tuesday morning. The winds aloft for the CWA will be 45 to 80 knots from the southwest both today and tonight. The synoptic scale energy for the CWA on the QG Omega fields is somewhat noisy today and tonight and pretty weak downward in nature anyway. The flow aloft seems to translate somewhat down to the low levels this afternoon and evening, with gusty southwesterlies surface winds progged fro a bit this afternoon. For moisture, the precipitable water fields show 0.50 to 1.10 inches over the forecast area today into this evening, with a tad of drying over the plains tonight. Instability wise, the CAPE is meager today into this evening, with the highest values over the far northeast corner this afternoon only. There is nothing over the CWA for the tonight period. The model QPF fields have limited measurable rainfall over the mountains, foothills and Palmer Ridge this afternoon and early evening only. Will keep the highest pops going over the mountains and foothills this afternoon. The plains can expect 0-10% pops for the first two periods. There may be some outflows around, but not as strong as Monday`s were. For temperatures, today`s highs are 2-5 C cooler than yesterday`s highs. The 90s F look to be over. && .LONG TERM /Tuesday through Sunday/... Issued at 300 AM MDT Mon Sep 16 2024 A strong negatively tilted upper level trough will lift northeast across Colorado Tuesday. Center of the trough at 12Z Tuesday will be over eastern Nevada with the axis extending into northwest Arizona. By 18Z, the trough axis will be over southwest Colorado and by 00Z it will be over northeast Colorado...very fast moving. Ahead of the trough axis showers and thunderstorms will form Tuesday morning over the Four Corners and northward into western Colorado. Best lift over north central and northeast Colorado will be Tuesday afternoon, lining up with peak heating. Pretty much all the high resolution models show a line or broken line of storms tracking across the area Tuesday afternoon. SBCAPE reaches 500-1000 J/kg, so the storms should have decent updrafts. Strong lower and mid level winds, inverted-V sounding, and DCAPE of 1000-1500 J/kg all add up to strong to severe winds from the thunderstorms. This looks to be a higher threat than most days with the NAMNest and HRRR models showing some gusts to 70 mph. The storms race east of the area by early to mid evening. For Wednesday and Thursday, an upper level low drops south along the west coast Wednesday and then slowly progresses eastward Thursday. By late Thursday the upper level low will be centered over California and Nevada. Ahead of this low, ridging in the southwest flow aloft will prevail over Colorado. The airmass dries out with mostly clear skies expected. Temperatures will be a little cooler, but still above normal with highs in the lower to mid 80s over northeast Colorado. Even though it will be dry (low relative humidities), winds will generally be weak, easing fire weather concerns. On Friday, the upper level low slowly moves east across the Great Basin and over the Central Rockies Saturday. Models still somewhat struggling to find run to run consistency. The latest 00Z runs of the GFS and ECMWF are slower than previous runs keeping the area precipitation free until Saturday. Ensemble members are not entirely on board with this solution. This low as it tracks across the Central Rockies could stay north of Colorado resulting in mainly dry conditions. If it takes a more southern and stronger route, much of the area will see a good shot of rainfall. Because of the uncertainty, will continue with the broad brush approach with 20-50 PoPs for Friday and Saturday. Temperatures will run at or below normal with highs expected to be in the 70s over northeast Colorado. Though if we happen to see a cloudy/rainy day, highs will likely be in the 60s. This storm system should be east of the area Sunday. With the uncertainty in the weather pattern, will keep low PoPs (10- 20%) in the forecast for Sunday. && .AVIATION /06Z TAFS through 06Z Tuesday/... Issued at 1156 PM MDT Sun Sep 15 2024 Normal drainage wind patterns should continue through about 15Z this morning. Fairly strong southwesterly winds aloft ahead of an approaching upper trough to our west, should translate down into the lower levels by afternoon. Will keep in the brisk southwesterlies in the TAF this afternoon as well as put in a TEMPO group for VRB20G40KT along with VCSH. Drainage winds are expected again by 03Z this evening. There will be no ceiling issues. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM....RJK LONG TERM.....Meier AVIATION......RJK