Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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869 FXUS65 KBOU 250226 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 826 PM MDT Tue Sep 24 2024 .KEY MESSAGES... - Warm and dry for the foreseeable future with very limited chances of precipitation. The mountains have a 10-20% chance of showers late Friday into Saturday. - Record highs possible on Thursday. && .UPDATE... Issued at 825 PM MDT Tue Sep 24 2024 Clear skies over the CWA this evening with current temperatures in the 50s to mid 60s for most of the forecast area. Winds were pretty light across the CWA as well. Will make a minor grid updates to winds and temperatures only. && .SHORT TERM /Through Wednesday/... Issued at 144 PM MDT Tue Sep 24 2024 Current observations show temperatures have made it to the mid 70s across the plains and mid 60s across the higher elevations so far this afternoon. Cloud coverage has decreased throughout the day, and clear skies are expected by this evening as a dry airmass settles in. By tonight, northerly flow aloft will take hold as Colorado will be downstream of an anomalous 500mb ridge pushing east towards the Four Corners. Quiet weather is expected overnight with overnight low temperatures forecast to dip into the 30s for our mountain valleys, 50s for the urban corridor, and mid to high 40s across the plains. Blue skies and warming temperatures are expected on Wednesday as the ridge anchors itself to the southwestern CONUS. With a dry airmass in place, persisting clear skies, and 700mb temperatures expected to reach 17C, this will translate to afternoon high temperatures 5 to 10 degrees warmer than today`s. && .LONG TERM /Wednesday night through Tuesday/... Issued at 144 PM MDT Tue Sep 24 2024 Very warm and dry weather will definitely be the norm over the rest of this week, into the weekend, and most likely into next week as well. A persistent 500 mb ridge will be in place until further notice. It will not help that Hurricane Helene will merge with a strong early fall trough over the southeast US. Once the two merge they just sit and spin over the southeast U.S. into the middle of next week, effectively preventing any sort of movement of the ridge. Even though it will be warm or hot during the day depending on personal perspective, the saving grace this time of year is that with dry air, light winds, and clear skies, temperatures will always cool off significantly each night, even with the urban heat islands. Lows throughout the period should be in the low to mid 50s across the plains, 40s for the cool river valleys, and 30s in the mountain valleys. The other bonus from this pattern is although it will be very warm and dry, winds will be light so we are not anticipating fire weather concerns for the next week. Starting with Thursday, it will be dry and mostly clear across the area. With 700 mb temps around +16 degC, 90 degrees is likely across most of the plains below 5500 ft elevation. "Literally likely" given NBM has a >50% chance of exceeding 90 in metro Denver to Greeley, then northeast to the Nebraska border the chances exceed 80%. A dry cold front is expected to move across Colorado late Thursday into early Friday, taking the edge off temperatures but 700 mb temps should still be around +12 degC, supporting highs in the 80s across the plains and 70s in the mountain valleys and foothills. The global models actually advect a little bit of moisture in from the northeast (which is via the stationary trough/hurricane remnants over the southeast U.S.), and generates weak rain showers over the high country in the evening hours. Overall this is a low chance (10-20%) and with how warm it should be, rain would fall below 12,500 ft elevation. This weekend will remain very warm and dry under the influence of the ridge overhead and the stationary trough to the east, expect mid 80s across the plains and mid 70s for the mountain valleys and foothills. Next week still looks to be above normal temperature wise and mostly dry. The overall pattern is still a ridge overhead but the GFS is more optimistic about a frontal passage early next week on the backside of a strong trough moving across the Dakotas. The EC and it`s ensembles are much weaker with that trough and thus any potential cool down. The ensemble systems likewise are all over the place in terms of temperatures, which is not surprising a week out and in early October. All three ensemble systems have 30+ degree temperature spreads Mon-Tuesday next week, though in general it still looks mostly dry with maybe 20-30% of the members showing mountain precip, but much less chance across the I-25 corridor and plains. We shall see if this ridge continues to dominate next week, but that`s what it looks like at this point. && .AVIATION /00Z TAFS through 00Z Thursday/... Issued at 825 PM MDT Tue Sep 24 2024 Winds look to be light and variable this evening. Weak normal drainage wind patterns are expected by 04-05Z. There will be no ceiling issues. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE.......RJK SHORT TERM...Bonner LONG TERM....Schlatter AVIATION.....RJK