Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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416 FXUS65 KBOU 110930 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 330 AM MDT Sat May 11 2024 .KEY MESSAGES... - There will be a 30-70% chance of showers and a few thunderstorms this after well into tonight for the CWA. Snow levels should remain around 10,000 feet. - Showers/thunderstorms will continue most of the day Sunday, with locally moderate rainfall. - Drier and milder Monday outside of a few mountain showers/storms. - Turning more active again Tuesday onward with increasing thunderstorm potential. && .SHORT TERM /Through tonight/... Issued at 330 AM MDT Sat May 11 2024 Satellite pictures are showing and upper level circulation over the northwestern corner of Arizona at this time. There is a batch of lower and middle cloudiness over the southeastern quarter of Colorado at this time moving northeastward. Observations and radars are showing some light rain showers to our south also moving northeastward. Temperatures across the plains and lower foothills are in the mid 30s to lower 40s F at this time, with 20s and 30s over the rest of the CWA. The upper low is progged to move eastward into the Four Corners later this afternoon around 00Z, then it progged to be over the southern CWA by 12Z Sunday morning. There is weak synoptic scale upward vertical velocity over the CWA today and tonight according to the QG fields. Moderate southerly low level winds are expected over the plains through the day, with weak normal drainage winds tonight. Models show moisture to increase today and tonight across the CWA with precipitable water values getting into the 0.50 to 0.80 inch range for the plains and foothills by 12Z Sunday morning. There is some instability this afternoon with CAPE values in the 200-800 J/kg range for much of the CWA. Will leave the "scattered" to "likely" pops going this afternoon and evening for the forecast area along with limited thunderstorms. The better heating and instability warrants it. The QPF fields keep minor measurable precipitation in overnight as well. With the warming expected, snow will be relegated to the mountains above 9,500-10,000 feet today into this evening, then come down a little overnight. For temperatures, today`s high are 1-4 C warmer than Friday`s highs. && .LONG TERM /Sunday through Friday/... Issued at 139 AM MDT Sat May 11 2024 The extended forecast period kicks off with relatively active weather, as the upper-level closed low pushes into the plains passing directly over southeastern Colorado Sunday. As it does so, healthy mid-level wrap around flow will provide for a notable increase in column moisture, and forecast soundings are relatively consistent in depicting PWAT values of 0.70-0.80" over the lower elevations Sunday morning. With enough cold air present aloft leading to marginally unstable conditions, the ingredients appear aligned for the development of more expansive showers and even a few thunderstorms during the morning hours. Guidance suggests the southern mountains/foothills, Denver metro, and Palmer Divide would be favored for the heavier and more persistent precipitation, in line with a period of enhanced northeasterly upslope flow. This is not well reflected in the NBM, which continues to show the higher precipitation potential for the afternoon period. While scattered afternoon showers/thunderstorms certainly appear likely (50-70% chance for most), believe the greater potential for healthier rainfall totals outside of the plains will occur in the morning. Thus, made significant upward adjustments to the PoPs to reflect this. It`s worth noting that QPF ranges are still rather significant amongst ensemble members, and it would not be entirely surprising for a few (localized) spots to pick up 1" or more of rain on Sunday. Most locations should see much less than that, however. Upper ridging builds in on Monday with flow aloft returning to a more typical northwesterly regime. Enough moisture aloft will remain to support scattered afternoon convection primarily in the high country, but subsident flow in the lee of the Front Range will result in Monday having the lowest precipitation potential of the next several days. Temperatures will also warm a few degrees. The thermal ridge amplifies some for Tuesday under continued subsident flow, leading to renewed warming and pushing high temperatures well into the 70`s for the urban corridor, and possibly even low 80`s for parts of the South Platte River Valley. With warm surface conditions in place and colder air moving in aloft ahead of a developing trough over the Intermountain West, instability will be on the rise, resulting in increased afternoon thunderstorm coverage. A few could be on the stronger side both Tuesday and into Wednesday, especially in the eastern plains where instability should be maximized. The trough and associated cold front are slated to move through the region on Wednesday, bringing cooler temperatures. Thursday looks to be on the drier side in general as upper-level flow becomes more zonal behind the trough and we begin to warm back up. .AVIATION /06Z TAFS through 06Z Saturday/... Issued at 127 AM MDT Sat May 11 2024 Models all show weak drainage winds overnight tonight, then south-south-easterlies winds all day Saturday. I went with a TEMPO group late in the day for -TSRA as there looks to be enough instability for a few thunderstorms. From mid afternoon into the evening hours DIA could see SCT-BKN030-050 and even BKN-OVC025-040 later tonight. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...RJK LONG TERM....Rodriguez AVIATION.....RJK