945 FXUS65 KPUB 020607 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 1207 AM MDT Thu Sep 2 2021 .UPDATE... Issued at 914 PM MDT Wed Sep 1 2021 Updated forecast to end flash flood watch across the mountains. Main wave is pushing east through the Sangres and I-25 corridor currently, with only some scattered lighter showers farther west. Given the general weakening trend on radar over the past hour and most CAMs showing high terrain precip tapering to isolated showers by 06z, heavy rainfall/flash flood threat looks minimal. && .SHORT TERM...(This evening through Thursday) Issued at 327 PM MDT Wed Sep 1 2021 The reminents of hurricane Nora is currently overhead, as well as a monsoonal tap from the Pacific Ocean, both of which are causing widespread showers and thunderstorms over the mountains and mountain valleys. Though there is abundant moisture (90th percentile and higher PWATs according to climatology at upper air sites), antecedent cloud cover across the region inhibited full heating across the western portions of the CWA and the moist atmosphere created moist adiabatic lapse rates created low CAPE values across the CWA. The HREF's maximum CAPE products has pockets of MUCAPE over the region, with the HREF's mean MUCAPE putting around 500-800J/kg across the region through the evening. Through the rest of the evening this looks like a widespread stratiform rain event with pockets of heavier rain that may cause flash flooding over the mountains, mountain valleys, the burn scars, the Chalk Cliffs region, and Poncha Pass. That main vorticity maxima that is passing overhead will propagate over the plains causing scattered showers and thunderstorms through around 12AM or so over the I-25 corridor and around 1AM or so over the far eastern plains. Weaker shortwaves will keep isolated to scattered showers over the mountains during the overnight, whereas the mountain valley and plains should experience dry conditions. The upper level flow will shift to the southwest as a complex of low pressure systems remain over the Pacific Northwest and western Canada and an upper level anticyclone forms over the Southern Plains. The upper level pattern continues to support water vapor flux increase over the region. Weak shortwaves will spark isolated to scattered thunderstorms, mainly over the Continental Divide tomorrow afternoon. The strongest of the weak shortwaves will propagate over Lake, Chaffee, Fremont, and Teller Counties and then will push a weak cold front over the eastern plains. Scattered showers and thunderstorms will be the result from the passing shortwave and cold front. El Paso County will start seeing scattered showers and thunderstorms by mid-day whereas the eastern plains will start seeing the precipitation during the beginning of the long term forecast (see below). Low temperatures tonight will be a bit warmer due to radiation being insulated through cloud cover and higher dew points from fresh and ongoing rainfall. Expect temperatures in the 60s to low 70s over the plains, the upper 40s to low 50s over the mountain valleys and Teller County, and the 40s over Lake County. High temperatures tomorrow will be a bit cooler due to the frontal passage and the fresh rainfall. Temperatures will be in the 80s to low 90s over the plains, the mid 70s over the mountain valleys, and the 60s over Teller and Lake Counties. .LONG TERM...(Thursday night through Wednesday) Issued at 327 PM MDT Wed Sep 1 2021 Thursday night-Friday night...Moderate west to southwest flow aloft continues across the region through the day Friday as embedded short energy continues to translate across the Northern Rockies. Passing energy sends a weak front across the eastern Plains into Thursday night, with models indicating enough moisture and lift in place to support isolated to scattered showers and storms across the eastern mountains and plains. Moist upslope flow developing across the plains behind the front will help to develop areas of stratus across the plains into Friday morning, with mid level waa keeping the potential for a few showers or storms across the eastern mts and plains as well. Drier air within the more westerly flow aloft continues to move into western Colorado on Friday, with moist upslope flow across the plains keeping low level moisture in place, with capes of 500 to 1500 j/kg progged across eastern colorado into Friday afternoon. This, along with the westerly flow aloft (bulk shear 25-35kts) will support the potential for a few strong to severe storms producing large hail and gusty outflow winds across the plains Friday afternoon and evening. The main concern/limiting factor for storms across southeastern Colorado on Friday is will it be too cool/stable for storms to initiate through the afternoon? With that said, some models are indicating the best chances of storms being across northeastern Colorado Friday afternoon, with convective outflows then helping to initiate storms across southeastern Colorado late Friday afternoon into early Saturday morning. Low temperatures look to be at to slightly above seasonal levels across the area, with Friday's highs being at to slightly below seasonal levels in the mid 70s to mid 80s across the lower elevations, and mainly in 50s and 60s across the higher terrain. Saturday continues to look like a transition day, as upper level ridging building across the Great Basin will keep moderate west to northwest flow aloft across the Rockies. Best available moisture continues to be across progged across the southern mountains and southeast plains, leading to continued chances of showers and storms initiating across the mountains Saturday afternoon, and then moving across the adjacent plains through the far southeast plains later Saturday afternoon and evening. Further west, more isolated and higher based showers and storms look to be in place Saturday afternoon and early evening. Temperatures on Saturday look to be around seasonal levels. Sunday-Wednesday...Upper level ridging across the Great Basin remains progged to slowly move east which will keep drier air and generally weak northerly flow in place across Rockies. This supports temperatures warming back to at and above seasonal levels, with only slight chances of diurnal showers and storms, mainly over and near the higher terrain, into the middle of next week. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1200 AM MDT Thu Sep 2 2021 VFR conditions will be predominant throughout the forecast period for all TAF sites as SHRA exits the area throughout the night, CIGs will remain fairly high based although they could come down a bit in SHRA or TSRA in the vicinity of all terminals for tomorrow afternoon and evening, however this looks to be very isolated and may not occur. Precipitation could also reduce VIS temporarily into possibly MVFR or even IFR criteria in heavier showers and/or storms. It is important to keep in mind that outflows can also cause sudden erratic wind shifts to occur at or in the vicinity of anyone of these terminals. Also be advised that some light to moderate CAT could be possible in the vicinity of KPUB during the afternoon and evening due to gusty surface winds. Winds for KALS will be light and variable, then increase tomorrow out of the SW and eventually shift back to the SE towards the end of the forecast period. For KCOS, they will mainly be out of the NNW- NNE throughout the entire forecast period. For KPUB, they will mainly be out of the west and then shift more to the NW and increase, and could be gusty at times up to 25 kts during the afternoon and evening hours. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...PETERSEN SHORT TERM...SKELLY LONG TERM...MW AVIATION...STEWARD