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Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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365 FXUS65 KBOU 130637 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1237 AM MDT Sat Jul 13 2024 .KEY MESSAGES... - Heat wave through Sunday with temperatures reaching 100 to 105 degrees across the urban corridor and plains. Important to take steps to limit outdoor activity, find ways to cool off, and stay hydrated as much as possible. - A Heat Advisory is in effect today through 8 pm for the I-25 corridor, expanding across all the plains for Saturday and Sunday. - Slight heat relief possible by Monday, but more so by Tuesday and Wednesday. Increasing chance of showers and thunderstorms for that period. && .UPDATE... Issued at 833 PM MDT Fri Jul 12 2024 Forecast updates are minimal for this evening. A warm night is in store with low temperatures well into the 60`s across the lower elevations, and even near 70F along the base of the foothills where downslope drainage winds will be more prevalent. Even the high mountain valleys should struggle to fall below about 45 degrees tonight. As mentioned below, we`ll have a slight increase in mid-level moisture tomorrow which should support a little more high-based afternoon convection, mainly in the mountains. Most of that convection is unlikely to bring wetting rain, so dry lightning will be a potential concern. However, instability still appears too marginal to sustain anything more than an isolated threat, so will hold off on fire weather headlines for our mountains for the time being. Lastly, it`s likely we`ll see a modest increase in smoke aloft late tomorrow, as smoke stemming from ongoing fires across the northwestern US rotates around the periphery of the high pressure into northern Colorado. Currently, thinking the higher concentrations are likely to hold off until the evening hours and mainly impact northeasternmost parts of our forecast area, so not expecting a notable effect on Saturday`s temperatures. Main impact will be slightly hazier skies, helped along also by increased ozone concentrations underneath the ridge. && .SHORT TERM /Through Saturday/... Issued at 205 PM MDT Fri Jul 12 2024 Limited cumulus development on satellite this aftn. There is still some potential for isold high based activity mainly along and south of I-70 over the higher terrain and across srn portions of Lincoln county. Radar also show a weak convergence boundary extending from Lincoln county into ern Washington county and Logan county. No cumulus along this boundary but not impossible an isold storm or two could develop along it, late this aftn or early this evening, where sfc based cape is maximized over Logan, Phillips and Sedgwick counties. Overnight through Sat, the center of a large upper level high will remain near the Four Corners area. Little change in 850-700 mb temps expected on Sat with highs staying in the 100-105 range across the plains. Record high at Denver is 100 on Sat, which should be broken. Meanwhile, there will be some increase in mid level moisture on Sat as water vapor imagery does show moisture over Utah rotating around the upper level high this aftn. As a result, will see at least widely sct high based shower/storms over the higher terrain Sat aftn. At lower elevations, with high T-TD spreads, could see isold high based showers, with mainly virga, producing gusty outflow winds across the I-25 Corridor as DCAPE values are decent. Over the far nern plains, sfc based CAPE is fcst to be from 500-1000 j/kg. Thus could see an isold strong storm or two if the cap can be broken by late aftn. && .LONG TERM /Saturday night through Friday/... Issued at 205 PM MDT Fri Jul 12 2024 Record to near record heat is expected to continue on Sunday as upper level high pressure dominates the Southern and Central Rockies. Max temperatures across the plains are expected to range between 100 and 105 degrees with 103 forecasted at DIA which would set a new record for the date. The high county will be quite warm as well with temperatures climbing above 80 in places such as Breckenridge, Dillon and Grand Lake. There should be enough mid level moisture around to produce isolated to scattered late afternoon and evening showers and storms, mainly over the higher terrain. Due to the lack of low level moisture, any showers and storms that form will most likely produce sprinkles and gusty winds. With the potential for dry lighting there may be some fire weather concerns across portions of the CWA. On Monday, the upper high is expected to weaken and flatten which will allow an upper level disturbance and associated cool front to move across Northeastern Colorado. Increased moisture behind the front should allow for a better chance of showers and storms which should result in somewhat cooler temperatures. Nevertheless, temperatures should still be hot across the plains with high ranging between 95 to 100 degrees. On Tuesday, the models are showing the upper ridge retrograding southwestward into Arizona in response to a potent shortwave moving across the Northern Great Lakes. Consequently, the upper flow aloft over Colorado should turn more northwesterly opening the door for occasional upper level disturbances and cold fronts. This should result in some relief in the heat along with higher precipitation chances, especially along and east of the Continental Divide. By Friday, temperatures may warm back up above 90 degrees on the plains with decreased precipitation chances. && .AVIATION /06Z TAFS through 06Z Sunday/... Issued at 1212 AM MDT Sat Jul 13 2024 VFR through the TAF period. Drainage flow has set in across the TAF sites and is expected to continue through the early morning hours. Today`s winds will be very similar to Friday`s pattern and turn to a northerly flow by the 17Z-19Z time frame. With more mid-level moisture expected for today and persistent dry lower- levels, high-based convection may develop in the afternoon causing gusty outflows that could lead to some wind gusts between the 35-45 kt range. Guidance indicates the strongest outflows will be at DEN and BJC. Guidance also shows some passing showers over the TAF sites, however, with the dry lower levels, these will likely be passing virga with any rainfall being the unlikely scenario. Drainage flow is expected to return overnight. && .FIRE WEATHER... Issued at 205 PM MDT Fri Jul 12 2024 Elevated fire danger will be in place across the plains foothills and higher valleys on Saturday due to hot and dry conditions along with low humidity levels. However, winds will be relatively light in most areas. && .BOU WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 10 AM this morning to 8 PM MDT this evening for COZ038>051. Heat Advisory from 10 AM to 8 PM MDT Sunday for COZ038>051. && $$ UPDATE...Rodriguez SHORT TERM...RPK LONG TERM...JK AVIATION...Bonner FIRE WEATHER...RPK