Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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663 FXUS65 KBOU 161656 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1056 AM MDT Sun Jun 16 2024 .KEY MESSAGES... - Warmer, drier, and breezy today with Heat Advisories across the southeast Denver metro. Well above normal temperatures will continue on Monday. - Critical fire weather conditions today and again on Monday. - Snowmelt producing minor impacts from high streams. Gradually diminishing flows next week. - Cooler for Tuesday and Wednesday && .UPDATE... Issued at 1016 AM MDT Sun Jun 16 2024 The cold front mentioned in yesterday`s discussion is indeed throwing a wrench into the forecast. The front has been a bit stronger than forecast and has raced across the Denver metro in the past couple of hours. It had warmed up considerably to the south of the boundary, with an 87F recorded at Centennial with Limon also up to 93F. Meanwhile, temperatures are still in the low to upper 70s north of the boundary with dew points in the upper 40s to low 50s. How the temperature/moisture gradient evolves today is still somewhat uncertain. The HRRR insists on quickly mixing out the shallow moisture later this afternoon with highs in the mid/upper 90s for the southeast metro, while other CAMs maintain a deeper moist layer that never fully erodes, leaving temperatures closer to 90F. Reality will likely be somewhere between these two scenarios with highs generally in the low 90s across Denver and into the mid/upper 90s southeast into Lincoln county. Ultimately could probably cancel the Heat Advisory for Denver itself but for simplicity will just let it roll until there`s an obvious sign one way or another. Ultimately did make several changes to the temperature grids today that are closer to the multi-model mean. How far the boundary sinks south will also play a role with the Red Flag Warnings which go into effect at noon. With mixing increasing this afternoon there should be fairly widespread critical fire weather conditions across the Palmer Divide and Lincoln county. Also can`t rule out an isolated storm or two later this evening, mainly along the I-76 corridor northeast of Fort Morgan... where a marginal risk was drawn by the SPC. It will be hard to get a storm to break through the CAP but models do have an unstable (MLCAPE ~1000 J/kg), sheared airmass that would support a hail/wind threat (especially with DCAPEs > 1500 J/kg). && .SHORT TERM /Through tonight/... Issued at 247 AM MDT Sun Jun 16 2024 Hot and dry weather will continue today. Expect mostly sunny skies today due to limited moisture and instability. CAMs are in favor of Denver cyclone development this afternoon but there is still uncertainty in where this will set up. Although wind direction is still in question, wind speeds between 15-20 mph will produce wind gusts up to 30 mph along the Palmer Divide and adjacent plains. This pattern combined with low relative humidities as low as 10 percent will lead to critical fire weather conditions this afternoon. Similar conditions will also occur for portions of Grand and Summit counties. Additionally, 700mb temperatures increase between 16-18C. This will likely lead to afternoon highs between 90-100 for the urban corridor and plains. Mountains and foothills also trend above normal this afternoon reaching mid 60s to upper 70s with a few mountain valleys reaching 80. A Heat Advisory covers portions of the Palmer Divide, metro Denver and southeast plains through 7 PM MDT this evening. Those sensitive to heat should limited exposure outdoors. A marginal risk of storms exists for the northeast corner where an isolated storm could occur clipping our area from the Nebraska Panhandle this evening. Tonight, low temperatures are slightly above normal and mostly clear skies are expected. && .LONG TERM /Monday through Saturday/... Issued at 247 AM MDT Sun Jun 16 2024 SW flow aloft will continue on Mon as an upper level trough moves into the nrn Rockies. As mentioned yesterday, will still have a boundary associated with convection to the north located somewhere over nern CO. Based on current data, it appears this boundary will be a tad further north and located near the CO-NE border. South of the boundary temps will be in the 95-100 degree range across the plains while closer to the NE border highs may stay in the upper 80`s to lower 90`s. Meanwhile, along and north of the boundary decent MLCAPE will be in place but capping inversion may still inhibit tstm development, so have kept pops in the isold category. For late Mon night into Tue, a cold front will move across the plains. This front will drop temps back into the upper 70s to lower 80s for aftn highs over nern CO. Any low level moisture with this front will move into the higher terrain, however, MLCAPE is marginal at best so any tstm development will be rather isold. Looking ahead to Tue night into early Wed, eventually the low level flow will become more easterly in the lower levels. This will allow for some return of deeper low level moisture. At this time, it`s not clear how far north this moisture will be as it may end up further south over the Palmer Divide and sern CO. Meanwhile, the flow aloft will remain from the SW. The blended solution has showers and tstms developing over the plains Tue night with rather high pops. Confidence in this is low at best since this activity could end up further to the east and south. Thus have lowered pops into the chc category. For the rest of Wed, the low level flow will become more southeast which will allow for deeper low level moisture to move across the plains. This should lead to somewhat better instability, however, may still have to contend with a cap, as convective temps may not be reached across the plains. Over the higher terrain, there will be a chc of aftn storms. Highs will only be in the mid 70`s to lower 80s across the plains. By Wed night into early Thu, both the ECMWF and GFS indicate a weak disturbance embedded in SW flow aloft may move across. This feature combined with a warm advection pattern may lead to a chc of elevated convection across portions of the plains. For the rest of Thu, MLCAPE should gradually increase by aftn with a chc of storms in the late aftn and evening hours. Highs will be warmer as readings rise into the mid to upper 80s. On Fri, the flow aloft will continue from the SW. Overall, there should be enough instability for at least sct storms across the area. && .AVIATION /12Z TAFS through 12Z Monday/... Issued at 509 AM MDT Sun Jun 16 2024 VFR conditions are expected through the TAF period. A Denver cyclone may lead to a tricky wind forecast in the afternoon as winds may shirt briefly northeast to southeast as the cyclone pushes east. By 20Z, expect wind speeds to increase between 11-15kts producing gusts up to 25kts. Drainage winds are possible by early evening. && .FIRE WEATHER... Issued at 247 AM MDT Sun Jun 16 2024 Critical fire weather conditions are likely for portions of Grand and Summit counties due to low humidity near 12-14 percent and southwesterly winds producing wind gusts up to 25 mph this afternoon. Additionally, similar conditions will occur for the Palmer Divide, and adjacent plains including metro Denver. Elevated to Critical fire conditions will be in place on Monday across the Palmer Divide, portions of the Denver Metro area and across South Park and Middle Park. Gusty winds, low humidity and well above normal temperatures will occur from midday Monday through early Monday evening. A cold front will move across on Tuesday which will decrease fire conditions in most areas. && .HYDROLOGY... Issued at 247 AM MDT Sun Jun 16 2024 Elevated flows continue in the mountain streams, with Flood Advisories remaining in effect for the streams above Granby and Grand Lake. Remain alert of the dangers of water that is running high and cold. Flows are expected to gradually decrease next week as the peak snowmelt is passing by. && .BOU WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 6 PM MDT this evening for COZ213-214-241- 245>247. Heat Advisory until 7 PM MDT this evening for COZ040-041-045>047. && $$ UPDATE...Hiris SHORT TERM...AD LONG TERM...RPK AVIATION...AD FIRE WEATHER...AD/RPK HYDROLOGY...AD/RPK