Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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083 FXUS65 KBOU 141545 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 945 AM MDT Sun Jul 14 2024 .KEY MESSAGES... - Heat wave and Heat Advisory continues today with highs reaching 100 to 105 degrees across the Urban Corridor. Across the plains highs may stay in the upper 90`s to around 100. Important to take steps to limit outdoor activity, find ways to cool off, and stay hydrated as much as possible. - Dry lightning threat and new fire starts possible today. - Strong and gusty microburst winds possible bothy today and Monday with scattered high based showers and isolated thunderstorms. - Only slight heat relief expected Monday, with far more relief by Tuesday. Increasing chance of showers and thunderstorms both Tuesday and Wednesday. - More typical summer weather for the latter half of this week with scattered afternoon showers and storms, and temperatures averaging closer to normal. && .UPDATE... Issued at 942 AM MDT Sun Jul 14 2024 An outflow boundary is moving across the northeast plains this morning and currently is along a New Raymer to Fort Morgan to Woodrow line. Behind this boundary temps are mainly in the 70`s while west of it readings are in the 85-90 degree range. Main question is will it move into the I-25 Corridor or washout. If it washes out then previous fcst highs along the I-25 Corridor should be reached. Behind this boundary readings may hold in the 90`s this aftn and not get above 100 degrees. Will continue to monitor trends over the next 1-2 hours and make temperature adjustments if needed. Meanwhile, there is more more moisture over the area today than yesterday so still expect better coverage of mainly higher based showers and storms. There still is some question as to how much lightning there will be over the higher terrain as activty may end up being more higher based showers than storms. Across the plains, behind the outflow boundary there is better low level moisture. Thus this will lead to better instability along with some potential for stronger tstm activity by late aftn into the early evening hours. Meanwhile, to the west of the boundary there will be larger T-TD spreads with a higher potential for microburst activity. && .SHORT TERM /Through Monday/... Issued at 228 AM MDT Sun Jul 14 2024 Day three of the Colorado heat wave will continue today as temperatures are expected to range from the upper 90s to 104 across the plains and urban corridor. Once again, a Heat Advisory will be in place from 10 AM to 8 PM for the aforementioned locations. With persistent dry conditions and potential for dry lightning across the higher terrain this afternoon, critical fire weather conditions will be a concern for today, therefore we have upgraded our Fire Weather Watch to a Red Flag Warning from 12 PM this afternoon through 9 PM this evening. See the Fire Weather section below for more details. The general pattern remains consistent with what has been discussed over the last week with heat headlines. Anomalous 500 mb heights (~5970 m) mixed with elevated 700 mb temperatures (~20C) will translate to surface temperatures reaching for the record books. The latest guidance shows a slight decrease in 700 mb temperatures from previous model runs (only by about 1-2C), and with increased cloud coverage expected for today, temperatures may be slightly cooler than previously expected. It will still be HOT...just maybe slightly less HOT. The forecast high temp for DIA is 101F, which is still a degree hotter than the daily record for this location (last observed in 1878). While we know today will be hot, there is some uncertainty regarding whether forecast temperatures across portions of the plains for today will come to fruition as current radar shows an MCS now entering northern Nebraska. This could bring a surge of northeasterly winds to the forecast area later this morning as it dissipates. With a similar occurrence yesterday morning aiding in temperatures being slightly lower than expected, we will monitor conditions this morning and adjust temperatures down if needed. More certainty resides in the high mountain valleys reaching the high 80s with mid 70s across the other higher terrain. With flow aloft transitioning to a more westerly flow later today, overnight temperatures along the base of the foothills may stay elevated slightly more than other locations due to compressional heating effects. Across the plains, mid to high 60s are expected, and mid to high 40s for the higher elevations. Forecast soundings indicate an environment capable of producing high- based convection and potential for gusty outflows with DCAPE values ranging from 1200-1900 J/kg throughout the afternoon. Instability still looks marginal, however, slightly higher than yesterday. CAMs show a greater coverage of showers than yesterday, and current satellite imagery shows increased mid-level moisture as well. Therefore, we are expecting scattered showers and isolated weak thunderstorms to develop this afternoon across the mountains and move eastward onto the plains through the evening. These will likely contain isolated dry lightning as well. These showers will be capable of producing light rainfall and gusty microburst winds to 50 mph or greater. For those of you considering recreating on the water, it would be a good day to be aware that gusty winds can occur suddenly in this environment and create dangerous conditions. && .LONG TERM /Monday night through Saturday/... Issued at 330 AM MDT Sun Jul 14 2024 While it will still be hot on Monday with a quick warmup and shallow inversions to start the day, we will see a little heat relief in the form of a weak backdoor "cool" front. This front appears to push across the plains in the morning but given the shallow inversions and expected strong mixing, the front or push will essentially lose its identity. That said, the turn to upslope winds and increasing mid/upper level moisture and cloudiness will serve to take a few degrees of today`s scorching heat. Mid to upper 90s should generally be the highs across the plains and I-25 Corridor. Shower and storm coverage should see an uptick with the increase in mid/upper level moisture as well as the upslope component and weak low level moisture advection. However, significant DCAPE near 1500-1800 J/kg still means strong, gusty outflow winds from any convective activity. Real relief from the heat will occur for Tuesday, as a reinforcing cold front pushes across the plains. This will also bring additional low level moisture, resulting in an increase in shower and storm coverage and propensity for more rainfall from storms for a change as storm intensity picks up. That uptick in convection should continue into Wednesday, along with cooler temperatures (80-90% chance of temperatures below normal across the plains for Wednesday). The deterministic forecast rides close to ensemble average of mid 80s across the plains. For Thursday through Saturday, there is reasonable agreement that the ridge retrogrades westward into the Desert Southwest and Great Basin, while a trough settles across the Great Lakes and Midwest. We`ll be on the edge of the more significant cooling in this northerly flow pattern, and hard to gauge when fronts with additional cooling could move through. Right now, the deterministic forecast is close to climatology with regard to temperatures and PoPs which seems fine, but one or two of those days will likely end up on the cooler side of guidance depending on timing of backdoor cold fronts. && .AVIATION /12Z TAFS through 12Z Monday/... Issued at 450 AM MDT Sun Jul 14 2024 The main concern for today will be high-based convection causing microburst winds up to 45 kts across the TAF sites. Increasing potential for this after 21Z. Drainage winds this morning are expected to transition to a northerly component by 17Z/18Z. VFR through the TAF period. && .FIRE WEATHER... Issued at 330 AM MDT Sun Jul 14 2024 Widespread elevated to near-critical fire weather conditions will remain in place across most of the area on Sunday and hot and dry conditions prevail. Additionally, isolated to scattered dry lightning will result in a heightened threat for lightning-induced wildfire ignitions, particularly in the mountains, foothills, and northern urban corridor. Thus, we`ve upgraded the Fire Weather Watch to a Red Flag Warning for these locations. Monday could continue a dry lightning threat with still dry and very warm low levels. However, overall moisture content in the atmosphere is increasing so most storms, at least in the mountains, should be producing at least some rainfall. && .BOU WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 9 PM MDT this evening for COZ211>218-238. Heat Advisory until 8 PM MDT this evening for COZ038>051. && $$ UPDATE...RPK SHORT TERM...Bonner LONG TERM...Barjenbruch AVIATION...Bonner FIRE WEATHER...Bonner