National Weather Service Forecast Discussion |
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000 FXUS65 KBOU 222011 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 211 PM MDT Wed Jul 22 2026 .KEY MESSAGES... - Storm coverage and intensity increases today and Thursday as monsoonal moisture moves into the region. Storms will be capable of producing locally heavy rainfall along with a localized threat of flash flooding. - Storm coverage expected to decrease again by Friday into this upcoming weekend, although mountain areas should see at least scattered storm coverage each afternoon and evening. - Temperatures will rise back into the upper 90`s to lower 100`s over northeast Colorado for the weekend into early next week. && .DISCUSSION /Through Wednesday/... Issued at 209 PM MDT Wed Jul 22 2026 Today and tomorrow will bring beneficial rainfall to a majority of the area with an isolated risk of flash flooding. High temperatures will reach the low to mid 90s once again today across the plains. There are already several storms ongoing across the high country and the Palmer Divide. Storms today will migrate into the plains by mid-afternoon and push east into the early evening. Scattered showers and thunderstorms will likely continue across our area through at least midnight tonight. Low-level flow is currently southeast which is continuing to provide ample moisture to our area. Additionally, we already have MLCAPE of 500-1000 J/kg and 20-30 knots of bulk shear as of early this afternoon. Storms will be outflow dominant, so any storm could produce gusty winds up to 50-60 mph with the highest risk across the plains. PWATs are at 150-200% of normal today and will approach climatological record high values on Thursday. We have a low flooding risk today given slow storm motions and the warm cloud layer depth approaching 5000 feet. The highest risk of flooding will be across the high country, mainly for burn areas and also where storms train or for areas that received significant rainfall yesterday (and thus have lower flash flood guidance). A shortwave moves through tomorrow during the day which should provide a slight increase in rainfall coverage tomorrow afternoon as well as high temperatures in the upper 80s for the plains. Storms will once again form in the high country by late morning to early afternoon and then move into the plains during the afternoon and evening. Storm motion will be faster than today (around 20 kts) given increased flow aloft, but tomorrow still carries a low risk for flash flooding. Additionally, the warm cloud layer should be deeper than today allowing for more efficient warm rain processes. Tomorrow will likely be the 3rd day in a row of rainfall for some areas. Rainfall rates could once again approach 2-3 inches per hour, so the WPC is now highlighting most of our area in a slight (2 out of 4) risk for flooding. In summary, there are several ingredients in place that lead us to be concerned about the potential for isolated instances of flash flooding in our area, but also some ingredients that will lessen the extent of the threat. Given the nature of these storms, there will be varying rainfall totals across short distances. Overall, additional rainfall totals across the area will generally be around 0.25 to 0.75 inches with some isolated totals of 2-3+ inches by Thursday evening. The high pressure will build back into the area starting Friday and strengthen through the weekend. The last several model runs have been keying in on the heat peaking on Sunday. This is when temperatures across the plains could reach 100 degrees F once again, given the thermal ridge aloft will be near 20 C and centered over our area. Record highs could be in play and a Heat Advisory could be needed as we get closer to the weekend. A chance for scattered showers is expected to continue through the weekend for the high country. By Monday and Tuesday, models show the ridge weakening and shifting slightly off to the southeast. At the same time, moisture from the remnants of Bertha could be pulled into the Southwest United States and into western Colorado. This will be something to watch as this could bring an increase in rain chances, mainly for the high country. Otherwise, highs should still be in the mid to upper 90s for the plains through much of next week. && .AVIATION /18Z TAFS through 18Z Thursday/... Issued at 1136 AM MDT Wed Jul 22 2026 Convection this afternoon remains the primary concern of the TAF period. KDEN recently reported an observation of 87F/55F, with ACARS soundings showing MLCIN quickly decreasing across the metro. Continued destabilization is likely over the next couple hours, with convection likely to develop sometime between about 20-22z. Forecast soundings would suggest the potential for at least some brief TSRA/+TSRA at the terminals, with relatively high confidence that this would occur sometime between 22-01z this afternoon. Scattered showers or a few thunderstorms could continue into the evening hours. Some guidance is fairly bullish on developing low stratus late this evening (~05z), with that potentially continuing through the overnight hours. This looks like it would be highly dependent on today`s convection, so at this time the only change was to add in a FEW010 group to DEN for most of the night. A reasonably similar forecast pattern is expected tomorrow. Guidance continues to advertise a favorable environment for slow moving SHRA/TSRA tomorrow afternoon, with the best chance of any storms coming after 21z Thursday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...MV AVIATION...Hiris