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864 FXUS65 KBOU 131112 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 512 AM MDT Wed Aug 13 2025 .KEY MESSAGES... - Hot weather Wednesday and Thursday. - Elevated fire weather concerns today. Critical fire weather conditions possible Thursday in the mountains due to dry lightning. - Moisture increases sufficiently for a chance of storms most areas Friday through the weekend. && .DISCUSSION /Through Tuesday/... Issued at 248 PM MDT Tue Aug 12 2025 Any isolated showers/weak storms that form over the mountains and higher terrain will be dissipating with the loss of daytime heating and instability early this evening. We`ll then see mostly clear skies overnight, with temperatures settling to near normal levels in the dry but warming airmass. Wednesday we`ll turn up the heat, as the upper level ridge axis and thermal ridge shift our way. High temperatures should reach the mid to upper 90s over the plains and I-25 Corridor. We still expect enough moisture and heating for isolated high based showers and storms again during the afternoon and early evening. In fact, we think we`ll reach convective temperatures so some virga with gusty winds/microbursts reaching the I-25 Urban Corridor can be expected. We`ve added some low chance of -TSRA with gusty winds attributes for that. Thursday features much of the same, with a slight further bump in temperatures and enough for a couple spots on the plains to reach 100F. The record for Denver is 100F set in 1962, and we`ll be getting close to that but most likely stay just shy around 98-99F given latest thermal prognostications. Once again, most convection will be high based due to deep mixing and dry low levels. At the same time, mid/upper level moisture starts to increase, and that should lead to higher weak shower/storm coverage. With that comes concerns for dry lightning and new fire starts, see more in the Fire Weather Discussion section below. Ensembles show good agreement that moisture increases further for Friday, so storms should be more numerous, a little stronger, and produce more meaningful rainfall. It`s not terribly rich though with precipitable water values just slightly above normal (100-120%) over the mountains. The increased clouds and showers should take a couple degrees off highs from Friday, but it will still be above normal. Ensembles are generally in agreement bringing a weak shortwave out fo the southwest by sometime Saturday. This could bring one more fairly active weather day but overall instability and moisture are not terribly high. Then, some drying would still be anticipated in the shortwaves wake, leading to less convective activity by early next week. Ensemble averages show temperatures averaging just above normal. && .AVIATION /12Z TAFS through 12Z Thursday/... Issued at 511 AM MDT Wed Aug 13 2025 S to SSW winds will become SW by 15z and then shift to the NNE by 19z. By 22z winds will have more of an easterly component. There is a low chance (10-15%) of a high based shower affecting the airports from 22z to 01z with brief gusty outflow wnds up to 40 mph possible. After 01Z winds will become S or SE and then become SSW by 06z. && .FIRE WEATHER... Issued at 511 AM MDT Wed Aug 13 2025 Today, hot temperatures will bring low humidity of 15% or less over the high mountain valleys, foothills, and I-25 Corridor and nearby adjacent plains. Winds will be relatively light and under critical values, although Fire Weather Zones 211, 213, and 217 will see gusts of 20-25 mph and thus at least elevated fire weather conditions there. On Thursday, critical fire weather conditions will be possible due to dry lightning. We expect an increase to scattered storm coverage as upper level moisture increases slightly. However, humidities will remain very low in the mountains due to very warm and dry low levels. Thus, dry thunderstorms (storms with lightning but little rainfall) will be possible, in addition to gusty outflow winds. && .BOU WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Thursday afternoon through Thursday evening for COZ211>218. && $$ DISCUSSION.....Barjenbruch AVIATION...RPK FIRE WEATHER...RPK