Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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279 FXUS65 KBOU 202347 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 547 PM MDT Sat Jul 20 2024 .KEY MESSAGES... - Isolated to scattered afternoon showers and storms this afternoon. An additional round of storms possible overnight tonight. - Cooler on Sunday, with continued rain chances. - Gradual warming trend next week with drier conditions. && .SHORT TERM /Through Sunday/... Issued at 220 PM MDT Sat Jul 20 2024 Satellite and radar this afternoon show a few weak storms across the forecast area, mainly over the northeastern plains. No significant updates to the forecast through this evening with additional storms likely developing across the Front Range mountains/foothills over the next few hours. As we get into tonight and tomorrow`s forecast, confidence decreases pretty quickly. Guidance has slowly warmed up to the idea of a cluster of showers and embedded thunderstorms late this evening/early tonight. This appears to be linked to the convection currently developing across central Wyoming. We maintained at least chance PoPs through the overnight. If you`re a fan of rain across the I-25 corridor, it will be worth watching short term model trends to see if models come into better agreement. From there, there`s a few more "ifs" to discuss. If we do get overnight rain... that may lead to some Sunday morning stratus. If we get morning stratus... that likely limits our daytime heating and subsequent afternoon destabilization... leading to less coverage of showers/storms during the day Sunday. On the other hand, a sunny start to Sunday would favor better instability and widespread showers and storms by late morning or early afternoon. As a whole, confidence of rain at any given hour is pretty low... but the pattern favors a good chance (>70% from the GEFS/ECME) of a wetting rainfall (>0.10") across the Front Range and adjacent plains by Sunday evening. Stay tuned! && .LONG TERM /Sunday night through Saturday/... Issued at 240 PM MDT Sat Jul 20 2024 The CWA looks to stay in relatively weak northerly flow aloft with high amplitude upper ridging to our west and northwest and upper troughing east of Colorado Sunday night through Tuesday night. The synoptic scale energy is expected to be weak downward motion to neutral through the five periods. The boundary level wind and surface pressure fields keep fairly normal diurnal surface wind patterns for the CWA. The precipitable water and boundary layer dew point fields show drying on Monday from Sunday; then more drying on Tuesday. CAPE is limited through the periods. As far as convective chances go, forecast soundings and QPF fields show the the best chances of measurable rainfall over the high country for late day Monday and only "isolated" coverage for the plains. Chances decrease further on Tuesday with less moisture availability and less instability. Heavy rain chances are marginal at best on Monday, decreasing further on Tuesday. For temperatures, Monday`s highs warm up a bit from Sunday`s readings but they still look to be below seasonal normals across the forecast area. On Tuesday, readings climb a bit higher but temperatures still look a tad below seasonal normals. For the later days, Wednesday through Saturday, the upper ridge to our west pushes eastward into and across Colorado through Friday night. By Saturday, some weak troughing gets into Colorado. Drying, subsidence and warming will be the rule into Friday. Rainfall chances get better again on Saturday along with some minor cooling. && .AVIATION /00Z TAFS through 00Z Monday/... Issued at 536 PM MDT Sat Jul 20 2024 A line of strong to severe storms is progressing through Morgan County as of this writing. These storms have formed along an outflow boundary that will move southwestward toward the terminals this evening. Confidence is growing greatly that this outflow boundary will produce storms with gusty winds. Winds up to 40 knots are possible. The best chance for these storms to occur is between 02-05Z. Therefore, a TEMPO group was added to all terminals. The storms will end this evening and light winds are expected throughout the night. There is a chance that stratus clouds develop in the morning around 3,000 feet. However, this chance is low enough that it wasn`t included in the TAFs at this time. Tomorrow afternoon, isolated showers and storms will form. These storms could produce gusty winds and reduce visibility. The chance for these storms to impact the terminals is around 30 percent so a PROB 30 was included. We also want to note that there is plenty of smoke in the visible satellite imagery that is headed to Colorado. It may impact visibility especially in the higher levels of the troposphere. && .HYDROLOGY... Issued at 220 PM MDT Sat Jul 20 2024 Despite relatively high chances for precipitation, the burn area flash flooding threat remains limited. Thunderstorms this afternoon will be widely scattered and may pose a brief heavy rain threat, but storm motions near 15-20kt will push storms off the burn areas quickly. Additional showers and storms are possible tonight but most guidance keeps these over the plains. Cooler temperatures tomorrow will likely limit instability and keep storms weak enough to avoid widespread issues. Storm motions should generally be slower tomorrow and if a strong storm or two manages to develop it could produce enough rainfall for isolated issues. A warming and drying trend is expected next week, with no significant hydrological concerns. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Hiris LONG TERM....RJK AVIATION...Danielson HYDROLOGY....Hiris