Marine Weather and Tide Forecast for Tall Timber, CO

DISCUSSION /Through Sunday/
Issued at 237 PM MDT Sun Jun 15 2025

Fairly interesting convective setup this afternoon. A broad instability axis has set up across far eastern Colorado this afternoon, with surface T/Tds in low 90s/upper 50s to low 60s.
Unsurprisingly, the SPC Mesoanalysis shows as much as 3500-4000 J/kg of MLCAPE across the far northeast corner of the state.
Though the airmass is largely uncapped, we haven't seen much in the way of a cumulus field develop, though there has been a robust attempt at convective initiation near the surface moisture/theta-e gradient in the past half hour. Meanwhile, there's been some fairly strong showers aloft across the Denver metro, though these have developed over the drier airmass over southwest Denver (where Tds are in the mid 20s). There's some fascinating moisture gradients across the I-25 corridor, with some mid 40s to mid 50s dew points noted from Broomfield towards Fort Collins.

It comes as no surprise that guidance isn't handling every aspect of this complicated Colorado setup. There is good agreement that a broad cluster of convection will gradually congeal into a more organized MCS/QLCS as it tracks across the Cheyenne ridge into the northern/northeastern edges of our CWA later this evening, with at least a modest wind/hail threat. I can't help but wonder if the convection will simply be too cold pool dominant (given only modest 0-3/0-6km shear) for the higher end severe threat to develop. One caveat will be the attempt at more isolated convection in Morgan county, which could produce at least a short-lived severe threat this afternoon if it can break through the very weak cap still in place.

Beyond that... it's hot today (high of 94F at KDEN), and will be hot again tomorrow. Guidance is in reasonably good agreement that there will be less convection across the I-25 corridor, with temperatures once again climbing into the low to mid 90s. Where better moisture resides to the northeast, a few strong to severe storms will be possible. In general CAMs favor a few supercells drifting southeastward off the Cheyenne Ridge tomorrow afternoon.

Tuesday will be the coolest day of the week. Deeper boundary layer moisture is expected to advect in from the east Monday night into Tuesday, leaving surface dew points in the 50s to 60s across the lower elevations, along with a chance of some low stratus. A shortwave is expected to track across the region during the day, and should be the focal point for at least scattered thunderstorms. Again, there is a good amount of uncertainty about storm coverage that will need to be worked out in the next day or so. Wednesday will see a return to slightly warmer temperatures and should be fairly dry across the region.

Attention then turns to what could be a few days of near record or record heat across the region from Thursday into the weekend, as a broad ridge expands across the south central CONUS.
Deterministic guidance continues to be quite bullish with the heat, advertising 2-3 days of temperatures of >100F over the Denver area (and hotter across the plains). That signal is also obvious in nearly every ensemble tool available... with GEFS/ECMWF ensemble guidance showing normalized 700mb temperature anomalies near 2-3 sigma (loosely translating to a recurrence interval of once in every 10-30 years). ECMWF EFI values are >0.90 both Friday and Saturday, which indicates good model certainty. All but one ensemble member has >100F temperatures at DEN. While I still think that some guidance is at least slightly overdone... there has been little change in the overall pattern and heat headlines look likely by as early as Thursday. Stay tuned.

In addition to the heat... there will also be some fire weather concerns as we get towards next weekend, with a dry southwesterly flow increasing as the ridge flattens and a broad trough axis deepens over the west. There is the potential for at least a couple of days of critical fire weather conditions, which will need to be monitored closely as we get later into the week.

AVIATION /18Z TAFS through 18Z Monday/
Issued at 1143 AM MDT Sun Jun 15 2025

VFR conditions are possible for the TAF period. Scattered elevated showers/storms with VRB gusty outflows will develop this afternoon as early as 21Z. There is a chance that these storms will initiate just east of DIA, however outflows up to 30 kts are still expected. Winds will return to drainage overnight.

A similar wind pattern is expected tomorrow, with drainage winds turning VRB by 16Z. Winds should prevail from the E/NE after that with gusty outflows from showers between 20Z and 00Z.

BOU WATCHES/WARNINGS/ADVISORIES
None.