Marine Weather and Tide Forecast for Brighton, CO

DISCUSSION /Through Wednesday/
Issued at 250 PM MDT Wed May 21 2025

Main forecast concern will surround thunderstorm chances and intensity as we head into the Memorial Day Weekend. Until then, we'll be in a warm weather pattern, but still a couple thunderstorms around (~20% coverage).

Breezy conditions and any lingering showers/weak storm over the mountains and northeastern plains will come to an end by this evening with a drying and stabilizing airmass. Temperatures will be just below normal given clearing skies and a fairly dry airmass in place.

Thursday will feature a continuation of our recent warming trend, with highs across the plains pushing into the 75-80 degree range as the thermal ridge shifts closer to the forecast area. Regarding shower and storm chances, we expect temperatures to get just warm enough to spark a few showers/storms over the higher terrain in the afternoon, shifting onto portions of the plains by very late afternoon and evening. Any showers and storms will be high based and light due to a deep and dry subcloud layer. A few of these could produce gusty outflow winds to 40+ mph given the inverted-v profiles and DCAPE growing to over 1000 J/kg.

Friday is still shaping up to be the warmest day of the week ahead, as the upper level ridge and thermal ridge shift across Colorado. We expect highs to push into the mid to upper 80s on the plains, with 70s in the foothills and high valleys, and mainly 60s in the mountains. Low level moisture starts to increase on the plains, and that will lead to increasing MLCAPE with up to around 1000 J/kg over the northeast corner, while west of that (roughly Sterling to Akron) it will be much drier. There will also be a battle between sufficient instability along that dryline/moisture interface for any stronger surface based convection. Typically these scenarios can offer a narrow ribbon where a couple stronger or even isolated severe storms could occur, so that's still something to watch on the eastern plains for Friday late afternoon and evening. SPC has moved the northeast corner of the state into Marginal Risk for Friday and that seems reasonable. Finally, it will be breezy again, but spring green- up is sufficient for fuels to be not receptive to fire spread at this time.

The weather pattern becomes more active this weekend, as an upper level trough, increasing low level moisture, and some upslope all join together. For Saturday, low level moisture is expected to increase further as east/southeast winds develop and advect higher dewpoints across the High Plains. This occurs as surface pressure falls are expected ahead of an upper level trough pushing east across the Great Basin and Northern Rockies. That would be more favorable for stronger and potentially a few severe storms. The trend in the models is for a stronger push of upslope, so this could more effectively push the threat of severe storms closer to the Front Range and I-25 Corridor. Meanwhile, the eastern plains could stay much cooler with light showers/drizzle around - effectively limiting a stronger storm threat there. For Sunday, there has been a continued trend toward cooler temperatures, which would limit instability and any severe storm threat. Sunday is also trending wetter with the arrival of the upper trough, QG lift, and deeper moisture. Showers and a couple thunderstorms will be likely (60-70%) chance across nearly the entire forecast area.

While considerable uncertainty still exists for the eventual weather pattern early next week (caught somewhere in between a trough to the east and a building ridge/weak zonal flow over the Great Basin or Northern Rockies), we'll likely see a continued chance of showers and a few storms each day. That will be due to lingering moisture in light flow aloft. Temperatures should begin a slow warming trend, which typically leads to increasing instability and a few stronger storms possible as we head toward midweek.

AVIATION /18Z TAFS through 18Z Friday/
Issued at 1213 PM MDT Thu May 22 2025

Forecast is looking on track. Main concern will be winds and possible outflows from a high based shower/storm late this afternoon/evening. Winds have already transitioned to E/SE, but a boundary is lurking just to the west of KDEN that will need to be monitored. We do think it eventually backs to the west through 00Z with increased mixing, but a small chance the boundary stalls very close to the west side of the KDEN field. Robust SE-S winds will then carry into the overnight period, with potential for gusts 22-30 kts between 22Z and 10Z. Isolated high based virga or even -SHRA will be possible 22Z-02Z, and may produce (20% chance)
of slightly gustier winds. Winds will be considerably weaker west of I-25 (e.g. KBJC). Winds will weaken 09Z-12Z Friday, and then turn clockwise through 18Z. VFR conditions will prevail for all terminals through the TAF period.

BOU WATCHES/WARNINGS/ADVISORIES
None.