Nunn, CO 80648 Weather

Key messages

- Areas of dense fog across portions of the plains through mid morning Friday. This fog will impact the morning commute from Denver north along I-25, northeast along I-76, and east along portions of I-70. More fog will be possible Friday night into Saturday morning.

- Mild and mostly dry to end the week.

- Unsettled weather returns late this weekend and early next week. Mountain snow is likely (>70% chance) above 8500ft during this time. High uncertainty remains for the foothills and plains.

.DISCUSSION /Through Thursday/: Issued at 1026 PM MDT Thu Oct 29 2026

For late tonight thru Fri morning main concern is how widespread dense fog may become along portions of the I-25 Corridor from Denver north to the Wyoming border and points eastward. HRRR has been consistent in showing fog developing over ern Larimer and Weld county by midnight and then spreading it southward into nrn portions of the Denver area by 3 am or 4 am. This fog would then linger thru the mid morning hours on Fri before lifting. In addition, soundings show some potential for drizzle as well.

Meanwhile, for the rest of Fri, the flow aloft will be SW with only isold showers possible in the mtns and far nern plains in the aftn. As for highs, readings will be in the lower to mid 60's across the plains, however, lingering low clouds could keep temps in the 50's over the far nern plains.

For Sat, little change is expected as SW flow aloft remains over the area. There still appears to be a weak disturbance embedded in the flow which may bring a chc of showers to portions of the higher terrain with an isold shower threat across the plains. Temperatures will remain in the upper 50's to mid 60's over nern CO.

Looking ahead to Sun and Sun night, there continues to be some uncertainty as to how an upper level trough along the West Coast evolves. The ECMWF and GFS now have a disorganized elongated upper level trough moving into the nrn Rockies and Great Basin by Sun night. Ahead of this feature, there will be quite a bit of subtropical moisture affecting the higher terrain, especially by Sun night. As a result, should see an increasing chc of showers over the higher terrain with snow levels dropping below 10000 ft late Sun night. Across the plains, it looks dry and windy thru Sun aftn as sfc low pres intensifies from ern WY into ern CO. By Sun night, latest data shows varying precip chances across the plains. For now, have kept in a chc of showers as a band of mid level QG ascent moves across overnight.

On Mon, the ECMWF and GFS have two main areas of energy associated with the elongated upper level trough. One piece stays over the nrn Rockies while a 2nd piece of energy moves across srn CO/nrn NM. If this occurs best chc of decent precip would stay mainly to the north and south of the area. Meanwhile, both models shows a stg cold front moving across the plains with gusty north winds behind it.

For Mon night into Tue, the ECMWF and GFS keep the two pieces of energy separated as the one piece over the nrn Rockies moves SSE across Colorado while the other piece of energy moves from nern NM into central Oklahoma. In addition, the GFS intensifies the upper level low as it moves into Oklahoma by late Mon night. The ECMWF has very little additional precip Mon night into Tue as much drier air spreads across the area. Meanwhile, the GFS has a band of precip over the ern plains Mon night but also decreases the chc of precip over the area on Tue. Winds will remain gusty over the plains Mon night into early Tue as well.

By Wed an upper level ridge will build over the area ahead of another possible system moving across on Thu. For now, Wed looks dry and warmer ahead of the next system.

.AVIATION /12Z TAFS through 12Z Saturday/: Issued at 532 AM MDT Fri Oct 30 2026

Fog will be the main impact during the TAF period. Steady LIFR conditions developed at DEN just prior to 09z and should continue through about 15z before the fog burns off.

A bit more of question mark at BJC and APA. BJC has remained on the edge of the fog bank for the last couple of hours, shown well by the FAA WeatherCam and surrounding webcams/surface observations. At APA, fog has started to creep towards the southeast metro, with BKF recently dropping to 1/2SM. Guidance still insists that fog will push further south over the next couple of hours, meaning that BJC should see more consistent 1/4SM visby soon: though it's appears unlikely to reach APA at this time.

Once fog burns off, light east/northeast winds are likely at the terminals through most of the day with VFR conditions prevailing. Weak drainage is expected again for tonight into Saturday morning. Both the HRRR and RRFS support another batch of dense fog for BJC/DEN, but favor slower development compared to today. Have kept just the VCFG in for now but may eventually need to introduce some LIFR, focused around the 12-15z window Saturday.

Watches, warnings and advisories

Dense Fog Advisory until 10 AM MDT this morning for COZ038>040- 042>044.

Dense Fog Advisory until 8 AM MDT this morning for COZ046-047.