735 
FXUS65 KBOU 250541
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1141 PM MDT Thu Sep 24 2026

.KEY MESSAGES...

- Patchy to locally dense fog Friday morning, primarily for areas
  north of I-70 and along and east of I-25.

- Another round of showers and isolated storms Friday afternoon
  and evening.
 
- Drier and warmer this weekend before an upper level trough
  brings cooler temperatures and potentially our next chances for
  showers/storms early next week. 

- Medium chances (40% to 60%) for mountain snow above 11,000ft 
  late Monday into Tuesday. 

&&

.DISCUSSION /Through Thursday/...
Issued at 1134 PM MDT Thu Sep 24 2026

Most of today's precipitation has cleared out of the area, with some 
small showers still hanging around over the foothills and up in 
northern Larimer County. Winds are starting to settle in a more east-
southeast pattern, and are expected to stay that way overnight, 
allowing for fog/low stratus to form over the plains and north 
Denver metro area. We expect the densest fog to be over the Ft. 
Morgan area and into southern Weld County, with patchy fog extending 
into the northern Denver metro. Fog/low stratus should dissipate in 
the morning but mid-level cloud cover should remain into the 
afternoon. 

Models are in pretty good agreement on tonight and tomorrow 
morning's south-southeast flow kicking off a Denver Cyclone by mid-
day. Upslope winds from the low-level cyclone coupled with the upper-
level shortwave forecast to move through the area in the afternoon 
should initiate some isolated to scattered showers off the higher 
terrain, which should then propagate east along the trough axis. How 
strong these showers become will be dependent on how much cloud 
cover we retain into the late afternoon, and subsequently how much 
surface heating we get. If we do end up with an isolated 
thunderstorm or two, we could see some localized heavy rainfall.

Most of the model guidance is in agreement on there being convection 
over the southern foothills/Palmer Divide and moving over the 
southern portions of our CWA, which could warrant some minor 
flooding concerns for the areas that have seen more precipitation 
over the last couple of days. Should the current HRRR and RAP 
solutions pan out, we could see more widespread coverage, with 
showers moving across most of the urban corridor in the late 
afternoon and into the plains in the evening.

Temperatures will warm above normal for the weekend as upper level 
ridging builds in behind the shortwave from Friday. A dryline is 
forecast to push east through the area late Friday into Saturday, 
bringing much lower dewpoints into the area. The drier air and 
ridging aloft will decrease rain chances and bring warmer 
temperatures through the weekend (highs in the 80s for much of 
the plains). 

The system next week still looks very uncertain. Models continue to 
jump back and forth between runs with the speed, strength, and 
positioning of the upper level trough next week. There are a few 
concerning model runs and ensemble members that bring more 
substantial rain totals to our area, but there are also a number 
of ensemble members (~30%) that bring very little rainfall for 
much of our forecast area. Right now, this system is a potentially
high impact, low confidence event, with serious bust potential 
depending on the track of the upper low. The main thing to watch 
is how Hurricane Polo gets absorbed into the flow aloft. The runs 
which have Polo moving a bit more north, with moisture from this 
tropical system flowing into the area from southwest flow aloft as
it moves into the continental U.S., and then have the upper low 
sitting just southeast of the area with wrap around moisture 
through the column are the more concerning solutions. Other 
solutions, keep the moisture associated with this tropical system 
and the better lift associated with the upper low to our 
southwest, leaving us with significantly less precip. 

We know that people are also very invested in the potential for 
mountain snow next week. Since the rain amounts are highly 
uncertain, the snow amounts are also highly uncertain. And with 
the snow we have the added uncertainty of temperatures next week.
Model spread is still pretty significant with the 25th to 75th 
percentiles differing by 8 to 15 degrees for a good portion of 
the Front Range and plains for Tuesday through Thursday. If we're 
on the cooler side, SLRs will be higher and snow level could drop 
a bit lower, giving us some higher snow totals. Right now, the 
best chances for snow look to be Tuesday morning above 11,000ft, 
with medium chances (40%-60%) for at least some light snow 
accumulations. The moral of the story: the forecast for Monday 
through Thursday will remain highly uncertain until we get closer,
and this system is definitely something to keep an eye on. Check 
back as we get closer for more details about potential snow and 
rain amounts.

&&

.AVIATION /00Z TAFS through 00Z Saturday/...
Issued at 538 PM MDT Thu Sep 24 2026

Moist upslope flow brought a few showers around and over the 
Denver TAF sites this afternoon, while they haven't been heavy
rainers, there were a few microbursts in fairly close proximity 
to KDEN/KAPA. Current radar shows many lingering boundaries reside
across the plains at this time, with some nearly stationary 
showers across Weld County. The PROB30 was kept in place through 
3Z this evening to account for shower potential as well as 
potential wind shifts due to the aforementioned boundaries. 
Expecting winds to turn to the southeast by around 3Z, turning the
greater shower potential towards the north, decreasing shower 
potential across the TAF sites. With showers expected to develop 
to the NW of the TAF sites, can't rule out potential for an 
outflow to slide south across the TAF sites, but will have to 
monitor as showers develop with the onset of the southeasterly 
winds. 

A cyclone is expected to develop Friday morning that brings low
confidence in wind direction and fog development in the early 
morning hours, and as such, will have some impacts on afternoon 
storm development too. If the airports manage to hold onto a more 
southerly wind component, fog may manage to stay just outside of 
the TAF sites, but any northerly winds will advect fog across the 
airfields. KBJC will have the highest likelihood of fog as there 
is some consistency amongst guidance that the cyclone will bring 
northerly winds between 7Z-9Z, with fog moving across the field 
between 12Z-15Z, but while the low certainty remains, there is 
enough confidence with the right ingredients in place for VCFG and
a TEMPO for a few hours of fog reducing VIS to around 1/2 SM 
between 11/12Z-15Z across all the TAF sites. 

Depending on how quickly fog and stratus clear out in the morning
may impact afternoon storm development. Guidance does show
consistency in stratus breaking up around 15Z-16Z, which does lead
to slightly higher confidence in afternoon storms moving across
the TAF sites for the later afternoon hours, especially with a
shortwave expected to trek across the area in the afternoon. A
TEMPO is now in place at all TAF sites, with storms expected to
impact KBJC around 21Z before shifting east across KAPA and KDEN
shortly thereafter. Expecting some stronger winds than today, 
with gusts between 35-40 kts possible with passing storms, and CIG
dropping as low as ~5,000 feet AGL. 

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...AP/AGS
AVIATION...9