074 
FXUS65 KBOU 240027
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
627 PM MDT Wed Sep 23 2026

.KEY MESSAGES...

- A disturbance moves through tonight and Thursday bringing 
  increased chances for showers/storms (40-70%) and cooler 
  temperatures Thursday. 

- Friday another disturbance is likely to move through bringing
  more chances for showers/storms. 
 
- Drier and warmer this weekend before an upper level trough
  brings cooler temperatures and potentially our next chances for
  showers/storms early next week. 

&&

.DISCUSSION /Through Wednesday/...
Issued at 253 PM MDT Wed Sep 23 2026

Current analysis shows the moist airmass from AZ/NM has infiltrated 
our area. PWATs sit at 0.8-0.9 in the foothills and Denver metro. 
Towards the eastern plains they increase to 1.0-1.3. Current radar 
depicts showers developing in the plains where some peaks of 
sunshine still remain. The next 36 hours or so of the forecast 
remain highly uncertain in regards to placement and development of 
convective activity. 

Model guidance displays a wide range of solutions, and combined with 
the cloud shield across the forecast area we are concerned this will 
limit instability significantly thus lowering the chances for 
shower development. Current ACARS DEN sounding also indicates we 
are capped, but with abundant moisture aloft. Furthermore, the 
shortwave that was advertised to move through has shifted to far 
Southeastern Colorado towards the Kansas border limiting 
widespread chances for our forecast area. Even with the lack of 
true lift, the amount of moisture present should be enough to 
produce showers for most of the area. Here is a breakdown of the 
chances. The eastern and southern plains will see the greatest 
rainfall from this system ~60-70% through around Thursday 
afternoon, and the urban corridor and Denver metro will see about 
a 40-60% chance. South Parks chances will increase to ~60-80% 
through Thursday evening. Some model guidance depicts drier air 
filtering in from the northwest so the Northern Mountains could 
see more limited activity, especially tonight. 

Thursday morning model guidance has convection shifting off to the 
south and east of our area, but as the afternoon approaches we 
should see another increase in shower activity in the higher terrain 
around noon (~60%), and urban corridor/Denver Metro later in the 
afternoon (~40-50%). Some CAMs depict a round of scattered to 
widespread storms moving pushing through the urban corridor to 
eastern plains in the evening while short term guidance like the 
NAMNEST and HRRR isn't exactly on board with this. It is also 
worth it to note storm motion for today and Thursday is between 
5-15kts and the 12,18Z runs of the HRRR indicate a storm that 
trains over the Cameron Peak burn scar area for a few hours. This 
is only one solution, but the potential for slow moving storms 
with localized flash flooding will be possible through Thursday 
evening. If enough cloud cover clears Thursday night we could see
the potential for patchy fog to develop mostly in the plains and 
mountain valleys. 

Friday most model guidance depicts a shortwave move into our 
forecast area bringing shower/storm potential. PWATs are still 
expected to be 170-190% above normal and forecast soundings indicate 
CAPE will increase with limited CIN. The GFS is an outlier currently 
and has the precipitation occurring further south of our area. 
Temperatures will warm back up to mid/upper 70s. 

Saturday and Sunday still trends drier and warmer up to the low/mid 
80s in the urban corridor with 60s in the higher terrain. Monday and 
Tuesday temperatures cool down due to the passage of an upper 
level trough potentially bringing our next best chance for 
precipitation.

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 548 PM MDT Wed Sep 23 2026

A few changes to the TAF this evening. Patchy showers have been in
place across the Palmer Divide and eastern plains for the past few
hours, with KAPA picking up a trace of rain late this afternoon.
Will keep the current PROB30 in place across the TAF sites through
2Z, though there may still be some lingering showers in the area 
for a bit longer, but confidence remains below 30%, but out of the
three TAF sites, KAPA would likely have the better chance of this
scenario. Latest guidance has brought slightly higher confidence 
in less than a 30% chance for showers at KDEN/KBJC in the early 
morning hours, so have removed the PROB30 at both locations. 
Guidance seems to have better agreement in showers staying 
slightly more south and east than previously shown, which keeps 
higher potential in showers at KAPA, therefore have left the 
PROB30 in place there. There is some uncertainty on stratus 
development late tonight/early Thursday morning, but with some 
consistency developing across the hi-res guidance latest updates 
showing some potential, have decided to add a FEW002 for now to 
act as a placeholder until there is better confidence. 

Winds should settle into drainage for the overnight at KDEN/KAPA,
with KBJC likely remaining light and variable. A northerly
transition is expected through the morning before becoming
northeasterly for the afternoon. Similar environmental conditions
are expected for Thursday with shower development possible in the
late afternoon/early evening. A PROB30 has been included at all
TAF sites through the end of the TAF period. 




&&

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

&&

$$

DISCUSSION...Schnell
AVIATION...9