113 
FXUS65 KBOU 240510
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1110 PM MDT Tue Sep 23 2025

.KEY MESSAGES... 

- The wet weather system will come to an end this evening. The
  main concern will be slick and icy roads above 9,000 feet
  tonight as temperatures fall below freezing. Rainfall totals may
  exceed 2" across the eastern plains.  

- Turning warmer and drier again for the rest of the week ahead. 

- The next system will be a weak wave that could bring light
  precipitation late Sunday through Tuesday. 

&&

.DISCUSSION /Through Tuesday/...
Issued at 235 PM MDT Tue Sep 23 2025

Water vapor imagery shows a closed trough becoming more of an open
wave across southern Colorado this afternoon. The imagery shows a
classic upslope, over-running event for north-central and 
northeast Colorado given the track of the low through southern 
Colorado. The VAD wind profile shows 35 knot east-northeasterly 
winds from 24,000-30,000 feet which is helping to push abundant 
moisture into northern Colorado. Warm air advection within the 
700-500 mb layer is also adding to the forcing for this event. 
Radar shows a pocket of heavier rain from Greeley to Fort Collins 
and southward to Boulder. Rainfall totals in those areas have 
mostly eclipsed 1" with another 0.25-0.5" of additional rain 
expected. There is another pocket of heavier rainfall near Fort 
Morgan, Akron, and Sterling. Some rain gauges have already picked 
up more than 2" there and an additional inch of rain could occur. 
As the system will be moving east-southeastward, that area will 
be the last to see the rainfall come to an end. Rain has been
lighter across the Denver metro this afternoon but the morning
rainfall along with last night's rain has added up to more than 
an inch near downtown Denver. 

As for snowfall, we have seen consistent snowfall throughout the
day mainly above 10,000 feet. Webcams show that roads are mostly
just wet below 11,000 feet so travel impacts are generally low.
Some of the ski area webcams show up to 5" of snow has 
accumulated.

Heading into this evening, the trough will become weaker and as it
departs our area to the east, it will bring one last wave of
precipitation from north to south ending around 7-8pm for most of
the area. There is some concern that mountain passes will become 
icy and slick due to temperatures dipping below freezing after 
sunset considering there is plenty of moisture on the roads. Low 
temperatures will be in the mid 40s across the plains and the 
mountains and mountain valleys will likely see lows in the upper 
20s. 

An upper level ridge will develop over Idaho and influence the
weather in Colorado through the end of the week. Each day through
Friday will have warmer temperatures with highs across the plains
in the low to mid 80s on Friday. There will be plenty of sunshine
and generally light winds. 

A weak cold front will move through Friday night resulting in
highs being 5-10 degrees cooler on Saturday than on Friday. Most
models agree that there will be a weak upper level trough that
moves towards Colorado late Sunday through Tuesday. The forcing
will be minimal with this trough and only light precipitation is
possible. 

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1107 PM MDT Tue Sep 23 2025

Ceilings will be in the 3500-4000 ft range overnight with a 
lingering chc of -shra thru 07z. Ceilings should breakup around 
12z with VFR conditions the rest of the period.

Winds will be light W or SW thru 12z and then become varible
around 16z.  Winds Wed aftn will become light SE by 20z.

&&

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

&&

$$

DISCUSSION...Danielson
AVIATION...RPK