168
FXUS65 KBOU 010020
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
620 PM MDT Wed Sep 30 2026

.KEY MESSAGES...

- Rain continues south and southeast of Denver with the heaviest
  amounts over Lincoln County.

- Little to no rain for the northern urban corridor and northeast
  plains.

- Rain ends Thursday morning over eastern Colorado.

- Warmer and drier for the weekend and early next week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 1158 AM MDT Wed Sep 30 2026

GOES satellite imagery shows the well defined, strong trough moving
east across the AZ/NM border, roughly dead center N-S across
those two states. The trough and remnants of Polo have fully
merged and the moist conveyor belt well east of the trough is
truly impressive, especially if you live in Texas, Oklahoma, and
Kansas. The best forcing from the trough will remain over New
Mexico and Oklahoma next 24-36 hours, and the TROWAL/deformation
zone of precip will impact mostly southern Colorado now through
tonight. Radar shows widely scattered showers across Lincoln
County and more stratiform rain along the crest of the Palmer
Divide. Over an inch of rain has fallen since early this morning
across far southern Lincoln County. The axis of best lift with
the deformation zone extends from Lincoln County west along the
Palmer to northwest Park County, where the moderate rain is
expected to continue into the late evening hours. There is no
lightning anywhere in the state as of midday, though there should
be some instability available this afternoon for a 10-20% chance
of a thunderstorm across that same area along the southern edge of
our CWA. Another inch, maybe 1.5" could fall across Lincoln
County through early Thursday morning, and across the Palmer
Divide to northwest Park County perhaps an inch total through
Thursday morning. The surface low currently is across the OK/TX
panhandles and weak pressure falls indicate it will move into
central KS after midnight. The southern track of the 500 mb
trough, and a 1004 mb surface low over the panhandles both meant
rainfall amounts would be limited across our area other than
Lincoln County. There is high confidence in the rainfall shutting
off entirely Thursday morning. Further north and west this
afternoon/evening, light rain is about all to expect along and
north of I-70 this afternoon and evening. North of I-76 and north
of CO-66 (more or less), probably no precip will occur. In terms
of mountain precipitation the rest of today into tomorrow, the
Park/Gore Ranges and the Front Range from RMNP northward are not
expected to see much if any accumulating rain or snow. The
Mosquito/Tenmile range and southern Front Range from JeffCo into
Park County should see several tenths of rain, and T-3" of snow
above 11,500 ft elevation. No travel impacts are expected. In
terms of temperatures, extensive cloud cover in the comma head of
the trough means temperatures will not get out of the 60s south
of I-76, but should reach about 70 across the norther tier
counties. Where it`s raining, temps should be in the 50s to low
60s. Thursday will see more sun, especially north and west of
Lincoln County, with temps across the plains warming to the low
70s, with 60s across the Palmer Divide and Lincoln County, and the
mountain valleys. South Park, with early morning rain showers and
some lingering cloud cover may remain in the 50s on Thursday.

The ridge builds over Colorado Friday through Sunday, and our entire
area looks to be dry with above normal temperatures trending well
above normal by the weekend. With the ridge overhead, winds will not
be an issue and thus we also don`t expected any fire weather
issues. Highs on Friday should be upper 70s to around 80 across
the plains, and 60s to lower 70s in the mountain valleys. On
Saturday, add 3-5 degrees across the board. Sunday and Friday will
be similar temperature wise as the thermal ridge at 700 mb slides
east of Colorado, cooling afternoon highs 3-5 degrees.

Next week looks dry across the plains, but there is quite a bit of
uncertainty in the Monday afternoon through Tuesday timeframe.  The
deterministic models show a weak short wave trough moving across
Colorado. Some sub-tropical moisture might make it northeast into
Colorado associated with the trough. At a minimum we have 15-30%
PoP across the high country, where available ensemble model output
indeed has increasing chances of rain, but even the 90th
percentile amounts are 0.1-0.2" this far out. It also looks far
too warm to snow below 12,000 ft. A handful of ensemble members
from each modeling system have any measurable precip for the I-25
urban corridor, and even fewer for the northeast plains. Well
above normal temperatures should continue across our area next
week with low 80s across the plains (perhaps even mid 80s, yikes)
and 60s in the mountain valleys and eastern foothills.

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 618 PM MDT Wed Sep 30 2026

Current radar imagery shows a few sprinkles in the vicinity of KDEN
and scattered showers over areas of the southeastern Palmer Divide.
Although these showers will likely weaken a bit before reaching the
Denver metro, we kept PROB30s and vicinity showers at KDEN and KAPA
until 05Z-06Z given that we do expect at least some additional
sprinkles to move in from the east during the evening hours.

Winds will remain very light (

NWS BOU Office Area Forecast Discussion