987
FXUS65 KBOU 180911
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
311 AM MDT Sat Jul 18 2026

.KEY MESSAGES...

- Hot weather continues through Monday. The hottest temperatures
  are still expected on both Sunday and Monday. A Heat Advisory
  remains in effect for the Denver Metro/I-25 corridor from 10 AM
  Sunday through 9 PM Monday.

- Scattered afternoon/early evening storms in the mountains
  expected through Sunday with the plains remaining dry.

- Significant monsoonal moisture and cooler temperatures still on
  track to arrive on Tuesday of next week. The thunderstorms that
  develop will be capable of producing locally heavy rainfall.

&&

.DISCUSSION /Through Friday/...
Issued at 229 AM MDT Sat Jul 18 2026

The overall theme of the upcoming week is still largely the same
as the past several forecast cycles, as a broad ridge slowly moves
from the Rockies into the southern Great Plains over the next
several days. In the near term, that means more of the same -
above normal temperatures and dry weather - before the more
favorable position of the ridge finally allows a plume of monsoon
moisture back into the CWA.

The upper ridge is currently centered somewhere over western
Colorado or southwestern Utah, per water vapor satellite and
current RAP analysis data. The ridge is expected to slowly
strengthen today, while slowly drifting closer to northern
Colorado. With the ridge almost directly overhead, the increased
subsidence and decreased moisture (evident per recent GOES Water
Vapor satellite imagery) will lead to less coverage of
showers/storms across the high country... with only a few clouds
expected across the plains. Mid-level temperatures are expected to
warm ~1 degC today, and as a response forecast highs should be a
degree or two warmer than Friday.

The ridge is not expected to move much on Sunday, but warming
mid-level temperatures will lead to even hotter temperatures
across the forecast area Sunday afternoon. Most guidance gets
700mb temperatures to around +18-20C, and upper 90s are likely
across most of the I-25 corridor... with perhaps slightly cooler
temperatures across the far eastern plains which remain on the
edge of the thermal ridge. Little change is expected on Monday,
with the ridge slowly beginning to elongate and shift to the
southeast. The GFS shows a rather ridiculous +22C 700mb
temperature Monday evening, which would be equivalent to the 5th
warmest 700mb T from Denver`s previous sounding climatology.
That`s led to some egregiously high forecast temperatures (GFS
MOS had 106F)... though the ECMWF/GEM`s 19-20C 700mb temperatures
would still lead to another day of upper 90s to low 100s across
the urban corridor. Given the forecast high temperatures, along
with above normal lows Sunday night, I saw no reason to adjust the
previously issued Heat Advisory.

Meanwhile, across the mountains... the ridge axis is expected to
shift just enough to allow for some return of monsoon moisture as
early as Sunday afternoon. Chances for showers and thunderstorms
are expected to increase both Sunday and Monday. A few of those
storms may try to make it into the plains Monday as a cold front
tries to work into the region. The more substantial plume of
moisture reaches the area by Tuesday/Wednesday. Forecast
precipitable water and 700/500mb specific humidity approach or
exceed the ECMWF ensemble climatology by Wednesday and Thursday,
with only a gradual decline in moisture later in the week. The
overall synoptic setup remains favorable for slow moving, heavy
rain producing thunderstorms across the higher elevations from at
least Tuesday through Thursday, with mean cloud layer winds
between 5-10kt.

Guidance also remains in good agreement that the more
impressive plume of moisture will push eastward into the lower
elevations by mid-week. Precipitation chances are expected to
increase on Tuesday and continue through most of the week. It
still remains a bit up in the air which days would feature the
highest chances of rain across the metro/plains. Daily
precipitation chances may end up dependent on a series of weak
fronts moving through the region, along with the evolution of any
stratus from day to day, which would impact
destabilization/capping potential. We`ll see how this evolves over
the next couple of days, but I would favor Wednesday/Thursday for
the best chance of widespread rain across the plains.

&&

.AVIATION /06Z TAFS through 06Z Sunday/...
Issued at 1142 PM MDT Fri Jul 17 2026

VFR conditions are expected through the TAF period. Winds are
expected to follow a similar pattern compared to the past few
days, with drainage turning to light and variable winds, before
settling on an easterly direction by around 18z. Winds should then
slowly turn to the southeast Saturday evening into Saturday night.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 10 AM Sunday to 9 PM MDT Monday for
COZ038>040-043.

&&

$$

DISCUSSION...Hiris
AVIATION...Hiris

NWS BOU Office Area Forecast Discussion