875
FXUS65 KBOU 191740
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1140 AM MDT Sun Jul 19 2026

.KEY MESSAGES...

- Hot weather continues through Monday, with highs pushing near
  100F over the I-25 Corridor and adjacent plains. 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 Sunday and Monday, with the plains remaining dry.

- Arrival of monsoonal moisture still getting delayed slightly,
  but once it arrives it should last into late next week. Storms
  from Tuesday or Wednesday onward will be capable of producing
  locally heavy rainfall.

- Only a slight cooling trend forecast this week with the arrival
  of better moisture.


&&

.DISCUSSION /Through Saturday/...
Issued at 236 AM MDT Sun Jul 19 2026

A broad upper ridge remains firmly in place across the Rockies
this morning... and much like the last few days, water vapor
satellite shows a dry airmass over most of our forecast area.

We expect today and Monday to be the warmest two days of the
upcoming week as the mid-level (700mb) temperatures increase to
18-20C over the forecast area. As a result, forecast high
temperatures across the I-25 corridor are in the upper 90s, with a
few of our warmer spots likely cracking 100F on one/both days.
While we`ll be close to some daily records today, perhaps the more
impressive part of this stretch of heat is the overnight lows.
Tonight`s lows so far have only managed to make it down into the
low/mid 70s... and we expect similar temperatures tomorrow night.
This is reflected well by WPC`s Heat Risk... which shows major
heat impacts both from Sunday/Monday high temperatures, but also
moderate to major impacts from Sunday night`s lows. I did not see
any reason to change the existing Heat Advisory.

Meanwhile, across the higher elevations, we`ll slowly start seeing
an increase in moisture over the next couple of days as the ridge
begins to meander off to the south and east. Most of the moisture
today ends up in the far northwestern corner of our forecast area,
meaning the best chance of rain will be across the northern
mountains and North Park, with decreasing chances across the I-70
mountain corridor. The plume of moisture is expected to crawl a
little bit further south/east on Monday with the best chances of
rain along/north of the I-70 mountains.

As the ridge continues to drift off to the east, this should
finally allow for the plume of monsoon moisture to reach the I-25
corridor and plains by Tuesday. Forecast precipitable water values
increase to about 1.2-1.3" by Tuesday evening, and continue to
increase on Wednesday and Thursday. Most guidance continues to
advertise 700-500mb specific humidity values near the 99th
percentile of the model climatology, with near record PWATs.

What days feature the best chance of precipitation? It could
really be any of Tuesday through Friday across the I-25 corridor. A
surface cold front is expected to push through the region Tuesday
morning, which could help increase surface upslope, but could
also potentially introduce some capping issues. Wednesday and
Thursday still look to feature the best combination of instability
and moisture across the lower elevations, and I`d lean slightly
towards the latter of those two days. As we`ve mentioned a few
times, any storms that develop this week would be slow moving and
capable of producing locally heavy rainfall, but it does not mean
that everyone will see significant precipitation this week. We`ll
continue to evaluate the day to day setups as we get through the
weekend. Of note, I am a rather skeptical of the handling of the
surface/boundary layer T/Td profiles from the GFS, and or that
reason I am a bit more optimistic than yesterday`s day shift in
terms of getting cooler temperatures and meaningful precipitation
across our forecast area.

While precipitable water does start to decrease a bit by next
weekend, there`s still broad support for above normal moisture and
sufficient instability... which means that daily chances of
showers/storms will continue through next weekend and potentially
into the following week.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1131 AM MDT Sun Jul 19 2026

VFR conditions expected through the TAF period. All terminals are
holding onto light and VRB winds this morning, however a more
easterly flow will set in the next hour or so. Typical diurnal
wind pattern expected today and this evening, with no ceiling
issues.

Isolated showers and thunderstorms will occur over the
high terrain and northern plains this afternoon, with no impacts
expected for the airports. However, while highly unlikely, an
outflow from a storm could bring a weak wind shift if it makes it
to the airports.

Similar wind pattern expected for tomorrow. Models have started to
hint at isolated convection over the I-25 corridor in the later
afternoon/early evening, which would cause gusty outflows at the
terminals. However, due to low confidence, have kept it out of the
TAF for now. If models continue to indicate this potential, will
have to introduce a PROB30 in the TAF.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM MDT Monday for COZ038>040-043.

&&

$$

DISCUSSION...Hiris
AVIATION...MAI