565
FXUS65 KBOU 211913
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
113 PM MDT Tue Jul 21 2026

.KEY MESSAGES...

- Storm coverage and intensity increases on Wednesday and Thursday
  as monsoonal moisture moves into the region. Storms from today
  onward will be capable of producing locally heavy rainfall and
  thus a low threat of flash flooding.

- Storm coverage expected to decrease again by Friday into this
  upcoming weekend, although mountain areas should see at least
  scattered storm coverage each afternoon and evening.

- Temperatures will rise back into the upper 90`s to lower 100`s
  over northeast Colorado for the weekend.

&&

.DISCUSSION /Through Tuesday/...
Issued at 110 PM MDT Tue Jul 21 2026

Smoke from fires in Canada and the West Coast pivoted into our area
this morning behind a weak cold front. This smoke has mostly
dispersed as of the early afternoon. Current satellite and radar
shows clouds and some pockets of light rain across northern Larimer
and Weld counties. Even behind the cold front, the hot stretch for
Northeast Colorado will continue with another day of 90`s forecast
in Denver- making this 19 out of 21 days this month at or above 90
F. Highs today across the plains will be slightly "cooler" than
yesterday, but still in the low to mid 90s.

The high pressure has elongated compared to yesterday, putting us
more on the periphery, and opening the door for scattered showers
and thunderstorms. These will favor the northern foothills and
mountains including the Cameron Peak and Alexander Mountain burn
scars today. It is still uncertain whether or not the Urban Corridor
and plains will receive any rainfall today, but any storms that form
would likely be associated with outflow boundaries from storms to
the north. The latest CAMs are not particularly excited about this
potential.

The pattern shift towards monsoonal moisture will be in full effect
by Wednesday and Thursday. The high pressure will shift off to the
south over TX and NM and it is becoming increasingly likely that a
shortwave will move through on Thursday. Low level southeast flow
will advect more moisture to the region, so dewpoints should
generally remain in the 50s for much of the week. Dewpoints could
even briefly reach the low 60s on Thursday as seen in recent model
guidance.

We still expect PWATs to be 150-200% of normal for Wednesday with
even a slight increase in PWATs on Thursday (approaching
climatological record high daily values). Storm motion could be slow
on Wednesday given weak flow aloft, but will increase on Thursday
with the arrival of the aforementioned shortwave. This should
slightly increase rain coverage. Each afternoon, convection will
start in the high country and spread into the plains by late
afternoon to early evening. Rainfall totals will generally be around
0.25 to 0.75 inches with some isolated totals of 1.00 to perhaps
2.00 inches by Thursday evening. The burn scars in our area will
need to be monitored, but rainfall rates should stay below flash
flood guidance across the area. The only exception would be if we
get training of storms. Given increased clouds and rainfall, high
temperatures will "cool" into the upper 80s to low 90s for both days.

The heat starts its return to the area on Friday and then increases
on Saturday and Sunday as the high pressure expands and shifts to be
centered near the Four Corners region. Scattered showers and
thunderstorms will remain possible on Friday, but likely will stay
confined to the mountains. We have continued to nudge highs up into
the upper 90s to near 100 for both Saturday and Sunday, thus record
highs could be in play. A Heat Advisory could also be needed as we
get closer to the weekend.

Ensemble guidance continues to depict warm temperatures with highs
just below 100 degrees for much of next week across the plains. The
ECMWF does try to shift the high pressure and bring some more rain
to the area by mid-week, but confidence remains low on this solution
at this time.

&&

.AVIATION /18Z TAFS through 18Z Wednesday/...
Issued at 1218 PM MDT Tue Jul 21 2026

Generally VFR conditions are expected through the TAF period.
Winds are currently light and variable but should become more
consistently east/southeast this afternoon.

There`s more uncertainty this evening. Most guidance has trended
towards a drier evening, keeping any convection well to the
north/northwest of the terminals. Subsequently, this limits the
chance of any outflow boundary or weak cold front pushing through
the region this evening and winds are now expected to follow a
more typical drainage pattern.

By Wednesday, guidance is in good agreement that scattered
SHRA/TSRA will be around by the early to mid afternoon hours,
which would likely continue beyond 00Z that evening.

&&

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

&&

$$

DISCUSSION...MV
AVIATION...Hiris

NWS BOU Office Area Forecast Discussion