406
FXUS65 KBOU 271111
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
511 AM MDT Mon Jul 27 2026

.KEY MESSAGES...

- Some relief from the heat today, with increasing chances of
  showers and afternoon/evening thunderstorms.

- Scattered to numerous showers and storms with locally heavy rain
  Tuesday and Wednesday. Temperatures settle back closer to
  normal.

- Drying out again later in the week. Heat returns for next
  weekend.

&&

.DISCUSSION /Through Sunday/...
Issued at 302 AM MDT Mon Jul 27 2026

Quite a bit of uncertainty exists today with convective evolution,
which will be affected by current weak disturbance lifting across
the state. Satellite and radar returns even hint at a weak
mesoscale convective vortex (MCV) left over from last night`s
convection. That feature early this morning was located over
Summit County, but only isolated to scattered light rain showers
remained on the northern and eastern fringes (downshear side) of
this feature. That will keep some showers and more clouds in the
forecast this morning over the northern sections of our forecast
area. That feature (and associated clouds) will also affect
redevelopment of any stronger convection this afternoon. The
most likely areas for reignition will be on the downshear
(north/east side) of the MCV, and also where daytime
heating/sunshine will be sufficient. Given the current trajectory,
that makes the eastern CO plains favored for convective
initiation (CI) this afternoon, as well as potentially the
mountains where more sunshine/destabilization may occur in the
wake of the MCV. For Denver metro, the highest chance of showers
and storms could very well hold off until early to mid evening
since we should initially stay on the upshear side of the MCV. If
that`s the case, then we`d have to wait til better storms come off
the mountains or outflows arrive from the expected stronger
storms over the eastern plains.

Storms that do fire will be capable of producing locally heavy
rainfall, given precipitable water (PW) values climb into the
150-200% of normal, and near climatological daily maximums. A
couple factors that would limit a flash flood threat would be high
LCLs and rather shallow warm cloud depths of only 2,000-3,000
feet. Storm motions should average 15-20 mph per mean cloud layer
wind fields. At this point, the threat is low enough to preclude
any Watches for flash flooding, especially considering the
uncertainty in convective evolution and what areas could be more
prone. Right now, it`s leaning toward the eastern plains which
typically can handle more rain.

For Tuesday and Wednesday, PW values remain high at 150-200% of
normal as the monsoonal moisture plume holds over the forecast
area. An embedded short wave or two riding across the top of the
ridge will be possible, increasing convective coverage. Once
again, the main threat with storms will be locally heavy rain. The
flash flood threat will increase slightly Tuesday afternoon and
evening as warm cloud depths grow to 4,000-5,500 feet as LCLs are
forecast to lower. However, there are signs of a little faster
storm motion of 15-25 mph as mid level westerly flow increases as
the ridge sinks southward. Similar conditions exist for Wednesday.
Temperatures both days should settle closer to seasonal normals,
although 90+F temperatures still expected for the majority of the
plains and I-25 Corridor.

Models still show more significant mid/upper level drying by
Thursday and especially Friday. This occurs as the upper level
ridge retrogrades into the Desert Southwest and puts us in
stronger northwest flow aloft. This would bring a reduction in
shower/storm coverage and also allow a slight bump in temperatures
(lower to mid 90s for the plains and I-25 Corridor). The only
thing that could offset the drying and warming would be a weak
backdoor cool front/surge or two.

The weekend is shaping up to turn hot and mainly dry again as the
ridge axis amplifies northeastward into Wyoming and the
Northern/Central High Plains. That means a growing/intensifying
mid level thermal ridge across our forecast area. While model
average push highs close to 100F across the plains once again,
some of the raw model output of +22-23C at 700 mb suggest we could
be a few degrees above that toward next Monday.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 511 AM MDT Mon Jul 27 2026

Appears we`ve had enough of a surge to bring winds around to more
N-NW at KDEN. Those should hold most of this morning per upstream
observations, although there`s still a low 30% chance they
briefly move back to 250 ish. Otherwise, look for N-NE winds to be
established by 17Z-18Z and hold through about 23-24Z, or when any
stronger convective outflows arrive. An isolated light shower or
sprinkle is still possible this morning as a weak disturbance
lifts over the area.

We expect an increase in shower and storm coverage late
today/this evening as more moisture moves across the region and
instability rebuilds. However, there is considerable uncertainty
in timing and location due to extensive mid level cloud cover,
slight cooling, and capping. Thus, we`ll maintain consistency at
this point with a period of gusty winds (TEMPO VRB G30kts) due
to -SHRA and/or -TSRA nearby. However, we have delayed the start
time til 22-23Z based on latest trends. We don`t expect much
convective threat after about 04Z-05Z with partial clearing
overnight. VFR conditions will persist outside of any storms.

&&

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

&&

$$

DISCUSSION...20
AVIATION...20

NWS BOU Office Area Forecast Discussion