045
FXUS65 KBOU 190613
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1213 AM MDT Wed Aug 19 2026

.KEY MESSAGES...

- Scattered thunderstorms late this evening into tonight. A couple
  strong to severe storms expected across the eastern plains
  through 3AM.

- Isolated storms again for Wednesday, though chances of stronger
  storms shift to the south.

- Warming and drying trend to end the week, before monsoon
  moisture attempts to return Sunday into early next week.

&&

.DISCUSSION /Through Tuesday/...
Issued at 1229 PM MDT Tue Aug 18 2026

A somewhat uncertain forecast for the rest of the day today.
While a weak surface boundary - I`m not sure it`s strong enough to
even be called a cold front - is working its way south towards
the Denver metro. Where virga and light rain has been falling in
North Park and south central Wyoming, temperatures are much
cooler. Understandably, short-term forecast models don`t seem to
have a great handle on both the initial wind shift we`re seeing
now, and with the eventual stronger push of cooler air later this
evening. In general, it seems the most likely scenario for the day
is two rounds of convection - with the first round developing
over the Front Range and generally remaining weak (given meager
surface moisture/MLCAPE), with chances of another round or two
along or behind the front later this evening. Initial
showers/storms this afternoon would be capable of producing gusty
winds as DCAPE increases to about 1200 J/kg. If the second round
of convection does develop, the environment would favor multicell
clusters or splitting supercells that would come with both a wind
and hail risk. SPC`s marginal risk with a CIG1 "hatch" for
hail/wind across most of our plains seems to be a good
representation of today`s conditional severe threat.

The flow aloft will turn a little more northwesterly on Wednesday
as the upper ridge tries to establish itself closer to the Four
Corners. Some moisture still lingers across the state, though
guidance keeps the majority of convection across the far southern
fringes of our CWA into south-central/southeastern Colorado during
the day. We should see at least isolated, weak convection across
most of the higher elevations, with precipitation chances dropping
off towards the north and east.

The rest of the week will be dominated by a large ridge off to
the south, leading to a return of above normal temperatures and
generally dry conditions. While temperatures will still be warm,
this round of heat looks much different than the previous spells
of heat earlier in the month. First, 700mb temperatures are
nowhere near as warm, with 700mb temperatures generally peaking
around 16-19C... meaning highs should reach the mid 90s. There`s
also still a decent amount of moisture trapped underneath this
ridge, with precipitable water values near or even slightly above
normal. We`ll likely at least see a few showers over the high
country each day, while the metro and plains stay dry.

The ridge is expected to weaken and slowly shift eastward by this
weekend into early next week, allowing monsoon moisture to drift
back into the forecast area. There`s some modest timing
differences in this period, but in general there`s a good signal
for rain across the region by Sunday. Guidance has generally been
a day or two too quick to break down ridges here over the summer,
so it`s possible the better rain chances will wait until early
next week.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1154 PM MDT Tue Aug 18 2026

There are some isolated to scattered showers and thunderstorms
near or over our 3 TAF sites as of midnight. Coverage of
thunderstorms is higher off to the east. Isolated storms will
exist near KDEN and KAPA for the next hour or two, with lower
chances for storms near KBJC. The main question we have going into
the overnight hours, is if the showers over the higher terrain is
going to survive and push off into the plains, impacting the
airports. Right now, we`re not expecting the showers to make it
to the TAF sites, but if the showers continue to strengthen and
look like they`re going to push off the foothills, there could be
an hour or two of rain as that moves east over the area. The most
likely timing for that activity would be around 07Z-09Z for KBJC
and 08Z to 10Z for KDEN and KAPA.

After the showers and thunderstorms move through, winds should
generally be from the south/southwest. In the mid morning, winds
will turn more westerly, then northerly, before eventually
becoming northeasterly around 17Z to 18Z. Chances for showers and
thunderstorms will be lower tomorrow, with the highest chances at
KAPA around 21Z to 01Z. Coverage will likely be lower than this
evenings convection. Starting around 03Z, breezy SE winds are
forecast to move into KDEN and KAPA, with gusts around 20 to 25
mph. Winds should start to decrease around 06Z and turn more
southerly.

&&

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

&&

$$

DISCUSSION...Hiris
AVIATION...AP

NWS BOU Office Area Forecast Discussion