174
FXUS65 KBOU 140550
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1150 PM MDT Wed Aug 13 2025

.KEY MESSAGES...

- Dry thunderstorms and new wildfire starts possible Thursday.

- Hot weather peaks tomorrow, then slight cooling but still above
  normal temperatures most of the week ahead.

- Moisture increases slightly for a chance of storms most areas
  Friday into the weekend.

&&

.DISCUSSION /Through Wednesday/...
Issued at 245 PM MDT Wed Aug 13 2025

The main concerns will be Thursday`s forecast, when record/near
record heat will combine with a threat of dry thunderstorms and
new wildfire starts. More on the fire danger in the Fire Weather
section.

With regard to Thursday`s heat, the upper level ridge and thermal
axis will shift across eastern Colorado. We`ll start off quite
warm with only shallow inversions as well, so it won`t take much
for temperatures to soar into the 90s. We think most of the
plains will be above 90F before 11 am, and in some cases as early
as 10 am. Highs will be very close to records, with strong
agreement of highs 98-99F for Denver, but a 20-30% chance we reach
100F given the location of the thermal ridge and dry ground.
Those kind of temperatures put us very close to Heat Advisory
levels, but at least some cumulus buildups and later day high
based showers/storms around the area will provide some cooling.
Those showers will also spell strong, gusty microbursts/outflows
for the late afternoon and early evening, given DCAPE near 1800
J/kg once again. Similar strong, gusty winds will be possible with
any high based showers we get this afternoon/early evening before
dissipating with the loss of daytime heating and instability.

For Friday, models are still advertising an uptick in moisture
around the periphery of the upper level ridge shifting to the
east. It`s not great, but at least precipitable water values climb
to near normal for this time of year. Thus, the threat of dry
thunderstorms should decrease slightly, and overall coverage will
increase. The most numerous showers and storms are expected to
occur in the mountains, with lesser coverage eastward over the
plains. Temperatures will still be quite warm given the proximity
of the upper ridge, but a few degrees cooler with the uptick in
moisture and shower/storm coverage. Saturday should be nearly a
repeat of Friday, with moderate moisture in southwest flow aloft.
Temperatures should continue their slight cooling trend - with
readings closer to normal.

There is more agreement to the ridge beginning to retrograde by
Sunday, and some drying behind Saturday`s potential weak shortwave.
Thus, Sunday into Monday appear drier at this point. Some
moisture does build east of the Front Range, so there will still
be a 20-30% chance of storms each afternoon/early evening.

Ensembles generally agree the upper level ridge then retrogrades
and rebuilds over western Colorado and eastern Utah by the middle
of next week. That`s not terribly favorable for rain or heat
relief. Overall, the main chance of rain would stay along/east of
the Front Range, with temperatures holding a few degrees above
normal through this period.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1146 PM MDT Wed Aug 13 2025

A boundary was moving across DIA with a wind shift
to the WNW.  Still expect winds will gradually go back
to a more SSW direction by 07z. By 12z winds will
trend to SW and then light northerly by 17z. By 20z
winds will have a more easterly direction. By 21z,there
will be a 30% chance of high based showers or a tstm.
Gusty and erractic outflow winds from 40 to 50 mph will
certainly be possible from 21z through 02z Thu evening.

&&

.FIRE WEATHER...
Issued at 245 PM MDT Wed Aug 13 2025

Hot temperatures and low humidity of 15% or less over the high
mountain valleys, foothills, and I-25 Corridor and nearby adjacent
plains will keep elevated fire weather conditions in place until
early evening. Winds are fortunately staying light, except near
isolated high based showers/storms/virga. The northern mountain
zones of 211, 213, and 217 also have slightly stronger winds with
gusts around 20-25 mph, but under critical thresholds.

On Thursday, critical fire weather conditions will be likely due
to dry lightning. With the slight increase in upper level
moisture, convection should become a little more pronounced.
Of importance, we are uncertain in how extensive the lightning
threat will be, as instability is quite limited. Thus, while
thunderstorms may only be isolated, the dry fuel conditions and
hot/low RH environment will be favorable for new fire starts.
Thus, we`ve opted to upgraded the Fire Weather Watch for the high
country to a Red Flag Warning.

Friday will still be quite warm and dry in the low levels, but
mid and upper level moisture will increase further. Therefore,
scattered storms with hopefully wetting rains will become more
numerous. There`s still a chance that a few storms could be dry
so we`ll watch this closely.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 10 PM MDT Thursday for COZ211>218.

&&

$$

DISCUSSION...Barjenbruch
AVIATION...RPK
FIRE WEATHER...Barjenbruch