963
FXUS65 KBOU 190533
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1133 PM MDT Wed Jun 18 2025

.KEY MESSAGES...

- Strong signal for record breaking heat from Friday into the
  weekend, along with potential for critical fire weather
  conditions.

- Dry conditions through Saturday, but chance of storms returns
  along with heat relief by early next week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 216 PM MDT Wed Jun 18 2025

Water vapor shows very dry air over Colorado and the Desert
Southwest this afternoon. There is subsident flow over our
forecast area resulting in a mostly sunny day with light winds.

An upper level ridge will move eastward on Thursday with 700 mb
winds becoming west-southwesterly across our forecast area. This
will allow for compressional warming that will result in
temperatures climbing well above normal. Most of the I-25
corridor will see a high in the mid 90s tomorrow with some
locations on the eastern plains seeing a high in the upper 90s.
With continued subsident flow, no showers or storms will form.

A strong trough will move across the Pacific Northwest on Friday
while a ridge strengths over the southeastern US. In between,
strong west-southwesterly flow throughout the troposphere will
develop over Colorado. This flow will advect in much warmer air
from the Desert Southwest. In addition, the I-25 corridor and
eastern plains will experience strong downslope winds which will
increase temperatures in the low levels. Furthermore, there will
be strong subsidence that will keep conditions mostly sunny for
the majority of the day. All of these factors will combine to
create very hot conditions which may break record highs. The
record high for Denver is 99 which is well within reach as the
current forecast has 100. The decision was made to issue a Heat
Advisory because temperatures will be around 100 degrees across
the I-25 corridor and plains, it is considered "early season heat"
(which is basically anytime before July for our area), and that
there will be mostly sunny conditions. However, there are a couple
of factors which may help us avoid too many heat illnesses and
those are windy conditions with gusts above 30 mph and very dry
conditions with relative humidity around 10 percent.

On Saturday, very similar conditions to Friday will exist. Models
have latched onto slight cooling at 700 mb which may keep
Saturday a degree or two cooler but otherwise the same high
temperatures are in the forecast. The decision was made to extend
the Heat Advisory through Saturday afternoon as the multiple days
of heat will impact people.

The aforementioned trough over the Pacific Northwest will enter
northwest Colorado on Sunday. Model guidance has a much larger
spread in the temperature forecast as two solutions appear
possible. One solution is that the trough is slow to arrive and
strong southwest winds continue to be over our entire forecast
area. If this were to be the case, very hot temperatures will
continue and the Heat Advisory may need to be extended to Sunday.
The other solution is the trough is quick to arrive and a backdoor
cold front moves through the plains. If that occurs, temperatures
would be much cooler and storms would be possible across the far
northeast plains.

The trough will then be over Colorado Monday through the middle of
next week. This will usher an active pattern of daily showers and
storms in the afternoon/evening with some having the potential to
reach severe limits. It will also be cooler during this period
with below normal temperatures.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1133 PM MDT Wed Jun 18 2025

Mostly clear skies will prevail through the TAF period with only a
FEW clouds above 12,000 ft AGL after 18Z. Winds will feature
fairly normal diurnal wind patterns, with an enhanced E/SE flow
picking up after 19Z Thursday. A few gusts to 17-22 kts possible
20Z-01Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM Friday to 6 PM MDT Saturday for
COZ038>051.

&&

$$

DISCUSSION...Danielson
AVIATION...Barjenbruch