101
FXUS65 KBOU 161823
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1223 PM MDT Wed Apr 16 2025

.KEY MESSAGES...

- Warmer temperatures today and Thursday.

- Critical fire weather conditions are possible over the southern
  third of the CWA on Thursday afternoon with low afternoon
  humidity and fairly strong west-southwesterly low level winds.

- The next storm will bring widespread precipitation for much of
  the forecast area Thursday night well into Saturday. It will be
  all snow by Thursday night.

- Much colder Friday and Saturday, with warming temperatures
  Sunday through Tuesday.


&&

.UPDATE...
Issued at 941 AM MDT Wed Apr 16 2025

Forecast is on track this morning with mostly sunny skies to start
the day, warmer temperatures, and then an increase in clouds with
high based showers developing late this afternoon and evening. A
couple shortwaves were already noted in the water vapor imagery
this morning, one tracking across far southeast Utah - timed for
this afternoon and evening, and another in northwest Arizona -
timed for overnight. The latter in conjunction with the left exit
region of an upper level jet will likely keep some showers going
through the night, especially in the northern mountains. Will
make slight adjustments there, and also add a little lower PoP
farther south on the plains very late this afternoon and evening
due to the weak forcing of the first shortwave.

&&

.SHORT TERM /Through Tonight/...
Issued at 308 AM MDT Wed Apr 16 2025

Upper level ridge axis slides east of Colorado today with west-
southwest flow aloft prevailing over the state. Water vapor
satellite imagery showing an area of moisture and lift over
southern California and western Arizona that is being produced by
a jet streak. This jet streak travels northeast and moves over
Colorado later today. Northern Colorado will be under the left
exit region of the jet which will help produce showers. Lower
airmass stays drive with the best moisture at the mid and upper
level. It also becomes slightly unstable this afternoon with CAPE
up to 300 J/kg. Most of the shower activity is expected to be
north of I-70. Any precipitation is expected to be light, but
gusty outflow winds to 30 mph will be possible. Main time frame
for the showers will be 4-8PM. The air warms a little more today
with highs climbing into the mid to upper 70s over northeast
Colorado. The showers dissipate this evening as the airmass
stabilizes and the jet streak lifts north of Colorado. Skies will
be partly to mostly cloudy tonight with some wind, but nothing
strong. This will lead to mild overnight temperatures with lows in
the mid 40s to mid 50s across northeast Colorado.

&&

.LONG TERM /Thursday through Tuesday/...
Issued at 404 AM MDT Wed Apr 16 2025

The main difference from what I saw last night is that Friday
looks cooler and a bit wetter from the divide eastward, including
over the plains and foothills. The late day Thursday cold front
may be a tad slower getting into the CWA according to model
consensus. Cross sections indicate the upslope is deeper and the
moisture is as well on the current 00Z models compared to last
night`s runs.

Models have strong southwesterly flow across the CWA Thursday and
much of Thursday night.  It decreases some on Friday and Friday
night but remains southwesterly.  By 12Z Saturday morning, models
have a closed upper low in and around the 4 corners with the upper
trough axis just getting into the northwestern CWA. The GFS is
a bit quicker with the upper circulation. The QG Omega fields
have upward vertical velocity over the CWA from Thursday through
Friday night. The low level upslope flow behind the front stays in
place Thursday night through Friday night; even into Saturday
morning on some models. The brunt of precipitation should be all
snow, even for the plains after 06Z Thursday night. Will have
likely or better pops in for much of the CWA from 06Z Thursday
night well into Saturday morning. Moisture is still not great, but
models are increasing it. Not certain how much snow will accumulate
over the plains on Friday, but it should stick by Friday night.
At this time, the QPF amounts from the models are not going "gang-
busters" so no highlights right now.

For temperatures, Thursday`s highs will be a bit cooler than
today`s readings, but still in the upper 60s to mid 70s for the
plains. Friday`s highs look to cool off significantly with only
30s over the plains.

For the later days, Saturday through Tuesday, upper troughiness is
still around Saturday into Saturday night for the CWA. Pops will
stay in the 30-60% range Saturday, then decrease Saturday night.
Zonal flow will dominate Sunday through Tuesday for the forecast
area. An upper trough well to the north of Colorado may impact
the CWA Monday night and Tuesday, mostly in the mountains however.
There could be a cold front for the plains later Tuesday as well.
Overall there may be enough moisture for alpine showers, but the
plains should remain mostly dry from Sunday onward. Temperatures
will remain below normal Saturday, then warm up to near normals
Sunday, with the plains seeing mid and upper 60s for Monday and
Tuesday.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1221 PM MDT Wed Apr 16 2025

VFR to prevail through tonight and into Thursday with sct-bkn mid
and high clouds. Main concern will be the winds.

Winds are expected to turn more west/northwest through the
afternoon, but could see variable winds due to passing high based
showers/virga. Most likely time for that would be 23Z-02Z. Winds
eventually settle back to a more organized south/southwest winds
03Z-06Z tonight.

Tomorrow`s concern will surround a cold front. An initial surge is
likely to at least approach KDEN 16Z-17Z, about the time we start
mixing the stronger west/southwest flow aloft more aggressively.
Thus, there is much uncertainty to the wind forecast tomorrow.
For now, we`ll have a VRB period 17Z-20Z at KDEN, then gusty WSW
as we mix again, and then the main blast of the cold front 22Z-23Z
Thursday. Gusts potentially could exceed 35 kts in the WSW, and
greater than 40 kts with the cold front from the NNE in the late
afternoon. Also a slight chance of some blowing dust restricting
visibility for an hour or two with the cold frontal passage.

&&

.FIRE WEATHER...
Issued at 404 AM MDT Wed Apr 16 2025

Models still show low afternoon humidity levels Thursday afternoon
for the southern third of the CWA. Wind speeds look fairly strong
as well during the afternoon with gusts to 40 mph possible in
that area. Will keep the Fire Weather Watch going. One saving
grace, is that fuels over some the area may not have dried out
yet. We will continue to monitor.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Thursday morning through Thursday
evening for COZ214-216-240-241-245>247.

&&

$$

UPDATE...Barjenbruch
SHORT TERM......Meier
LONG TERM.......rjk
AVIATION...Barjenbruch
FIRE WEATHER....rjk