829
FXUS65 KBOU 182334
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
534 PM MDT Sat Apr 18 2026

.KEY MESSAGES...

- Dry and warmer weather continues through Wednesday.

- Elevated to critical fire weather conditions are expected on
  Wednesday.

- A series of Pacific storm systems should result in unsettled
  weather Thursday and beyond.

&&

.DISCUSSION /Through Saturday/...
Issued at 1146 AM MDT Sat Apr 18 2026

The rest of today will see plenty of sunshine and warming
temperatures, with highs in the 50s across the plains and 40s in the
mountain valleys. Northwest winds are gusting over 30 mph across
the northeast plains right now and should continue that way until
6-7 PM. RH at midday is around 20-25% but with additional heating
and downslope, they should bottom out around 15%. Thus, the Red
Flag Warning will remain in place this afternoon.

Tonight, winds decouple and drier air moves in, but also some
warming aloft moves in.  Between drainage winds and warmer air
aloft, low temperatures tonight should remain above freezing for
much of the plains and I-25 corridor.  The exception will be the
South Platte Valley north of Denver all the way to Nebraska, and the
lowlands near and southeast of Limon. In the river valleys they
will fall into the low to mid 20s, but given how hard it froze
early this morning, there is no need for another Freeze/Frost
highlight. The mountain valleys will be seasonably cold in the
teens to low 20s.

Sunday through Tuesday will see a warming trend as the 500 mb ridge
builds and remains overhead.  Temperatures across the plains will
warm from the 70s on Sunday to the 80s Monday and Tuesday.  The
mountain valleys will also warm from the 50s on Sunday to the 60s
Monday and Tuesday.  Even though a few members of GEFS from prior
model runs had a little mountain snow late Monday into Tuesday, the
12Z run does not, and the official forecast is free of PoP as well.
Though it will be warm and very dry, winds should remain light
enough through Tuesday to keep elevated fire wx conditions at bay
until Wednesday.

On Wednesday the strong trough off the West Coast U.S. comes on
shore.  Southwest flow aloft over Colorado will increase
significantly while simultaneously pushing the ridge off to the
east. 700 mb temps should be between +10 - +13 degC with the
coolest temps across the North Park. Regardless, that`s really warm,
and with WSW flow increasing at and below 700 mb resulting in
downslope warming, it will be very warm and windy at the surface
across the entire area. Expect highs in the 80s across the plains
and even upper 80s near the KS/NE border. The mountains will also
be quite warm with highs in the 60s in the mountain valleys all
the way to at least 9,500 ft elevation. Combined with sustained
southwest winds 20-30 mph and RH dipping below 10 percent, pretty
much all of the plains are likely to see critical fire weather
conditions. The eastern foothills and South Park will also be
dry/windy enough for critical fire weather conditions. It will
almost definitely be dry across the plains throughout Wednesday,
though some ensemble output is hinting that could be some
moisture in the southwest flow for light snow across the central
mountains, where roughly 1/3 of the EC members, 3/4 of the GFS,
and 1/2 of the Canadian ensemble solutions have light snow as soon
as midday Wednesday. For now 10-20% PoPs across the highest
terrain look appropriate this far out.

Model uncertainty is high Thursday, Friday and beyond as the
short wave trough quickly moves east and a long wave trough
develop upstream and to the north of us. All models show a pretty
deep trough extending from N NM all the way to Canada, with
potential for a fair amount of synoptic lift across Colorado as
the trough axis moves across the state later next week. Ensemble
data suggest a high (> 50%) chance of measurable precipitation
across the area sometime in that window. In terms of potential for
significant precipitation, here are probabilities of exceeding a
quarter inch for the I-25 urban corridor: GEFS 25%, ENS and GEPS
33%. It`s a little less than that across the northeast plains.
For the Front Range Mountains looking at exceeding 0.50" liquid:
GEFS 25%, ENS and GEPS 33%. It`s a long ways out yet and much is
likely to change between now and then. Finally, working a little
DESI magic to find the joint probability of wet bulb below 34 degF
and measurable precip (e.g. probability of snow), shows that
unless it`s overnight, p-type is likely to be rain if/when it
precipitates, and for the overnight hours from Thursday through
Saturday the joint probabilities max out around 20-30% for snow at
any one time.

&&

.AVIATION /00Z TAFS through 00Z Monday/...
Issued at 530 PM MDT Sat Apr 18 2026

VFR through the TAF period. Light and variable winds this evening
should turn towards drainage near or a little after sunset. Winds
are expected to again shift to the east or east-northeast tomorrow
afternoon, with a similar turn to drainage Sunday evening. No
ceiling or visibility concerns are anticipated.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for COZ242-244-
248>251.

&&

$$

DISCUSSION...Schlatter
AVIATION...Hiris

NWS BOU Office Area Forecast Discussion