Severe Thunderstorm Warning 20, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
530 PM MDT Sat Apr 26 2025

.KEY MESSAGES...

- Isolated late afternoon and evening thunderstorms across the
  plains.

- Warm and windy Sunday with critical fire weather conditions in
  the afternoon across the plains and South Park.

- Seasonal conditions next week with a chance of afternoon showers
  or thunderstorms most days, especially in the high country.

&&

.SHORT TERM /Through Sunday/...
Issued at 139 PM MDT Sat Apr 26 2025

SW flow aloft will be over the area tonight as an upper level low
moves into Nevada by 12Z Sun. Currently, there is a well defined
boundary which has been moving slowly north across portions of the
Denver area into central portions of Weld county. MLCAPE is
around 500 j/kg where low clouds have eroded this aftn, however,
there is still a capping inversion in place. Still can't rule out
a few isold storms developing, along this boundary, thru the early
evening hours. Another possible area of tstm development would be
over srn Lincoln county with a few storms moving across the rest
of Lincoln county this evening. Confidence in either scenario
isn't real high so will leave pops mainly in the slight chc
category.

On Sun, an upper level low will move into the Great Basin with stg
SW flow aloft over the area.  At the sfc, low pres will intensify
along the front range with gusty south to southwest winds across the
area.  There will be a chc of aftn showers along with an isold tstm
over the higher terrain where some mid level moisture will combine
with decent lapse rates.  Across the plains it will be windy and
dry.  Highs across the plains due to downslope lo level flow will
rise into the upper 70s to lower 80s.

&&

.LONG TERM /Sunday night through Saturday/...
Issued at 139 PM MDT Sat Apr 26 2025

Temperatures will be 10-15 degrees cooler on Monday in the post-
frontal airmass, and the drier air will be relegated closer to the
surface. With marginal instability in place despite cooler
conditions, a few high-based showers and weak thunderstorms could
occur in the afternoon. By late afternoon and evening, another
front will bring breezy north winds to the plains and sustain a
chance of showers. The southernmost of our lower elevations (south
of the I-70 corridor) could still see humidity lower into the
low/mid teens in the afternoon, with lingering fire weather
concerns as a result.

We'll remain on the cooler side Tuesday with only minor changes in
temperatures, and a generally stable environment outside of the
high country which should keep afternoon precipitation changes
confined mostly to our mountains and foothills.

Synoptically, the pattern remains troughy on Wednesday, albeit
quite disorganized. Although instability doesn't look too
impressive, PWAT values will be healthier and between 150-200% of
normal. With a surface front progged to descend into Colorado as
well, it suggests better chances for precipitation relative to
previous days, and ensemble mean QPF fields validate this.

It's tough to draw any overly distinct details in the forecast
beyond Wednesday. We'll likely still hold on to a fairly
progressive upper-level pattern and some moisture and instability
for Thursday, with signs somewhat favoring a transition to ridging
and a warmer/more stable environment Friday into Saturday.

&&

.AVIATION /00Z TAFS through 00Z Monday/...
Issued at 529 PM MDT Sat Apr 26 2025

Gusty south/southeast winds to 25-30 kts will likely continue
through about 03Z, as boundary has finally pushed northwest of
KDEN. There will be another boundary moving in by 01Z to enhance
that flow, despite the opportunity for a couple high based
showers. We think the chance of thunder til about 03Z is only
around 10%. Enhanced southerly drainage winds should continue
through most of the night, although there's a slight chance we go
more westerly with a cyclone development. If that occurs, then
there's a chance we could get fog wrapped back to KDEN but right
now that's only about 10-20% chance.

On Sunday, strong south/southwest winds will increase 16Z-21Z,
with gusts close to 35 knots from the south/southwest 20Z SUN-02Z
MON. At least there shouldn't be any significant boundaries
interfering with landing ops at KDEN for a change, as the
southerly boundary gets pushed well to the north.

&&

.FIRE WEATHER...
Issued at 139 PM MDT Sat Apr 26 2025

Critical fire conditions will develop by late Sunday morning and
early afternoon across most of the plains and across South Park.
Gusty south to southwest winds of 20 to 30 mph with gusts to 45
mph will occur with humidity levels dropping to 10 percent.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM to 8 PM MDT Sunday for COZ214-
240>247-249.

&&

SHORT TERM...RPK
LONG TERM...Rodriguez
AVIATION...Barjenbruch
FIRE WEATHER...RPK

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1006 AM MDT Sat Apr 26 2025

COZ030>051-271615-
Jackson County Below 9000 Feet-
West Jackson and West Grand Counties Above 9000 Feet-
Grand and Summit Counties Below 9000 Feet-
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Central and Southeast Park County-
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Northeast Weld County-Central and South Weld County-Morgan County-
Central and East Adams and Arapahoe Counties-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County-
Southeast Elbert County Below 6000 Feet/South Lincoln County-
Logan County-Washington County-Sedgwick County-Phillips County-
1006 AM MDT Sat Apr 26 2025

This hazardous weather outlook is for northeast and north central
Colorado.

.DAY ONE...Today and Tonight

It will be windy this afternoon with gusts up to 45 mph across
the eastern plains. An isolated thunderstorm or two is possible
late this afternoon as well over the plains.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Warm, dry, and breezy conditions will create widespread elevated
to critical fire weather conditions Sunday afternoon. There is
also a slight chance of strong to severe thunderstorms in the late
afternoon and early evening in areas east of Sterling and Akron.

For the coming week, there will be a chance of afternoon and
evening thunderstorms each day, mainly in the mountains. Wednesday
afternoon and evening looks like the most active day. The threat
of severe weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight.

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