Severe Thunderstorm Warning 270, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
256 PM MDT Fri Aug 1 2025

.KEY MESSAGES...

- Severe thunderstorms expected over the northeast plains late
  this afternoon and evening with up to tennis ball size hail, 80
  mph winds, and possibly a few tornadoes.

- Severe thunderstorms possible Saturday afternoon/evening over
  far northeast Colorado.

- Chance of thunderstorms gradually decreases this weekend.

- Dry and hot early to mid portion of next week, with increasing
  fire danger Jackson and Grand Counties.

&&

.DISCUSSION /Through Friday/...
Issued at 256 PM MDT Fri Aug 1 2025

The 18Z HRRR and NAMNest models continue the 12Z model trend of
showing strong/severe thunderstorms late this afternoon and
evening across the northeast Colorado plains. Satellite imagery
showing decreasing stratocumulus clouds over the northeast plains.
As of 2PM temperatures have reached the mid 70s to lower 80s over
the northeast plains. SPC Mesoscale Analysis page shows MLCAPE of
2000- 2500 J/kg already and may reach 3000 J/kg later this
afternoon. Dew points are higher than forecasted with readings
mainly in the 60s. Shear is better today than the past few days
with 0-6km bulk shear peaking at 30-40 knots. Given decent
moisture, instability, and shear, some of the storms should become
severe with large hail (slightly larger than golf balls), and
strong damaging winds to 70 mph. Can't also rule a few tornadoes
with decent low level shear and low LCLs (Lifted Condensation
Level).

Farther west, it is drier with less shear and instability.
Scattered showers and thunderstorms will spread eastward through
the rest of the afternoon and early evening. Brief heavy rain,
small hail, and wind gusts to 50 mph will be possible with the
stronger storms along the Front Range.

On Saturday, a lee-side trough/dry line shifts east across the
area during the afternoon. Across the higher terrain, urban
corridor, and nearby plains, westerly winds will bring slightly
drier air. However, there still looks to be enough moisture and a
weak wave to produce scattered thunderstorms. The storms are
expected to begin late morning over the mountains and then spread
eastward through the afternoon. Brief heavy rain, small hail, and
gusty outflow winds to 50 mph will be possible with the storms.
Better moisture and instability hangs on over far eastern Colorado
where a couple severe storms will be possible before they push
eastward into Nebraska and Kansas.

A weak cold (cool) front pushes south through the area early
Sunday. This will bring slightly cooler air and drier into the
area. The air will be drier as well with precipitable water values
falling to 50- 75 percent of normal. The eastern plains may again
hold onto some moisture where scattered thunderstorms will be
late in the day.

For next week, the upper level high will intensify over the Central
and Southern Rockies with Colorado feeling the full effects of
the high by Tuesday. Mostly dry and hot conditions are expected
for Tuesday through Thursday with highs reaching the mid to upper
90s across northeast Colorado. Precipitable water values fall
below normal and will be well below normal Tuesday through
Thursday. So we are looking at a week of very little rainfall
across the area. We may begin to see some relief from the heat
next Friday as a longwave trough moves into the northwest part of
the country and may start to push the ridge off to the south.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1055 AM MDT Fri Aug 1 2025

Smoke has increased this morning, but surface visibility is
expected to stay above 6SM. However, slantwise approach visibility
may be impacted and therefore added smoke to the TAF through mid
afternoon (21Z). The HRRR model (which did well handling the
increase in smoke this morning) decreases the smoke mid to late
afternoon. Will continue with the PROB30 for thunderstorms, which
looks on track. Gusty outflows producing wind shifts are expected
21-02Z.

Other than possible smoke impacts, VFR conditions are expected
tonight and Saturday. Scattered thunderstorms are expected again
Saturday with about 30 percent chance for one near DEN, but
outflow winds will likely produce wind shifts after 19/20Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

DISCUSSION...Meier
AVIATION...Meier

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1104 AM MDT Fri Aug 1 2025

COZ030>051-021715-
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-
1104 AM MDT Fri Aug 1 2025

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

.DAY ONE...This Afternoon and Tonight

Scattered thunderstorms will develop over the mountains early this
afternoon and push east across the plains late this afternoon and
evening. Brief heavy rain, small hail, and wind gusts to 50 mph
will be possible with the storms along the Front Range urban
corridor.

As storms progress eastward onto the plains later this afternoon
and evening, a few will likely become severe with 2 inch diameter
hail and 70 mph winds possible. A brief tornado is also possible.
The stronger storms will also produce very heavy rain, although
the faster motion of storms today should limit the threat of flash
flooding.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Storm chances are expected to gradually decrease through this
weekend, as a drier airmass spreads back across the region.
Temperatures are expected to return to normal summer heat by this
weekend, and then warm to above normal levels for the first half
of next week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated today or tonight. However,
any reports of damaging winds, hail, or heavy rain will be
appreciated.

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