406
FXUS65 KBOU 062338
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
538 PM MDT Sun Jul 6 2025

.KEY MESSAGES...

- Scattered afternoon/evening thunderstorms today and Monday.

- Some strong to severe storms are possible with large hail and
  damaging wind gusts today and Monday, mainly across the eastern
  plains, but a few are possible across the urban corridor.

- Hot temperatures expected Wednesday with the upper 90s expected
  across the plains. It is possible the hot temperatures extend
  into Thursday.

&&

.DISCUSSION /Through Sunday/...
Issued at 238 PM MDT Sun Jul 6 2025

Satellite and radar show two main areas of convection this
afternoon. One area is along a boundary that has setup from near
Woodrow in western Washington County across to Kiowa. There are
good levels of instability feeding these storms with mixed-layer
CAPE around 1,500 j/kg. Strong updrafts have formed along this
boundary as a result. The issue these storms are currently having
with reaching severe limits is the lack of deep layer shear.
Surface to 6 km shear values are around 25 knots so storms may
struggle to maintain updrafts long enough to produce severe hail
although a report or two of 1" hail is possible. However, severe
wind gusts will be possible out of these storms throughout the
afternoon and evening given steep lapse rates and downdraft CAPE
around 1,700-1,800 j/kg. The other area of storms is along and
just south of the Cheyenne Ridge. This area will have the
potential for storms to congeal into a line as it heads east from
around Cheyenne, WY. As it heads further east, the instability
will increase with mixed-layer CAPE around 2,000 j/kg over the
far northeast corner of Colorado. It is expected that these storms
will produce damaging wind gusts up to 70 mph. A Severe
Thunderstorm Watch has been issued for areas along and east of
I-25 until 8pm tonight. Denver County was withheld from this watch
as dew points have dropped to the low 40 there and instability is
lower than other areas.

Some model guidance is showing that storms could continue into the
overnight hours tonight across the eastern plains. That threat
will depend on how much instability the storms this afternoon and
evening "use up." If there are fewer storms this afternoon and
evening, scattered coverage of storms could occur after midnight.
However, it is more likely that only a stray storm or two forms.

Better moisture will stay in place over the eastern plains on
Monday with dew point values in the low 60s from Akron and
eastward. With steep lapse rates, most unstable CAPE values are
forecast to exceed 3,000 j/kg in the northeast corner of Colorado.
This is ample instability for strong to severe storms to form. The
uncertainty with Monday`s forecast will come from the amount of
shear and what boundaries are left behind from overnight
convection. A weak shortwave aloft will enhance deep layer shear
with values around 35 knots across the far northeast corner. These
factors will lead to the development of an MCS that could produce
severe wind gusts up to 70 mph mainly east of a line from Fort
Morgan to Limon. SPC has an enhanced risk of severe weather and it
seems reasonable for the far northeast corner. The Denver metro
and I-25 corridor will mostly likely avoid much of the severe
weather assuming the best moisture stays further east.

The axis of an upper level ridge will move northeastward into
Colorado on Tuesday. This will increase temperatures aloft and
will decrease the chance for storms. However, enough lingering
moisture could produce an isolated storm near the Cheyenne Ridge.
High temperatures will begin to warm up to the mid 90s across the
plains.

Wednesday is still on track to be the warmest day of the upcoming
week as the best subsidence and warmest air aloft will be overhead
that day. Temperature forecasts still have Denver flirting with
100 degrees. With the NBM and ECMWF MOS mean forecasting a high of
98, the forecast was left at that number. However, Denver does
have a chance of reaching the record daily high temperature of 100
degrees. A Heat Advisory may be needed especially if it appears
cloud cover will be minimal.

Models have converged on a trough moving through our forecast area
on Thursday but this may only reduce the heat by 2-4 degrees from
Wednesday. A cold front moves through Thursday night with much
cooler conditions on Friday.

&&

.AVIATION /00Z TAFS through 00Z Tuesday/...
Issued at 530 PM MDT Sun Jul 6 2025

Considerable uncertainty in the first few hours of the TAF this
evening. Convection has developed in the wake of a strong outflow
boundary which pushed through DEN near 23z, with additional weak
TS in the Front Range foothills. Adding to this complexity, a
boundary collision appears imminent north of DEN by/before 00z.
With guidance of little use in the near term, our initial thoughts
are that TS/outflow boundaries will continue to be an issue for
the terminals through 02z, though confidence of direct TSRA
impacts at any of the TAF sites isn`t high enough to justify a
prevailing/TEMPO.

The initial convective activity will likely have significant
impact on the wind evolution through the evening hours. I changed
little in the 02-06z period and will wait until there is a more
obvious solution in that timeframe. However, drainage should
eventually prevail overnight. There is still a low chance of some
stratus if a better push of high-surface moisture air can advect
in from the eastern plains overnight.

Tomorrow looks to be a little quieter across the region (though
again, somewhat dependent on this evening/tonight`s evolution).
Guidance generally develops TS east of the terminals with a lower
chance of impact in general. Still kept the PROB30s in for now but
wouldn`t be surprised if those end up removed later on. Winds
should generally remain light with some sort of northeast
component by the afternoon hours.

&&

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

&&

$$

DISCUSSION...Danielson
AVIATION...Hiris