634
FXUS65 KBOU 051123
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
523 AM MDT Sat Jul 5 2025

.KEY MESSAGES...

- A chance of afternoon and evening thunderstorms and above normal
  temperatures are expected for the weekend into early next week.

- Some strong to severe storms are possible with large hail and
  damaging wind gusts across the eastern plains this weekend and
  Monday.

- Hot temperatures expected Wednesday with the upper 90s expected
  across the plains.

&&

.UPDATE...
Issued at 317 AM MDT Sat Jul 5 2025

Models never did pick up on the scattered showers and isolated
thunderstorms that tracked across the area the past few hours.
Even though we saw some drying and subsidence last evening, the
best I can tell, they are being triggered a nose of a 60-70 knot
jet and the push of northerly winds which helped increase low
level moisture. Most of the activity has shifted east onto the
plains and is expected to end in the next few hours.

For today, the best moisture will be at the lower levels. Where
we can keep an easterly wind, this will help hold in the low level
moisture. Cross sections and water vapor satellite imagery
showing the mid and upper levels being dry. This will favor the
plains for thunderstorm activity this afternoon and evening.
Isolated to scattered storms are expected to form early this
afternoon along the Front Range. As they track east onto the
plains, they will encounter a more moist and unstable atmosphere.
There`s decent agreement among the hi-res models that a broken
line of storms moves across the northeast plains late this
afternoon and early evening. A few of these storms will be strong
to severe with damaging winds and large hail possible. This
pattern of drier air over the higher terrain and low level moist
air over plains continues for Sunday and Monday. The main forecast
challenge for these days will be how far west the moist airmass
advances and where the strong/severe threat sets up.

&&

.DISCUSSION /Through Friday/...
Issued at 225 PM MDT Fri Jul 4 2025

SPC mesoanalysis shows 1,000 j/kg of surface based CAPE across the
plains this afternoon with higher values exceeding 2,000 across
the northeast corner by Nebraska. With 500 mb winds around 20
knots, deep layer shear is lacking today so the severe weather
threat is rather low. However, the easterly winds and healthy dew
points in the upper 50s will help to create storms that will
merge into a line during the late afternoon. This line may have
wind gusts up to 50 mph associated with it and there could be one
or two severe wind gusts above 60 mph especially in the far
northeast corner of the state since there is better instability
there. Across the I-25 corridor, some weak showers and storms may
linger into the early evening hours. But with subsidence aloft due
to the departing shortwave trough, the only thing keeping the
storms going is the daytime warming. Therefore, showers and
storms are expected to end at sunset with minimal threat to
evening firework shows.

Saturday and Sunday will have similar setups. There will be weak
zonal flow aloft on the northern edge of a ridge. There will be
weak lee cyclogenesis over northeast Colorado which will keep
surface winds light out of the east. The easterly winds will keep
in decent moisture and moderate instability especially east of
DIA each day. High resolution models indicate isolated to
scattered storms will form over the eastern plains and they may
become strong to severe with large hail and damaging wind gusts.
The shear will be the limiting factor so storms are not expected
to be particularly long-lived. This will keep the severe threat in
the marginal or slight SPC categories.

Monday may be the day with the best severe setup since similar
instability and moisture will be in place. However, there will
likely be a shortwave aloft that will increase deep layer shear
and forcing so better coverage of strong to severe storms is
expected. This threat may require a slight or enhanced SPC risk if
the timing of the shortwave is roughly in the afternoon or evening
Monday.

A ridge will strengthen and move north over Colorado on Tuesday
and Wednesday. This will result in dry conditions and much warmer
temperatures. Wednesday appears to the be warmest day with highs
reaching the upper 90s across the plains with some locations like
Greeley having a chance to hit 100.

&&

.AVIATION /12Z TAFS through 12Z Sunday/...
Issued at 523 AM MDT Sat Jul 5 2025

South-southwest winds expected for the rest of this morning
(18Z). Winds then become light and variable before becoming
easterly. Best chance for thunderstorms will be east of the Denver
area. Having some sort of easterly wind component seems on track
through 00Z Sunday. Still about a 30 percent for thunderstorms at
DEN and APA, slightly lower for BJC. The chance for storms
decreases after 01Z Sunday with southeast winds expected to
prevail. The southeast to south winds are then expected to persist
through Saturday night and into early Sunday morning.

&&

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

&&

$$

UPDATE...Meier
DISCUSSION...Danielson
AVIATION...Meier

NWS BOU Office Area Forecast Discussion