947
FXUS65 KBOU 140548
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1148 PM MDT Fri Jun 13 2025

.KEY MESSAGES...

- Drying trend this weekend with the chance for thunderstorms
  mostly confined to the northeast plains.

- Summer heat this weekend through Monday. Brief respite Tuesday
  and Wednesday, but then hot again end of next week.

&&

.DISCUSSION /Through Friday/...
Issued at 217 PM MDT Fri Jun 13 2025

Water vapor satellite imagery showing drier air has moved over
the area and even drier air is upstream for this weekend. For the
rest of this afternoon/evening we`ll see high-based showers and
thunderstorms form and then progress eastward across the higher
terrain and urban corridor. Wind gusts up to 50 mph will be
possible with the showers/storms, any rainfall is expected to be
short lived. As storms continue eastward, they will encounter an
increasingly unstable airmass over eastern Colorado. MLCAPES of
1500-2500 J/kg are more than enough for severe storms with large
hail and damaging winds. However, shear won`t be that great with
0-6km bulk shear of 25 to 35 knots. The stronger flow aloft and
better shear will be to the north of Colorado. So we don`t expect
strong supercell thunderstorms, but the multicellular storms still
could produce golf ball sized hail and 70 mph winds. The greatest
threat window is 6PM to 10PM and the area will be east of a line
from Cheyenne to Fort Morgan to Limon.

Upper level ridging centered over the Central and Southern
Rockies this weekend, then shifting slightly eastward on Monday.
This will result in very warm temperatures all 3 days with highs
in the 90s across northeast Colorado. Cross sections show some mid
level moisture, which is expected to result in isolated high-
based showers. Chances rainfall reaches the ground are low, but
gusty winds will likely occur during the mid afternoon to early
evening hours each day. Over eastern Colorado, southeast lower
level winds will help hold moisture in place. The warm
temperatures combined with the moisture will yield 1500-3000
MLCAPE. However with the ridge overhead, mid level temperatures
will be warm and flow aloft will be weak, greatly limiting the
severe weather threat. However, the far northeast plains will see
the strongest flow aloft and have the greatest chance at seeing
strong/severe storms each day (Saturday-Monday).

On Tuesday, an upper level trough pushes eastward across the
Central Rockies Tuesday. This will bring a cold front and cooler
temperatures with highs in the 80s across northeast Colorado. This
system will also bring a chance for showers and thunderstorms.
The ECMWF ensembles generally favor showers and storms, while the
GFS ensembles lean on the drier side. Will keep a mention of
showers and storms in the forecast for Tuesday. The trough shifts
east of the region by Wednesday. Northwest flow behind the trough
will bring drier weather back to the region. Temperatures will
stay below 90F one more day on Wednesday before the upper level
ridge rebuilds over the Central and Southern Rockies. The ridging
overhead will bring very warm air back to the area for Thursday
and Friday with highs in the 90s across northeast Colorado. The
heat continues into next weekend (June 21st & 22nd) with a strong
summer ridge over the region or just east of us. Highs are
expected to continue to be well into the 90s with a few low 100s
possible.

&&

.AVIATION /06Z TAFS through 06Z Sunday/...
Issued at 1148 PM MDT Fri Jun 13 2025

Another, but last, easterly outflow surge from storms in northeast
Colorado, Southwest Nebraska, and Northwest Kansas is headed in,
so expect a more easterly or southeast component to stick around
for a few hours before trending back to southerly. We`re not
totally in the clear with regard to any stratus potential, but
with a relatively quick return to drainage overnight before the
coolest temperatures we think the odds would be 20% or less of any
lower cloud impacts.

Normal diurnal wind patterns expected during the day Saturday, but
there`s still a small (20-30%) chance of high based showers or
virga around that could cause disruptions and variable gusty winds
to 35+ kts, so something to watch. More likely, is a potential
surge from the northeast during the evening hours (02Z-05Z ish)
due to storm outflows originating near the Wyoming border. So
opted for VRB at 03Z Sunday to account for that - then normal
drainage winds developing later again toward 09Z Sunday.

&&

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

&&

$$

DISCUSSION...Meier
AVIATION...Barjenbruch