512
FXUS65 KBOU 072150
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
350 PM MDT Fri Jun 7 2024

.KEY MESSAGES...

- Hot and dry this afternoon, with gusty outflow winds.

- Shower and storms likely this weekend into early next week, with
  strong to severe storms possible, especially on Saturday.

- Minor snowmelt impacts from rising streams, mainly in Grand
  County. Thunderstorms this weekend could further increase stream
  flow.

- Hot and mainly dry weather towards the middle to end of next
  week. There is potential for a day or two to need a Heat
  Advisory, most likely Thursday.

&&

.SHORT TERM /Through Saturday/...
Issued at 209 PM MDT Fri Jun 7 2024

Satellite and radar have shown an increase in high-based
convection over the past couple of hours. Unsurprisingly, this
convection has had little precipitation and a lot of wind with it.
A decaying shower over Boulder county has produced a substantial
swath of 50-60+ mph wind gusts across the northwest metro. This
will likely be the theme of the afternoon across the lower
foothills and plains given how hot/dry the airmass currently is.
An 18z sounding launched by CSU from Fort Collins showed DCAPE
near 1250 J/kg, and DCAPE is likely a bit higher further
south/east.

Convection should wane towards sunset as the modest surface-based
instability decreases. A quiet night is expected with mild
overnight lows.

Near-surface moisture will increase substantially by Saturday as
easterly low-level flow develops. Surface dew points are forecast
to rise back into the low 50s across most of the plains, with
precipitable water values around 150-200% of normal. Aloft, a
subtle shortwave/speed max should track across the region during
the late morning to mid-afternoon hours, which should be the focus
for convective initiation across the area. Forecast soundings
would generally support both a severe hail and wind potential
given ample shear and >1000 J/kg of CAPE in the early afternoon.
While most models show straight line hodographs that would favor
splitting cells and more of a hail threat, there are a few that
show more curved hodographs east of the metro that could support a
brief tornado threat. Storm mode remains a question, though CAMs
quickly congeal any early convection into a larger MCS that tracks
across eastern Colorado and into Kansas. There are also still some
questions regarding the degree of capping/surface heating before
storms initiate, but those likely won`t be answered until tomorrow
morning.

&&

.LONG TERM /Saturday night through Friday/...
Issued at 209 PM MDT Fri Jun 7 2024

Storms will be ongoing Saturday evening but they are expected to
mostly move out of our forecast area by the late evening.

A risk for strong to severe thunderstorms will again be present on
Sunday. During the afternoon, there will be moderate instability
that forms with mixed-layer CAPE up to 2,000 j/kg. The instability
profile is consistent with some of the larger severe hail cases we
have seen. In addition, there will be light upslope flow in the
low levels and adequate moisture levels for thunderstorm formation.
The question will be the forcing. There is weaker flow aloft than
previous days with winds at 500 mb at only 30-40 knots. There
does not appear there will be a shortwave trough at this time but
models may be able to resolve one at short time ranges. There will
also be an inversion around 700 mb that may put a cap on storms.
The most likely scenario seems to be that there will be enough
forcing for strong to severe storms mainly across the I-25
corridor and adjacent eastern plains. However, there is a chance
the forcing will not be enough and very few strong storms form.
The primary threat would be large hail but severe wind gusts and a
tornado or two could occur as well.

Upper level ridging will move over Colorado on Monday with warmer
temperatures aloft. This will reduce instability and there will be
lower coverage of storms compared to the weekend. A couple of the
storms could be strong with hail possible. There will not be a
widespread severe threat given the reduced instability.

A strong upper level ridge will dominate Colorado`s weather
Tuesday through the end of the work week. 80 F high temperatures
are expected on the plains on Tuesday with the 90s coming back on
Wednesday. These days may have stray showers or storms mainly
across the higher terrain. The ensemble guidance is in rather good
agreement that Thursday will be very hot. The warm 700 mb
temperatures along with downslope winds and plenty of sunshine
will allow temperatures to get to the mid to upper 90s across the
plains. When focusing on DIA, the ECMWF has the majority of its
ensemble members at 95 F or above and there is one showing a high
of 100 F. Given the early season heat, it is possible that a Heat
Advisory will be needed for the I-25 corridor. Friday could also
be just as hot or hotter but the confidence in the heat is much
lower. High temperatures will depend on the timing of a shortwave
trough that moves from off the Baja California coast to Colorado
by Friday evening. If this trough is slower than expected to move
across (which can be typical for these cut-off troughs), highs
will once again be in the upper 90s to around 100 F across the
plains. However, if the trough moves through quickly, showers and
storms will keep temperatures down to around normal.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1132 AM MDT Fri Jun 7 2024

VFR through the TAF period, with afternoon convection the main
focus both today and Saturday. Wind shift arrived a little ahead
of schedule this morning, and generally northwest to northerly
winds are likely through the afternoon hours. As high
showers/storms develop, variable and gusty winds will be
possible... especially after 21z. Some of this activity may linger
into the evening hours.

Drainage flow is expected tonight, with a turn to northeast or
easterly winds by Saturday morning. Better moisture and an
approaching shortwave trough should provide better focus for
more organized convection as we approach 18z Saturday.

&&

.HYDROLOGY...
Issued at 209 PM MDT Fri Jun 7 2024

Elevated flows continue across the upper Colorado River basin and
additional rainfall this weekend could lead to further increase in
the flows. Remain cognizant of the dangers of these cold flows,
and be aware of any Flood Advisories.

Thunderstorms will be likely across the recent burn areas Saturday
through Monday. The strongest storms may occur on Saturday but
with strong winds aloft, they will be moving quickly. Therefore,
there is a minor threat of flash flooding Saturday. The flow aloft
will weaken on Sunday and Monday which will lead to slower moving
storms. Considering strong storms are still possible on Sunday,
there will be a moderate threat for flash flooding. By Monday,
storms will likely be weaker and the threat will be minor again.

&&

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

&&

$$

SHORT TERM...Hiris
LONG TERM...Danielson
AVIATION...Hiris
HYDROLOGY...Danielson