279
FXUS65 KBOU 202347
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
547 PM MDT Sat Jul 20 2024

.KEY MESSAGES...

- Isolated to scattered afternoon showers and storms this
  afternoon. An additional round of storms possible overnight
  tonight.

- Cooler on Sunday, with continued rain chances.

- Gradual warming trend next week with drier conditions.

&&

.SHORT TERM /Through Sunday/...
Issued at 220 PM MDT Sat Jul 20 2024

Satellite and radar this afternoon show a few weak storms across
the forecast area, mainly over the northeastern plains. No
significant updates to the forecast through this evening with
additional storms likely developing across the Front Range
mountains/foothills over the next few hours.

As we get into tonight and tomorrow`s forecast, confidence
decreases pretty quickly. Guidance has slowly warmed up to the
idea of a cluster of showers and embedded thunderstorms late this
evening/early tonight. This appears to be linked to the convection
currently developing across central Wyoming. We maintained at
least chance PoPs through the overnight. If you`re a fan of rain
across the I-25 corridor, it will be worth watching short term
model trends to see if models come into better agreement.

From there, there`s a few more "ifs" to discuss. If we do get
overnight rain... that may lead to some Sunday morning stratus. If
we get morning stratus... that likely limits our daytime heating
and subsequent afternoon destabilization... leading to less
coverage of showers/storms during the day Sunday. On the other
hand, a sunny start to Sunday would favor better instability and
widespread showers and storms by late morning or early afternoon.

As a whole, confidence of rain at any given hour is pretty low...
but the pattern favors a good chance (>70% from the GEFS/ECME) of
a wetting rainfall (>0.10") across the Front Range and adjacent
plains by Sunday evening. Stay tuned!

&&

.LONG TERM /Sunday night through Saturday/...
Issued at 240 PM MDT Sat Jul 20 2024

The CWA looks to stay in relatively weak northerly flow aloft
with high amplitude upper ridging to our west and northwest and
upper troughing east of Colorado Sunday night through Tuesday
night. The synoptic scale energy is expected to be weak
downward motion to neutral through the five periods. The boundary
level wind and surface pressure fields keep fairly normal diurnal
surface wind patterns for the CWA.

The precipitable water and boundary layer dew point fields show
drying on Monday from Sunday; then more drying on Tuesday. CAPE
is limited through the periods. As far as convective chances go,
forecast soundings and QPF fields show the the best chances of
measurable rainfall over the high country for late day Monday and
only "isolated" coverage for the plains. Chances decrease further
on Tuesday with less moisture availability and less instability.
Heavy rain chances are marginal at best on Monday, decreasing
further on Tuesday.

For temperatures, Monday`s highs warm up a bit from Sunday`s
readings but they still look to be below seasonal normals across
the forecast area. On Tuesday, readings climb a bit higher but
temperatures still look a tad below seasonal normals.

For the later days, Wednesday through Saturday, the upper ridge to
our west pushes eastward into and across Colorado through Friday
night. By Saturday, some weak troughing gets into Colorado. Drying,
subsidence and warming will be the rule into Friday. Rainfall
chances get better again on Saturday along with some minor cooling.

&&

.AVIATION /00Z TAFS through 00Z Monday/...
Issued at 536 PM MDT Sat Jul 20 2024

A line of strong to severe storms is progressing through Morgan
County as of this writing. These storms have formed along an
outflow boundary that will move southwestward toward the terminals
this evening. Confidence is growing greatly that this outflow
boundary will produce storms with gusty winds. Winds up to 40
knots are possible. The best chance for these storms to occur is
between 02-05Z. Therefore, a TEMPO group was added to all
terminals.

The storms will end this evening and light winds are expected
throughout the night. There is a chance that stratus clouds
develop in the morning around 3,000 feet. However, this chance is
low enough that it wasn`t included in the TAFs at this time.

Tomorrow afternoon, isolated showers and storms will form. These
storms could produce gusty winds and reduce visibility. The chance
for these storms to impact the terminals is around 30 percent so a
PROB 30 was included.

We also want to note that there is plenty of smoke in the visible
satellite imagery that is headed to Colorado. It may impact
visibility especially in the higher levels of the troposphere.

&&

.HYDROLOGY...
Issued at 220 PM MDT Sat Jul 20 2024

Despite relatively high chances for precipitation, the burn area
flash flooding threat remains limited. Thunderstorms this
afternoon will be widely scattered and may pose a brief heavy
rain threat, but storm motions near 15-20kt will push storms off
the burn areas quickly. Additional showers and storms are
possible tonight but most guidance keeps these over the plains.

Cooler temperatures tomorrow will likely limit instability and
keep storms weak enough to avoid widespread issues. Storm motions
should generally be slower tomorrow and if a strong storm or two
manages to develop it could produce enough rainfall for isolated
issues.

A warming and drying trend is expected next week, with no
significant hydrological concerns.

&&

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

&&

$$

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