186
FXUS65 KBOU 031114
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
514 AM MDT Mon Jun 3 2024

.KEY MESSAGES...

- Summer heat through most of this week, with a few 90 degree
  readings over the plains

- Chance of showers and storms tonight

- Breezy but a little cooler Tuesday

- Return to more normal temperatures and a chance of storms this
  upcoming weekend.

&&

.SHORT TERM /Through tonight/...
Issued at 334 AM MDT Mon Jun 3 2024

GOES water vapor imagery currently shows the next approaching
shortwave over the PNW early this morning heading east. As we begin
today under weak ridging, northwesterly flow aloft and mostly clear
skies across the CWA, this broad, low amplitude shortwave will
continue eastward across the northern US putting Colorado downstream
of its axis. Cross sections indicate mid and upper-level moisture
will increase throughout the day, increasing cloud coverage with it.
With marginal instability from daytime heating and synoptic forcings
mixed with orographics, chances for showers and embedded
thunderstorms increase into the evening hours across the high
elevations mainly after the 2Z to 3Z time frame. With dry low levels
portrayed in forecast soundings, there is high potential for high-
based virga showers to develop across the plains. These could cause
dry microbursts as the NAM shows DCAPE values over 1000 J/kg in the
afternoon. Chances for storms and showers will diminish early
Tuesday morning as the shortwave exits the area and is replaced with
northwesterly flow aloft. It will be another warm day with another
chance of reaching 90 across portions of the plains.

&&

.LONG TERM /Tuesday through Sunday/...
Issued at 334 AM MDT Mon Jun 3 2024

Tuesday will feature breezy to windy conditions across the plains
and Front Range mountains as unseasonably strong west/northwest
flow dominates in the wake of tonight`s shortwave. There are
indications for a near mountain top stable layer, and combined
with 40-45 kt cross mountain component will support potential for
gusty winds up to 40-60 mph above timberline and some of the wind
prone slopes in the higher foothills early Tuesday morning. Those
gusty winds, albeit lighter, will spread across the plains in the
late morning and afternoon given daytime heating and mixing, and
large scale subsidence. Most gusts on the plains should range
between 20 and 30 mph, except near the windy Wyoming border where
gusts will likely range between 30 and 40 mph. Temperatures will
be a few degrees cooler than today given some cold advection
associated with tonight`s disturbance. Outside of a couple
lingering morning showers in the mountains, dry weather will
prevail although a fair amount of high level cloudiness is
possible per latest model cross sections.

Wednesday and Thursday are still looking quite warm and dry.
Downslope flow on Wednesday will likely contribute to highs near
90F across most of the plains and I-25 Corridor. Thursday may end
up a couple degrees cooler with potential for a backdoor cold
front.

The main change in tonight`s forecast package was to delay any
sort of cooling and lower the PoPs a little for Friday. Model
ensembles were a little farther east with the Great Lakes region
upper low, which means a delay and uncertain timing regarding
additional backdoor cold fronts. There is still reasonable
agreement in the EC ensembles for a cooldown starting Saturday
into Sunday, although the 00Z GEFS was now showing less. We still
think we`ll trend at least a little cooler by next weekend with
closer to normal temperatures. And, enough moisture advects in
from the Central Plains under persistent but weak easterly flow
for a higher chance of showers and storms.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 513 AM MDT Mon Jun 3 2024

Main concern is potential for VRB winds and gusty outflows from
passing virga/light showers anytime from 22Z-08Z.

South/southwest winds will start the period, and then likely
become light/variable by 18Z. After that, there are uncertainties
regarding wind direction as guidance displays a bunch of different
scenarios, and even potential for microbursts starting any time
after 22Z. DCAPE around 1000 J/kg and dry adiabatic profile to
around 600 mb would suggest gusts generally around 30 kts, but
couldn`t rule out something a little stronger. Timing any of these
will be tough, as initial development could serve up the first
round of VRB gusty outflow winds, and then a second round potentially
occurs with the upper level trough support closer to 03Z-08Z when
virga or even a light shower would be possible. Any ceilings
should stay above 13,000 ft MSL, even with the passing
showers/virga given very dry subcloud layer.

By late tonight and after the last passing virga, winds should
settle to a southwest to westerly flow regime. On Tuesday, winds
will transition to more northwesterly with daytime heating and
mixing, with gusts to around 25 knots expected after 16Z-17Z.

&&

.HYDROLOGY...
Issued at 300 AM MDT Mon Jun 3 2024

Alpine snowmelt will increase runoff the next several days with
the arrival of summer heat.  Hydrologic forecasts from the River
Forecast Centers now show a few streams getting to action stage
later this week, which means flows will be high and fast but
flooding threat limited. Please use caution and respect these fast
moving and cold flows in the high country.

&&

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

&&

$$

SHORT TERM...Bonner
LONG TERM...Barjenbruch
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch