000
FXUS65 KBOU 050307
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
907 PM MDT Sun Jun 4 2023

.UPDATE...
Issued at 900 PM MDT Sun Jun 4 2023

Showers are decreasing as expected, with not much lightning left.
There is still a batch of showers that will likely move through
the Front Range cities in a couple of hours, then there should be
quite a bit less after that. Fog is an interesting question as
there is still quite a bit of high cloudiness across most of the
area. However it is thinning and should be eroding from the
northeast as well. We did bump up the areas of fog for a few hours
in the morning, though it could be mostly stratus off the ground.
This is especially true for Denver where weak south winds should
provide a little drying/mixing. Monday`s forecast looks alright
although if there is more extensive/persistent morning stratus it
could lower the high temperatures and delay the development of
showers/storms in the afternoon.

&&

.SHORT TERM...(This evening through Monday)
Issued at 158 PM MDT Sun Jun 4 2023

Yet another very wet day across northeast Colorado today, with
widespread rainfall amounts of 0.75-2" across the foothills and
urban corridor over the past 24 hours. And there`s more to come.

The blocking high anchored over the northern plains and Canada,
combined with a dissipating weak trough of low pressure over the
central plains, has continued to funnel abundant Gulf moisture
into the Front Range. ACARS soundings from KDEN indicate PWAT
values around 0.95", very close to the daily maximum value for
June 4th per SPC sounding climatology. As expected, precipitation
is becoming increasingly intermittent and even slightly convective
over the plains this afternoon, with help from some partial
clearing and a few surface boundaries. Marginal instability will
creep into the northeast plains this afternoon and should be
sufficient for a few thunderstorms. Can`t rule out one or two
surviving into the urban corridor, but anything severe is
unlikely. Another widespread 0.25" can be expected for almost all
of our foothills and I-25 corridor today, and some spots impacted
by the heaviest showers/thunderstorms may pick up an additional
0.50-0.75" by tonight. Rain has generally been light to moderate
and steady, tapering flood concerns. Greatest potential for
flooding impacts remains in and around the Cameron Peak burn scar.
If a heavier cell or thunderstorm moves over the scar later this
afternoon, given the 1"+ of rain that`s already fallen, flash
flood concerns would be considerably heightened. Elsewhere, only
minor flooding of poor drainage areas is likely.

Ample clouds will linger overnight and with plenty of low-level
moisture after today`s rain, areas of fog can be anticipated by
early Monday morning for parts of the plains and urban corridor.
The cloud cover will sustain relatively mild overnight lows in the
low 50`s, similar to last night.

For Monday, the aforementioned closed low dissipates, and winds
over the plains become southeasterly, with generally westerly
flow returning to the high country. As a result, PWAT amounts look
to fall closer to average values for the lower elevations,
although will remain up to 200% of normal in the high country.
With slightly better clearing tomorrow afternoon, a few hundred
J/Kg of MLCAPE are likely in the plains, which may support some
isolated late afternoon/evening convection. However, the bulk of
the precipitation tomorrow will remain confined to the high
country, where moisture will be maximized. Weak steering level
flow will make for slow-moving showers and thunderstorms, and
sustain at least a limited threat of flash flooding for recent
burn scars. This slow movement may also limit how much activity is
able to drift eastward into the urban corridor and plains.
Overall, will be a much drier day across the lower elevations.

.LONG TERM...(Monday night through Sunday)
Issued at 231 PM MDT Sun Jun 4 2023

Models continue to show a blocking upper high over the northern
central U.S. Monday night through Wednesday night and on into the
extended period. There is neutral to weak upward synoptic scale
energy for the CWA. Models also continue to show east and
southeasterly low level winds through most of the CWA well into
the mountains. For moisture, surface dew point progs show 50S F
for the plains and foothills with precipitable water amounts in
the 0.70 to 1.10 inch range for those areas. Models show surface
temperatures to warm up a bit both Tuesday and Wednesday with CAPE
coming up as well. So instability will be a bit better each day.
This and the moisture should keep the pops in the "likely"
category both Tuesday and Wednesday.

For the later days, Thursday through Sunday, models show the upper
high center to move a west and north to be over southern and central
parts of Alberta and Saskatchewan all four days. There will still be
upper ridging over the CWA through the period.  Models continue to
show plenty of moisture and QPF through the four days, so the cool
moist late Spring weather should continue.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 900 PM MDT Sun Jun 4 2023

Scattered showers will produce areas of MVFR conditions. In the
Denver area, these will mostly be between 04z and 06z. Later
tonight, areas of IFR ceilings/visibilities are likely to develop
after 08z. Dissipation is expected betwen 14z and 16z. Scattered
thunderstorms will develop after 20z with localized MVFR
conditions and wind gusts up to 30 knots.

&&

.HYDROLOGY...
Issued at 231 PM MDT Sun Jun 4 2023

Scattered showers and even an isolated thunderstorm will continue
to impact all areas east of the Continental Divide through this
evening. Rainfall rates will mostly stay below 0.30"/hr, however a
few smaller cells/thunderstorms may produce brief rainfall rates
to 0.75-1"/hr. Low confidence in such rates reaching the Cameron
Peak burn scar, but if that were to occur, today`s widespread
0.75-1.50" over the burn area would serve to increase the
potential for flash flood impacts for any heavier showers. Gauges
in and around the burn scar, such as along Buckhorn Creek, the
Cache la Poudre, or North Fork Big Thompson have exhibited stage
rises of approximately 0.5-1 ft. Additional rises are possible
with additional precipitation this afternoon and evening.
Elsewhere, only minor flooding/ponding is expected in poor
drainage and urban areas.

For Monday, more showers and thunderstorms are expected,
particularly in the high country. These may be slow moving thus
sustain a threat of flash flooding on the burn scars, including
those west of the Divide.

The long period of recent rainfall has made the soils pretty
saturated in many areas of the CWA.  There should be higher CAPE
values most of next weak and plenty of moisture is still expected as
well. As a result, flash flooding is possible for much of the CWA
and especially over the burn areas in the mountains.

&&

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

$$

UPDATE...Gimmestad
SHORT TERM...Rodriguez
LONG TERM....RJK
AVIATION...Gimmestad
HYDROLOGY....Rodriguez/RJK