805
FXUS65 KBOU 051140
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
540 AM MDT Wed Jun 5 2024

.KEY MESSAGES...

- Summer heat through the rest of this week, with a few 90 degree
  readings over the plains, with today and Friday the hottest
  days.

- Increasing chances for showers and thunderstorms this weekend
  into early next week, along with slightly cooler temperatures.

&&

.SHORT TERM /Through tonight/...
Issued at 335 AM MDT Wed Jun 5 2024

For today, the forecast area will be under increasing influence
of a large and hot dome of high pressure over the Southwest U.S.
Mid level temperatures will show significant warm advection, with
700 mb temperatures rising 5C from yesterday. Given full sunshine
and still some downslope winds, that spells high temperatures in
across almost all of the plains and I-25 Corridor reaching the
lower 90s for the first time this year.

For tonight, a weak backdoor cool front arrives late this
evening. That front is dry with a continuation of mostly clear
skies. The lighter winds behind the front will allow for stronger
low level inversions, and cooler temperatures to spread back to
the foothills (versus this morning`s downslope induced warm
temperatures in the 60s in some spots).

&&

.LONG TERM /Thursday through Tuesday/...
Issued at 335 AM MDT Wed Jun 5 2024

There is good agreement on upper level ridging generally dominating
the upper level pattern for the extended period. Thursday will be a
degree or two cooler than Wednesday with the passage of a
backdoor cold front. Easterly component flow settles in across the
plains for much of the day. Temperatures will still likely be
above normal across the I-25 corridor and plains with highs in the
mid to upper 80s. Conditions will be mainly dry. There is some
very marginal moisture/instability for the higher elevations south
of I-70, so kept in low chances (< 20%)for a few showers/storms
in the afternoon.

By Friday, the upper ridge shifts further east over Colorado
accompanied by a mid-level thermal ridge. Warming 700mb temperatures
and downslope flow will support a good chance for highs in the upper
80s to low 90s for plains/urban corridor.

Ensembles show a signal for anomalous moisture advecting into the
region Friday through the weekend. Ensemble guidance shows mean
precipitable water values 130-175% of normal. Within this
timeframe, a few weak shortwave troughs move through the
northwesterly flow aloft bringing periods of weak synoptic ascent.
Slight cooling aloft will help bring more instability to promote
showers and thunderstorms. Details still remain fuzzy on the
timing and progression/track of the shortwave troughs with notable
differences among deterministic guidance. Overall, the weekend
into early next week looks slightly cooler with scattered/likely
showers and thunderstorms.

By mid-week next week, the upper pattern favors a warming and drying
trend as another ridge builds in from the west.

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 540 AM MDT Wed Jun 5 2024

VFR will persist through tonight under mostly clear skies.
West/southwest winds should prevail through about 16Z-17Z, but a
couple brief periods of light/variable possible as the enhanced
drainage winds subside. Then, winds are expected to turn more WNW
and increase as weak inversions break and tap into west/northwest
flow aloft. Occasional gusts of 17-24 kts possible through about
00Z before winds decouple again and become lighter. Expect a weak
backdoor cold front to arrive with a shift to northeast winds 8-12
kts toward 05Z-06Z, followed by a gradual transition to southeast
flow for Thursday morning.

&&

.HYDROLOGY...
Issued at 335 AM MDT Wed Jun 5 2024

Mountain snowmelt and runoff is accelerating with warmer
temperatures, and high country streams will continue to see
increasing flows through the end of the week. Hydrologic forecasts
continue to show elevated flows, with a few sites along the
Colorado and Fraser Rivers in Grand County reaching Action Stage
by Friday. Action Stage means flows will be high and fast with
near bankfull levels, but so far the threat of any flooding
appears limited. Many other streams, including those along the
Front Range, are seeing quick rises as well given the very warm
temperatures. Use caution along these streams, and respect the
fast moving and cold flows.

Meanwhile, the threat of burn area flash flooding will gradually
increase this weekend into early next week as a moist airmass
advects into the region. Confidence is low for any given day, but
something worth watching as we get closer to the weekend.

&&

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

&&

$$

SHORT TERM...Barjenbruch
LONG TERM...Mensch
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch/Mensch