460
FXUS65 KBOU 061141
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
541 AM MDT Thu Jun 6 2024

.KEY MESSAGES...

- Slight cooling today, back to 90F+ across the plains and I-25
  Corridor Friday

- Minor snowmelt impacts from rising streams, mainly in Grand
  County

- Increasing chances for showers and thunderstorms this weekend
  into early next week, along with cooler temperatures. A couple
  storms could be strong.

- Gradual trend towards warmer/drier weather towards the middle of
  next week.

&&

.SHORT TERM /Through tonight/...
Issued at 344 AM MDT Thu Jun 6 2024

Water vapor imagery shows the forecast area under a dominating and
dry upper level ridge. We did have a weak frontal push in the
late night hours, which will help us start off a little cooler,
and likely stay a couple degrees cooler than yesterday. In fact,
the latest guidance is pointing at mid to upper 80s for highs
across the plains and I-25 Corridor due to the slight low level
cooling and upslope flow that we`ll experience today.

With regard to precip chances, the only real chance of any showers
or storms will be in the Park County area late this afternoon,
perhaps spilling east onto the crest of the Palmer Divide this
evening. That`s the easiest place to get enough influence of the
low level moisture advection combined with the weakest cap. But
even then, don`t expect anything more than isolated coverage of
generally weak convection.

&&

.LONG TERM /Friday through Wednesday/...
Issued at 344 AM MDT Thu Jun 6 2024

Ensemble guidance is in good agreement for the return of moisture to
the region by the weekend, bringing increased shower/storm chances
through early next week.

Friday, the upper ridge shifts further east over Colorado
accompanied by a mid-level thermal ridge. Warming 700mb temperatures
and downslope flow to support highs in the upper 80s to low 90s for
plains/urban corridor. A plume of moisture will also begin to round
the ridge, nudging into Colorado. Model soundings show moisture more-
so in the mid-levels. A weak shortwave trough also moves through the
NW flow aloft by the evening. This will bring back instability with
MLCAPE values around 500-1000 J/kg across the plains. Scattered
showers and thunderstorms return to the forecast by Friday
afternoon. The eastern plains may see a few stronger to severe
storms with hail and winds are the primary hazards.

By the weekend, anomalous moisture reaches the forecast area as
ensemble mean precipitable water values increase to 150-180% of
normal. Model soundings also show a deeper moisture profile with
increased lower level moisture. Details still remain a little
fuzzy on the exact timing and strength of a shortwave or two that
moves through in the Sat-Mon timeframe. There should again be
sufficient instability around (500-1000 J/kg MLCAPE) on Saturday,
with better instability shifting more west into the urban
corridor. We`ll have to see if a stronger consensus arises on the
timing of the waves which would support a more organized push of
showers/storms. Models are starting to hint at Sunday being more
stable in between the waves which would keep precipitation chances
slightly lower and the higher chances more south. The unsettled
pattern continues through Monday with scattered showers and
storms. It will also be cooler over the weekend into early next
week as well with highs in the mid 70s to near 80 across the urban
corridor and plains.

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 Friday/...
Issued at 541 AM MDT Thu Jun 6 2024

VFR will persist through the TAF period. Light and variable winds
will prevail through about 15Z. Then there will be a transition to
normal diurnal easterly flow around 10 kts which will hold
17Z-01Z. Winds will then begin their normal return to
south/southwest flow during the overnight at KDEN and KAPA, but
speeds will average close to 15 knots for the 05Z-12Z period.

&&

.HYDROLOGY...
Issued at 344 AM MDT Thu Jun 6 2024

Mountain snowmelt and runoff accelerated yesterday as seen by a
spike in river/stream gauges in the high country. The main focus
is up in the headwaters of the Colorado River including the Fraser
River where minor flooding (minimal impacts) of a few low lying
areas anticipated. Many other streams, including those in the
Front Range, are seeing quick rises as well but remain well below
Action Stage. That said, flows along Clear Creek, Boulder Creek,
and the Cache La Poudre to name a few are on the rise. Continue to
respect the fast moving and cold flows.

In addition, there is a limited threat of burn area flash flooding
this weekend into early next week, as an anomalously moist airmass
advects into the region. Scattered showers and thunderstorms are
forecast most afternoons, which would be capable of brief heavy
downpours. However, mean cloud-layer flow should be strong enough
(15-25kt) to keep the overall chances of heavy rain/flash flooding
low.

&&

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

&&

$$

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