609
FXUS65 KBOU 170557
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1157 PM MDT Tue Jul 16 2024

.KEY MESSAGES...

- Chance of showers and thunderstorms on Wednesday, with an
  uptick in storm intensity and some severe threat.

- Temperatures cooling to below normal levels for Wednesday.

- More typical summer weather for the latter half of this week
  with scattered afternoon showers and storms most days and near
  normal temperatures.

&&

.UPDATE...
Issued at 938 PM MDT Tue Jul 16 2024

There is still isolated convection occurring this evening, mainly
over the foothills and the I-70 corridor in the mountains. There
are a few cells over the eastern plains. For the update, will
adjust pops down for the rest of the evening, based on reality and
high resolution model output. The increased atmospheric moisture
and cooler temperatures are welcome.

&&

.SHORT TERM /Through Wednesday/...
Issued at 330 PM MDT Tue Jul 16 2024

Current mid-level water vapor imagery shows a plume of moisture
rounding the ridge aloft, pushing into Colorado this afternoon. This
has helped provide a considerable uptick in moisture compared to the
last several days. ACARS soundings reflect this well with observed
soundings showing a sufficient layer of mid-level moisture.
Instability across the region is marginal (MLCAPE < 600 J/kg). So
far this combined with 20-30 kts of shear has brought mainly showers
and weak storms with the stronger storms containing small hail. For
the rest of the afternoon, expect this activity to continue with
gusty outflow winds, small hail, lightning being the main threats.
Can`t rule out a stronger storm or two. Most showers/storms will
diminish and exit to the east early this evening.

Wednesday, the upper level ridge centers over the Four Corners
region with Colorado on the eastern periphery in northerly flow
aloft. Low level moisture increases from Tuesday with additional
upslope flow combined with subtropical moisture. A weak disturbance
moves through the flow to provide weak synoptic ascent. This
environment will favor another day of scattered to numerous showers
and thunderstorms in the afternoon through the evening. Above normal
moisture with precipitable water values above an inch will support
localized heavy rainfall. The marginal instability (MLCAPE 800-
1800j/kg) and sufficient shear will support a few strong to severe
storms. Temperatures are expected to be cooler with highs in the low
to mid 80s across the I-25 corridor and plains.

&&

.LONG TERM /Wednesday night through Tuesday/...
Issued at 330 PM MDT Tue Jul 16 2024

The ridge across the western US widens some on Thursday. We`ll see
QG descent become prominent over the region, with subsident flow
helping lead to warming of ~5 degrees area-wide. PWAT values will
drop closer to 0.80" for the urban corridor, only exceeding 1" in
the far eastern plains, although surface moisture won`t be too bad
with easterly low-level flow sustaining dewpoints in the 50`s much
of the day east of a weak dryline in the eastern plains. It`s
there that instability will be maximized, with MLCAPE values above
1,000 J/Kg. Resultant storm coverage will be less than previous
days, with generally weaker storm coverage. Nonetheless, a few
stronger to severe storms will remain possible across the eastern
plains.

Activity should get a boost on Friday as a weak shortwave
traverses the north-central US plains, and moisture advection
increases aloft. PWAT will climb to or above 1" across the I-25
corridor, although again the more favorable instability axis will
be found across our eastern plains. Regardless, expect a slight
increase in storm coverage and some higher potential for locally
heavier rainfall with any stronger storms.

The placement of the upper-level ridge will experience little
chance as we head into the weekend, keeping our area under largely
north/northwest flow aloft. Thus, the more anomalous heat will
remain to our west, with near-normal temperatures expected to
continue through the extended forecast period. No day looks
entirely dry from Saturday onward, with afternoon
showers/thunderstorms making a return each afternoon and just
minor fluctuations in coverage. Storms will likely be most
numerous across the higher terrain.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1156 PM MDT Tue Jul 16 2024

Main concern will be thunderstorms on Wednesday afternoon and
early evening. Guidance suggests another pretty early start to
convection (around 20Z), and at least scattered coverage. That`s
enough to have TEMPO VRB winds gusting to 35-40 kts and -TSRA in
the forecast...starting at KBJC and KAPA by/shortly before 20Z,
and 21Z at KDEN. Most storms should be out of the area again
before 00Z, with only a small chance thereafter. Outside of the
storms, fairly normal diurnal wind patterns and VFR conditions
will prevail.

&&

.HYDROLOGY...
Issued at 330 PM MDT Tue Jul 16 2024

Above normal moisture remains in the region Wednesday. Model
soundings shower deeper moisture in place than Tuesday with
precipitable water values 1-1.20" for the plains and .45-.65" for
the high country. Some storms will be capable of locally heavy
rain. Overall, the threat of flooding remains relatively low as
storms should be outflow driven and moving along at 20-25 mph.
There will be at least a limited threat of flash flooding for the
2020 burn scars given the uptick in moisture, as the locally
stronger storms in the high country will be capable of producing a
quick one half to three quarters inch of rain in 30 minutes.

&&

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

&&

$$

UPDATE.......RJK
SHORT TERM...Mensch
LONG TERM....Rodriguez
AVIATION...Barjenbruch
HYDROLOGY....Mensch/Rodriguez