558
FXUS65 KBOU 160935
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
335 AM MDT Tue Jul 16 2024

.KEY MESSAGES...

- Higher chance of showers and thunderstorms today and 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.

&&

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

Latest upper air data and ACARS soundings show airmass has cooled
about 3-4C from yesterday. At the surface, high pressure was over
the Northern Plains and Upper Midwest. The first cool front had
moved into the Southern High Plains, and another surge is waiting
behind a stationary front stretching from Central Montana into
South Dakota. This latter front will get another push today,
most likely arriving early this evening. Low level moisture had
increased with current dewpoints ranging from the lower 50s around
metro Denver to the lower 60s over the far northeast plains.

The cooling aloft means we`ll see temperatures returning to near
normal today. That means highs near 90F across the plains and
I-25 Urban Corridor, with mid 70s to mid 80s in the foothills, and
60s to mid 70s mountain locales.

With regard to storm coverage and intensity, there is a fair
amount of uncertainty. The northeast plains will have higher low
level moisture and MLCAPE, but also potential to be more strongly
capped. The Front Range will likely see higher shower and storm
coverage with less CIN, while developing north/northeast low
level flow favors the highest coverage from the Front Range
Mountains and Foothills possibly into the Denver metro area and
more likely Palmer Divide. MLCAPE is more limited here, so the
severe storm threat is marginal. Farther north and east, we have
two factors that may play a role in storm initiation very late
this afternoon and evening; 1) convective outflows from the Front
Range convection and 2) that next cold frontal surge. MLCAPE is
likely to range between 1000 and 1700 J/kg over the east central
plains and shear is sufficient, so if storms can get going a
couple severe storms are probable. CAMs were not very enthusiastic
but it is worth watching potential today.

For later this evening and overnight, we expect the typical
diminishing coverage of showers and storms, partially clearing
skies, and near normal low temperatures.

&&

.LONG TERM /Wednesday night through Monday/...
Issued at 217 AM MDT Tue Jul 16 2024

Wednesday and Thursday, the 500 MB high will be centered over the
Four Corners Region with a weak to moderate northwesterly flow aloft
over Colorado. A moist southeasterly flow combined with ample
subtropical moisture and an upper level shortwave should lead to
scattered to numerous afternoon and evening showers and
thunderstorms across the forecast area, most numerous over the Front
Range Mountains, Foothills and Palmer Divide. With PW`s over an inch
on the plains, some of the storms could produce locally heavy
rainfall. In addition, some of the models suggest the potential for
one or two strong to severe storms across the plains due to ample
instability (1000 J/KG to 1500 J/KG) and some directional wind
shear.

On Thursday, models are showing some drier air moving into the CWA
from the northwest with a downsloping flow east of the divide. If
this verifies, we should see less coverage and intensity in the
shower and thunderstorm activity across the region with
temperatures warming back above 90 degrees on the plains.

On Friday, we may see an uptick in precipitation chances as the
upper high nudges westward over the Great Basin and an upper level
shortwave moves across the state from the northwest.

Over the weekend into early next week, the flow aloft over Colorado
is progged to become more northerly as the upper high over the
Intermountain West amplifies. This pattern should allow occasional
cold fronts and upper level disturbances to move across
northeastern Colorado. As a result, cooler unsettled weather is
expected with the best chance for precipitation focused from the
Continental Divide eastward across the Southern Foothills into the
the Palmer Divide where locally heavy rainfall will be possible.

&&

.AVIATION /06Z TAFS through 06Z Wednesday/...
Issued at 1145 PM MDT Mon Jul 15 2024

Convective activity has ended for the evening. There are still a
few showers on the western slope of Colorado, but these wouldn`t
be anything more than sprinkles if they survive. Winds are
settling down to normal south/southwest flow by 08Z.

Main concern for Tuesday is another round of scattered showers and
thunderstorms. We think probabilities are high enough to mention
TEMPO VRB wind gusts to 35 kts and -TSRA from about 21Z-24Z.
Winds will likely transition to northwest by 15Z, and then
north/northeast increasing to 10-15 kts after 17Z. Then
thunderstorm outflows will dominate after 21-22Z before settling
back late tomorrow evening around 04Z-06Z.

&&

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

Atmospheric moisture content will be higher today and Wednesday,
with precipitable water values nearing the 90th percentile.
However, the airmass is still quite warm with relatively high
cloud bases and a limited warm cloud depth of 1000-2000 feet.
Those values could improve slightly for Wednesday. Locally heavy
rain will be possible from the stronger storms, but overall 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.

&&

$$

SHORT TERM...Barjenbruch
LONG TERM...JK
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch