497
FXUS65 KBOU 161827
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1227 PM 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.

&&

.UPDATE...
Issued at 1013 AM MDT Tue Jul 16 2024

Quiet morning weather-wise with only very minor adjustments
needed to the forecast. Satellite shows little cloud cover across
the plains and cumulus developing in the mountains and foothills.
A few convective showers are beginning to develop in the
mountains and foothills. Added in low PoPs to reflect the earlier
development of isolated showers late this morning in parts of the
high country. Chances for scattered showers and thunderstorms
increase after 12PM for the mountains/foothills then extending to
the adjacent plains and Palmer Divide after 1 PM.

&&

.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 /18Z TAFS through 18Z Wednesday/...
Issued at 1226 PM MDT Tue Jul 16 2024

VFR conditions likely for the TAF period. Scattered showers and
thunderstorms will be the main concern for impacts this afternoon
and early evening. Early this afternoon, already seeing storms
moving off the foothills onto the adjacent plains toward the
terminals. The most likely timeframe to see thunderstorms will be
20-00Z. Storms may contain gusty/variable outflow winds 25-35 kts.
The TEMPO is currently covering 21-00Z, but can`t rule out an
earlier storm closer to 20Z. Most storms will have exited by 02Z.
Wind-wise, expect N/NNE winds with periods of winds dominated by
outflows of surrounding showers/storms. Winds settle S/SW 02-06Z.
Early Wednesday morning, 10-13Z timeframe, a weak push of
northerlies moves through. Light winds eventually transition NE/E
in the afternoon. Scattered showers and thunderstorm are expected
Wednesday afternoon.


&&

.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.

&&

$$

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