Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/23/23
Area Forecast Discussion
National Weather Service Denver/Boulder CO
836 PM MDT Tue Aug 22 2023
.UPDATE...
Issued at 710 PM MDT Tue Aug 22 2023
The forecast is performing well with only minor updates this
evening.
We expired our Heat Advisory this evening as temperature
gradually moderated after sunset.
The 00Z synoptic analysis shows the big ridge to our east has
barely moved since the last dataset, still centered about over
northern Missouri and the synoptic situation fairly persistent
over Colorado. There are a few high clouds around and some
scattered cloudiness and light rainfall across the high country,
but not much else for us.
The daily record high minimum temperature for today is in
jeopardy (69 F in 1960). The low temperature so far is 73 F, and
it is not expected to fall below 69 F by the end of the climate
day (1 AM MDT).
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 244 PM MDT Tue Aug 22 2023
A few weak showers can be seen on radar across the higher terrain.
Current ACARS soundings display between 0.60-0.70 PWATs near KDEN
meaning there is sufficient moisture. This pattern will continue
through this evening as scattered showers and storms pose a limited
flash flood over the burn areas. Latest CAMs keep showers and storms
mainly west of the Divide but there is enough MLCAPE near 300-400
J/kg to support an isolated shower or two could occur for the
northern foothills and Cheyenne Ridge this evening. Expect
decreasing cloud cover to occur for the entire CWA overnight into
Wednesday morning. The daily record low of 69 in 1960 for Denver may
be broken overnight.
Starting Wednesday afternoon, mid-level moisture increases as
tropical moisture wraps on the upper level high. Diurnal heating
and weak instability should support scattered thunderstorms and
shower Wednesday afternoon mainly for the mountains and valleys
once more. Some relief to the heat should occur as Wednesday`s
highs trend 3-8 degrees cooler than Tuesday`s for the entire
region.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 244 PM MDT Tue Aug 22 2023
...Pattern change coming soon...
Key Messages...
1. The strong upper level ridge over the Great Plains/Midwest will
break down this week, bringing relief from the near-record heat
2. The remnants of now-Tropical Depression Harold will bring a
substantial amount of moisture to the region by late-week
3. Locally heavy rainfall will be possible Thursday into the
weekend across portions of the forecast area
Details...
Deterministic and ensemble guidance is largely in good agreement
on the overall pattern over the next several days. By Thursday,
the upper ridge to our east should be significantly weaker and
centered over the southern Great Plains. Meanwhile moisture
associated with the remnants of ex-Tropical Storm Harold will
rotate around the southern/southwestern edge of the ridge.
The result will be a fairly stormy Thursday across the high
country, where PWAT normalized anomalies are projected to be as
high as 2-3 sigma (values 0.75-1 inch). With ample instability,
widespread showers and storms should develop west of the divide,
with less coverage further east. Low-level flow isn`t particularly
strong, so some locally heavy rainfall would be a concern.
Moisture increases more on Friday as the tropical remnants glide
northward towards the UT/CO border. Guidance shows PWATs
increasing yet again during the day, with soundings showing a
fairly favorable profile for heavy rainfall across the
mountains/foothills and lower elevations. This would potentially
be aided by some upslope component to the low/mid-level flow as
well. There`s still the usual caveats about cloud cover limiting
instability, but this does look like a solid setup for widespread
rain... potentially heavy at times... across most of our forecast
area Friday into Friday night.
Beyond Friday, the details get a little less clear. A weak
shortwave may try to push across the region Saturday into Sunday,
which would reinforce the cooler, upslope flow regime and lead to
another round of widespread showers/storms in the area. Ridging is
expected to build back into the region to start next week, with a
gradual warming/drying trend likely.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 710 PM MDT Tue Aug 22 2023
Expect VFR conditions through the period. Breezy southeasterly
winds should gradually diminish through this evening, and come
around more southerly, eventually southwesterly drainage for
tonight. Breezy winds may persist into the night. There should be
another period of relatively calm winds in the morning, then
breezy outflow from scattered convection in the mountains is
likely by late afternoon. There may be some thunder in the
vicinity by mid to late afternoon. Cloud bases are expected to
remain above 6000 feet. Winds should again gradually diminish and
come around to drainage tomorrow night.
&&
.HYDROLOGY...
Issued at 244 PM MDT Tue Aug 22 2023
As PWATs approach 0.50-0.60 inches across the mountains and valleys,
scattered storms and showers could lead to a limited flash flood
threat over the burn areas Wednesday.
Moisture will increase quite a bit late in the week, leading to an
increasing threat of burn area flash flooding. With weak steering
flow likely, slow-moving thunderstorms will be capable of
producing heavy rainfall at times. If the wetter solutions offered
by guidance pan out, flash flooding would also be possible along
the I-25 corridor and other flood prone areas across the plains.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM MDT this evening for COZ040-044-045-
048>051.
&&
$$
UPDATE...EJD
SHORT TERM...AD
LONG TERM...Hiris
AVIATION...EJD
HYDROLOGY...AD/Hiris