365
FXUS65 KBOU 151539
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
939 AM MDT Wed May 15 2024

.KEY MESSAGES...

- Cooler today, with some scattered afternoon/evening showers and
  thunderstorms.

- Warmer and generally drier starting Thursday, with lesser but at
  least isolated daily afternoon showers/thunderstorm coverage,
  highest for the mountains.

- A return to more active weather early next week with a better
  chance for afternoon and evening showers and storms.

&&

.UPDATE...
Issued at 939 AM MDT Wed May 15 2024

Upper level trough axis and jet streak are producing showers over
far northeast Colorado at this time. The lift and showers will
shift east of the state by this afternoon. Subsidence behind the
trough is expected to limit showers and storms over the northeast
plains this afternoon. The trends with the 12Z models has been for
fewer showers and storms over much of northeast Colorado, but
more so for the northeast plains. Northeast low level flow will
enhance lift in and near the foothills today. Plenty of moisture
around this morning as well with dew points in the 40s. The
upslope flow and moisture combined with modest instability (500
J/kg) still should produce scattered showers and thunderstorms
this afternoon and into early evening along the Front Range and
Palmer Divide.

&&

.SHORT TERM /Through tonight/...
Issued at 140 AM MDT Wed May 15 2024

The region will be under the influence of upper-level troughing
today, with cooler temperatures as a result. Highs will be close
to 10 degrees below yesterday`s values for the lower elevations,
and around 5 degrees cooler in the high country. There will be a
few showers around extending along the northern tier of our
forecast area this morning, including both the mountains and
plains. Instability will be tapered today, but still sufficient
for isolated to scattered thunderstorms in the afternoon, most
numerous after 2 PM. Any thunderstorms today should remain sub-
severe, but may produce brief heavy rain and small hail.

Later this evening, a weak front associated with a secondary
fast-moving wave carrying a more southward trajectory will advect
slightly deeper moisture into the area, and inject more
northerly/northeasterly near-surface winds into the plains and
urban corridor. This will provide for a slight increase in
precipitation coverage for southwestern portions of our forecast
area, where shallow upslope flow will favor some local
enhancement (mostly the southern foothills/Palmer Divide and
adjacent parts of the Denver metro, and also Park County). Under
generally stable conditions it would largely come in the form of
more stratiform rain and some high elevation snow above ~9,500 ft.
Precipitation intensities shouldn`t be too high with this second
wave but a few tenths of an inch look likely for a few locations
when all is said and done, especially closer to the foothills.
Precipitation will taper off for most areas by midnight though a
few lingering showers will be possible overnight across southern
Park, Jefferson and Douglas Counties.

&&

.LONG TERM /Thursday through Tuesday/...
Issued at 140 AM MDT Wed May 15 2024

A departing trough along with convergent flow aloft will lead to
strong subsidence across norther Colorado on Thursday. The vast
majority of our forecast area will remain dry although a few showers
and weak storms could form over the higher terrain south of I-70.
Highs will warm to the 70s across the plains in what will be a
gorgeous weather day.

Zonal flow aloft will develop on Friday and Saturday as an upper
level ridge will influence the weather in Colorado. Subsident flow
along with downslope winds will lead to warm conditions. Highs
will warm well into the 80s across the plains on Friday with a
cold front early Saturday morning keeping highs slightly cooler
on Saturday. On Sunday, a return of downslope flow will result in
highs well above normal. The warm, dry, and breezy conditions
Friday through Sunday will create elevated fire weather conditions
across portions of the plains. The only area that may near Red
Flag Warning criteria is just south of the Cheyenne Ridge as winds
will be strongest there.

A trough will move over the western US during next work week and
will stall out. There will be southwesterly flow aloft with
numerous shortwave troughs that move across Colorado throughout
the week. These troughs will provide forcing for storms to form
most afternoons. Models do not show much moisture return to
eastern Colorado during the week but if moisture is better than
forecast, there will likely be severe thunderstorms.

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 528 AM MDT Wed May 15 2024

Seeing some partial scattering at mid-level on satellite imagery
on the back end of current deck of BKN mid-level clouds. Forecast
leans towards increased scattering later this morning before
coverage increases again in the afternoon with cumulus buildups as
isolated to scattered thunderstorms develop. This convection
should hold off until 20Z at least, possibly closer to 21Z, and
convective bases will likely be lower than previous days, around
040 or 050. Light drainage or variable winds early this morning
will transition to NNE or NE flow past sunrise, strengthening some
through the morning.

By Wed evening (00-02Z), thunderstorms should become less numerous
with a modest and temporary reduction in cloud cover, along with a
counter-clockwise rotation in winds back to light west or
southwest winds for the remainder of the evening and overnight
period. More stratiform rain showers should then begin to fill in
through the evening, most persistent across the foothills and
southwest metro, but likely impacting all Denver area terminals at
times for most of the evening with a return to lower CIG heights
in the 015-025 range. Some potential for minor vis restrictions of
5-6SM in BR dependent on extent of evening precipitation and exact
cloud bases.

&&

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

&&

$$

UPDATE...Meier
SHORT TERM...Rodriguez
LONG TERM...Danielson
AVIATION...Rodriguez