155
FXUS65 KBOU 130630
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1230 AM MDT Mon May 13 2024

.KEY MESSAGES...

- Drier/warmer Monday, with scattered mountain showers/storms and
  more isolated coverage for lower elevations. Snow levels should
  be around 11,000 ft MSL

- Scattered showers and a few thunderstorms on Tuesday. Cooler and
  more widespread precipitation expected on Wednesday into early
  Thursday.

- Turning warmer and drier again late in the work week.

&&

.UPDATE...
Issued at 907 PM MDT Sun May 12 2024

Radar shows the last of the showers moving across the western I-25
corridor and foothills. Conditions continue to dry out overnight
with decreasing cloud cover as a ridge aloft moves in. No changes
needed to the current forecast. Warmer tomorrow with a chance of
showers/storms mainly confined to the higher terrain. There is a
low chance for a few showers to stray onto the plains.

&&

.SHORT TERM /Through Monday/...
Issued at 150 PM MDT Sun May 12 2024

GOES-16 shows the trough responsible for the localized extremely
wet weather has finally moved east and is along the CO/KS border
in southeast Colorado. The deformation band of precipitation has
likewise shifted south and will exit our area this evening. Rain
showers should continue across the Palmer Divide and east of a
Sterling to Fort Morgan to Castle Rock line for several hours, as
well as snow above 8500 ft in Park County. Another inch or two of
snow is possible into this evening in Park County, but road
conditions have improved quite a bit other than around Wilkerson
Pass. The advisory will be allowed to expire at 3 PM.

Tonight things dry out and clear out, but temperatures don`t drop
too far given some warming aloft. Expect lows in the low to mid
40s across the plains, and around 30 degrees in the mountain
valleys. South Park should cool into the 20s with the impressive
snow cover from the last 18 hours.

On Monday, a 500 mb ridge begins to build into Colorado, and 700
mb temperatures increase from 0 degC to +6 degC, and combined with
mostly sunny skies through midday, temperatures will warm up
nicely. Expect mid 70s for highs across the plains and urban
corridor, and temps around 60 degrees for North and Middle Park.
South Park`s temperatures may lag behind on Monday due to the snow
cover, but still should get into the 50s. The low level warming
combined with residual moisture looks to result in 100-400 J/kg
CAPE, primarily for the mountains/valleys and foothills. Scattered
showers and isolated thunderstorms (20-50% for the high country)
will form over the mountains and drift southeast during the
afternoon, weakening as they encounter less instability and dry
low level air. The chances of those storms dropping measurable
precip east of I-25 are very slim (<20%). Expect gusty winds and
virga for the most part across and east of the I-25 corridor.

&&

.LONG TERM /Monday night through Sunday/...
Issued at 150 PM MDT Sun May 12 2024

Weak zonal flow should spread across the region by Tuesday with
plenty of mid-level moisture in place across the area. Despite
the increase in moisture, temperatures should be reach the mid 70s
across the plains, aided by weak downslope from the westerly
flow. Though CAPE values will be modest, there should be a good
enough combination of moisture and surface heating to allow for
widely scattered showers and storms, spreading east from the high
country into the plains during the afternoon hours. Main concern
would be gusty outflow winds and lightning, with organized severe
weather unlikely.

Warmer weather will be short lived, as a cold front drops into
the forecast area sometime Wednesday. Moisture and upslope flow
increase behind the front, which should result in widespread
stratiform rain. There is still some uncertainty about the timing
of the front and the moisture quality behind it, but ensemble
guidance has consistently dialed in on the Wednesday
afternoon/Wednesday night period. Across the high country, some of
this precipitation may fall as snow, with snow levels slowly
falling down to ~9000ft. Suppose we`ll need to watch this
potential as spring storms don`t always cooperate (as we`ve seen
today).

Cool/unsettled weather may linger into Thursday, but the general
trend will be towards a warmer and drier pattern as a ridge builds
off the West Coast. Guidance generally agrees on a return to
mid/upper 70s by Friday into next weekend. As we transition to
more of a summer-like pattern, widely scattered, fairly weak
afternoon showers/storms will likely be the theme across the high
country, with mostly quiet conditions for the plains.

&&

.AVIATION /06Z TAFS through 06Z Monday/...
Issued at 1229 AM MDT Mon May 13 2024

Watching an outflow moving westward towards DIA from the east at
this time. I put a wind shift in the DEN TAF for it, however, it
is slowing down and fading away. I doubt it will make it. Current
winds at DIA are more westerly than the normal drainage patterns
for this time of the night. Models show weak winds at DIA through
the morning hours with some north to east directions this
afternoon and early evening. Little to no convection is expected
later today and this evening. There should not be any ceiling
issues.

&&

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

&&

$$

UPDATE.......Mensch
SHORT TERM...Schlatter
LONG TERM....Hiris
AVIATION.....RJK