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503
FXUS65 KBOU 051801
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1201 PM MDT Sun May 5 2024

.KEY MESSAGES...

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- Warmer, windier conditions developing today.

- Periods of snow showers in the mountains late tonight through
  mid week. There could be travel impacts for the Monday morning
  commute along the I-70 Mountain Corridor.

- Highs winds possible in the mountains and foothills Monday into
  Tuesday with 50% Confidence Level.

- Across the plains, expect very windy conditions Monday and
  Tuesday with critical fire conditions across southern Lincoln
  county.
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&&

.UPDATE...
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Issued at 1057 AM MDT Sun May 5 2024

An interesting start to the morning across the Denver metro today.
Deep mixing has already commenced across the southeastern half of
the metro, with temperatures in the mid to upper 60s with gusty
southerly winds. Meanwhile, in Boulder we`re stuck near 50F with
almost no wind, with a fairly thick mountain wave cloud stuck over
the area.

As the afternoon progresses, we should see the mixing/warmer
temperatures spread across the entirety of the I-25 corridor, with
highs peaking in the mid to upper 70s. Further east, a fairly
impressive convective environment should develop across far
eastern Colorado, but a weak cap should keep things quiet,
especially given a lack of meaningful surface based convergence
along the dryline and/or any sort of upper level support.

Have only made some minor changes in the near term to better
capture the existing T/wind gradient, with no other significant
changes to note through tonight.
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&&

.SHORT TERM /Through tonight/...
Issued at 333 AM MDT Sun May 5 2024

Various METARs this morning display breezy southeasterly winds
across the eastern plains. This will continue this afternoon as deep
mixing will occur increasing our surface winds for northeastern
Colorado. Our upper level ridge pattern will shift east as the next
trough enters Colorado this afternoon. 500mb wind increase between
50-60kts. As daytime heating occurs, afternoon temperatures increase
between 70-77 for the plains and 48-60 for the mountains and
valleys. Southeasterly winds increase this afternoon producing wind
gusts up to 45 mph for the mountains, foothills, and valleys.
Additionally, wind guts up to 50-55 mph will occur across the
eastern plains. With wind gusts varying this afternoon and evening,
it is possible a few spots throughout the eastern plains could
reach 60 mph briefly. This will likely lead to elevated fire
weather conditions mainly for the urban corridor this afternoon as
humidities drop near 17-20 percent. Tonight, mid-level moisture
increases through the 500-700mb layer and winds across the
mountains shift west. Light orographic snow begins for areas above
8 thousand feet north of I-70 through Monday.

&&

.LONG TERM /Monday through Saturday/...
Issued at 333 AM MDT Sun May 5 2024

A strong storm system will move quickly across the area Mon morning
and then move rapidly northeast into wrn South Dakota by late
aftn. As this feature moves across, there will be a quick shot of
stg QG ascent which will bring snow to the mtns in the morning.
Across the plains, expect a band of showers and possibly a tstm
as the activity moves rapidly across in the morning hours.

By late morning thru the aftn there will be a decent amount of
subsidence over the area as the storm system moves rapidly out of
the area.  Cross-sections still show some potential for a period of
high winds, in some mtn areas and foothills, from mid morning
thru the aftn. Cross-barrier flow will be in the 50-55 kt range
but really don`t have a decent mtn wave. Thus, not sure how
widespread higher winds will be at this point. Overall, the ECMWF
has more coverage than some of the other higher res models. For
now will issue a watch for Mon. Across the plains, it will be
very windy as well but wind gusts look to be below high wind
criteria. Meanwhile, cross-sections show lingering moisture in the
mtns with favorable orographics so will continue to see periods
of lighter snow thru the aftn. As far as highs, readings will drop
back in to 60s over the plains.

For Mon night into Tue, an intense storm system will be over the nrn
high Plains with rather stg WNW flow aloft across the area.
Cross-sections show decreasing moisture in the mtns Mon night so
will see a decrease in snow shower activity. However, moisture
will increase again on Tue which will lead to periods of
orographic driven snow thru the aftn. Across the plains, it will
be dry Mon night into Tue with very windy conditions. Highs will
remain in the 60`s. Finally, over the higher terrain, there could
be some threat for higher winds Mon night if a mtn wave becomes
better defined as cross-barrier flow remains in the 50-55 kt
range.

By Tue night, a disturbance will move across nrn CO which will allow
for periods of light snow in the mtns.  On Wed, the storm system
will be over the Dakota`s with westerly flow aloft.  Latest cross-
sections show a drier airmass over the area so snow chances will
decrease in the mtns with dry conditions elsewhere.  Highs across
the plains will remain in the 60`s.

Looking ahead to Thu, the main upper level low will begin to move
eastward while a 2nd weaker piece of energy is over the Great Basin.
Overall, there could be a chc of light precip on Thu but the set up
doesn`t look as favorable as yesterday.  Highs may stay mostly in
the 50`s across nern CO.

On Fri, the GFS has is a weak upper level low over Nevada while the
ECMWF has this feature further south.  The GFS has quite a bit of
moisture over the area while the ECMWF is much drier.  For now will
just go with the blended solutions as it`s not clear how things may
evolve late next week.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
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Issued at 1155 AM MDT Sun May 5 2024

Gusty winds will be the main impacts in the TAF forecast through
Monday afternoon. At DEN/APA, southerly winds have already mixed
down with a few gusts of 20-25kt already noted. Further northwest
(BJC), light/variable winds continue, with a well- defined
boundary between mixed/stable air stretching from downtown Denver
to the NW side of the field at the moment.

Winds should continue to increase through the day today, and also
spread into BJC. As the stronger flow aloft reaches the area later
this afternoon, we should see a few gusts >30-35kt.

Wind forecast gets much more challenging tonight into tomorrow as
a bora event develops. Winds should slowly turn from south to west
tomorrow morning, with westerly flow continuing through the rest
of the day. There may be one or two periods of enhanced flow
Monday AM and again sometime later Monday afternoon, but those
timing details are difficult to determine at this point.
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&&

.FIRE WEATHER...
Issued at 333 AM MDT Sun May 5 2024

Elevated fire weather conditions are possible along the urban
corridor this afternoon for humidities near 17-20 percent and
wind gusts up to 40-50 mph.

Gusty winds and lower humidity will be over the plains Mon and
Tue. However, there is still some question as to how dry the
fuels are due to decent precip in the latter half of April.
The only area that didn`t receive decent precip was over portions
of srn Lincoln county. Thus that would be an area to watch for
critical fire conditions in the afternoon and early evening
hours.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 PM this evening to 6 PM MDT
Monday for COZ031.

High Wind Watch from Monday morning through late Monday night
for COZ033>036.

&&

$$

UPDATE...Hiris
SHORT TERM...AD
LONG TERM...RPK
AVIATION...Hiris
FIRE WEATHER...RPK/AD