811
FXUS65 KBOU 270536
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1136 PM MDT Wed Mar 26 2025

.KEY MESSAGES...

- Mostly dry weather through Friday, with much above normal
  temperatures. Record/near record warmth Thursday.

- Complicated storm system late Friday through this weekend. Light
  snow likely across the mountains Friday into Saturday, with continued
  snow chances across the high country through early next week

- Rain showers, possibly mixed with snow, across the lower
  elevations this weekend. Best chance of precipitation late
  Saturday into Sunday.

- Cooler, unsettled pattern looks to continue next week, with
  lower than normal confidence.

&&

.UPDATE...
Issued at 833 PM MDT Wed Mar 26 2025

The one little shower we got near Elbert came and went, and the
remaining clouds will be dissipating in the next hour or so. We
made some minor changes to the lows, mainly warmer on the mountain
ridges, but also a little colder in valley cold spots and a
little warmer on the west side of the metro area.

&&

.SHORT TERM /Through Thursday/...
Issued at 145 PM MDT Wed Mar 26 2025

There is a bit of weak convective cloudiness over the
southwestern quarter of the CWA at this time. Temperatures have
climbed into the 70s across the plains. Winds remain fairly light
in most areas.

Upper ridging will continue to dominate the weather for the CWA
tonight and Thursday with benign synoptic scale energy in place.
Low level wind and pressure fields point to normal diurnal wind
patters tonight and Thursday.

For moisture, the cloudiness over the southern portions of the CWA
should dissipate after sunset.  Models show enough moisture and heat
on Thursday for a bit more convective cloudiness, mostly over the
mountains and Palmer Ridge.  Will keep the minor pops going Thursday
afternoon.  Not sure if anything will make to to the ground.

For temperatures, thickness fields continue to show near record highs
on Thursday across the plains, with low 80s possible.

&&

.LONG TERM /Thursday night through Wednesday/...
Issued at 123 PM MDT Wed Mar 26 2025

We`ll likely end the week with one more warm day, before cooler
weather arrives this weekend and continues into next week.

A broad trough axis will shift eastward on Friday from the
Pacific coast into the intermountain west. Southwesterly flow
aloft should prevail through the day, with guidance keeping the
thermal ridge axis overhead through the afternoon hours. While
temperatures won`t be as warm as Thursday, mid/upper 70s still
seem fairly likely across most of the lower elevations. The
increasing flow could also lead to some elevated/critical fire
weather conditions across the plains, but those details will need
to be worked out later.

The lead shortwave associated with the broader/longwave trough is
expected to race across the region late Friday into Saturday.
Deterministic guidance is in reasonably good agreement with the
track of this wave, but vary quite a bit on timing - with the
ECMWF solution roughly 6 hours faster than the GFS. There should
be a few showers across the higher elevations by Friday afternoon,
gradually spreading across the lower elevations during the
evening/overnight. Temperatures would support a snow level of
roughly 8-9kft MSL overnight with generally light accumulation.

The rest of the weekend forecast looks remarkably uncertain at
this point. A second shortwave is expected to track across the
Rockies sometime Saturday or Sunday, with a more pronounced
surface cold front along with a deeper push of moist upslope
flow. Beyond that, I find it difficult to talk about too many
details, so instead I`ll talk about all of the things that make
this weekend`s forecast frustrating.

First, the lead wave will likely work to limit the amplification
of the secondary, stronger wave that arrives late Saturday/early
Sunday. This is further complicated by a relatively
messy/disorganized trough axis in general. I count as many as 3-4
embedded shortwaves, each with different timing/strength/positions
across the 00z/12z deterministic suites. Unsurprisingly, this has
led to poor consistency between models, along with some notable
differences in d(model)/dt fields. While subtle differences don`t
show up across the smoother ensemble means, WPC cluster analysis
suggests that each cluster is dominated by a single ensemble
suite, with little overlap in solutions across the
GEFS/CMCE/ECMWF. The current forecast is close to the NBM/multi-
model mean, which may be a tad too aggressive with PoPs through
the weekend, but does capture the general area where precipitation
is most likely.

The pattern continues to look murky for next week, with guidance
advertising one or two more troughs across the Western U.S.
through the long term forecast period. At least the first couple
of days of the week look to have near/below normal temperatures
across the region. Less confidence as we get towards the middle of
next week, with a 40-50 degree difference (highs from the 30s to
near 80F) across various ensemble members.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1135 PM MDT Wed Mar 26 2025

VFR through the period. Main concern will shift toward potential
for gusty outflow winds from passing virga/sprinkles after
21-22Z. Given the inverted-V profiles, the odds of seeing gusty
VRB winds is increasing (to about 40-50%) for KDEN, and 60% for
KAPA and KBJC where we have gone to TEMPO VRB winds to 28kts in
the 21Z-01Z period. Most likely direction for those stronger gusty
winds would be from the south, southwest, or west. Otherwise,
normal diurnal wind patterns expected through about 18Z, then
likely trending VRB with no significant signals in whether diurnal
easterly or mixed light west/northwest would prevail. After
convection ends by 01Z-02Z Friday, we`ll return to normal
south/southwest drainage winds through early Friday morning.

&&

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

&&

$$

UPDATE...Gimmestad
SHORT TERM....rjk
LONG TERM.....Hiris
AVIATION...Barjenbruch