co discuss
Office: BOU
FXUS65 KBOU 281115
AFDBOU
Area Forecast Discussion
National Weather Service Denver/Boulder CO
515 AM MDT Thu Mar 28 2024
.KEY MESSAGES...
- Accumulating snow and minor travel impacts across the Park
Range/Rabbit Ears Pass tonight. Mainly lighter accumulations
across the remainder of the Northern Mountains.
- Occasional snow showers in the mountains and scattered showers
for the northern plains Friday through Saturday.
- Mountain snow, with a mix of rain and snow likely for the
plains, late Sunday into Monday. Mostly light but there could be
some impact for the mountains and foothills.
&&
.SHORT TERM /Through tonight/...
Issued at 356 AM MDT Thu Mar 28 2024
The flow aloft will become more westerly today and then switch to
a more WSW component tonight. Mid and high level moisture will be
embedded in the flow, however, most mtn areas will stay dry thru
the aftn. Only exception would be in the Park Range where a few
snow showers may develop by late aftn. Across the plains, it will
be dry and warmer as highs rise into the 60's.
For tonight, cross-sections show moisture will improve in the mtns
overnight. In addition, position of an upper level jet should help
enhance snowfall, in the nrn mtns, favored by WSW orographic
component. Looks like portions of zn 31 could get close to advisory
criteria by 12z Fri.
&&
.LONG TERM /Friday through Wednesday/...
Issued at 356 AM MDT Thu Mar 28 2024
Model trends today include a continued emphasis on a little wave
bringing lift over the northern mountains and northern border
areas Friday night, then lifting the frontal zone aloft northward
with less moisture across most of the area Saturday through early
Sunday. There's also a continuation of Wednesday's trend back
towards a slower movement of the larger trough with a circulation
center developing in the middle of it, over eastern Colorado or
Kansas Monday. There's low confidence in that trend and the
details of the development. Ensembles continue to mostly trend
slower/weaker with the southern portion of the trough than the
operational runs, with only 10-20% showing a stronger/colder and
also slower solution that could bring more substantial snow to the
foothills and even into Denver Monday night.
NBM is reasonable for the most part in smoothing out these trends.
We still have scattered showers forecast for the mountains, mainly
north, and the northern plains areas with higher coverage in the
northwest part of our area late Friday into early Saturday. We
bumped up PoPs again on Monday. Part of the issues is timing as
there should be some showers and perhaps a period of steadier
rain/snow on Monday but since the model timing keeps changing it's
hard to generate higher NBM PoPs. Conceptually the main time for
this should be with and behind the main trough passage which
should be mainly during the day Monday. We did raise PoPs Monday
night given the current model trends with some runs threatening
rain/snow on the plains into Tuesday morning. That seems a bit
much, but continuing chance PoPs overnight seems prudent. Overall
there's a trend towards slightly warmer temperatures and a lower
chance of snow for the I-25 corridor Monday, but slowing the
precipitation into Monday night would bring a better chance of a
changeover then. In any event, warm temperatures will limit
impacts, especially below 7000 feet.
Slower ensemble members are slower with the warmup behind the
trough Tuesday and Wednesday. Runs that are more aggressive with
the trough moving east and the ridging behind it could have us
near 60 Tuesday and near 70 Wednesday. With most runs slower than
that, we'll stick with the NBM that's about 5 degrees less than
that.
&&
.AVIATION /12Z TAFS through 12Z Friday/...
Issued at 513 AM MDT Thu Mar 28 2024
VFR conditions will continue today thru tonight. SSW winds
this morning will eventually shift to a more westerly
direction by 20Z. For this evening, winds will gradually
become SSW by 07z.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...RPK
LONG TERM...Gimmestad
AVIATION...RPK
Office: PUB
FXUS65 KPUB 281005
AFDPUB
Area Forecast Discussion
National Weather Service Pueblo CO
405 AM MDT Thu Mar 28 2024
.KEY MESSAGES...
- Relatively quiet and warm weather conditions expected today,
though with near to spotty critical fire weather conditions across
the plains.
- Mountain snow increases overnight Thursday, with dry conditions
elsewhere.
- Increasing fire weather conditions Friday into the weekend.
- Chances for snow continue into next week across the mountains.
- A new system moves in early next week, bringing cooler, wet
conditions to the area.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 404 AM MDT Thu Mar 28 2024
Today: A relatively quiet Thursday is expected for south central and
southeastern Colorado. A ridge of high pressure will be pushing
eastward, keeping increased subsidence over the region. With the
ridge in place, dry conditions are anticipated for the day, though
an isolated snow shower can't be ruled out along the central
mountains where orographic forcing will slowly increase throughout
the day. In addition to that, near to spotty critical fire weather
conditions are expected across the plains today, as dry air pushes
across the region and winds increase some during the afternoon.
Looking at temperatures, a warm day is in store for much of south
central and southeastern as clear skies prevail and downsloping
southwesterly winds overspread the area. Given all of that, the
plains will warm into the 60s to low 70s, the valleys rising into
the 50s, and the mountains reaching into the mid 20s to 30s.
Tonight: Heading into the overnight hours for Thursday, relatively
quiet weather continues, though with some more mountain snow. The
ridge of high pressure in place during the day Thursday will
continue its trek eastward, with a shortwave following behind it.
While the main core of this wave will stay to the north, enough of
it will pass over the region to bring some modest increases in
forcing. With the uptick in forcing, snow showers will rise in
coverage across the mountains, especially the central mountains,
where forcing will be greatest. Elsewhere across the area though,
dry conditions are anticipated given the strongest forcing/support
will remain further north. As for temperatures, a cool night is
expected. Mostly clear skies will allow for better radiational
cooling, though downsloping westerly winds will bring some warming.
With all of that said, the plains will sink into the 30s, the
valleys cooling into the 20s, and the mountains dropping into the
10s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 404 AM MDT Thu Mar 28 2024
Friday...
West-southwest flow aloft will increase on Friday as the jet passes
over our forecast area. As a result, strong winds will be mixing
down to the surface while downsloping westerly flow dries and warms
most of the plains. As a result, spotty critical fire weather
conditions will be possible during the afternoon hours, most
prevalent over our far southeast counties. However, consistent wind
gusts have been lacking in recent model data, especially over Baca
County. With critical conditions remaining somewhat short-lived,
have not upgraded the Fire Weather Watch with this package.
Temperatures across the plains will be several degrees above normal,
with afternoon highs in the 60s to low-70s. The high valleys will
remain in the 50s.
Saturday-Sunday...
Flow aloft will increase more as we move into the weekend as the
area continues to dry out at the surface. Stronger southwest winds
will result in more consistent critical fire weather conditions on
Saturday for the southeast plains. Humidity will also be a bit lower
along with daytime highs thanks to the generally dry airmass. As an
upper-level trough approaches from the west, winds will further
increase across the entire area on Sunday, and given the persistent
warm and dry conditions Sunday is looking to be our most widespread
fire weather day. Temperatures will also increase a few degrees over
the plains, with some places seeing high temperatures around 80.
Meanwhile, snow will increase over parts of the Continental Divide
Friday and Saturday, and start to spread east to the rest of the
higher terrain as our next system approaches. By Sunday,
precipitation will spread to all of our mountains and valleys, as
well as the Pikes Peak Region/Palmer Divide. The higher elevations
will see snowfall while the lower elevations will only see rain
thanks to warmer temperatures.
Monday Onwards...
Current long-term model guidance still shows a lot of variability
between solutions for next week's system. In general, consensus
shows a broad upper trough moving in from the west coast, but that's
where the similarities largely end. The GFS sends a closed low into
Colorado, while current runs of the EC and Canadian have a more
broad, open wave. Differences in speed and amplitude of the
approaching wave will have a large impact on how much precipitation
we get across the area. The mountains are almost guaranteed to see
some more snow, while the plains vary in precip amounts that will
most likely fall entirely as rain. Additionally, the incoming trough
will bring a cold front with it, which the NBM has dropping Monday's
highs by about 20 degrees out east. However, despite how messy this
system looks between models, the general consensus has it moving
fairly quickly, with temperatures expected to return to near-normal
by midweek at the latest.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 404 AM MDT Thu Mar 28 2024
KCOS, KPUB, and KALS: VFR conditions are expected over the next 24
hours. Winds will remain relatively light this morning and later
tonight, with southwesterly sustained winds and gust increasing this
afternoon, especially for KALS. Otherwise, dry conditions are
expected today, with increasing mid to high level clouds during
the afternoon.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Friday morning through Friday evening
for COZ233-237.
&&
$$
SHORT TERM...SIMCOE
LONG TERM...GARBEROGLIO
AVIATION...SIMCOE
Office: GJT
FXUS65 KGJT 281137
AFDGJT
Area Forecast Discussion
National Weather Service Grand Junction CO
537 AM MDT Thu Mar 28 2024
.KEY MESSAGES...
- Warmer and breezy conditions expected today with showers
developing over the northern and a few central mountain
locations.
- A cold front will move into northern portions of Utah and
Colorado overnight providing a focus for heavier
precipitation. Travel over northern mountain routes will be
impacted after sunset through Friday morning.
- There is a low (>40%) chance of a persistent band or bands
of heavier snow developing between I-70 and Highway 40
overnight...which could bring significant snow amounts.
- Unsettled conditions will continue through the weekend and
into Tuesday morning. Sunday and Monday and look like the core
of the storm, with the greatest snowfall accumulations for
the period.
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 358 AM MDT Thu Mar 28 2024
A transitory ridge is passing through the Rockies this morning
providing the advertised short break in precipitation. This ends
later this morning as it slides onto the Plains and a persistent
SW flow pattern sets up with low pressure digging along the
Pacific coast. There is a decent AR plume caught up in this flow moving
over the crest of the northern Sierras and spreading moisture
across the Intermountain West thanks to a 120kt jet. We are
currently on the fringe of this moisture as indicated by the
thickening high cloudiness. Large scale forcing will increase
through the late morning and into the afternoon hours as the jet
begins to dip farther south and bring the core across Utah. Some
light orographic snow is likely to break out over some of our
our high peaks of the northern and possibly central mountains by
mid day as top down saturation commences. However we will get
the most bang for our buck when the energy crossing the Northern
Rockies forces a frontal band southward into our NW CWA early
this evening. Expect a breezy day over much of eastern Utah and
western Colorado in this pre-frontal environment. The front
looks to slowly progress across the northern CWA and hang up on
the high plateaus and northern mountains under the SW flow
pattern. This is when things get interesting. Low level forcing
along and behind the front will be coupled with the larger
scale ascent aloft by a tightening thermal gradient in the
indirect circulation of the jet core aloft. This should produce
at better defined SW-NE oriented band of heavier precipitation
for at least a few hours overnight. In addition negative
EPV/static stability profiles favor other bands of precipitation
over the central and northern CWA as the synoptic/mesoscale
lift and likely orographics release this instability. The big
question attm is how widespread/prolonged will the moderate to
heavier precipitation rates in these bands occur. Ptype is
likely to be snow in most lower to mid elevation areas in the
post frontal environment. Expect some decent snow in the higher
elevations of our northern mountains with Rabbit Ears the most
likely to be impacted overnight. Lower elevation roadways are
likely to be able to take some snowfall after a warm
day...though still near to below normal...but if a persistent
heavier snow band sets up all bets are off. Overall confidence
not currently high enough to hoist winter headlines and there is
chance this may occur on the fly if the expected banding
becomes reality tonight. Bottom line is from the I-70 mountain
corridor to the northern border the possibility exists for this
snow banding and quickly changing conditions tonight into
Friday morning. Frontogenesis will slowly ease though the
afternoon as the jet lifts northward and overall the lower
profile should begin to warm enough to limit snowfall potential
on the roadways below pass level. Instability remains and
banded/convective precipitation will continue through tomorrow
afternoon with likely some decent heavy snow showers at times in
the mountains along with threat of graupel/snow pellets and/or
lightning about anywhere else. Unfortunately all the action will
in the north with this first round of precipitation with the
southern mountains missing out. This will only be temporary
however with more details below. Temperatures in the south will
have the best chance of getting up to or exceeding normal the
next few afternoons with highs well into the 60s over red rock
country. Farther north clouds and precipitation will keep things
much cooler.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 358 AM MDT Thu Mar 28 2024
Weak shortwaves...embedded within southwest flow and acting on
a nearly stationary boundary draped over the northern half of
the CWA... will continue to support intermittent valley rain and
mountain snow showers across northeast Utah and northwest
Colorado Friday night into Saturday. Most of the snow will be
confined to the higher elevations across the Flat Tops, the Park
Range, and the Eastern Uinta Mountains where a few inches or
more can be expected. And while conditions will be fairly
unsettled along and north of the boundary through the first half
of the weekend, south of it will be a much different story.
Warm advection and deeper mixing across southeast Utah and
southwest Colorado will help to boost high temperatures well
into the 60s to near 70 for many places. Additionally, the
deeper mixing will tap into a belt of strong winds aloft and
bring frequent gusts of 35 to 45 mph down to the surface. The
one potential fly in the ointment is cloud cover, given the
enhanced moisture streaming in from the southwest. Depending on
how thick the clouds are, temperatures and wind gusts could end
up lower than progged. For now, we'll assume enough breaks and a
strong late March sun angle will be enough to keep current
forecasts on track.
Heading into Sunday, attention then turns to a large and deep low
pressure system making landfall across the Desert Southwest. As this
system tracks through the Great Basin and Four Corners states
through Monday, dynamic forcing will increase and precipitation will
become more widespread. There's not a whole lot of cold air to work
with given mild Pacific origins, but elevations above 6000 to 7000
feet will still be favored to pick up some more snow. Most valleys
will only see plain rain, perhaps mixed with a little snow as the
storm wraps up. Forecast snowfall amounts in the mountains still
look drawn out enough to be sub-advisory for now, but that can
change in the coming days. Since the system is likely to be a slow
mover, any increase of QPF or precip intensity could drastically
increase snow totals. Something to keep an eye on going forward.
Either way, cooler and unsettled weather will be the rule from
Sunday through early Tuesday. High temperatures will generally be
near to slightly below normal for this period.
In the wake of the storm, another ridge of high pressure builds in
across the Great Basin and Four Corners on Wednesday. Dry and warm
weather will round out the long term period as a result with high
temperatures quickly rebounding back above normal by 4 to 8
degrees.
&&
.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 536 AM MDT Thu Mar 28 2024
High level cloudiness over the region today will lower and lead
to increasing mountain showers through the day across northern
Utah and Colorado. This moisture is moving in ahead of the main
system and a cold front arriving this evening to the north.
Precipitation will become widespread along and behind this front
and also the central Colorado high mountains. Expect MVFR or
lower to develop at KHDN as this front arrives and snow spreads
across the lower elevations of northwest Colorado. Along the
I-70 corridor TAF including ASE clouds will lower and showers
will be in the vicinity of the airfields. Confidence not as high
for MVFR or below but ILS will likely be met overnight as
terrain obscuration becomes more widespread. Gusty southwest
winds ahead of this system will bring gusts over 25 mph to many
of the TAF sites. Stronger winds aloft will also lead to pockets
of LLWS and mountain wave turbulence through the forecast.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...15
LONG TERM...MDM
AVIATION...TGJT