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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