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FXUS65 KPUB 030503 AFDPUB

Area Forecast Discussion National Weather Service Pueblo CO 1103 PM MDT Thu May 2 2024

KEY MESSAGES

- Isolated showers and storms will be possible along and east of the mountains later today.

- A front will approach the area tomorrow evening, bringing increased chances of strong to severe storms out east.

- Critical fire weather conditions are expected for the San Luis Valley on Friday afternoon through early evening.

- Scattered showers and thunderstorms, along with high elevation snow, will be possible on Saturday through Sunday morning.

- Thunderstorms will be possible, mainly over the eastern plains, on Sunday afternoon.

- Snow will move in over the mountains Sunday evening through Monday morning.

- Fire weather concerns across the lower elevations will be more spotty on Sunday, then become more widespread Monday through Wednesday.

- Chances of snow will continue across portions of the higher terrain from Monday through Wednesday.

SHORT TERM /THROUGH FRIDAY/
Issued at 251 PM MDT Thu May 2 2024

Breezy westerly flow aloft will continue to set in overhead as the upper low to our north slowly continues to push eastwards. Over the higher terrain, gusty west winds will continue throughout the day, leading to continued critical fire weather conditions across the San Luis Valley. For the plains, post-frontal easterlies will remain in place through most of the day, turning a bit more southeasterly this afternoon. While moist air remained in place across much of the region this morning, the southerly shift in the winds will help dry things out faster, dissipating much of the cloud cover. Today's highs will be in the mid-high 60s, with some places over the plains warming into the low-70s. Later this afternoon, some warm air advection into the higher terrain could fire off a few weaker showers and storms, which some models have drifting east through the area. Models have generally backed off a bit on precipitation today, so any showers we get over the lower terrain would be mostly isolated.

For Friday, the upper low will continue to move northeast and away from our area, as a secondary embedded wave moves past Colorado.
This will result in another day of warm temperatures and gusty west- southwest winds over the higher terrain. As such, critical fire weather conditions will continue for the San Luis Valley through a good portion of the day. High temperatures will increase as well, putting most areas in our CWA into the low-mid 70s. During the late afternoon hours, a cold front will push south across the plains as the upper-trough axis swings past to the north, causing some more active weather through Friday Night. With the influx of more moist air and some low-level convergence, we'll be seeing an increased chance for some strong to severe thunderstorms over our eastern counties. This could be further enhanced by afternoon dryline placement to the east, and though most models keep it east of the KS border, the potential is still there for some enhanced lift along with some locally enhanced CAPE.

LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
Issued at 251 PM MDT Thu May 2 2024

Friday evening...

A major shortwave trough will propagate to the north of the region by later in the day, and allow for southwesterly flow ahead of it to increase during the afternoon hours. Given how dry the lower levels will be for the San Luis Valley, this will result in there still being critical fire weather conditions that will last through until the early evening hours as winds remain rather strong as gusty. RH values will be slightly more modified over the plains, and conditions favorable for fire weather criteria will only exist where there will be some gap flow winds in the vicinity of Walsenburg.
However, since fuels are not critical over this portion of the CWA at this time due to recent green up, there is not much of concern at needing additional fire weather highlights at this time. As the trough continues to progress over the plains by later in the day and slightly deepen due to lee-side troughing as it does with a meso-low forming over the lower Arkansas River Valley through the evening hours. This will allow for there to be a cold frontal boundary that will progress southward over the plains through the evening.

This boundary will help to spark off some convection over the eastern mountains and then over the plains as it drifts further southeast throughout the course of the evening. There will be storms developing along the boundary, and further to the east where the air will be juicier and more unstable, given that LI indices are forecast to be around -6C, MUCAPE will exceed 1600 J/kg in some areas, and a healthy amount of effective shear, there could be some severe storms right along the CO/KS border or perhaps further west depending on where the dryline sets up and the timing of the frontal passage. CAMs indicate that there could also be a few stronger cells developing ahead of the boundary that merge into almost an MCS over Prowers County and drops south into Baca County by around 10 PM. There is still some time for high res models to resolve and get the timing and occurrence of this even more precisely in the next couple of runs. Winds will also increase and become very strong and gusty behind the front out of the northeast direction and advect in much cooler temperatures.

Saturday through Sunday...

Any remaining storms over the southeastern plains during the early morning hours will continue to move out of the CWA and/or dissipate as the cold air advection takes over and stabilizes the PBL. That being said, there could still be some showers continuing over the far southeastern plains until sunrise. Cooler air will bring down temperatures over the plains, with highs being generally about 10 to 15 degrees cooler in departure from where they will be on Friday.
With recycled moisture in place over the higher terrain, as well as increasing southwesterly mid-level flow ahead of the next wave, enhanced by orographics, to help kick off some more convection during the afternoon over the higher terrain. With flow turning more westerly later in the day on Saturday, this will help to push out thunderstorms over the plains by later in the afternoon and through the evening. Going into Sunday, the next major shortwave trough will continue to approach the region, which will increase southwesterly surface winds and result in there being some spotty fire weather conditions over the San Luis Valley and portions of the plains, although not as widespread given that the lower levels will still be a bit more modified with cooler temps and high moisture content given the recent frontal passage. There will also be increasing snow showers over the Contdvd by later in the day on Sunday.

Monday through Wednesday...

By this time in the forecast period, there will be a general and broad longwave trough over the entire western half of the CONUS, which will keep the westerly flow in place with shortwaves moving through which will do one of two things, increase fire weather potential over the lower elevations, and increase chances of snow showers, and possibly even a few thunderstorms, over the higher terrain. This will continue to also keep temperatures somewhat cooler overall, but generally warmer over the eastern plains, due to downsloping westerly winds. -Stewey

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
Issued at 1102 PM MDT Thu May 2 2024

KCOS and KPUB: VFR conditions are expected over the next 24 hours.
Winds will lessen overnight with relatively clear skies. Winds will start to increase, with a mostly southerly component, through tomorrow afternoon in response to a developing lee cyclone. Winds will quickly shift to become more northerly during late afternoon to early evening as the lee cyclone treks eastward and pulls a decently strong cold front southward, with winds then remaining northerly and gusty through the end of this TAF period. Otherwise, dry conditions with afternoon clouds are expected.

KALS: VFR conditions are expected over the next 24 hours. Winds will remain light overnight, with winds quickly becoming gusty tomorrow morning and remaining gusty through much of the day. Winds will start to lessen during the evening hours as diurnal mixing lessens.
Otherwise, dry conditions with afternoon clouds are expected.

PUB WATCHES/WARNINGS/ADVISORIES
Red Flag Warning from 11 AM to 8 PM MDT Friday for COZ224.

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