Area Forecast Discussion
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
723 FXUS65 KPUB 211212 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 612 AM MDT Sat Sep 21 2024 .KEY MESSAGES... - Widespread showers developing from south to north through the day, with a second round spreading north and east across south central and southeast Colorado late this afternoon into tonight. - Isolated to scattered thunderstorms, greatest coverage south of Highway 50, with a low confidence for strong storms this afternoon for the San Luis Valley and southern mountains. - Snow levels may drop down to around 9000 feet tonight, though accumulations up to 10 inches to stay across the higher peaks above 10kft. - System departs on Sunday with continued higher mtn snow and rain across the plains early which diminishes late morning through early afternoon. - Another Frost or Freeze possible for the San Luis Valley Sun night/Mon AM. && .SHORT TERM /THROUGH SUNDAY/... Issued at 357 AM MDT Sat Sep 21 2024 Current water vapor imagery indicates upper low across southwestern Arizona, with showers and thunderstorms spreading out ahead of the system across central and into northeastern Arizona early this morning. Further east, prefrontal trough across the southeast plains has breezy southerly winds keeping dew pts in the 50s south and east of trough, while north and west, dew pts have started to come down into the 20s and 30s. The winds and associated mixing have kept temperatures up with 3 am readings in the 50s and 60s across the plains, and in the 30s, 40s and 50s across higher terrain. For today, latest models continue to indicate the Arizona upper low to lift out into the Four Corners region by 00Z, with moisture and lift increasing across south central and southeast Colorado within increasingly diffluent southerly flow aloft. At the surface, a cold front, currently moving across the Colorado/Wyoming border, will continue to push south across the Palmer Dvd between 12Z-14Z, with breezy northerly winds of 15 to 30 mph in its wake across the southeast plains through the late morning, with winds across the plains slowly turning more east to northeast through the afternoon. With that said, we will see showers and thunderstorms developing across the southern tier of Colorado this morning, with precipitation increasing in coverage as its spread north across the region through late morning and afternoon. Most of the latest high res models, along with the latest SPC Day 1 outlook, are keeping the potential for severe storms south of area in New Mexico. However, the HRRR does continue to indicate a stronger line of storms and helicity swaths across the San Luis Valley between 22Z Sat and 00Z Sun, which conceptually seems plausible, with the expected strong shear and diffluence aloft as the upper low moves across the Four Corners. Will need to monitor latest models and trends for the potential of strong to severe storms across the southern tier this afternoon. Southerly flow aloft across the region will keep snow levels rather high aoa 11,000 feet through the day, though with strong diabatic cooling, could see some light accumulations down to 10,000 feet this afternoon. A second round of precipitation, associated with the deformation band of the upper low, will develop and spread north and east across south central and into southeast Colorado later this afternoon and evening with the low progged to lift out across the Pikes Peak Region early Sunday morning. Best coverage remains over and near the higher terrain, where easterly upslope flow will be maximized. Latest qpf have also trended that way, with 1/2 to 1 inches expected over and near the eastern mountains. Snow levels come down to around 9K feet this evening, with the potential for some light accumulations at this level, however, the most impactful snowfall will remain aoa 10-11K feet, with 5-10 inches of snow possible across the higher peaks of the central mtns into the Pikes Peak region, where a winter weather advisory remains in effect through the day Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Issued at 357 AM MDT Sat Sep 21 2024 Upper low lifts into NE CO by mid day Sunday with fairly extensive showers and higher elevation snows across the southeast mountains/plains early Sunday morning. These should gradually wane as the upper low lifts off to the northeast during the late morning and afternoon. Pikes Peak region will still be under a moderate rain/snow band early Sunday morning with snow levels dropping to around 9000 feet early Sun morning. There could be some snow flakes mixing down to 8500 feet if diabatic cooling from heavy precipitation can produce an isothermal layer. However, most accumulation should stay above 10000 feet given the warmth of the ground, with the higher peaks seeing up to 10 inches of accumulation. The majority of southern CO will see rain which will diminish through the afternoon, though lingering instability behind the system will keep at least some isolated showers through the afternoon across the mountains. Temperatures will be quite a bit cooler with highs in the 50s to near 60 across the lower elevations, and a mix of mid 20s and 30s across the mountain peaks and 40s to lower 50s for the lower mountain communities. Should be a cool night across southern CO behind the system Sunday night with lows dropping into the 40s and upper 30s across the plains. Conceptually this should bring a freeze to the San Luis Valley with National Model Blends indicating a 50-80% probability of sub freezing temperatures, though probabilities of a killing freeze (less than 28 degrees) decreases rapidly to less than 20%. Guidance keeps lows for KALS in the low to mid 30s. Will hold off on a freeze watch for now given some discrepancies in guidance as some models keep dew points up with the possibility of some fog formation. But suspect some sort of frost or freeze highlight will be needed. Temperatures rebound for Monday then another trough drops in from the northwest for late Monday into Tuesday. EC is farther east than its earlier runs from yesterday, and more in line with the other long range models, but is still the strongest with developing a cut off low across eastern CO/western KS by 00z Wed. Canadian is similar with this scenario, while GFS is faster and more open with the energy as it moves across CO. Ensemble means are more open with the system. Moisture will be more limited with this next wave, with isolated to scattered showers possible Monday night into Tuesday. Did decrease pops some from the National Model Blends which likely carries some influence from earlier runs with the more western cut off low. A reinforcing cool surge will knock temperatures back a few degrees for Tuesday keeping readings below normal. Upper ridge eventually returns for mid to late week with drier weather and a gradual warming trend expected. -KT && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 552 AM MDT Sat Sep 21 2024 Upper level low across western Arizona will move north and east across south central Colorado through the evening, which will continue into northeastern Colorado by the end of this taf period. This system will develop widespread precipitation, with showers and thunderstorms spreading north and east across the central Rockies through tonight. For COS and PUB...A cold front, pushing south of FNL attm, is expected to move across the terminals between 14Z-16, with gusty northerly winds of 20-30kts continuing through 18Z before diminishing and becoming east to northeast through the rest of the afternoon. A secondary cold front will bring breezy northerly winds again through the tail end of the taf period. VFR conditions with lowering cigs expected through at least 18Z. Developing showers and possible thunderstorms will bring chances of MVFR cigs and vis through the rest of the taf period. ALS...Plains cold front looks to back up across the lower eastern slope of Sangre de Cristos, allowing for an easterly surge into the San Luis Valley and the terminal between 18Z-20Z. VFR conditions with lowering cigs expected through at least 16Z. Developing showers and thunderstorms will bring chances of MVFR cigs and vis through the rest of the taf period. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from noon today to noon MDT Sunday for COZ058-060-082. && $$ SHORT TERM...MW LONG TERM...KT AVIATION...MW