930 FXUS65 KPUB 101753 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 1053 AM MST Wed Jan 10 2024 .KEY MESSAGES... - Wind chills as low as -20 are expected across portions of the San Luis Valley, where a Wind Chill Advisory is in effect until 9 AM this morning. - Snow continues over the high country today through Thursday, with highest totals over the central and San Juan mountain ranges, where a Winter Weather Advisory goes into effect at 5 PM this evening through 5 PM Thursday evening. - Snow spreads across portions of the adjacent plains on Sunday bringing some light accumulations during the afternoon/evening commute. - Arctic cold front moves into southern CO on Saturday with bitter cold temperatures and wind chills along with light snow for Sunday and Monday && .SHORT TERM /THROUGH TONIGHT/... Issued at 412 AM MST Wed Jan 10 2024 Currently.. Satellite imagery depicts a low over southern Saskatchewan this morning, with another low pushing into the Pacific Northwest. Mostly zonal flow exists across the forecast area, with snow showers ongoing over our central mountains. West winds are gusting over the high country, with gusts up to 53 mph being recorded at Leadville this hour as the trough axis is moving overhead. Many of our plains locations have remained warm through the overnight hours thanks to continued west winds as well, with obs showing temperatures still in the 20s and 30s as of 3 AM. Even Alamosa has gone from -9 at midnight to +2 at 3 AM thanks to continued winds. Today and Tonight.. Models indicate that our flow aloft becomes slightly more northwesterly as the low to our northwest approaches throughout the day today. This will mean continued lift and moisture over the high country which, in combination with orographics, should mean continued snowfall over our central mountains, and another round of snow coming in later this afternoon over the La Garitas and the San Juans as well. We'll see a bit of a lull in snowfall this morning, but expecting increasing snowfall rates after 5 PM this evening, when Winter Weather Advisories go into effect over portions of the central and San Juan mountain ranges. Wind gusts up to 50 mph as expected to continue over the central mountains this morning, but should begin to weaken through the early afternoon hours, as the trough and upper-level jet supports continues to push off to our east. Blowing snow could make for very difficult travel conditions this morning, and again later on this evening and into the overnight hours, especially over mountain passes. For the plains, expect daytime highs in the upper 30s to low 40s, with lots of sunshine and breezy winds. Wind gusts up to 40 mph are possible over our mountain adjacent plains, to include the I-25 corridor, especially through Pueblo County. Today's winds will likely keep our apparent temperatures in the 20s and low 30s for most locations. Overnight lows look to fall to near normal temperatures with continued west winds and increasing cloud cover. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Issued at 412 AM MST Wed Jan 10 2024 Upper trough moves across southern CO Thursday through Thursday evening. Moderate snow will be ongoing across the Continental Divide and will be quickly expanding eastward into the Sangres Thursday morning and into the adjacent plains by afternoon as the cold front drops southward through the plains. The heaviest snowfall for the plains will impact the southern I-25 corridor and northern Raton Ridge region aided by some banding snow coming off the mountains, better moisture/instability in model soundings and northerly upslope flow on the Raton. Could see an inch or two of accumulation across the southern I-25 corridor but greatest probabilities for this hug the terrain along and to the west of I-25 and south of highway 50 in national model blends. Have continued Winter Weather Advisories for the central and southwest mountains through Thursday afternoon as lingering moisture and instability from the cold air aloft could keep some moderate snow bursts continuing through the afternoon before the drier air behind the trough axis spreads in from west during the evening. One area to watch will be the southern Sangres where the higher elevations may need a winter weather advisory as well, depending on how much moisture spills over from the west. Current storm total snow for Thursday-Thursday evening has around 4 to 8 inches of snow for this area though this is trending towards the 90th percentile of the NBM members. Will let later shifts re-assess the need to expand advisories into this region. Otherwise, low level winds don't really achieve much of an easterly component for upslope on the east facing slopes of the southeast mountains which should keep snow totals light elsewhere. This will be spreading in during the afternoon/evening commute with temperatures falling quickly behind the front. This could cause deteriorating travel conditions for the southern I-25 corridor if we can overcome the initial T/Td deficit quickly enough. System moves east of the area Thursday evening with clearing skies. Southern CO is in between systems for Friday with westerly downslope flow into the lee side surface low across the plains. This should boost temperatures above freezing for Friday across the plains. Northwest flow will spread increasing moisture into the central mountains with snow ramping up across the orographically favored Sawatch/Mosquito ranges Friday afternoon. The next upper low drops into the northern high plains Friday night/Saturday sending an arctic cold front backdooring into eastern CO on Saturday. Timing of this front has trended faster, and have cooled off MaxT grids across the plains accordingly. This first push will be shallow at first, with a ribbon of warmer temperatures across the lower eastern slopes in the morning before the cold air deepens and banks up against the lower mountain slopes in the afternoon and spreads up the Arkansas River Valley into Fremont county. Temperatures will be most vulnerable to change (and error) in these areas depending on how quickly the cold front moves in. MOS Guidance is in good agreement on highs of around 10 degrees at KLAA on Saturday even though NBM spreads range from 7 to 20 degrees in 25th to 75th percentile range. MOS tends to handle these arctic intrusions better so have leaned towards colder solutions for the southeast plains. Sunday will be the coldest day as more energy drops southward out of Canada and drives a deeper surge of colder air southward into the plains. Would not be surprised to some widespread light snowfall develop across the southeast plains Sunday into Monday as energy drops in from the north and soundings saturate within the favorable dendritic growth zone temperature range. As the column cools Sunday night dendrites will transition to plates and needles with much lower snow/liquid ratios. Overall, QPF is quite light from this event and any snowfall will be dry in nature. Main concern will be the bitter cold and potential for wind chill advisories and/or warnings beginning Saturday night across the plains and continuing through Sunday night into Monday. Suspect wind chill highlights will become necessary as the event gets closer. Temperatures Sunday may struggle out of the single digits across most of the plains with NBM spreads decreasing as models and ensembles converge towards the colder solutions. Lows Sunday night will drop below 0 across much of the area...though to some degree will be mitigated by clouds across the plains. Monday will see some minor recovery but temperatures are still likely to max out in the lower teens at best across the plains. Interior valleys will remain warmer with highs in the 20s. With clearer skies, Monday night has the potential to be even colder, especially over the colder valley locations. Additional minor recovery can be expected for Tuesday as temperatures rebound to near freezing again. Kept temperatures on the cold side of guidance as northwesterly flow aloft doesn't typically bode for a quick eastward retreat of the arctic airmass. Flow aloft tries to transition to a more westerly component for Wednesday bringing the potential for a return of lower 40 readings across the plains. -KT && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1053 AM MST Wed Jan 10 2024 VFR conditions are expected to prevail for KCOS and KPUB throughout the forecast period. At KALS, VFR conditions are expected throughout most of the forecast period, although it will become IFR after 12Z due to lowering CIGS with -SHSN and BR expected. Winds will be synoptically driven at all terminals, mainly stronger and gusty this morning through the afternoon hours today. Gusts could be as high as 39 kts at KPUB, 35 kts at KCOS, and 25 kts at KALS. There will be a FROPA occurring at KCOS around 15Z and at KPUB around 16Z, which will cause a windshift to a more NNW'ly direction at KCOS, and NNE'ly direction at KPUB, as well as increasing and becoming rather gusty again through the rest of the forecast period. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 5 PM this afternoon to 5 PM MST Thursday for COZ058-060-068. && $$ SHORT TERM...EHR LONG TERM...TORGERSON AVIATION...STEWARD