####018011163#### FXUS65 KPUB 032045 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 245 PM MDT Fri May 3 2024 .KEY MESSAGES... - Severe thunderstorms will be possible later this afternoon and through the evening over the eastern plains. Wind gusts in excess of 60 mph, hail of up to 2 inches in diameter possible. A brief landspout or weak tornado cannot be ruled out. - A cold front will move through later this evening over the plains, with colder temperatures and gusty winds out of the northeast behind it. - General thunderstorms are possible elsewhere over the plains and over the eastern mountains, which will continue throughout the night for some areas, mainly over the far southeastern plains and Raton Mesa area. - Frost conditions will be possible tonight over El Paso County. - Increasing winds and fire danger early next week with a trend towards cooler and wetter conditions for late week. && .SHORT TERM /THROUGH SATURDAY/... Issued at 224 PM MDT Fri May 3 2024 Currently and through tonight... A major shortwave trough is continuing to approach the region, with the development of a lee-side low by later in the afternoon as the trough axis moves overhead. As this pushes out over the plains a slightly deepens, it will force a cold frontal boundary to move down from the north over the plains. A dryline is going to establish itself, where there are currently 50+ dewpoints over northeastern New Mexico that will make their way up over far southeastern Colorado later this afternoon, this will act as a triggering mechanism for pre-frontal convective development once the cap completely erodes and the convective temp is achieved, which may turn severe given the higher dewpoints and thus increased low-level instability. An increasing low-level jet out out of the southwest will also increase shear necessary for further updraft enhancement and may allow for severe thunderstorm development for the next couple of hours, mainly over Las Animas County and east. A consensus of the latest high res guidance has the front beginning to move over northern El Paso County by as early as 7 to 8 PM, and then push through the CWA by around midnight. The timing of the front could be sooner, depending on whether or not if it is accelerated by outflow from convection that develops along and behind the boundary. Currently, there have already been multiple cells that have initiated over this area, which will likely continue to develop as the lower levels further destabilize by early evening as the low- level jet increases with effective shear of a magnitude around 30 kts or greater. MLCAPE is also going to increase to 1000 J/kg or greater, especially over Prowers and Baca counties, mainly after 4pm. With this, the potential for thunderstorms becoming severe will increase going into the later afternoon/early evening hours, especially anywhere from La Junta to Kim, and eastward. There are also going to be general thunderstorms possible over the eastern mountains and along portions of the I-25 corridor, mainly south of Pueblo County, that will continue to move off to the east-northeast after development. Dry conditions, with low relative humidity values and gusty southwesterly winds will continue to keep fire weather conditions going until around 9 PM in the San Luis Valley, although RH values should recover enough to allow the Red Flag Warning to come down by this time. The latest CAM guidance and HREF helicity tracks favor development of stronger, and possibly severe, cells over Prowers and Baca counties between 6 to 8 PM. In addition, the latest HRRR model also puts the development of a cell over Baca, with easterly winds turning into it at 00Z (7 PM), suggesting that there could be increased SRH values right around this time and possible supercell development, with the capabilities of producing a brief landspout and/or weak tornado. It also has something similar right around the same time over Prowers County, as well as the development of a strong cell right on the edge of northeastern Kiowa County. The NAM4km Nest has also been persistent with the past couple of runs of having a pre-frontal cell develop with over the northwestern Baca County/Bent County and then move into Prowers County right around the same time. Colder air advection moving in behind the frontal passage that will occur later this evening will allow for temperatures to continue to drop, especially as skies further clear. This will allow for temperatures over El Paso County to drop to near, or below, the freezing mark. Due to this, there will likely be some areas of frost. Stratus will also develop, mainly along the I-25 corridor from Pueblo County and northward to Monument. There could still be some showers, and possibly a thunderstorm, continuing into the early morning hours of tomorrow. As the lower levels continue to stabilize, showers will also continue to diminish and move southeastward and out of the CWA towards daybreak. Lows will bottom out into the 30s to low 40s over most of the plains, and generally in the upper teens and 20s for high country. Tomorrow... With colder air already in place, it will be more stable over the plains, and notably cooler. Highs will likely remain in the 60s over a majority of the plains and San Luis Valley, and only 40s to 50s for the higher terrain. With residual moisture, and increasing mid- level flow out of the southwest coupled with orographic lifting, there will be showers and thunderstorms developing in the afternoon hours over the higher terrain. This will get pushed out over the plains by later in the day. These should be more of your "garden variety" type thunderstorms, although there could be an isolated storm or two that is on the stronger side. With more of an inverted- v profile, some of these storms may result in some gusty outflow winds to 50 mph or greater, and there could be hail up to 1/2 inch with the stronger storms. The plains will likely remain dry with more stable air in place, although a few of the showers/storms could move out over the adjacent plains and portions of the I-25 corridor. -Stewey && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Issued at 224 PM MDT Fri May 3 2024 Weak wave in southwest flow ejects across CO Saturday evening with cool stable upslope flow maintaining across the plains. A few showers may drift off into the adjacent plains but they should diminish as the move off the mountains into the more stable airmass. Have trimmed eastward extent of pops into the I-25 corridor during the evening. Showers and thunderstorms will diminish across the mountains behind this feature in the evening but could regenerate across the far eastern plains late Saturday night as the low level jet increases. Any isolated nocturnal convection will have limited CAPE resulting in some weak elevated showers/thunderstorms into Sunday morning. Temperatures then rebound for Sunday as southerly flow increases across the region ahead of the next upper low moving into the Great Basin. Will need to watch the San Luis Valley for potential Critical Fire Weather conditions until green up occurs. For now, coverage and magnitude looks too limited with RH the most limiting factor for Sunday. Showers and thunderstorms will redevelop across the Continental Divide as moisture increases ahead of the upper low. Out east it remains largely dry. Will need to monitor the position of the dry line but for now dew point return and CAPE looks limited with little to no initiation along the boundary in the afternoon. Upper low lifts out across northern CO Sunday night and Monday. With the more northern storm track, this puts southern CO under the dry and windy region of the storm. Latest NBM shows potential for wind gusts greater than 50 mph in the 70-90+ percentile, especially along and south of highway 50 Monday morning. We could be looking at brief near high wind potential Sunday morning if we can mix 50-60 kts down to the surface Sunday morning as the cold front moves through. In spite of the cool down, it will be very dry and likely a critical fire weather day for the San Luis Valley and southern portions of the southeast plains where fuels are still critical. The Continental Divide will pick up some snow Sunday night through Monday morning with a diminishing trend in the afternoon as the storm ejects to the northeast. The windy and mostly dry pattern continues for Tues and Wednesday with temperatures rebounding. Then we trend towards a cooler and potentially wetter pattern as low pressure stalls out over the western U.S. and a cold front moves through the plains bringing post frontal upslope flow Thurs into next weekend. Thursday could potentially be the coolest and wettest day with snow levels dropping to around 7000 feet across the southeast mountains. Still some details to resolve on the track and strength of the low which will drive the degree of upslope and precipitation amounts. EC is weaker with the upper low and magnitude of upslope, and therefore has less QPF/snow. Probabilities of greater than 3" of snow accumulation is less than 30 across all but the central mountains from the National Blend of Models. Central mountains fair a little better with probabilities for up to 6 inches up to 40%. This will bear watching as details become more certain. -KT && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 224 PM MDT Fri May 3 2024 VFR conditions are expected to prevail for KALS and KPUB, and mostly for KCOS, throughout the forecast period. There will be some lower decks moving in later which will reduce CIGs to MVFR criteria during the morning hours at KCOS from approximately 11 to 13Z. CIGs will should remain elevated enough to be above MVFR criteria for KPUB from 13 to 15Z. FROPA will occur for KCOS around 01Z and KPUB around 02Z, which will result in a windshift with gusty NE'ly winds thereafter, with gusts close to 40 kts at both terminals. Winds will be synoptically influenced at all terminals. There is very low confidence (less than 10 percent) of SHRA or possibly TSRA to be in the vicinity of KCOS and KPUB right around the time of FROPA, although due to the lack of confidence, this was left out of the TAF. Winds will become more diurnally influenced towards the end of the forecast period as they further weaken. -Stewey && .PUB WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM MDT this evening for COZ224. Frost Advisory from midnight tonight to 9 AM MDT Saturday for COZ084-085. && $$ SHORT TERM...STEWARD LONG TERM...KT AVIATION...STEWARD ####018006427#### FXUS65 KLKN 032047 AFDLKN Area Forecast Discussion National Weather Service Elko NV 147 PM PDT Fri May 3 2024 .SYNOPSIS...Robust weather system impacts the forecast region Saturday and Sunday with strong winds and accumulating rain and snow expected. Low probabilities for precipitation contnue early next week with mostly dry weather expected by the end of the week. && .SHORT TERM...Tonight through Saturday night Weather remains fair tonight with light and variable winds and increasing cloud cover from the northwest the latter half of the night. Overnight low temperatures reside mostly in the 30s. Robust upper low and strong attendant cold front begin influencing the forecast area Saturday morning as the feature moves into NorCal and Nevada. Dynamically driven weather is expected with an increase in south/southwesterly winds Saturday. Advisory and warnining level winds will persist into Saturday night with blowing dust and damaging gusts around 60 mph expected for central Nevada including the US-50 corridor where the high wind warnings are in place. Advisory level sustained winds of around 30 mph are expected across much of southern and eastern Elko county. Strong winds trend lighter while shifting northwesterly in conjunction with the frontal passage Saturday night. That said, winds ceratinly remain at least breezy into Sunday morning. Cold front also brings widespread rain and snow showers to the forecast region with activity generally focused within a broad band situated along the front. Main concern will be rapidly lowering snow levels Saturday night. Based on timing of the frontal progression, White Pine County will be the primary focus of accumulating snow Saturday night and into Sunday morning. IMpacts will also be felt across the Ruby Mtns/E Humboldt Range as well as northern Elko County. Lower probabiloities for accumulatiing snow elsewhere. Pass routes across the eastern half of the foreacst area likely see slush ups and light accumulations which will be primarily snowfall rate driven, and produce adverse travel conditions late Saturday night/early Sunday morning. Most valley snow totals Saturday night will be around an inch or less. Pass routes in and near WHite Pine COunty, where the greatest impacts are expected, could see 2-5 inches of accumulation. Daytime high temperatures reside in the low 60s to low 70s with overnight lows pluimmeting to the low 20s to mow 30s. && .LONG TERM...Sunday through next Friday A low pressure system and cold front is expected to move across the forecast area Sunday through Monday, bringing gusty winds, cooler temperatures, and snow showers. Winds will pick up in the afternoon out of the west-northwest to 20-25 mph with gusts 30-35 mph. Snow levels lower to about 4500-5000 feet by Sunday morning. Light snow showers are possible in the valley locations with some of the locations in central Nevada receiving one to three inches along US Highway 50. Some locally higher amounts will be possible in the high mountain areas of White Pine County, Northern Elko County, and the Ruby Mountains. A 20% chance of isolated to scattered thunderstorms exist in portions of central and northern NV as the cold front moves southeastward. By Monday, the trough moves moves east with lingering showers and breezy winds. On the heels of the exiting trough, an upper level wave moves through northern NV Monday afternoon, bringing another round of showers and thunderstorms mainly north of I-80. Northwest flow continues mid to late next week with mostly dry conditions over the region. Highs will be in the 50s and 60s with lows in the 20s and 30s. Winds will be breezy to locally windy each afternoon with gusts of 20 to 30 mph in the windier locales. && .AVIATION...VFR conditions expected for all terminals through tonight. A strong low pressure system from the northwest will approach the region by Saturday. Breezy winds from the S-SW expected to affect all TAF sites, increasing to 20-25 knots with gusts as high as 30-40 knots at northern terminal sites. Gusts will reach to 40-50 knots at KELY and KTPH, with BLDU possible given the strong winds. Meanwhile, increasing mid to upper-level cloud cover (5KFT and above) will move from west to east as the system moves across the area. -SHRA/VCSH expected at KWMC and KBAM Saturday morning and afternoon with CIGs lowering to MVFR conditions at times, but confidence is low. KWMC is AMD not SKED due to communication issue. && .HYDROLOGY...Elevated flows continue across several streams, creeks, and rivers throughout northern Nevada due to seasonal snow melt. A strong low pressure system will bring widespread rain and mountian snow to much of northern and central Nevada over the weekend. Over half an inch of liquid equivalent precipitation is expected across north central Nevada in northwestern Elko county where most of the flood concerns remain. This will increase flows on several streams and rivers. The Humboldt River at Battle Mountain resides in action stage and is forecast remain in action stage while gradually decreasing for the next several days. The Humboldt River at Comus continues to slowly rise and is now in minor flood stage and is expected to remain in minor flood stage for the next several days. Wildhorse Dam currently resides in action stage and is forecast to remain in action stage for the next several days. The Owyhee River near Mountain City currently resdies near action stage. The river is forecast to contiue to reside and slightly fluctuate around action stage for the next several days. && .LKN Watches/Warnings/Advisories... Wind Advisory from 8 AM Saturday to 2 AM PDT Sunday South Central Elko County...Southeastern Elko County. High Wind Warning from 8 AM Saturday to 2 AM PDT Sunday Northeastern Nye County...Ruby Mountains and East Humboldt Range...White Pine County. High Wind Warning from 8 AM to 11 PM PDT Saturday Northwestern Nye County...Southern Lander County and Southern Eureka County. Wind Advisory from 8 AM to 11 PM PDT Saturday Southwest Elko County. && $$ 92/90/90