Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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085 FXUS65 KCYS 091032 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 432 AM MDT Thu May 9 2024 .KEY MESSAGES... - Winter Weather Advisory remains in effect for accumulating mountain snow, especially on northern slopes of the North Laramie Range. - Scattered rain/snow showers expected to continue through Thursday afternoon and evening. Minimal snow accumulation expected, if any. Severe weather is not expected at this time. - Warming trend likely headed into the weekend with the return of above normal temperatures for mid-May. && .SHORT TERM /THROUGH FRIDAY/... Issued at 428 AM MDT Thu May 9 2024 The Winter Weather Advisory remains in place for the Northern Laramie Range where an additional 6 to 8 inches of snow is possible through Thursday morning. The generally northerly flow will continue to favor the north facing aspects, especially the North Laramie Range. As part of the low departs to the east and an additional part retrogrades southwestward, rain showers will continues to move across southeast Wyoming and western Nebraska. Precipitation will be mainly snow or a rain/snow mix west of the Laramie Range and rain east of the Laramie Range. HiRes guidance is showing the next wave of precipitation moving in from South Dakota between now and early this afternoon. This initial wave is followed by another this afternoon into early evening which mainly stays along and north of the North Platte River Valley. Along with these rain/snow showers we may see a few rumbles of thunder. The HREF has 100-500 J/kg of CAPE in east-central Wyoming and the Nebraska panhandle this afternoon and early evening which is sufficient to kick off a weak thunderstorm. Main shower and thunderstorm activity will be winding down between 7 PM and 11 PM. By Friday the low continues to circulate in central Nevada, blocking the ridge from really getting into southeast Wyoming and western Nebraska and being able to warm and dry out the air. That being said, temperatures are still forecast to be a few degrees warmer, but precipitation chances will stick around. The best chances for showers and thunderstorms will be along and west of the Interstate- 25 corridor. The continued moisture and easterly flow at 700 mb, as well as orographic enhancement from the Laramie Range will allow for the potential for isolated to widely scattered showers and a rumble of thunder Friday afternoon. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Issued at 428 AM MDT Thu May 9 2024 The long term forecast will begin to look more spring-like with chances for isolated afternoon thunderstorms possible over the weekend, with better chances for more scattered showers and thunderstorms next week. Temperatures are also expected to increase beginning this weekend into next week with temperatures likely to remain in the upper 60s to low 70s throughout much of the long term forecast period. The weekend chances for showers and isolated thunderstorms will be driven by a slow moving and large upper level low moving across the Four Corners region Friday and into Saturday. Much of the dynamics associated with the upper level low are confined along the southern periphery as this upper level low taps into the subtropical jet. Models are advertising a setup where this upper level low is south of a ridge building across the northern Pacific northwest with another upper level low sitting in near northern Michigan. This overall setup of upper level low and high pressure systems looks like a messy col setup across the Front Range states. The wind fields show the col pattern better as light easterly winds in close proximity of light westerly winds suggest that some type of stationary or quasi-stationary front will be located across SE Wyoming and the Nebraska Panhandle. This boundary will be the focal point for potential convective initiation Friday and again on Saturday. These storms that do develop will be in a weakly shear and low CAPE/instability environment so not expecting much in the way of deep convection, but towers that go up along the boundary or are orographically supported could reach heights enough to foster the development of some storms that could produce small hail. This overall pattern remains in place well into Saturday evening before the closed upper low across the Four Corners begins to weaken and open into an open wave trough as it crossed through southern Colorado. Remaining stationary boundary should still be draped somewhere across the Front Range and we will also have lingering outflow boundaries in play on Saturday IF we can get a few deeper convective cores going on Friday. This system begins to speed up on Sunday but the threat for some afternoon diurnal convection will again be possible. Monday may be quiet day across the region as a weak upper level ridge axis moves but this too will quickly move east of the region throughout the day on Monday. We will see the benefits of some warmer 700mb temperatures which will allow for temperatures to jump into the 70s across much of SE Wyoming and the Nebraska Panhandle. Heading into Tuesday and beyond, we will have to start watching for the potential for a chance for some lower bound severe weather events. Our region gets locked into this northwest flow that will have multiple shortwaves and vorticity lobes transversing through. This type of setup usually suggests some severe weather is possible as the cool NW flow aloft encounters somewhat warm surface temperatures. The determining factor in these events is just how much boundary layer moisture we can advect into the region. Something to keep an eye on as we head into next week. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 428 AM MDT Thu May 9 2024 While the overnight wave of rain/snow showers has departed, MVFR to IFR CIGS are likely to continue until 19Z-23Z as the next wave of showers is expected to begin moving in from the northeast impacting KCDR first before spreading across southeast WYoming and western Nebraska early this morning. These precipitation chances continue on and off through the afternoon and evening, ending mainly between 01Z and 05Z. While thunderstorms are possible, it is uncertain whether they will directly affect the terminals or not. The best chances for thunderstorms across the High Plains is between 11 AM and 9 PM with KCDR, KBFF, and KAIA having the highest chances for thunderstorms to directly affect a terminal, and KCYS and KSNY having lower chances. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Weather Advisory until noon MDT today for WYZ103. NE...None. && $$ SHORT TERM...LEG LONG TERM...AW AVIATION...LEG