Area Forecast Discussion
Issued by NWS Goodland, KS
Issued by NWS Goodland, KS
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923 FXUS63 KGLD 211944 AFDGLD Area Forecast Discussion National Weather Service Goodland KS 144 PM MDT Fri Jun 21 2024 .KEY MESSAGES... - Continued very windy today with 20%-40% chances for afternoon and evening thunderstorms, mainly along/north of I-70, some of which could become severe. - Weekend looks to remain hot with highs in the 90s to low 100s. Could be a few thunderstorms Sunday afternoon/evening. - Skeptical regarding how quickly the upper level ridge retrogrades west going into next week. Depending on where the ridge is will dictate where storms will move through. - If ridge is delayed, the arrival of the hottest temperatures will be delayed too. - Chances for storms each day next week. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 143 PM MDT Fri Jun 21 2024 We currently have a 250mb high pressure system over Texas and a low pressure system north of Montana. These two features are creating a jet streak from the southwest over the Colorado Rockies and into the northern High Plains. Starting this afternoon and continuing over the weekend, the high stays in place while the low moves on to the east. This afternoon and overnight, the jet streak will strengthen, while staying northwest of the CWA, giving us some upper level support for convection. In the lower levels, a lee low will eject off the Rockies in northern Colorado. Looking at current observations, the low and associated cold front have already formed and has nearly stalled out in eastern Colorado. A weak surface ridge from Texas up into central Kansas is working to stall the low, but this ridge will erode throughout the day. Around 22-1Z, the ridge is mostly gone and the low is expected to start moving again. As the cold front starts gathering speed, it is expected to trigger convection. This will be our main round of storms for the evening. However, before we talk more about the main event this evening, CAMs are showing a line of convection forming around 21Z between Goodland and McCook. This looks to be convective temperature initiated and will quickly move out of the area to the east. Probability of these storms forming are low, about 20%. Back to the main event; severe weather is possible with the storms, mainly between 0-4Z, but confidence is only about 10-20% severe weather will occur. The biggest threat this evening will be wind gusts. The storms will be fairly quick, about 40 kts of downshear speed, about 2,000 J/kg of CAPE, 1,000 J/kg of DCAPE, with PWATS ranging from 1.2-1.6. This is leading to the potential of a wet microburst set up with quick moving storms. Gusts up to 60-65 MPH are possible with the storms if they are able to vertically load a heavy amount of precipitation. Hail will also be possible, but with the 0C line being about 16,000 ft AGL, a fairly moist melting layer, and effective shear only about 30 kts, large hail seems unlikely. We could see a few stones around 1-1.5 inches if a storm lasts long enough for hail to grow that large. Otherwise, SPLASHie (Storm Producing Large Amount of Small Hail) storms or extremely heavy downpours are expected from majority of the storms. The storms are expected to form in our Colorado counties and move east-northeast, generally staying north of a line of Sharon Springs to Ludell. A small cluster or two of storms, or isolated cells are forecast for this event, so widespread heavy rain is NOT anticipated. The storms look to start decaying around 4-6Z with some light showers possible afterwards until maybe 3Z at the latest. Northwesterly dry air will then move in and end any remaining precipitation. Overnight, the cloud ceilings will continually ascend, even into tomorrow afternoon, making skies mostly clear by then. Winds will follow a similar trend and weaken gradually overnight and into tomorrow, becoming northwesterly then northeasterly as time goes by. Lows tonight in the east will be kept a bit warmer due to the cloud cover, but temperatures will cool into the lower 60s to mid 70s. Back up at 250mb, tomorrow sees the high stay in position over Texas as the low continues on east, giving us mostly zonal flow. This perpetuates through Sunday night, giving us a fairly stable upper- level. At 500mb, the high pressure system retrogrades from the southeastern US to the Southern Mississippi River Valley, continuing to reduce the potential of organized convection through the weekend. In the lower levels, we can expect southwesterly flow to continue which will have little moisture content through the period. This will also contribute to low PoPs. There are some near 30 PoPs in the western CWA due to orographically forced showers and storms moving into our area and decaying. Temperatures will be a bit cooler tomorrow, due to the cold front this evening, with highs in the upper 80s to mid 90s. Tomorrow night will see mostly clear skies that allow the area to cool into the lower to mid 60s. Sunday will start a warming trend and highs will be in the upper 90s to lower 100s. This will be a very hot day and precautions should be taken to stay cool Sunday! && .LONG TERM /MONDAY THROUGH FRIDAY/... Issued at 1252 PM MDT Fri Jun 21 2024 This part of the forecast will be greatly influenced by the upper level ridge. Models have the ridge entrenched over the Southern Plains, centered over TX. With the ridge south of the forecast area, models have zonal flow over us. Within the zonal flow, upper level short wave troughs move overhead almost daily. This may lead to precipitation chances for us. However am skeptical of the ridge being centered over TX before next week starts. Models have been moving the ridge west too fast, which is to be expected when the ridge is a blocking high pressure. For this reason am doubtful the ridge will scoot west as quickly as currently forecast. A delay in the ridge moving west should cause the upper level flow over the forecast area to be more from the southwest than the west. This would influence where storms will track across the forecast area, and affect how hot the forecast area becomes. If the ridge does end up being slower to move west, the hot air under it will stay more to the east. Even though models have upper level short wave troughs moving through the flow over the forecast area, am thinking the storm coverage should be on the low side. This is more reflective of a summertime pattern in which storms are isolated to scattered at best. If the current forecast is on track, there may be a brief respite from heat midweek as a weak cold front moves through. However high temperatures rebound by the end of the workweek. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1117 AM MDT Fri Jun 21 2024 Generally VFR conditions will be observed at both KGLD and KMCK, but strong winds, made worse with storms this afternoon and evening, will make for some tricky conditions. Models are having a difficult time figuring out exactly what is going to happen over the next 8 hours, but we are currently expecting two waves of storms. The first will form around 21Z and move away from the TAF sites by 0Z. The second wave, the wave with higher confidence, will impact KGLD around 1Z and should stay south of KMCK. This second wave is expected to produce strong winds as it progresses eastward. If any of the stronger cells moves overhead of either TAF site, heavy rainfall will reduce visibility significantly. The heavy rain is the only concern for IMC throughout the period. Later in the period, winds will weaken and become northwesterly. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...None. CO...None. NE...None. && $$ SHORT TERM...CA LONG TERM...JTL AVIATION...CA