Area Forecast Discussion
Issued by NWS Goodland, KS
Issued by NWS Goodland, KS
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390 FXUS63 KGLD 220814 AFDGLD Area Forecast Discussion National Weather Service Goodland KS 214 AM MDT Sat Jun 22 2024 .KEY MESSAGES... - 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. && .UPDATE... Issued at 849 PM MDT Fri Jun 21 2024 With storms exiting the area, it was decided to cancel the Severe Thunderstorm Watch early for our extreme Southwest Nebraska counties. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 150 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 9Z 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 /TUESDAY THROUGH FRIDAY/... Issued at 210 AM MDT Sat Jun 22 2024 Overview: Long range guidance indicates that the Tri-State area will initially be situated on the northern periphery of an upper level ridge (centered over the Desert Southwest and Southern Plains), at the southern fringe of the mid-latitude westerlies (on Tuesday).. and that the aforementioned ridge will consolidate/amplify over the Desert Southwest and extend northward to the 4-Corners and central Rockies (Wed-Thu).. then flatten and regress southward to the Desert Southwest/Southern Plains (Thu-Fri) as an upper level low moving ashore the Pacific NW progresses eastward across the northern Rockies/ Dakotas.. and cyclonic flow aloft envelopes the Intermountain West. Tue-Wed: Well above average temperatures are apt to persist. Precipitation chances /convective development/ in this period will highly depend upon the evolution of the ridge. 00Z 06/22 operational ECMWF guidance indicates that the magnitude, position and orientation of the ridge will be such that (1) synoptic subsidence may largely suppress diurnal convective development along the Colorado Front Range/Palmer Divide and (2) that low-level forcing/moisture may be insufficient for in-situ convective development on adjacent portions of the High Plains (i.e. northwest KS). 00Z 06/22 operational GFS guidance indicates a similar, albeit less pronounced, ridge.. with the mid-latitude westerlies in closer proximity to the Tri-State area on Wednesday.. a somewhat more favorable pattern for late aft-eve convective development. Thu-Fri: 00Z ECMWF/GFS operational guidance are in relative good agreement that upper level flow will back to the SW over the central Rockies and adjacent High Plains in this period.. as cyclonic flow aloft envelopes the western CONUS.. and that the Tri-State area will remain on the far southern fringe of the mid-latitude westerlies (southwesterlies, in this case). Despite relatively good agreement on the synoptic pattern, sensible weather conditions depicted by the GFS are at considerable odds with those depicted by the ECMWF on Friday, an indication that mesoscale processes -- e.g. latent heat release and/or airmass augmentation assoc/w deep convection both upstream and well- removed from the Tri-State area -- may highly influence the outcome. With the above in mind, forecast confidence decreases precipitously by the end of the week. Broadly speaking, expect above average temperatures and a relative greater potential for convection. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 1047 PM MDT Fri Jun 21 2024 Generally VFR conditions will be observed at both KGLD and KMCK, with southwesterly winds gusting to 20 kts for the first few hours in the period. Overnight, winds will shift to be out of the northwest at ~10 kts with scattered to broken ceilings. Winds will shift throughout the day tomorrow towards the north then south-southeast by the end of the period, remaining light. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...None. CO...None. NE...None. && $$ UPDATE...KMK SHORT TERM...CA LONG TERM...Vincent AVIATION...KMK