Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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756 FXUS63 KLBF 251734 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 1234 PM CDT Sat May 25 2024 .KEY MESSAGES... - Strong to severe thunderstorms are possible across much of western and north central Nebraska this evening. - Additional showers and thunderstorms are expected Sunday, though the threat for severe weather appears low at this time. - A brief lull in precipitation is on tap for Memorial Day, before a more active weather regime and a potential return of severe weather middle to late week. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 345 AM CDT Sat May 25 2024 Currently, temperatures have fallen into the 40s to low 50s across the area, with scattered high clouds streaming in aloft from the west. Winds have begun to transition southerly, in response to increasing lee cyclogenesis across eastern Colorado. Aloft, broad zonal flow was noted, with an upper low centered over southeastern Manitoba. Another shortwave trough was moving eastward into the Intermountain West. For today, the primary concern will be the threat for strong to severe thunderstorms, in association with the aforementioned shortwave trough and associated surface low, progged to eject eastward out of Colorado into western Kansas this evening. As surface cyclogenesis persists into this afternoon, a warm front is expected to lift northward through the southern and central Plains, reaching potentially as far north as south central Nebraska late this evening. Current dewpoints across western and north central Nebraska sit in the upper 30s to low 40s, with 50F+ dewpoints as far north as northern Oklahoma and 60F+ dewpoints locked south of the Red River. This lends some uncertainty to the exact nature of any severe threat today, and trends in moisture return bear watching as we head into this afternoon. As southerly flow strengthens this afternoon, dewpoints are progged to rise out of the 40s into the lower 50s by early evening. Wind gusts of 30-35 miles per hour are anticipated across the entire area this afternoon from the south. More "just in time" moisture of ~55F dewpoints may reach as far north as areas south of I-80 and east of HWY 83. The limited boundary layer moisture will hold instability back, though ample cold air aloft and steep lapse rates in the mid- levels will overcome this enough to promote some threat for strong/severe storms. By 3-4 PM CDT, high based convection should begin to initiate across the high terrain of WY, as the surface low ejects eastward into far western Kansas, dragging an associated cold front into the Panhandle. High-res guidance continues to come into better agreement with the handling of this convection, with at least a broken line of convection ahead of the front translating quickly from west to east across the area. This should approach the HWY 83 corridor around 6-8 PM CDT and then begin to exit into eastern Nebraska by 10-11 PM CDT. Forecast soundings ahead of the frontal boundary are characterized by ample deep layer shear, with rather long and largely straight hodographs with height. This, along with the steep lapse rates aloft, would at least support some hail threat locally. However, the expected more strongly forced linear storm mode would likely hinder this threat somewhat. That said, will have to watch the southern most storm on the line for a higher threat for hail, especially considering this portion of the line segment would have the richest boundary layer moisture/instability to work with. The most prevalent threat for much of the area looks to come in the form of damaging winds. High LCLs and deep inverted-v low level thermodynamic profiles suggest ample sub-cloud layer evaporation, and the potential for acceleration of downdrafts. In fact, some high-res guidance paints the potential for localized gusts approaching as high as 70mph in the fast moving line this evening. Any tornado threat looks to be limited to the southern end of the line, where the deeper moisture reaches (likely areas near/south of I-80 and east of HWY 83). This would also likely be tied to the low level jet strengthening near/after sunset, though boundary layer stabilization after dark does add additional uncertainty. The surface cold front clears the area by Midnight Sunday, with at least a brief period of increasing cold advection in its wake. This will lead to highs ~5-10F cooler tomorrow than today. Additionally, scattered shower and thunderstorm development is expected into Sunday afternoon, in response to another shortwave quickly moving through the area immediately behind Saturday`s shortwave trough. Some instability remains across the area Sunday afternoon, though weak deep layer shear should keep any threat for strong to severe storms low. Any showers/thunderstorms look to quickly exit the area Sunday evening, as the shortwave begins to exit the area and subsidence increases aloft. && .LONG TERM /MONDAY THROUGH FRIDAY/... Issued at 345 AM CDT Sat May 25 2024 Next week looks to begin quieter, as upper ridging begins to amplify across the central Plains on Memorial Day. In fact, the holiday looks to be a pleasant weather day, with highs in the low to middle 70s and sunny skies, though winds will be breezy from the northwest. The brief lull in the active regime looks to come to an end by midweek, as upper troughing establishes over the Intermountain West by Wednesday. This leads to strengthening and broad west-southwest flow aloft across the Plains. Low-level flow looks to remain persistent southerly, with guidance indicating the best moisture return of the season into Thursday (low/mid-60 dewpoints). This looks to lead to a multi-day threat for severe thunderstorms, potentially beginning as early as Tuesday and persisting until a cold front arrives sometime Friday. Longer range deterministic/ensemble guidance is already hinting at daily convection rolling eastward off the higher terrain, reaching the area in the late afternoon/evening hours. The overlap of strong, deep layer wind fields and ample instability (especially Thursday) suggest a favorable background environment for supercellular convection across western Nebraska Wed- Thursday. This is also supported by pattern recognition of past severe weather episodes for western Nebraska. Mesoscale details will likely drive the threat each day, though this will need to be monitored closely for an increasing threat for (significant?) severe weather in the middle part of next week. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1233 PM CDT Sat May 25 2024 There are no flight concerns across wrn/ncntl Nebraska until 22z this afternoon. Thereafter, two areas of storms are expected to develop; both of which will move east thru the region. First, scattered to numerous storm activity should develop across ern WY by 19z this afternoon and enter or approach wrn Nebraska by 22z. This activity will move east and exit ncntl Nebraska by 05z. A second, less certain, area of storms may develop across ern Colo and move east through swrn Nebraska; exiting this area by 03z. Another flight concern is expected to develop from 06z tonight through late Sunday morning. With the passage of a cold front tonight, MVFR/IFR ceilings are expected to develop along and north of highway 2 across nrn Nebraska. Improvement to VFR/areas of MVFR are likely in this area by 18z Sunday. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Brown LONG TERM...Brown AVIATION...CDC