Area Forecast Discussion
Issued by NWS North Platte, NE
Issued by NWS North Platte, NE
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375 FXUS63 KLBF 180610 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 110 AM CDT Tue Jun 18 2024 .KEY MESSAGES... - Thunderstorms this afternoon and into the overnight will lead to an increasing threat for severe weather, with very large hail, damaging wind, and isolated tornadoes. - The redevelopment of heavy rainfall this evening and overnight across north central Nebraska could lead to an increased threat of flooding where heavy rains fell last night. - ECMWF EFI values point to an unusually cool day relative to the M- Climate on Wednesday. There is nearly a 30% chance that high temperatures remain at or below 65F in North Platte. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 357 PM CDT Mon Jun 17 2024 Latest analysis from 20z shows that the warm front has been slow to lift north, this is due to abundant stratus remaining across the Sandhills and north central Nebraska. To the south, temperatures have warmed into the lower 90s across far southwest Nebraska, but still hang in the upper 70s and lower 80s along I80 in Lincoln County. Looking regionally, very little developed cumulus is noted, though there are signs of increased agitation across southeastern Colorado and High County of the central Rockies. Overnight there was an abundance of heavy precipitation across north central Nebraska with widespread reports of 3" or greater from eastern Cherry to Keya Paha County. The flood advisories that were out for much of the day have been allowed to expire. A special thanks to the NSSL group who gave us an early look at their 19z sounding. As expected with the delayed burnoff of the stratus, the capping inversion is quite strong near LBF. Uncertainty is the word of the day with the CAMs very bearish on the severe potential for later this afternoon and evening, though the environment would suggest otherwise. Looking aloft, southwesterly flow prevails, which is currently ushering increasing PVA as noted by the developing CU over SE Colorado. Cyclogenesis has ensued over the High Plains and subjectively now sits over far NE Colorado or south of KOGA, near Grant. Southeasterly flow at the surface has ushered TDs into the lower 70s as far north at KBBW and KLBF with mid 60s as far west as the Highway 61 corridor. The warm front is subjectively north of KLXN, but not as far as KBBW. Steep lapse rates along the front are contributing to nearly 4k MLCAPE where moisture is pooling just south of the boundary. HRRR soundings reveal an uncapped solution, but we know that is not the case, especially north where substantial CIN remains. That being said, we believe with the increasing upper level support, isolated to scattered severe storms will form eventually, which will be in the vicinity of the lifting warm front and sfc low. Once CI occurs, the environment will be very supportive of rotating updrafts, which given the current situation, the Sandhills looks prime, with the latest soundings indicating near pure streamwise vorticity in the lowest few KMs of the hodograph. This is due to a strengthening low level jet as evening progresses. With southwesterly flow in the mid levels, hodographs will be quite long which would point to all hazards with any supercell that develops, though south of the boundary, large hail/wind will be the primary concerns. As sunset occurs, increasing CIN would lead to elevated storms with the concern being hail, wind, and heavy rainfall. The storms should weaken as nightfall arrives, but if storms maintain into north central Nebraska and/or eastern Cherry County, will need to monitor for flooding as heavy rainfall occurred last night. Lastly, mechanical mixing will allow for gusts of 40-45 mph overnight south of the lifting front. A cold front slides across the area tonight and tomorrow, but remains a focus for storms Tuesday afternoon. At this point, most of the activity will be east of the forecast area, but locations along and east of a Frontier to Custer to Eastern Holt County could see additional storms. Otherwise temperatures will be cooler in a post frontal regime tomorrow afternoon with highs largely in the 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 357 PM CDT Mon Jun 17 2024 A cold front is projected to be east of the area by the start of the forecast period, though additional showers and storms are possible as convection forms on a mid-level area of convergence. The area of concern would be from Hayes County northeast through Custer, Wheeler and eastern Holt Counties, though the heaviest QPF is expected to be just outside of the forecast area. A post frontal regime will usher in unseasonably cool temperatures mid-week. The latest guidance suggest widespread 60s to lower 70s across the entirety of the forecast area. Climatologically, highs on Wednesday will run some 10-20 degrees below normal. The threat for light showers continue, though continues to have highest chances to the east. Deeper low level moisture returns Wednesday night with easterly upslope flow projected. WAA spreading from the west may aid in the continuation of precipitation /thunderstorms/ well into Thursday morning. The return of southerly flow late week and early next weekend will keep the atmosphere unsettled with daily chances for QPF, though late Saturday into Sunday, coverage looks less promising. Severe weather, at least isolated coverage, would be possible as the the pattern switches from southwesterly to northwesterly aloft. Building heights from a central Rockies dome of high pressure and decreasing cloud coverage would allow a return to above normal temperatures early next week. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 105 AM CDT Tue Jun 18 2024 The primary concern this TAF period will be strong southerly winds gusting at or above 40kt along with low level wind shear through the first part of the valid period. A cold front will push through TAF sites toward daybreak and push the axis of the low level jet eastward, shifting winds to the northwest and ending the low level wind shear. While winds behind the front will still be gusty for a while, speeds will gradually relax behind the front through the afternoon. Flight conditions will be VFR except for a couple of hours either side of the frontal passage as a band of clouds moves through with the front. KVTN will see CIGs on the lower side of MVFR but the best potential for IFR is just to the north in South Dakota. KLBF will be on the low side of VFR with probabilistic guidance indicating only a 30 percent chance for sub-VFR conditions. Will monitor sky trends closely and amend if needed before the new TAF issuance at 12Z. There may be some widely scattered showers with the frontal passage, along with potential for some diurnal convection later this afternoon. However indications are that the coverage will be quite sparse so will maintain dry conditions this valid period and amend if trends in radar or surface observations begin to favor more coverage of precipitation. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Jacobs LONG TERM...Jacobs AVIATION...MBS