Area Forecast Discussion
Issued by NWS Tulsa, OK
Issued by NWS Tulsa, OK
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692 FXUS64 KTSA 220242 AFDTSA Area Forecast Discussion National Weather Service Tulsa OK 942 PM CDT Tue May 21 2024 ...New UPDATE... .UPDATE... Issued at 932 PM CDT Tue May 21 2024 Strong to severe thunderstorms producing large hail & damaging winds were ongoing across E OK and parts of NW AR this evening along/ ahead of a cold front. As of writing, a 3" hailstone was the largest reported this evening... associated with the thunderstorm which had moved through the south Tulsa metro area. The frontal boundary has slowed down/ stalled for portions of NE OK this evening. With subsidence & lack of low level forcing occurring north of the ongoing activity (along the I-40 corridor in E OK), believe any chance of additional storms in the wake of earlier convection should remain fairly minimal this evening into early tonight. Otherwise, storms in E-Central OK and NW AR will continue to drift south and east over the next few hours, with the coverage & severe threat becoming more isolated by late this evening/ early tonight as forcing wanes. Thus, will allow the Tornado Watch to expire at 10 PM. As 850mb winds shift out of the south again later tonight east of a low pressure center in N TX, increasing elevated instability will surge back northward across C & E OK. At the surface, the frontal boundary is forecast to sag south before stalling near the I-40 corridor through the overnight hours. Expect elevated showers and storms to redevelop late tonight/ early tomorrow morning across E OK as low-level isentropic ascent increases associated with the strengthening LLJ. This is supported by CAMs which begin to produce a fairly large precip footprint during the 09-12z timeframe. The environment will continue to support a threat for severe weather during this time, with all hazards possible along the boundary and primarily a large hail threat to the north. Other than editing PoPs to match current trends, much of the ongoing forecast was in good shape with only some other minor edits to temps and dew points. && .SHORT TERM... (Through Tonight) Issued at 119 PM CDT Tue May 21 2024 Warm, humid, and breezy conditions will continue through this afternoon and evening. Storm chances will ramp up later this afternoon and into the evening, continuing into the overnight hours as a cold front moves into the area from the northwest. Model guidance continues to show a deeply unstable atmosphere with MLCAPE in excess of 3000 J/Kg through the afternoon and evening south of the front. Surface-850 hPa specific humidity will be near the 99th percentile for this time of year with IVT also near the 99th percentile as a consequence of an usually strong low pressure to the northwest enhancing the southerly flow. Initial convective initiation has already begun in south-central OK. These elevated storms will move into southeast OK the next 2 hours. The main severe hazard will be hail. Convective initiation along the front is expected around 3-6 PM with a line of storms forming along it. There will also be the potential for additional isolated cells anywhere east or south of the front. These storms will be capable of all severe hazards, including large hail, damaging winds, tornadoes, and heavy rainfall leading to flash flooding. CAMs remain a bit uncertain with respect to how far south along the boundary storms will form. They also remain uncertain with the coverage and intensity of storms ahead of the front. With this in mind, the best coverage and intensity of storms will likely be across far northeast OK and northwest AR during the early evening. By late in the evening more widespread storm activity will develop across southeast OK. Further north, storms will continue to develop along the front, which will slowly sag south in the vicinity of I- 40. Some areas with repeated rounds of storms will see localized flash flood potential. Due to recent rains, as well as the expectation of continued heavy rain Wednesday, and low level moisture remaining near the climatological max for this time of year, a Flood Watch was issued through Friday morning to account for this threat. CAM guidance shows a resurgence of elevated storms along and behind the front in the 9-12Z period across the area, but southeast OK in particular. These storms will once again have the potential to become severe. Discrete cells and cells north of the front would be hail dominant, but any storms near the boundary would be capable of all severe hazards. && .LONG TERM... (Wednesday through Tuesday) Issued at 119 PM CDT Tue May 21 2024 The cluster of storms mentioned at the end of the short term period will progress east to northeast into northwest AR bringing widespread heavy rainfall with some severe potential continuing. As storms (presumably) grow upscale into a line, the threat of strong winds would become dominant, but other severe hazards would remain possible. CAM guidance is all over the place for later in the day Wednesday, but the general theme is that multiple rounds of additional showers and thunderstorms are likely, but will continue to focus in southeast OK and northwest AR. As the cold front will be near or south of the Red River by Wednesday, high temperatures will be much lower. Highs in the mid 70s will be common north of the boundary, except perhaps low 80s near the Red River. Low temperatures north of the boundary will be in the low to mid 60s and low 70s near and south of it. For Thursday the remnant cold front will lift north, but it will become diffuse and wash out. With warm and humid air streaming back through the area and yet another shortwave trough moving through, widespread storms are expected to develop again. Similar to the preceding days, anomalous instability, moisture, and wind shear will be present so severe weather is expected. Areas of heavy rainfall will also occur. Ensemble guidance is in decent agreement that we will get a break from the storms Friday, with just some lower potential across the terrain in Arkansas. Saturday will see storm chances resume, with some lingering probabilities into Sunday. By early next week ensemble guidance is in excellent agreement that a large ridge will build across the Great Basin, bringing much warmer air back into the area under northwest flow. However, smaller scale details such as how strong the ridge will be or where it will center are still unknown. About 40% of guidance position the ridge in a way that would be favorable for nocturnal MCS activity, but given the lead time will just go with NBM PoPs for now. && .AVIATION... (00Z TAFS) Issued at 631 PM CDT Tue May 21 2024 Across the NE OK sites, additional thunderstorms will be possible in the 11z-16z time frame. MVFR cigs/vsbys can be expected in this period of convection. Coverage of storms appears to be lowest near KBVO, so will not include any mention with this issuance. Further east and south, several periods of convection will be possible with this issuance, and most likely time periods have been identified with tempo and prob30 groups. MVFR cigs and vsbys can be expected in periods of TSRA, though prevailing cigs should rise to VFR levels across the SE OK and AR sites during the afternoon. && .PRELIMINARY POINT TEMPS/POPS... TUL 89 62 76 63 / 30 30 40 40 FSM 89 69 80 66 / 20 50 70 70 MLC 87 67 77 65 / 10 30 80 70 BVO 89 59 76 58 / 10 20 40 30 FYV 86 65 77 61 / 30 70 80 70 BYV 87 63 74 61 / 50 70 70 60 MKO 87 65 75 64 / 30 50 70 60 MIO 86 57 74 61 / 40 30 50 40 F10 87 63 75 63 / 30 50 70 60 HHW 87 70 80 66 / 10 10 80 70 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...Flood Watch through Thursday evening for OKZ049-053-072>076. AR...Flood Watch through Thursday evening for ARZ019-020-029. && $$ UPDATE...43 SHORT TERM...06 LONG TERM....06 AVIATION...23