Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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684 FXUS63 KOAX 290839 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 339 AM CDT Mon Apr 29 2024 .KEY MESSAGES... - Quiet weather is expected today, letting the area catch its collective breath. - Showers and storms return Tuesday afternoon, with a 15-30% chance of severe storms. Large hail and damaging winds are the primary threats, but tornadoes cannot be ruled out. - Storms redevelop Wednesday and linger into Thursday, with potential for severe storms once again. In addition, prolonged rainfall could lead to flooding. && .DISCUSSION... Issued at 339 AM CDT Mon Apr 29 2024 Early morning analysis showed a surface low spinning over southwest MN, ushering in some clouds into the northern half of the forecast area. There were perhaps a few spotty sprinkles, but overall it was very quiet overnight. The quiet weather will continue today as the low pushes to the northeast and any remaining clouds exit the area. Temperatures will be right around average for this time of year, with highs in the mid 60s to lower 70s. Unfortunately the quiet weather doesn`t last long, as storm chances return Tuesday through Thursday. First on Tuesday, a shortwave currently off the Pacific Northwest coast will slide eastward into the Dakotas, along with a surface low. This will induce strengthening southerly low level flow in our area during the day, bringing in some warmer air (highs generally in the mid 70s to mid 80s) and a little moisture, with dewpoints in the mid 50s to around 60. However, still some questions on moisture depth and just how far north it will make it before the wave and a surface cold front start to slide through and lead to storm development. Initial development looks to be across southern SD into north-central/northeast NE (closer to the stronger forcing with the shortwave) by late morning or early afternoon with additional storms forming south-southwest along the front as we go through the afternoon. 29.00Z HREF guidance suggests SBCAPE values around 1500 J/kg into northeast NE, though larger scale models are a little less aggressive. Still, it should be good enough alone for at least some stronger storms and will combine with sufficient deep layer shear for storm organization, meaning severe weather is on the table. Currently thinking we`ll see a large hail threat with any initial discrete storms before the threat transitions to damaging winds as storms organize into a line and push east. Latest guidance does suggest some low level hodograph curvature, indicating some tornado potential, but if moisture is limited, that potential could remain on the lower side. These storms should exit to the east by 8-9 PM or so giving way to a quiet overnight. However, a larger scale trough will be digging into the western CONUS, with additional shortwave energy ejecting eastward and spinning up a surface low over southeast CO, in turn pushing a west-east oriented warm front northward into the forecast area by Wednesday afternoon. Expect storm development in vicinity of this front with plenty of instability and shear for large hail, damaging winds, and tornadoes. In addition, could see prolonged, possibly heavy, rainfall and a flooding risk along the front into Thursday given precipitable water values in the 1.2 to 1.5 inch range and warm cloud depths around 3500 m. The big question will be just how far north the front makes it, with guidance still showing a fair amount of spread in exactly where it sets up. That said, general consensus would say somewhere between I-80 and the NE/KS border. Beyond Thursday, zonal flow sets up with hints at various weak bits of shortwave energy sliding through and bringing additional precip chances into the weekend, though confidence in exact timing is low at this time. Otherwise, temperatures will remain pretty consistently in the mid 60s to mid 70s through Sunday. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1236 AM CDT Mon Apr 29 2024 MVFR ceilings expected to linger overnight at OFK, with possible spotty MVFR conditions at OMA as well. These clouds should push off to the northeast by late morning/early afternoon, giving way to mostly clear skies. Expect westerly winds, around 10-12 kts, with perhaps an occasional gust to 18-20 kts through Monday afternoon, before they weaken and become more southeasterly by the evening. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...CA AVIATION...CA