Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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938 FXUS63 KOAX 032253 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 553 PM CDT Mon Jun 3 2024 .KEY MESSAGES... - A few spotty thunderstorms possible (10-15% chance) this afternoon in far southeast Nebraska and far southwest Iowa. - Higher storm chances Tuesday afternoon (60-90%) with a 15-20% chance of severe storms, mainly in southeast Nebraska and southwest Iowa. Large hail and damaging winds are the primary threats. - Saturated soils continue to keep flooding a concern as showers and storms move through northeast Nebraska tomorrow afternoon. - Mostly dry Wednesday into the weekend with highs in the mid 70s to mid 80s. && .DISCUSSION... Issued at 316 PM CDT Mon Jun 3 2024 Today and Tomorrow: Water vapor imagery this afternoon features a vigorous shortwave trough entering the Pacific Northwest, with a broad band of ascent stretching ahead of it from CA to WY/MT. To the east, an MCV over Kansas continues to power an MCS traveling the ArkLaTex region while additional shortwaves continue to waft to the north and east. Drilling down to the surface, a local surface low was analyzed over far northwest Kansas with a surface trough/convergent boundary stretching north/northwest into eastern Montana. To the direct south of the forecast area, the aforementioned MCS has turned over much of eastern Kansas, but has left southeast Nebraska into southwest Iowa with leftover instability on the order of 1500-2000 J/kg. A combination of convergence in those areas and some northward component of the advection of the MCV to the south will help create a few pop up showers and storms in extreme southeastern Nebraska and possible into southwest Iowa. While there is some decent instability, shear will be on the low end with HRRR forecast soundings depicting around 3 kts of shear, giving storms little to work with and maintain healthy updrafts for any meaningful amount of time (with any chances diminishing by 7 PM). Highs will continue to peak in the mid-to-upper 80s with light winds and provide a splendid evening for those getting off work. The main concern of the forecast period comes into focus tomorrow, as the aforementioned trough moves east towards the area dragging a cold front. Increasing warm air advection will being to develop after 7 AM, and could help spark a few morning storms in eastern Nebraska ahead of the incoming front, where dry low levels could result in a stray strong gust or two due to evaporative cooling. During the afternoon, sufficient instability is expected to develop and strong convergence along the front is expected to result in an increasing-in-coverage line of showers and storms. Timing of any showers and storms continues to lean towards an initiation time of 3 or 4 PM to the northwest of the Omaha and Lincoln Metros, with those storms exiting to the east by 9 PM. Weak shear of less than 20 kts will lower the ceiling of any severe threat with storms tomorrow afternoon. The highest potential for severe storms is expected to occur at peak heating and shortly after when instability is maximized, with largely straight line hodographs pushing the main hazard towards damaging hail and wind (though a tornado can`t be ruled out in far southeast Nebraska and southwest Iowa). One wildcard to watch would be a slow progression of the MCV to the south, which could increase cloud cover and limit instability if it moves east slower than models anticipate ahead of the front. Additionally, it won`t take much rainfall to create flooding issues for already saturated soils and watersheds. Wednesday and Beyond: With the front moving off to the east for Wednesday, we`ll find ourselves in a northwesterly mid/upper flow pattern with the main jet streak settled nearly overhead to just north of the area. Rain chances for the remainder of the work week remain low, but there could be a pop up storm or two that develops as a shortwave moves through the flow Wednesday or Friday evening. Highs during this time will remain nice in the upper 70s to 80s with typical afternoon winds of 20 to 25 mph keeping things from feeling stagnant outside. Beyond the forecast period, our next best chance for widespread showers and storms return Monday as a more dynamic system swings south and across the area. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 547 PM CDT Mon Jun 3 2024 Southerly winds are expected to persist at all TAF sites through the overnight hours, with sustained speeds under 12 knots. Between 09Z and 13Z, there is a low chance of a stray shower or two moving through or near KOFK. Though non-zero, the probabilities are too low to include in TAFs at this time. May put in a TEMPO group for these if the signal persists at the 06Z TAF issuance. Otherwise, after 18Z, scattered thunderstorms are expected to develop across southeast Nebraska and southwest Iowa (KOMA and KLNK). Will likely include a TEMPO group for these storms in a subsequent TAF issuance as well. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Petersen AVIATION...Darrah