Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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259 FXUS63 KOAX 040900 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 400 AM CDT Thu Jul 4 2024 .KEY MESSAGES... - Scattered showers and thunderstorms are expected to develop across far eastern Nebraska and Iowa this afternoon. A storm or two may be strong to severe, though the bulk of this activity should be east and south of the region. - Another system will bring the chance for scattered strong to potentially severe thunderstorms Saturday evening. - Ridging out west will largely keep things drier next week, though occasional chances for isolated afternoon thunderstorms will be possible. && .DISCUSSION... Issued at 304 AM CDT Thu Jul 4 2024 ...Today and Tomorrow... A cold front currently extending from central South Dakota into central Nebraska is expected to sweep across the region late this morning into early this afternoon. By noon, this front should roughly be in line with the Missouri River. By this time, scattered showers and thunderstorms are expected to begin developing along and head of the front. Modest instability on the order of 1000-2000 J/kg and bulk shear ranging from 50 to 60 knots will help these storms organize fairly quick. With the progressive movement of this front, activity should quickly push east of the region by mid-afternoon. Nonetheless, there will be a period this afternoon, likely between noon and 4 PM, where scattered strong thunderstorms may develop (40 to 50 percent chance of rain), primarily across southwest Iowa. The primary hazards with these storms will be hail up to the size of quarters and wind gusts up to 60 mph. Behind this front, there will be some residual instability due to steep lapse rates aloft. As such, there is a low chance (20 percent) of isolated showers developing across northeast Nebraska between 3 PM and 10 PM this afternoon and evening. Any convection that is able to develop will be diurnally driven and should dissipate shortly after sundown. Tomorrow, though the front should be well to the east and south of our area, the upper-level disturbance will still linger over the northern Plains and upper Midwest. This will maintain steep lapse rates aloft via cold air advection. As such, there will be enough instability to again result in diurnally driven showers developing across northeast Nebraska and into west-central Iowa. The coverage, if these develop, will be isolated (any given location seeing a 15 to 25 percent chance of rain). ...Saturday and Sunday... The upper level pattern beginning this weekend will favor ridging over the western CONUS. As such, northwesterly flow aloft will prevail over the Plains. To our northwest, a shortwave trough from Alberta will dive southeast over the central CONUS. At the surface, a cold front is expected to stretch somewhere from central South Dakota into central Nebraska by midday on Saturday. The airmass ahead of the front is expected to destabilize by the afternoon, with CAPE ranging from 1500 to 2500 J/kg. As such, scattered thunderstorms (40 to 50 percent chance of rain) are expected to develop across eastern Nebraska by early afternoon. With bulk shear likely exceeding 40 knots, convection that is able to develop and mature will likely become organized to some degree, bringing the threat for strong to severe thunderstorms for much of the area. While there are still some questions with regards to when storms will initiate and the mode of convection that will be favored, confidence is growing in scattered strong thunderstorms traversing the region Saturday afternoon and evening. There are some slower model solutions that suggest the front will stall across southeast Nebraska into south-central Iowa. As such, a potential second day of thunderstorms would be possible Sunday afternoon across portions of southeast Nebraska and southwest Iowa. These storms, however, are not expected to be severe at this time should they develop in our area. ...Monday through Wednesday... The ridge that is forecast out west is expected to amplify next week, pushing disturbances diving southeast out of Canada east of our area for the most part. This will keep conditions seasonal and dry, with highs in the mid to upper 80s. Nonetheless, there is still a signal amongst medium-range guidance that suggest embedded low-amplitude disturbances may periodically traverse the northern Plains. Should PVA ahead of these disturbances coincide with peak diurnal heating across our area, isolated thunderstorms may develop. Uncertainty in timing and magnitude of these disturbances precludes any further discussion on specific days of concerns. The main takeaway for this part of the discussion is that though next week will likely be much drier than the last few weeks, there will still be a day or two with low end precipitation chances. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1144 PM CDT Wed Jul 3 2024 The line of storms to our west has fallen apart quickly and mostly showers remain with only a few isolated thunderstorms. It now looks like thunderstorms seem highly unlikely to impact KLNK and KOMA tonight. We will see a front move through later tonight which will lead to a wind shift to northwesterly across eastern Nebraska. We will see post-frontal showers move through Thursday morning with a few embedded thunderstorms possible. Confidence in thunderstorms impacting the terminals is too low at this time to include in the TAFs, but could be added later with an amendment. We may also see a period of MVFR cigs as the showers move through. Once the showers clear around 18-19Z, expect clearing skies and increasing winds out of the northwest. We`ll see winds gust to 20-22 kt during the afternoon dropping back down to around 5-8 kt by Thursday evening. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Darrah AVIATION...McCoy