Official NWS Forecast for Lincoln (Click to Enlarge)

However, precipitation chances will increase once
again across southeast Nebraska and southern Iowa Friday afternoon
and evening as convection develops along the cold front trailing
behind the aforementioned departing low. There`s a marginal risk
for large hail and damaging winds across southeast
Nebraska/southwest Iowa Friday afternoon and evening. And, while
heaviest rain is expected to remain just to our southeast in
Kansas and Missouri, there is still the potential for an inch or
more of heavy rain across extreme southeast Nebraska and southwest
Iowa. Therefore, we included this area in a Flash Flood Watch for
this morning through early Saturday morning.

Another developing surface low will pass through eastern Nebraska
Saturday afternoon, draping another frontal boundary across the
southeastern half of the CWA. Steep lapse rates, abundant low
level moisture, and moderate deep shear and instability will lead
to yet another severe weather risk over the area. Large hail and
damaging winds will be the primary threats once again.

24 Hour Rainfall Forecast from the WPC

Beneath the belt of fast southwesterly flow, a weak baroclinic zone is forecast to extend south-southwestward across the Plains, while a weak warm front lifts slowly northward across the Midwest. The specific location of the aforementioned Plains front remains uncertain -- largely due to outflow associated with ongoing convection expected to linger into the beginning of the period. As this outflow/frontal conglomerate will play a substantial role in subsequent diurnal convection, narrowing down possible areas of more concentrated risk stemming from afternoon storms.

With that said, the overall environment will feature a moist/destabilizing warm-sector airmass, and with the belt of enhanced flow aloft collocated with the favorable thermodynamics, strong/locally severe storms will result. While flow across the Plains will exhibit at least some west-of-south orientation across much of the area, little veering with height is expected, which should limit tornado potential across much of the region, with large hail and locally damaging winds the main risks. Exceptions would be near any possible remnant convective circulations, and also over the upper Midwest region (parts of the Iowa/southern Wisconsin/northern Illinois vicinity) near the weak warm front. Resulting, more favorable low-level directional shear suggests slightly greater risk for a couple of tornadoes across these areas. After reaching a diurnal peak, a slow decrease in convective coverage and intensity is expected into the evening. Storms may maintain intensity longer over the upper Midwest/southern Upper Great Lakes area, where a 50-plus kt southwesterly low-level jet is expected to evolve.

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There could be lingering showers in the morning for eastern areas, but renewed shower/thunderstorm development is expected south of I80 Friday afternoon through Friday night, with rain chances across the entire area Saturday as another weak front settles southward into the region. It`s at that point that we`ll have to monitor for day-to-day rainfall south of I-80, and may eventually become concerned with saturated soils. Heaviest rains appear to continue to set up across KS/MO just south, but a few counties in southwest IA and extreme southeast NE could be at risk for flooding as well. Highs both Friday and Saturday in the upper 70's to lower 80's, above normal.

Friday
Richer low-level moisture with mid-upper 60's F dewpoints will advect northeast through the mid-upper MS Valley warm sector during the day, and this should contribute to a corridor of moderate instability (1500-2000 J/kg MLCAPE) as the boundary layer warms.

Some storms may be ongoing on cool side of the warm front as well as farther west across KS in vicinity of the cold front. The cold frontal storms should diminish early in the day, but additional storms will probably develop along the cold front or residual outflow boundaries as the atmosphere destabilizes during the afternoon. Flow in the lowest 3 km is forecast to weaken and the strongest mid-upper winds will likely remain north of the warm sector which could be limiting factors for a more robust severe threat. Nevertheless, winds aloft will be sufficient for 45-55 kt largely unidirectional effective bulk shear.

Where boundary layer destabilization occurs, the parameter space should promote some risk for strong to severe storms with large hail and damaging wind the main threats. A conditional risk for tornadoes will exist especially if boundary layer recovery can occur in IA and northern IL where low-level hodographs will be more supportive along and just south of the warm front.

Saturday
​ Current indications are that a surface front will stall from southern WI southwest into southeast NE and western KS with a dryline extending farther south through west TX. Rich low-level moisture with dewpoints in the mid-upper 60's F will reside south and east of these boundaries contributing to potential for moderate to strong instability. Weak impulses embedded within a broad fetch of moderate southwest winds aloft combined with dryline and frontal convergence will contribute to potential for thunderstorm initiation as the boundary layer destabilizes during the afternoon.

Vertical wind profiles will be sufficient for organized storms including supercells, but activity may eventually grow upscale as it progresses east during the overnight. Large hail, damaging wind and a few tornadoes will be possible.

Monday
Day 5 (Monday) Thunderstorms associated with the lead impulse will continue through the upper MS Valley region early. Destabilization is expected upstream, and storms may redevelop along a southward-advancing cold front across the central Plains and possibly some distance southward along the dryline. Have introduced a risk area for the area of most likely redevelopment from near the triple point across western KS, northeast along the sharpening cold front.

Temperatures

Friday Sunday

Saturday Monday

Precipitation through 8 am Sunday