Outlook for Saturday, August 15

Note on Medium Range Outlooks

You are looking at an outlook that is part of the medium range forecast (the outlook for days 4-8). The most important thing to note is that
lack of a risk does not mean zero risk.
Generally speaking, confidence has to be pretty high for the Storm Prediction Center to have an outlook area this far into the future.

If you bookmark this page, it will continue to update with each new outlook that is issued.


Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0305 AM CDT Sat Aug 08 2020

Valid 111200Z – 161200Z


Tuesday/Day 4 and Wednesday/Day 5

The medium-range models including the ECMWF, GFS, UKMET and Canadian move a low-amplitude upper-level ridge across the northern high Plains on Tuesday. The models suggest that severe thunderstorms will be possible ahead of the ridge in parts of the eastern Dakotas and Minnesota Tuesday afternoon and evening. However, the upper-level ridge and lack of large-scale ascent could limit convective coverage.

On Wednesday, the models move the upper-level ridge eastward across the northern Plains and maintain a corridor of moderate to strong instability in the eastern Dakotas. Thunderstorm development may again be isolated Wednesday afternoon and evening but if convection can initiate along the instability corridor, a localized severe threat will be possible.

Thursday/Day 6 to Saturday/Day 8

On Thursday, the models are in general agreement that an upper-level trough will move across the northwestern states as west-southwest mid-level flow becomes established in the northern Plains. Strong to severe thunderstorms will be possible Thursday afternoon and evening in parts of eastern North Dakota and northwestern Minnesota along the northwestern edge of a moist airmass. But convective coverage again is problematic due to uncertainties concerning the timing of the trough to the west.

The model solutions diverge on Friday and Saturday especially at mid-levels. The models are in a bit better agreement at low-levels with a moist and unstable airmass in eastern Nebraska and southeastern South Dakota. If this where to pan out, isolated thunderstorms would be possible along the instability axis both afternoons on Friday and Saturday.

Overall, predictability remains too low and forecast convective coverage appears too isolated throughout the Day 4 to 8 period for an outlook area.

..Broyles.. 08/08/2020


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