Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Wed May 04 2022
Valid 071200Z - 121200Z
...DISCUSSION...
...Saturday/Day 4 to Monday/Day 6...
A low amplitude progressive upper-level trough is forecast to move
across the western U.S. on Saturday, as moisture advection takes
place across the Great Plains. By afternoon, an axis of moderate
instability is forecast across the southern and central Plains.
Thunderstorms will likely develop at the northern end of the
instability corridor across the Dakotas and Nebraska. The best
combination of instability and shear is currently forecast over
Nebraska, where a severe threat would develop near the exit region
of a broad mid-level jet. Large hail and wind damage would be the
primary threats. A 15 percent contour is added across parts of the
central Plains for Saturday afternoon and evening.
On Sunday, the models maintain southwesterly mid-level flow across
the central U.S. and continue moisture advection across eastern
parts of the Great Plains into the Ozarks and Arklatex. The northern
end of this unstable airmass is forecast across eastern parts of the
central Plains into the lower Missouri Valley. Even though forcing
could be minimal, thunderstorms would develop in areas where
low-level convergence becomes locally maximized. Strong deep-layer
shear should exist along the instability axis creating favorable
conditions for severe storms. Any severe threat would remain
isolated, but a 15 percent contour seems warranted due to the
forecast quality of low-level moisture and instability.
For Monday, southwest mid-level flow is likely across the
north-central states. This will enable low-level moisture advection
to continue across eastern parts of the Great Plains and over the
western Mississippi Valley. Surface dewpoints could reach the 70s
across parts of the Upper Midwest. Thunderstorm development would be
possible Monday afternoon along an axis of moderate to strong
instability from the mid Missouri Valley northward into the upper
Mississippi Valley. Again, considering the quality of low-level
moisture, a 15 percent contour seems warranted, in spite of the
uncertainties.
...Tuesday/Day 7 and Wednesday/Day 8...
On Tuesday and Wednesday, model forecasts develop a belt of strong
southwest mid-level flow across the western and northern states. A
moist and unstable airmass is forecast to remain over the eastern
Great Plains and western Mississippi Valley. Mid-level flow is
forecast to become more meridional on Wednesday as an upper-level
low develops across the southwestern U.S. As a result, the stronger
flow is forecast to shift westward into the High Plains. Although
thunderstorms may develop along the corridor of low-level moisture
further to the east, uncertainty is substantial concerning the
magnitude of deep-layer shear that will be in place. Also, a lack of
large-scale ascent will be problematic. These factors are too great
to warrant adding a severe threat area at this time.
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