Valid 261200Z – 271200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
…SUMMARY…
The threat for organized severe storms is expected to remain low
today
…Synopsis…
A shortwave trough that will be traversing the Great Lakes region at
the start of the period will move eastward into New England by later
tonight, as an upstream shortwave moves into the northern Plains
this afternoon/evening. The persistent upper low over the Southwest
is forecast to gradually weaken and evolve into more of an open
wave, as it begins to progress eastward later in the period. At the
surface, a cold front draped across the southern Plains/Ozarks this
morning will move northward as warm front this afternoon/evening, in
response to a deepening cyclone over the southern Canadian Prairies.
..Southern Plains through middle Mississippi Valley region…
Thunderstorms are likely to be ongoing across portions of eastern OK
into western AR at the start of the period this morning, though this
activity is expected to generally be subsevere. Redevelopment along
the northward-moving warm front and any remaining outflow boundaries
cannot be entirely ruled out this afternoon, but negligible
large-scale ascent should tend to limit thunderstorm coverage during
peak heating/instability. MLCAPE of 1500-2500 J/kg would support a
conditional risk of downbursts and/or marginally severe hail from
northwest TX into portions of OK this afternoon/evening, but the
unconditional risk appears too low to justify any severe
probabilities.
Late tonight, a strong low-level jet will become focused into the
mid-Mississippi Valley region, aiding in the development of
scattered elevated thunderstorms across portions of IA/northern
MO/western IL. Moderate MUCAPE and effective shear of 20-30 kt will
support the potential for a few strong thunderstorms by early Friday
morning. Some marginal hail threat cannot be ruled out with this
activity, though confidence is too low at this time to add any
probabilities.
…Southwest…
Buoyancy/shear are forecast to be somewhat diminished compared to
previous days across southeast CA into AZ, as the upper low
continues to gradually weaken. In areas where some diabatic
heating/destabilization can occur, a few strong storms capable of
producing gusty outflow winds will be possible, but the overall
severe risk is expected to remain rather low.
..Dean/Cook.. 09/26/2019
$$