U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 250555 


Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1255 am CDT Fri may 25 2018 


Valid 261200z - 271200z 


..there is a marginal risk of severe thunderstorms across portions 
of Montana and the adjacent High Plains...as well as over portions 
of Florida... 


... 
Isolated severe storms are possible across Montana into the western 
Dakotas. A tornado or two may also occur with Gulf-low-associated 
convection over portions of the Florida Peninsula. 


... 
Gradual eastward progression of the upper pattern is progged for 
Saturday, as a closed low shifts across the Great Basin vicinity and 
a weaker trough moves slowly across the Great Lakes/Ohio Valley 
region. 


At the surface, a weak/remnant front is progged to extend westward 
from southern New England across the Midwest and into the northern 
plains, while a Lee trough persists over the High Plains. Finally, 
a low of tropical/sub-tropical origin is progged to shift northward 
across the central/eastern Gulf of Mexico. For additional 
information on this low, please see the latest tropical weather 
outlook from the NHC. 


..Montana vicinity into the northern High Plains... 
Despite rather modest moist advection across the northern High 
Plains and into Montana, steep mid-level lapse rates northeast of 
the upper low center in the vicinity of the Great Basin will support 
moderate afternoon destabilization across the Montana vicinity. 
Expect storms to develop across this region during the afternoon, 
within an environment of moderate/veering flow with height. The 
anticipated cape/shear combination should be sufficient to support a 
few stronger multicell clusters or even a couple of storms with 
mid-level updraft rotation -- and thus attendant/limited risk for 
locally damaging winds and hail remains apparent. 


As a southerly low-level jet develops across the High Plains during 
the evening, some potential for a cluster of storms to shift out of 
Montana and into the Dakotas is apparent, with limited risk for 
severe weather possibly accompanying any cluster of storms into the 
evening hours. 


..southern and western portions of Florida, and the Keys... 
While the track of the evolving low -- now centered near the Yucatan 
Peninsula -- remains variable per different forecast models, general 
consensus is that a slowly deepening low will drift north across the 
western/central Gulf of Mexico Saturday, with the low-level wind 
field gradually increasing across portions of Florida as a result. 
Most models suggest that by afternoon/evening, the low-level wind 
field surrounding the system will likely have increased sufficiently 
such that enhanced low-level updraft rotation will be possible. As 
such -- stronger cells evolving within bands of convection streaming 
northwestward may pose some risk for brief tornadic spin-ups as a 
result. Greatest risk at this time would appear to be over South 
Florida and then Keys, and then northward along a West-Coast 
sea-breeze boundary through the Tampa vicinity. Risk may continue 
through the overnight hours. 


..maximum risk by hazard... 
Tornado: 2% - marginal 
wind: 5% - marginal 
hail: 5% - marginal 


.Goss.. 05/25/2018 


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