U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 180533 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1233 am CDT Wed Sep 18 2019 

Valid 191200z - 201200z 

..there is a marginal risk of severe thunderstorms over the 
northern High Plains... 

At least isolated storms producing large hail are possible Thursday 
evening and overnight across the northern High Plains. 

An upper trough will swing east across the Great Basin, with 
increasingly meridional upper-level winds into Wyoming and Montana. Ahead of 
this trough, height rises will occur over the northern plains, upper 
MS valley, and Great Lakes with the upper high centered over the 
central Gulf Coast states. High pressure will remain at the surface 
over much of the east as low pressure develops over the northern 
High Plains. This will maintain southerly winds across the plains 
with a warm front lifting north across the Dakotas. The moistening 
air mass along with cool temperatures aloft will result in moderate 
destabilization over the northern plains, and will support scattered 
strong storms mainly late in the day and overnight from eastern Montana 
into ND. 

Elsewhere, the remnants of tc Imelda will bring heavy rain to parts 
of East Texas as it drifts north, with warm temperatures aloft 
minimizing instability. 

..eastern Montana/Wyoming into the western Dakotas... 
As low pressure deepens over Wyoming and Mt, southeast winds will 
increase across the northern plains, with 30 kt southeast flow at 
850 mb by late afternoon. This will allow for moistening, but most 
of the area will remain capped through the day. Steeper low level 
lapse rates will exist over Wyoming and eastern Mt, and into far western 
South Dakota and NE closer to the surface trough. At least isolated late-day 
storms are expected in this zone, with increasing storm coverage 
through the evening due to warm advection with the low-level jet. 
Cool temperatures aloft and marginal deep-layer shear will favor a 
few cells capable of large hail. Winds aloft decrease with eastern 
extent, but cool temperatures aloft and a persistent low-level jet 
will likely support elevated hail into parts of ND overnight. 

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

.Jewell.. 09/18/2019