U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 181242 
Storm Prediction Center ac 181240 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0740 am CDT Mon Jun 18 2018 

Valid 181300z - 191200z 

..there is a slight risk of severe thunderstorms over the northeast 
states...and parts of Iowa...Nebraska...Colorado... 

Severe thunderstorms will be possible this afternoon and evening 
across parts of the northeast, Central Plains, and northeast 

A band of relatively fast mid-level winds extends across the Great 
Lakes region and into the northeast states this morning. A surface 
cold front will sweep southeastward across the northeast US this 
afternoon and evening, with multiple lines/clusters of thunderstorms 
expected along and ahead of the front. Early visible satellite 
imagery over this region shows the potential for substantial daytime 
heating, with afternoon highs well into the 80s or even lower 90s f. 
This will yield steep low level lapse rates and MLCAPE values over 
1000 j/kg. While storm Mode and low/mid level winds appear 
favorable for a more organized severe wind event, poor mid-level 
lapse rates appear to be a limiting factor. Storms should spread 
across much of New England through mid-evening and eventually move 
offshore and weaken after dark. 

Uncertainty exists regarding the western extent of more substantial 
severe potential. Have extended the slight risk area into western NY, 
but parts of lower Michigan and Ohio/PA will need to be monitored in later 
updates for the potential of greater storm coverage and a possible 

A significant shortwave trough over eastern Colorado is forecast to track 
northeastward and into NE today. Lift and enhanced wind fields 
ahead of this system will promote the development of scattered 
afternoon thunderstorms along a persistent surface boundary 
extending from eastern NE into Iowa. Strong heating and dewpoints in 
the 70s f south of the boundary will help yield ample cape. A few 
severe storms capable of hail and damaging winds are expected during 
the peak-heating hours. 

..northeast Colorado... 
A surface cold front has surged southward across northeast co, where 
temperatures have dropped into the mid 50s this morning. Overnight 
cam solutions are consistent in backing the surface winds over this 
region through the day, with a strengthening Denver cyclone by 
mid/late afternoon. It appears likely that one or more supercells 
will form in this region, tracking eastward across the slight risk 
area. Large hail appears to be the main threat. 

..central Wyoming... 
A strong upper trough is rotating across Utah and will affect Wyoming this 
afternoon. Scattered thunderstorms are expected to form across this 
region after 18z, lifting northward toward the Montana border. Forecast 
soundings suggest sufficient cape/shear for a few storms producing 

.Hart/Kerr.. 06/18/2018 


Mesoscale Discussion

acus11 kwns 180235 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 180235 

Mesoscale discussion 0778 
National Weather Service Storm Prediction Center Norman OK 
0935 PM CDT sun Jun 17 2018 

Areas affected...portions of northern and central Wisconsin 

Concerning...Severe Thunderstorm Watch 185... 

Valid 180235z - 180430z 

The severe weather threat for Severe Thunderstorm Watch 185 

Summary...while isolated risk for locally damaging winds and hail 
continues, the risk continues to diminish as storms gradually 

Discussion...the latest radar loop shows storms continuing to 
gradually diminish over most of the northern half of Wisconsin, with 
the strongest convection -- and accompanying/limited severe threat 
-- now approaching the Green Bay area. Some uptick in organization 
has also been noted with the band of convection moving across 
Northern Lake Michigan, but expect downstream risk to remain minimal 
given the stabilizing boundary layer observed over northern lower 

Given present trends, it appears that cancellation of ww 185 may be 
possible prior to its scheduled 18/05z expiration. Until then, 
local risk for a damaging wind gust or marginal hailstone continues 
-- mainly with the small cluster of storms approaching Green Bay. 

.Goss.. 06/18/2018 

..please see www.Spc.NOAA.Gov for graphic product... 


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44818949 45108823 45278751