U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 191631 
Storm Prediction Center ac 191630 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1130 am CDT Thu Apr 19 2018 

Valid 191630z - 201200z 

..there is a marginal risk of severe thunderstorms across portions 
of New Mexico and far West Texas... 

Isolated severe thunderstorms may impact parts of central and 
southern New Mexico and far West Texas late this afternoon and 
evening with a risk for downburst winds and hail. 

..New Mexico and far West Texas... 
A southern-stream upper low will continue eastward over the southern 
Great Basin and lower Colorado River valley toward The Four Corners 
vicinity by early Friday, with downstream height falls occurring as 
far east as the southern High Plains. The main limitation for 
today's severe risk will be meager low-level moisture, although 
moisture will gradually increase and somewhat higher moisture 
content will be focused along the interior mountains and higher 
terrain of New Mexico. 

At least isolated thunderstorms should develop this afternoon into 
evening mainly along/just east of the mountains of interior New 
Mexico and far West Texas. Where storms do occur, steep lapse rates 
and weak buoyancy might support some hail, while a relatively 
deep/well-mixed boundary layer could yield severe-caliber wind gusts 
this afternoon into evening. 

.Guyer/Kerr.. 04/19/2018 


Mesoscale Discussion

acus11 kwns 181457 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 181456 

Mesoscale discussion 0277 
National Weather Service Storm Prediction Center Norman OK 
0956 am CDT Wed Apr 18 2018 

Areas affected...portions of northern and northeast Iowa 

Concerning...heavy snow 

Valid 181456z - 181800z 

Summary...heavy snowfall rates ranging from 1 to 1.5 inches per hour 
are expected through midday. 

Discussion...water-vapor imagery this morning shows an eastward 
migrating shortwave trough over Iowa while the left exit region of a 
100-kt 300mb jet is placed over eastern Iowa. Strong DCVA (170m 12 
hour height fall per Omaha, NE 12z radiosonde observation data) coupled with low- to 
mid-level frontogenesis is resulting a west-east corridor of snow 
from Sioux Falls to the MS river. Weak convection as evidenced by 
lightning is moving east on the leading edge of stronger ascent 
located within the warm conveyer. 

Model forecast soundings show weak buoyancy co-located with a 
dendritic growth layer for a few hours this morning. Expecting the 
heavy snowfall rates to continue through midday across northern and 
northeast Iowa before gradually diminishing this afternoon. Although 
the precipitation shield will spread east into southern WI, models 
suggest a gradual reduction in the spatiotemporal character of the 
heavy snowfall rates as this area moves east into WI. 

.Smith.. 04/18/2018 

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


Latitude...Lon 43649405 43619142 43449111 43159119 43059146 43169388 
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