U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 140532 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1232 am CDT Tue Aug 14 2018 

Valid 141200z - 151200z 

..there is a marginal risk of severe thunderstorms across parts of 
Wyoming...southeast Montana...far western South Dakota and far 
western Nebraska... 

Marginally severe thunderstorms will be possible late this afternoon 
and early this evening across parts of Wyoming, southeast Montana, 
far western South Dakota and far western Nebraska. 

..central and northern rockies/central and northern High Plains... 
A shortwave trough will move eastward across the central and 
northern rockies today. At the surface, upslope flow will be in 
place across much of the central and northern High Plains. In 
response, a narrow corridor of maximized low-level moisture is 
forecast to extend from western Nebraska into eastern Wyoming where 
surface dewpoints should be in the lower to mid 50s f. As surface 
heating takes place today, MLCAPE values are forecast to reach the 
1000 to 1500 j/kg range along the moist corridor. Convection should 
initiate in the higher terrain during the afternoon with 
thunderstorms moving eastward into the lower elevations late this 
afternoon into early this evening. Rap forecast soundings at 
Sheridan and Casper at 00z/Wednesday show 0-6 km shear in the 40 to 
50 kt range with 0-3 km lapse rates approaching 9.0 c/km. This 
should be enough for an isolated severe threat. Marginally severe 
wind gusts will be possible with the stronger cells. Steep lapse 
rates in the mid-levels will also support a threat for hail. 

.Broyles/Wendt.. 08/14/2018 


Mesoscale Discussion

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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 132243 

Mesoscale discussion 1284 
National Weather Service Storm Prediction Center Norman OK 
0543 PM CDT Mon Aug 13 2018 

Areas affected...parts of northeastern New Mexico 

Concerning...severe potential...watch unlikely 

Valid 132243z - 140015z 

Probability of watch issuance...5 percent 

Summary...isolated storms may be capable of brief, marginally severe 
hail and strong, gusty winds through this evening. Watch issuance is 
not anticipated. 

Discussion...ascent on the fringe of a mid-level vorticity Max has 
combined with terrain-induced circulations to produce isolated 
storms over northeast New Mexico late this afternoon. Although 
surface dew points are relatively low (in the 40s to lower 50s), 
mid-level cooling/saturation has yielded adequate elevated buoyancy 
for a couple stronger cells. As they move south, a storm or two may 
acquire transient mid-level rotation, owing to modest deep-layer 
shear provided by 20-30 kt of northerly 500mb flow. Any such cell 
will be capable of isolated hail. A few stronger gusts may be 
possible as well, given the deep/well mixed boundary layer 
environment. Despite this potential, a lack of greater coverage and 
organization is expected to preclude watch issuance. 

.Picca/grams.. 08/13/2018 

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


Latitude...Lon 34160483 34430546 34790580 35230587 35650566 36540535 
36910367 36220320 34860321 34250367 34160483