U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 270514 
Storm Prediction Center ac 270512 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1212 am CDT Fri Apr 27 2018 

Valid 271200z - 281200z 

..there is a marginal risk of severe thunderstorms across parts of 
the Pacific northwest and intermountain west... 

Isolated strong thunderstorms capable of downburst winds and hail 
may occur from parts of eastern Oregon into southwestern Idaho late 
this afternoon into the evening. 

..eastern Oregon/southwest Idaho/far northeast Nevada... 
An upper-level low will approach the Oregon coast today as a belt of 
stronger mid-level flow moves inland into the Pacific northwest. At 
the surface, a trough will deepen from northern Nevada into eastern 
Oregon and southeast Washington. Thunderstorms are expected to 
develop along the surface trough late this afternoon due to warming 
surface temperatures and increasing large-scale ascent associated 
with the approaching system. Forecast soundings during the early 
evening along the surface trough show MUCAPE values up to 500 j/kg 
with 700 to 500 mb lapse rates of 8.0 to 8.5 c/km. This combined 
with moderate deep-layer shear could be enough for a marginal severe 
threat. Hail and strong gusty winds will be the primary threats. 

.Broyles/Gleason.. 04/27/2018 


Mesoscale Discussion

acus11 kwns 261814 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 261813 

Mesoscale discussion 0290 
National Weather Service Storm Prediction Center Norman OK 
0113 PM CDT Thu Apr 26 2018 

Areas affected...southwestern into portions of central Georgia 

Concerning...severe potential...watch unlikely 

Valid 261813z - 261945z 

Probability of watch issuance...5 percent 

Summary...probabilities appear fairly low, but the evolution of an 
isolated severe storm or two may not be out of the question across 
parts of southwestern Georgia, perhaps as far north as the Macon 
area, through the 3-5 PM EDT time frame. 

Discussion...as a fairly vigorous short wave impulse maintains an 
eastward progression through portions of the central Gulf Coast 
states, a few thunderstorms have recently initiated across far 
southeastern Alabama into southwestern Georgia. This appears on the 
southernmost periphery of stronger mid-level forcing for ascent, 
where the latest rapid refresh suggests that a seasonably modest 
influx of boundary layer moisture off the Gulf of Mexico is 
supporting weak cape on the order of 500 j/kg. 

Generally south of the mid-level cold core of the system, forecast 
soundings indicate that capping mid/upper-level layers may remain 
problematic to sustained vigorous thunderstorm activity. However, a 
window of opportunity may still exist for an isolated intensifying 
storm or two across parts of southwestern into central Georgia 
through about the 20-21z time frame, before the mid-level wave 
begins to pivot northeastward toward the southern Appalachians. If 
this occurs, it will do so in a strongly sheared environment (near a 
50-60+ kt 500 jet) capable of supporting supercell structures and at 
least some severe weather potential before encountering a more 
stable low-level environment across central Georgia. 

.Kerr/Hart.. 04/26/2018 

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


Latitude...Lon 32438432 32608359 31338385 30858495 31258519 32438432