U.S. Severe Weather Forecast (Convective Outlook)

نن، نن ورځ: نن، نن سبا
سبا: سبا، ګانده: راتلونكى وخت
Day Three

acus01 kwns 220036 
Storm Prediction Center ac 220035 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0635 PM CST Tue Nov 21 2017 

Valid 220100z - 221200z 

..no severe thunderstorm areas forecast... 

the risk for severe thunderstorms appears negligible across the U.S. 
Through tonight. 

..01z outlook update... 
The remnants of one short wave impulse within the southern branch of 
split mid-latitude westerlies appears likely to accelerate 
northeastward in the vicinity of the southern through middle 
Atlantic coast overnight, as a much more prominent upstream northern 
branch impulse pivots through the Ohio Valley. Associated forcing 
for ascent is expected to continue to support weak instability and 
scattered thunderstorm development near a frontal zone along/east of 
coastal areas. Ongoing thunderstorms near Jacksonville are expected 
to gradually shift offshore through the 02-04z time frame, with the 
bulk of continuing or new thunderstorm development probably 
remaining offshore. However, weak thunderstorms based within 
lower/mid tropospheric warm advection still appear possible inland 
of the North Carolina coastal plain after 06z. 

Elsewhere, guidance remains suggestive that another southern stream 
impulse, currently digging across Texas, could support weak 
thunderstorm development near and south/southeast of middle Texas 
coastal areas as early as the 03-06z time frame. It appears that 
the tendency will be for this activity, and any lingering 
thunderstorm activity near Louisiana coastal areas, to then spread 
southeastward with the forcing for ascent through the northwestern 
Gulf of Mexico. 

.Kerr.. 11/22/2017 


Mesoscale Discussion

acus11 kwns 182324 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 182324 

Mesoscale discussion 1773 
National Weather Service Storm Prediction Center Norman OK 
0524 PM CST Sat Nov 18 2017 

Areas affected...portions of Tennessee and northern Alabama 

Concerning...Severe Thunderstorm Watch 517... 

Valid 182324z - 190130z 

The severe weather threat for Severe Thunderstorm Watch 517 

Summary...a squall line will continue east within and near watch 517 
this evening, with an attendant threat of a few damaging gusts and 
perhaps a tornado. The line should gradually weaken with eastward 
extent this evening, such that downstream watch issuance is not 
currently anticipated. 

Discussion...a nearly continuous line of thunderstorms is advancing 
across Tennessee and northern Alabama early this evening. Over the 
last hour, there was a localized uptick in tornado potential 
south/east of the Nashville area, with three distinct tornadic 
debris signatures in Rutherford, Wilson, and Trousdale counties. 
While cells will continue to outpace remaining low-level buoyancy, 
impressive low-level shear may still yield a quick tornado across 
middle Tennessee over the next hour. Otherwise, an isolated damaging 
wind threat will likely persist through the 01z expiration time of 
watch 517. 

Farther south, convection has at times consolidated into a few 
stronger segments over northern Alabama. Local observations have yet 
to indicate severe wind gusts, but considering the strength of 
low-level flow and presence of weak mixed-layer cape, isolated 
damage will remain possible for the next couple hours, before 
surface-based buoyancy is shunted farther south. 

.Picca.. 11/18/2017 

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


Latitude...Lon 34048819 36588602 36588440 36278421 34978545 34268621 
33988719 33918800 34048819