U.S. Severe Weather Forecast (Convective Outlook)

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

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acus01 kwns 230536 
swody1 
Storm Prediction Center ac 230535 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1235 am CDT sun Apr 23 2017 


Valid 231200z - 241200z 


..there is a marginal risk of severe thunderstorms across much of 
the southeast... 


... 
Scattered thunderstorms will develop across much of the southeast 
Sunday. A few storms will produce gusty winds and hail. Severe 
threat may increase across eastern Georgia into South Carolina after 
dark where one or two tornadoes could be observed. 


... 


00z short-range model guidance is in good agreement regarding the 
evolution of upper low as it progresses across the mid-south into Georgia 
by sunrise Monday morning. Large-scale 12hr mid-level height falls 
on the order of 90m will develop ahead of this feature as 70kt 500mb 
speed Max digs toward the Florida Panhandle by 24/12z. Associated 
surface front is expected to extend from northwest Georgia into the Florida 
Panhandle at 18z...then advance into eastern Georgia during the overnight 
hours. 


Scattered thunderstorms may be ongoing along the frontal zone early 
in the period across Alabama as high-level diffluent flow remains 
supportive of deep convection. However, strongest mid-level flow is 
expected to lag the wind shift and forecast soundings do not exhibit 
particularly strong shear or buoyancy early in the period. While a 
few storms may produce gusty winds or even marginally severe hail 
during the morning hours it appears the most robust convection 
should occur later in the afternoon, or during the overnight hours 
when low level jet increases across SC. 


Have opted to maintain marginal threat for severe thunderstorms, both 
for diurnally driven frontal convection during the day and for 
overnight activity driven by low-level warm advection. Forecast 
soundings are not particularly unstable ahead of the front across 
Georgia/northern Florida during the day but deep southwesterly flow with 
surface-6km bulk shear on the order of 35-40kt could support 
organized storms. Of more concern is the convection that will 
evolve after dark across eastern GA/SC. Low level jet will increase markedly 
after 00z and shear profiles become more supportive of organized 
rotating updrafts. If sufficient buoyancy can evolve across this 
region severe probabilities will need to be adjusted to account for 
overnight supercells capable of producing hail/damaging winds and 
even tornadoes. Later outlooks will address this threat and adjust 
accordingly. 


.Darrow/leitman.. 04/23/2017 


$$ 

Mesoscale Discussion


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acus11 kwns 222341 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 222340 
ncz000-gaz000-tnz000-alz000-msz000-230045- 


Mesoscale discussion 0549 
National Weather Service Storm Prediction Center Norman OK 
0640 PM CDT Sat Apr 22 2017 


Areas affected...extreme southwest Tennessee /western NC...northwest 
Georgia...portions of central into northeast Alabama 


Concerning...Severe Thunderstorm Watch 158... 


Valid 222340z - 230045z 


The severe weather threat for Severe Thunderstorm Watch 158 
continues. 


Summary...a general weakening trend is expected heading into the 
evening hours. A few strong/marginally severe storms may persist 
another 1-2 hours, producing strong wind gusts and perhaps small 
hail. However, threat will diminish with time and eastward extent 
and a downstream watch is not expected. 


Discussion...scattered strong to severe thunderstorms along a line 
from far western NC/southwest Tennessee through central Alabama into southern MS 
will continue to track east this evening. In general, recent 
weakening trend should continue with loss of daytime heating and a 
stabilizing boundary layer. Modest midlevel lapse rates and adequate 
deep layer shear should sustain storms into the evening, and in the 
short term /next 1-2 hours/ some strong gusts and small hail will be 
possible. Given the marginal nature of the threat downstream of ww 
158 and overall weakening trend, a downstream watch is not expected, 
and ww 158 likely will be able to be canceled before the 02z 
expiration time. 


.Leitman.. 04/22/2017 


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


Attention...WFO...gsp...mrx...ffc...bmx...hun...mob...Jan... 


Latitude...Lon 32238702 32038744 32008793 32128832 32668837 33378757 
34448630 35258490 35408431 35328391 35088375 34848384 
34298447 33978487 33048597 32238702