U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Day Three

acus01 kwns 260518 
Storm Prediction Center ac 260516 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1216 am CDT Tuesday Jul 26 2016 

Valid 261200z - 271200z 

..there is a slight risk of severe thunderstorms across parts of South Dakota and 

..there is a marginal risk of severe thunderstorms across parts of the northern 
and Central Plains... 

..there is a marginal risk of severe thunderstorms from Kentucky into the middle 

The greatest potential for severe thunderstorms on Tuesday will be 
across portions of South Dakota and Nebraska during the afternoon 
and evening. More isolated severe thunderstorms will be possible on 
Tuesday elsewhere across portions of the northern and central Great 
Plains eastward to Upper Michigan...and across parts of the 
middle-Atlantic and central Appalachians. 

Very moist air mass will encompass much of the eastern Continental U.S. Tuesday and 
scattered thunderstorms will be common during the afternoon and early 
evening from The Rockies...east to the middle Atlantic coast. There 
are two main areas where robust thunderstorms may produce a severe 
threat...the northern/Central Plains and the middle Atlantic and central 

1. Northern and Central Plains. Several weak middle-level 
disturbances will progress across the northern rockies into the plains 
during the upcoming day1 period. These features will ensure the 
ridge remains flat across Montana/Wyoming into the Dakotas. WV imagery 
depicts one well defined disturbance over scntrl Montana at 26/05z. This 
feature should drift toward the northern Black Hills region by late 
afternoon enhancing thunderstorm activity by peak heating. Convection is 
expected to initiate over both the Black Hills and along adjacent 
east-west surface boundary...just north of Lee surface low. This activity should 
mature within a modestly unstable air mass characterized by SBCAPE 
on the order of 3000 j/kg and surface-6km bulk shear...more than 
adequate for organized rotating updrafts. Current thinking is 
initial activity may be supercellular in nature but storm mergers 
during the low level jet intensification phase after dark may result in an 
mesoscale convective system-type complex propagating southeastward toward central Nebraska. Hail and 
wind are the main threats. 

2. Middle Atlantic and central Appalachians. 20kt 500mb westerly flow 
is expected to persist at the latitude of the marginal risk from 
Kentucky...eastward across Virginia Tuesday. Strong boundary-layer heating will 
contribute to destabilization sufficient for thunderstorm development by 18z 
across this region as surface temperatures soar into the lower 90s. Any 
updrafts that form within this high precipitable water air mass...on the order of 2 
inches...could certainly produce gusty downbursts...potentially 
reaching severe levels at a local level. Convection will be 
strongly diurnal and should weaken with loss of daytime heating. 

.Darrow/leitman.. 07/26/2016 


Mesoscale Discussion

acus11 kwns 252307 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 252306 

Mesoscale discussion 1399 
National Weather Service Storm Prediction Center Norman OK 
0606 PM CDT Monday Jul 25 2016 

Areas affected...portions of eastern WV...northern Virginia...Maryland and Delaware 

Concerning...Severe Thunderstorm Watch 416... 

Valid 252306z - 260030z 

The severe weather threat for Severe Thunderstorm Watch 416 

Summary...strong to severe wind gusts will continue to be possible 
across eastern portions of ww 416 the next few hours. Further west 
into WV and portions of northern Virginia...the severe threat appears to be 
diminishing quickly. 

Discussion...strong to severe thunderstorms across southern PA and New Jersey 
will continue to track S/southeast this evening. Strong instability and 
favorable deep layer shear is expected to maintain these storms as 
they track across eastern portions of ww 416. Some boundary layer 
stabilization is occurring with loss of daytime heating...but some 
strong to severe wind gusts will still be possible until storms move 
offshore. Further west across parts of WV and northern Virginia toward the 
mountains...conditions appear less favorable for any new development 
and ongoing storms have weakened over the last hour. Expect the 
severe threat to diminish quickly across these western portions of 
ww 416. 

.Leitman.. 07/25/2016 

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


Latitude...Lon 39707913 39677768 39487451 38217459 38377922 39707913