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Area Forecast Discussion (AFD)

Issued by Kansas City/Pleasant Hill, MO (EAX)

FXUS63 KEAX 182310

National Weather Service Kansas City/Pleasant Hill MO
610 PM CDT Sat May 18 2019

Issued at 359 PM CDT SAT MAY 18 2019

An outflow boundary moved into the area from the NW overnight and 
stalled along out southern area from Sedalia to Linn Co KS. This 
created a large cold pool from that up through northern Missouri as 
isentropic accent from the morning LLJ allowed continual shower and 
storm development on the cold side. This feature change the entire 
set up for severe weather early on and changed this system from a 
potential scattered severe event to a heavy rain event with possible 
flooding going into this evening. The boundary stalled in a SW-NE 
orientation out in central Missouri near Moberly setting up a 
training storm pattern and dropped around a 1.5 to 2" swath of 
precip with some minor flooding. This area will need to be monitored 
with the main line going through currently as all rain will quickly 
become runoff. As the warm surge in eastern KS moved into our area 
earlier this afternoon it had just enough MLCAPE (1500 J/kg) to keep 
storms strong with some isolated severe winds near KMCI as a storm 
looks to have collapsed in that area. Typically this type of linear 
system can become a major wind threat, but this storm was formed 
more form a WAA process and convergence opposed to a cold frontal 
boundary surging eastward. Due to there being no real veering of the 
winds in the profile the 0-3km bulk shear vectors remained southerly 
which is not allowing the line to balance correctly for the line to 
get too aggressive. There may still be times when the overall 
shear and cold pool balance leading to some higher winds and 
possibility severe level winds as this features pushes through, 
but this will mainly be focused down along and south of that 
original outflow boundary. If surface winds shift to SE ahead of 
this boundary there may be enough surface vorticity along for some
mesocyclones to form along the line if there is a strong enough 
updraft. Very heavy rainfall moved through Johnson CO Kansas with 
the initial push of storms leading to 2-3" of rainfall in that 
area, this will need to be monitored with any new storm activity 
as soils are not saturated which could lead to flash flooding. 
There are a couple more rounds of possible convection as the 
shortwave pushes through late tonight then again overnight with 
the cold front so this will be the main area of focus for flash 
flooding with those events. This system will push out quickly on 
Sunday leading to a nice Sunday afternoon through Monday with 
below average temperatures in place. 

Looking into Tuesday I had to double check the date because the 
synoptic setup in every model was completely different than they 
were showing yesterday. Yesterday it was looking like a potential 
major flood pattern with a west to east warm front that move through 
the area. Today the warm front is quite a bit further north with 
it only clipping NW Missouri late Monday into Tuesday morning, 
which is a good placement as that area has received the least 
amount of precip from today's event. This boundary quickly goes 
north leaving our area into the warm sector of the system and 
changes the threat from flooding to a potential severe weather 
threat with wind being the main issue. The timing of the cold 
frontal passage will be the main deciding factor on how much 
MLCAPE can develop Tuesday afternoon with heating. The NAM seems 
to be the fastest model brining the front through before we can 
really establish much instability. MLCAPE of 1000-1500 J/kg will 
still be enough with strong 0-6km shear of 50-60kts of shear with 
0-3km bulk shear vectors more SW oriented and 35-40kts. Strong 
environmental winds of 40-50kts will mix down quickly with frontal
passage, so any added cold pool like surge could result severe 
level winds along that likely QLCS assuming the models keep this 
new trend. This system clears out quickly leaving a nice day in 
place for Wednesday.

A shortwave will push through Thursday along a frontal boundary that 
looks to stall over the area. This boundary will become the next 
active weather trigger through the end of the week into the weekend 
as a cutoff like low over the Rockies will continually send 
shortwaves over this boundary keeping us rather wet for 3-4 days. 


.Aviation...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 605 PM CDT SAT MAY 18 2019

Overall dry conditions are expected through the early evening 
hours before the next round of storms and rain showers approaches 
the terminals tonight. MVFR conditions are expected during that 
time, along with brief gusty winds within stronger storms. Should 
see an eventual return to VFR conditions as precip clears to the 
east around 09Z, though MVFR ceiling heights could linger longer 
than currently anticipated. Gusty northwesterly winds are expected
in the wake of activity beginning Sunday morning and into the 
afternoon hours.