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Area Forecast Discussion (AFD)

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

FXUS63 KEAX 211755

National Weather Service Kansas City/Pleasant Hill MO
1255 PM CDT Wed Aug 21 2019

Issued at 410 AM CDT WED AUG 21 2019

Satellite imagery shows a northwest flow developing across the 
northern and central Plains early this morning in response to a 
trough that is shifting into the northern Plains States, where it
will sweep across the Great Lakes in the coming days. And, it is 
this trough that will be primarily responsible for the nice 
weather (afternoon highs in the 70s to low 80s) expected to 
prevail for the tail end of the work week and the coming weekend 
as it sweeps a seasonally cool surface high sweeps into the 
region. But, first we will have to deal with a couple days of 
stormy weather.

Looking across the Plains, a lee side surface low has developed 
across the front range of the Rockies in response to the cool 
surface high the northern Plains trough is ushering into the 
States. This has resulted in a frontal boundary stretched from 
west central Kansas through southeast Nebraska into central Iowa 
early this morning, which a diffluent nocturnal jet has developed 
along, inducing strong warm air and moisture advection across 
northern Kansas and southern Nebraska, where precipitable water 
values of 2.1 inches has pooled. All this, in turn, has sparked a 
line of strong to severe thunderstorms across central Nebraska 
southeast into extreme northeast Kansas and far northwest 
Missouri, which will be of concern well into the morning, and will
perhaps set the stage for more storms later today. 

Storms in northeast Kansas and northwest Missouri will continue to 
percolate along through sunrise as the low level jet keeps feeding 
warm, moist air into the storms from the southwest. These storms 
will be rather strong, but pulsy, as there is lots of instability to 
work with (MUCAPE values > 4000 J/KG) but hardly any shear. This 
will make large hail and damaging winds possible with these morning 
storms, but will also bring a threat of flash flooding as the storms 
look to train over the same locations of northeast Kansas and 
northwest Missouri during the morning hours. There is some 
expectation that the storms will spread east across far northern 
Missouri this morning, which could lay out an effective boundary 
from the rain induced cold pool for the afternoon hours. Models key 
a bit on this cold pool as the shortwave trough swings through the 
northern Plains to generate more scattered storms through the 
afternoon hours. Confidence in the development of the afternoon 
storms is a bit low, but can not ruled out, so have kept likely 
POPs going for now. 

Tonight into Thursday the cool surface high across the northern 
Plains will slide farther south, and with it the frontal boundary 
along its leading edge. This will move the focus for storms south 
late this afternoon and through the overnight hours, with any late 
night storms likely being rather strong, as there will be plenty of 
instability aloft to work with.  Additionally, flash flooding may be 
a concern given that precipitable water values pooled along the 
boundary will be just over 2 inches. And, while we do expect the 
activity late tonight to slowly settle south, it will do so slowly 
enough to leave storms likely from eastern Kansas across central and 
southern Missouri into Thursday afternoon. 

Thursday on into the weekend...will see lovely temperatures in the 
70s to low 80s prevail as a cool surface high slides across the 
region. This will also move the focus for storms into Southern 
Missouri for Thursday and Friday nights. Can't rule out any more 
storms thanks to the nocturnal jet and abundant moisture in place 
across the Plains States, but for now much of the weekend looks dry 
across our section of Kansas and Missouri.


.Aviation...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1255 PM CDT WED AUG 21 2019

A cold front is working its way through the area and is currently
located just northwest of I-35. This will be the main focus for 
storm chances this afternoon and overnight. Isolated to scattered 
storms are expected to start developing this afternoon with
coverage gradually increasing to widespread for the overnight 
hours. Generally, the best chances for storms will be south of HWY
36 this afternoon and evening and then south of the MO River 
overnight as the front slowly moves south. Storms won't move out 
until late tomorrow morning. Winds will shift to the northwest as 
the front moves through then should shift to the northeast 
overnight as high pressure moves south and east across the 
Midwest. Ceilings and vis will likely drop to MVFR with storms 
overhead. Once storms start exiting the area, ceilings are 
expected to drop to low end MVFR and perhaps IFR along I-70 and 
south. Conditions should quickly improve in the late morning and 
early afternoon across the entire area as high pressure builds in 
from the north.