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FXUS63 KEAX 202322

National Weather Service Kansas City/Pleasant Hill MO
622 PM CDT Wed Sep 20 2017

Issued at 348 PM CDT WED SEP 20 2017

Another nice day across the Central Plains is setting the stage for 
some thunderstorms later this evening across parts of eastern Kansas 
and Missouri as a weak frontal boundary sweeps into northern 
Missouri and stalls out overnight.

Early afternoon satellite imagery shows a large trough, spread from 
the northwest Pacific Coast across the CONUS to the northern 
Plains. The leading trough, currently pivoting into Ontario, 
emanating from the larger parent trough back to the west will drag
a weak cold front into northern Missouri where it is projected to
stall tonight, allowing for thunderstorm development along it
overnight as the nocturnal jet develops. Most recent surface 
observations show the front beginning to nose into the far 
northwest corner of Missouri this afternoon, with it expected to 
stall out in the vicinity of I-35 in Northwest Missouri. However, 
while the front is on schedule to sag into Missouri this evening,
current development along the front in Iowa is struggling to get 
going; as evident from the radar returns and lack of vertical 
development noted on the visible satellite imagery. Storms are 
having a hard time overcoming the cap out there, which looks 
reasonable given that analysis of upper air soundings indicate 
temperatures above the front at 700mb are running around and above
10C, which can be considered a decent cap. That said, as the 
front moves into northern Missouri it will find plenty of 
instability to work with as MLCAPE values this afternoon are noted
above 3500 J/KG. However, shear values --even effective shear 
values-- are still looking disconnected from the instability as 
all the better dynamics from the upper level trough are well to 
the north. As a result, have slowed the onset of storms in our 
forecast area this evening and focused more of the activity in 
areas north of the Missouri River for the late night hours as the 
nocturnal jet gets going. The severe threat looks low tonight; 
though small hail and-or gusty winds may still be possible as 
storms collapse along with quick torrential rainfalls. 

Depending on the nature of tonight's storms, there might be some 
lingering activity into the post-sunrise hours of Thursday morning, 
but once beyond that it is looking like it will be hot and dry as
the large trough to the west keeps the southwest flow and 
southerly winds prevailing across the Central Plains through the 
weekend. As a result, expect highs well into the 80s, and maybe 
low 90s at times. Next chance for rain will likely hold off till 
early next work week --Monday or Tuesday-- as the western trough 
begins to shift into the Plains, forcing what looks to be an 
active storm track from the front range of the Rockies across the 
northern Plains into the Central Plains and upper Great Lakes 
region, at which point we will also likely see cooler temperatures


.Aviation...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 620 PM CDT WED SEP 20 2017

Probability for thunderstorms to reach KC terminal airspace 
continues to decrease, with most activity expected to remain just 
north of the city. Pulled MVFR conditions and prevailing 
thunderstorms out of forecast, and will monitor trends through the 
evening. Otherwise, with front stalling north of terminals, do not 
expect wind shift, with southerly winds becoming breezing during the 
mid-morning hours.



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