Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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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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