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

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348
FXUS63 KEAX 121717
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1217 PM CDT Sat Aug 12 2017

.Discussion...
Issued at 340 AM CDT SAT AUG 12 2017

High pressure over the Great Lakes extends surface ridging over our
area today resulting in a very nice Saturday.  Winds will be light
out of the NE-SE with temperatures in the upper 70s to lower 80s.
This ridge appears to hold off a developing shortwave over the
northern plains leaving most of the area with fair weather once
again this weekend. A shortwave over Oklahoma will slide just
under this surface ridge allowing the possibility of some shower
and thunderstorms to develop along the KS/MO border in the SW
portion of the CWA. These storms will be mainly diurnally driven
and are not expected to be severe if they do develop.

Monday the upper level shortwave over the northern plains will shift
to the SE and start a series of active weather for the region. A N-S
convergent boundary will form along this shortwave from TX up through
MN providing the forcing for scattered thunderstorms.  This feature
will track to the east and finally move into our CWA Sunday night
into Monday morning, mainly effecting NW Missouri with elevated
convection. Some showers will remain over the area Monday afternoon
but weak upper level ridging ahead of a more pronounced shortwave
over the West Coast will keep most of Tuesday relatively
precipitation free until after sunset.  An elongated area of lower
pressure will develop over the Plains with a pronounced LLJ forming
from TX up into Canada Tuesday night into Wednesday.  The southern
finger of the LLJ will help develop nocturnal convection over
eastern KS and western MO.  MUCAPE values near 3000J/kg and bulk
shear values between 30-35kts indicate that severe weather may be
possible with this first wave of convection. This strong southerly
flow will also bring humidity back to the region with dewpoints
rising above 70 degrees Wednesday. The rise in dewpoints will bring
with it heat index values in the mid to upper 90s for the first time
in a while. This added moisture and unstable airmass will also lead
to possible strong to severe storms Wednesday afternoon across the
region as this boundary pushes through. Model skew-t data does
indicate a possible capping inversion but does show some erosion of
as the boundary pushes through so it will be something to monitor as
the forecast gets closer.

This boundary will push east on Thursday with some remnant storms
remaining through the early morning only to clear out by the
afternoon. Weak ridging behind this feature looks to keep Friday
relatively PoP free with dewpoints dropping slightly to make it feel
a little less humid over the region.

&&

.Specifics for the Total Solar Eclipse on August 21st...
Issued at 601 AM CDT SAT AUG 12 2017

The latest runs of the GFS and Canadian indicate a more zonal pattern
over the region going into the weekend prior to the eclipse with a
shortwave pushing into the area Sunday evening. Both models indicate
a LLJ developing over KS Sunday night with nocturnal convection over
the KS/MO border region reaching into Missouri the morning of the
Eclipse. The zonal patterns does appear to push this cloud
coverage and precipitation rather quickly to the east, but any
shift west in this pattern would result in possible cloudy
conditions over most of northern Missouri. Looking at the GEFS
ensemble for that timeframe the spaghetti plots for 500mb indicate
a fairly strong signal for a zonal pattern over our region with
Missouri being on the more active downstream side of this feature.
Some hope for the event still lies with the ECMWF solution which
develops a more meridional pattern and ridging over the northern
plains Sunday into Monday, keeping the area relatively clear of
precipitation and cloud cover for the event. With lack of full
model consensus there is still quite a bit of uncertainty as to
the actual cloud coverage during this event, but hopefully we will
start to narrow down a solution in the coming days.

&&

.Aviation...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1217 PM CDT SAT AUG 12 2017

VFR conditions will persist through the forecast period. Passing
cirrus will remain scattered in coverage, and the majority of
diurnal cu should remain to the south and east of the terminals.
Winds will remain a bit variable in direction but mainly out of
the E to ESE, at speeds less than 10 kts.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

Discussion...Barham
Aviation...Laflin
Eclipse...Barham



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