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

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FXUS63 KEAX 281152

652 AM CDT Sun Sep 28 2014

Issued at 417 AM CDT SUN SEP 28 2014

Today - Monday Night:

Today will be the last day that we`ll have to deal with the small
but pesky closed upper low that is now currently over western IA.
This feature has been trapped within a broad upper ridge
characterized by very light wind fields. A large upper low/trough
covering much of the far western states is expected to begin moving
east and out of the region. This will then force the IA low to track
southeast through the CWA. Individual vorticity maxima circulating
around the low will spin through the CWA today. Upward motion in the
eastern quad of the low will interact with modest moisture and
instability to generate isolated afternoon convection over the
eastern CWA. MLCAPES in excess of 1000 J/kg and moderately steep mid
level lapse rates may be sufficient for a few thunderstorms as well.
Don`t forget there have been cg strikes the past several days with
this feature.

A slight uptick in the 925mb and 850mb temperatures highly favor max
temperatures at or slightly above Saturday`s max readings.

Above normal temperatures will continue on Monday as a progressive
shortwave ridge migrates east through the Plains and Mid MO River
Valley. Don`t see any change in airmass so persistence is likely the
best route to take wrt temperatures.

Tuesday - Thursday Night:

This period is expected to be very active with a number of rounds of
convection associated with a wavy cold front that will translate
eastward across the Plains and eventually through MO. Medium range
models remain consistent and even a little faster than earlier
forecasts with the initial onset of precipitation. While the bulk of
Tuesday will be rain-free the far northwest portion of MO could see
some showers by late in the day. One more day of above normal
temperatures are likely before significant cooling takes place.

A large and broad upper trough is expected to evolve as a shortwave
trough dives southeast through the Pacific Northwest and ejects the
the Northern and Central Plains northward into south central Canada
by Wednesday. An associated cold front is expected to shit east and
initially stall just west of the CWA late Tuesday. Scattered
convection is possible near this boundary and could be close enough
to reach far northwest MO Tuesday afternoon. As falling heights
spread east through the Plains Tuesday night this front will likely
press further east. Rain chances will ramp up Tuesday night through
Thursday as gulf moisture is lifted northward and into MO. While
precipitable water values a tad above 1.5 inches is not too far
above normal there remains a risk for moderate to heavy rainfall due
to the longevity of the rains as well as the potential for some
training cells.

Much cooler temperatures will follow on Wednesday and Thursday.
First due to the extensive cloud cover and rain-cooled air and then
cold air advection with the passage of the cold front.

Friday - Saturday:

Model timing differences of the upper trough axis will dictate the
degree of cloudiness on Friday as well as the possibility of wrap
around light showers. The 00z GFS drops another shortwave trough
into the mean trough while the 00z ECMWF is progressive and does not
introduce this feature. However, both models do show a secondary
cold front that quickly drops southeast through the CWA on Friday so
high temperatures on this day of around 20 degrees colder than
Monday and Tuesday looks reasonable under either model solution.

Saturday is more questionable as far as temperatures are concerned.
The latest ECMWF shows pronounced warming spreading back into the
region whereas the GFS is delayed considerably. The differences in
h8 temperatures is quite revealing. By 18z Saturday the GFS shows +2
to +4C temperatures while the ECMWF has h8 temperatures in the +12
to +17C range. Given that the airmass moving into the Plains on
Saturday is of Pacific origin believe the GFS is too cold with its
temperatures while the ECMWF looks too warm. So using a model blend
is the best route to take.


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 646 AM CDT SUN SEP 28 2014

Patchy fog in the river valleys and low lying areas will burn off
quickly this morning leaving VFR conditions for the rest of the
forecast. Isolated showers and possibly a thunderstorm are two are
possible over northeast and central MO this afternoon as an upper
level system slides southeast through northern MO today.

Will likely see patchy fog form early Monday morning over the river
valleys again.




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