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Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO
1157 PM CDT Fri Sep 19 2014

Discussion...
issued at 355 PM CDT Friday Sep 19 2014

Tonight through Saturday night:
this will likely be the most active portion of the forecast as two
frontal boundaries drop through the region Saturday/Saturday night.

First we'll address what's been a daily challenge in handling the
stratus over eastern KS/MO. Tonight will be the last of the stratus
problem for awhile. Just enough mixing and warmer/more humid air was
finally able to at least generate some breaks in the cloud deck.
Current thinking is we'll once again clear off shortly after sunset
but with the moisture still trapped under the low-level inversion am
expecting to see low stratus/fog reform over the western County Warning Area.
Fortunately there should be sufficient mixing to lift and break up
the clouds by mid morning.

Good warming through h8 via southwesterly winds will give US our
warmest weather in a number of weeks. An amplifying upper trough
over the western Great Lakes will force a cold front through WI/Minnesota
while a trailing trough gently shifts south through Iowa/NE,
eventually settling into northern MO Saturday morning. Any
convection along the surface trough tonight should weaken and may
not even make it into the County Warning Area. Ample advection of moderately
unstable air...MLCAPES upwards of 3000j/kg...ahead of this feature
will enhance afternoon/evening convection along the boundary.
However, a veered wind profile does not favor organized severe
weather. 0-6km shear of 25-30kt may be just enough to support a
renegade severe storm during peak heating. Believe convection along
the boundary will be scattered vs a solid line so 40-50% pops seem
appropriate.

An upstream cold front will quickly drop south from Minnesota and reach
northern MO after midnight. This may energize stalled convection
near the MO river and force it out of the County Warning Area by Sunday morning.

Sunday through Monday night:
broad area of Canadian high pressure will surge south and send much
drier and cooler air through the County Warning Area and remain in place through
Monday.

Tuesday through friday:
water vapor satellite imagery depicts our next weather maker just
off the central California coast in the form of a closed upper low. The
medium range models are in good agreement in dislodging this feature
and ejecting it northeast into the northern/Central Plains by
Tuesday. However, this system will then be moving into an upper ridge
which the models tend to have difficulty in handling the finer
details of energy moving through a mean ridge. So, overall confidence
on how soon any associated convection reaches the County Warning Area is modest at
best. For now the eastward extension of any convection will be held
to mainly northwest MO. Temperatures will see a slow but steady
increase during this period and remain slightly below average.

&&

Aviation...(for the 06z tafs through 06z Saturday night)
issued at CDT Friday Sep 19 2014

Confidence in IFR/LIFR categories is starting to dwindle a bit as the
boundary layer remains rather mixy with southerly winds persisting
around 7 to 10 kts. Expect these winds of around 5 to 10 kts to
persist through most of the night, which will mitigate fog potential.
Given how moist the air mass is and temperatures dropping through the
night, still think some light visibility restriction is in order through
sunrise. Regarding the stratus, even less confidence in that
occurring, as model soundings and guidance indicate that low level
stratus will have a hard time forming, especially with mid level
clouds currently gliding through the area. Will keep the mention for
stratus in the forecast for now, but will need to monitor closely and
amend as necessary, should the stratus not form. VFR expected after
sunrise, however thunderstorms are possible along an advancing cold
front Saturday afternoon and evening. Coverage will be isolated to
scattered, so exact timing of heavy rain and gusty winds at the
terminals is unclear at this time. Gave a window of most likely
precipitation for each terminal using thunderstorms in the vicinity group.

&&

Eax watches/warnings/advisories...
Kansas...none.
MO...none.
&&

$$

Update...mj
discussion...mj
aviation...Leighton

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