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

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FXUS63 KEAX 170808
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
308 AM CDT Wed Sep 17 2014

.SHORT TERM...(Today through Friday Night)
Issued at 308 AM CDT WED SEP 17 2014

Out of the gate this morning...initial concerns remain focused on
early morning convection and prospects for additional shwrs/storms
later today as a frontal boundary slowly approaches the area. Fcst
models in recent days have been hinting at decent isentropic ascent
along the 305 and 310K theta surfaces as a 35 kt low-level jet
ascends the boundary. One thing that does appear a little different
with today/s models is the indication that upper jet dynamics will be
a little more conducive to support modest divergence aloft. This
combined with the aforementioned isentropic ascent along with some
weak mid-level vorticity advection should keep the threat for
scattered shwrs/storms going through at least early afternoon. With
MUCAPE values exceeding 1000 Joules this morning...along with 0-6 km
bulk shear values remaining near 40 kts...modestly sheared updrafts
will be capable of small hail with today/s convection. By mid to late
afternoon...upper shortwave should be exiting to the southeast which
should allow for a gradual decrease in precip from north to south as
the day progresses. Temps a little tricky today as cloud cover and
precip may hinder optimal heating. In any event...decent warm air
advection as referenced above...combined with warming 850 temps
should allow mid to upper 70s across most areas...with a few low 80s
possible from the KC metro west into eastern KS.

For tonight...main frontal boundary will again be suppressed to the
south and west as strong sfc high pressure builds into the upper
Great Lakes. As this occurs...models suggest an influx of drier air
as sfc ridging extends all the way west to the lwr Missouri Vly.
Still cannot rule out some light shwr development across western
portions of the fcst area thanks for frontogenesis circulations...but
overall confidence is waning given current model trends. In any
event...will hold on to low chc pops across the far south and
southwest...while maintaining dry conditions for our eastern zones.
Overnight lows have the potential of varying widely...with low 50s
possible across the far northeast in drier and cooler air...while low
60s are likely to the west in closer proximity to the frontal
boundary.

With frontal boundary shunted to the west on Thursday...expect
slightly cooler temps to those experienced today. Overall prospects
for rain look low as front remains west and thus have maintained a
dry fcst for now. By Thursday night...models suggest the possibility
of developing shwrs as a weak disturbances embedded in the polar jet
passes well to our north. After careful inspection of several model
fields...having a hard time finding a suitable triggering mechanism
to get convection going. As a result...have a dry fcst was maintained
which agrees well with surrounding offices.

Large scale pattern shift to get underway on Friday as upper flow
begins to back to the southwest in advance of a large scale upper low
developing over central/southern California. The end result will be
for building heights downstream across our region with returning
southerly flow allowing 850 temps to warm into the upper teens. This
should allow temps to warm well into the lower to middle 80s for
daytime highs...with a warm night then in store through Saturday
morning. Both Friday and Friday night look to remain dry with precip
chances increasing beyond this as remnant Hurricane Odile circulation
approaches. More details below.

.LONG TERM...(Saturday through Tuesday night)
Issued at 308 AM CDT WED SEP 17 2014

The potentially active weekend weather continues to be of focus for
the extended period. The upper pattern should feature a closed low
developing over southern California, with a well-defined vort max
from the remnants of the tropical system Odile heading northeast
from the Desert Southwest into central Missouri. To the north, a
strong shortwave trough will quickly dive towards the Great Lakes
states and begin to amplify into a large trough over the eastern
CONUS. Models deviate some to the speed of these features,
especially the Euro that is approximately 6-12 hours slower with the
arrival of remnants of Odile and the associated vertical
ascent/tropospheric moistening. The lack of consistent timing places
additional uncertainty to the forecast, but the overall signal still
suggests many areas in the CWA should receive rainfall Saturday into
Saturday night. The overall large scale ascent has trended a little
weaker than earlier model runs, perhaps in part to a slower westward
amplification to the approaching upper trough, and likewise models
have gradually lowered QPF amounts. Went with a forecast blend, not
ready to fully buy into any one solution, and considering the ample
moisture projected to advect into the area. While the heaviest
precipitation may fall to the southwest of the CWA, an average of
one-half inch of rainfall still appears possible prior to a cold
front moving through the forecast area Saturday night into Sunday.
Upon the frontal passage, drier air will filter into the region for
the remainder of Sunday into Monday, yielding mostly sunny skies,
northerly winds, and a dry forecast. With the large upper trough
slow to move east, relatively tranquil conditions are anticipated
through midweek as the western periphery of surface high pressure
remains in control.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
Issued at 1153 PM CDT TUE SEP 16 2014

Short range hi-res models cont to develop thunderstorms acrs ern KS
tonight btn 08Z-09Z which may move into the VC of the terminals
around 10Z but the bulk of pcpn should remain south of the terminals.
Models also cont to introduce MVFR cigs at the terminals around 10Z
as well and keep them at the terminals through the morning hours.
Cigs should finally sct during the afternoon around 2-3kft with just
sct high clouds expected during the evening. Winds will be light thru
the pd backing fro the SE to the E.

&&

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

$$

SHORT TERM...32
LONG TERM...Blair
AVIATION...73






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