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

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FXUS63 KEAX 310842
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
342 AM CDT Sun Aug 31 2014

.SHORT TERM...(Today through Tuesday)
Issued at 342 AM CDT SUN AUG 31 2014

In the short term, the main concern will be severe weather chances
late this evening through Monday morning, and again Monday afternoon
as a shortwave trough and associated cold front push through the
region.

A few light showers and isolated storms may drift into northwest MO
this morning from their current position in central KS, but any
precipitation and most cloud cover is expected to diminish by early
afternoon, allowing instability to build across the CWA during the
afternoon hours. Up to 2000-2500 J/kg MUCAPE will spread over the
area this afternoon into the early evening ahead of the approaching
cold front, and a weak cap over southeast NE, southwest IA, and
extreme northwest MO may allow a few very isolated storms to pop up
by late afternoon or early evening in those areas. Coverage of these
storms -- should they develop -- should be low enough to prevent any
significant modification of the mesoscale environment, and weak deep
layer shear values should keep the severe threat low during the
afternoon and early evening period. Significant capping across the
remainder of the CWA should suppress any afternoon/early evening
convection in areas southeast of the MO/KS/NE border to Bethany.

Severe chances will increase after 03z as the low-level jet starts
to crank up and the upper trough approaches, bringing 0-6 km shear
values into the 40 to 50 kt range while MUCAPE remains more than
adequate in the 1000-2000 J/kg range. Storms are expected to develop
initially near the cold front in southeast NE and southwest IA, then
will likely form some sort of cold-pool driven complex/MCS that could
dive east southeast across the northern half of the CWA. Any outflow
boundaries that are thrown southward from evening convection also
have the potential to initiate convection, and storm mode could be
initially supercellular before developing into linear segments.
Large hail and perhaps an isolated tornado are possible before
midnight across extreme northwest MO, but as storms become more
linear and move into areas that will be capped throughout the day,
damaging winds will become the much more likely severe threat.

As the early Monday morning hours wear on, flash flooding will
become a concern due to the increasing LLJ, deepening warm cloud
layer, and PWATs increasing to around 2 inches. Multiple rounds of
storms are also possible if the storm complex propagates off the
cold front and redevelopment occurs along the front, and shear
vectors oriented nearly parallel to the front will likely support
training storms. However, if a strong MCS develops, it may move
quickly enough to prevent significant flash flooding, and may also
work over the trailing environment enough to suppress robust storm
development along the main cold front. The primary potential for
flooding will be in areas north of the MO River, but have not issued
a flash flood watch with too many uncertainties in how storms will
evolve tonight.

The cold front will gradually slow on Monday morning, eventually
stalling near the southern CWA border. Deep layer shear values will
remain in the 40 to 50 kt range over the boundary on Monday even as
the LLJ diminishes due to increasing flow aloft. The main shortwave
trough axis will pass over the boundary during the afternoon and
evening hours Monday, supporting another round of storms near the
stationary front; however, their intensity will depend entirely on
how storms evolve on Monday morning and how quickly they clear out
of the area. Should at least some clearing occur by the afternoon,
another round of severe weather will be possible along the front
Monday afternoon and evening. Supercells are possible during the
afternoon, creating a threat for large hail, damaging winds, and
perhaps an isolated tornado. By early evening, the shortwave trough
will begin to advance the cold front southward again, transitioning
storm mode to linear segments and pushing storms out of the CWA. For
our forecast area, the severe threat should be ending by 9PM - 12AM
as the front exits to the south.

The front may meander back northward on Tuesday, bringing highs back
into the upper 80s to lower 90s and spreading storm chances back
across the region; however, severe weather is not expected behind
the departing shortwave trough.


.LONG TERM...(Wednesday through Saturday)
Issued at 342 AM CDT SUN AUG 31 2014

The forecast for midweek into the weekend continues to look on
track. The surface boundary that will reside south of the CWA on
Tuesday is expected to retreat northward as a warm front on Wednesday
as heights begin to rise across the region in response to the upper
pattern flattening. Models are fairly consistent in developing
convection Wed morning as the front begins to lift north. Otherwise,
weak upper ridging will take shape over the area by late Wed into
Fri, with H85 temps warming to around 22C. This will result in
afternoon temperatures exceeding seasonal normals, with highs in the
middle 80s to lower 90s each day.

A longwave positively-tilted trough should evolve across the Pacific
NW and Intermountain West by the end of the week. A shortwave trough
is projected to eject along the southern Canadian prairie on Friday
before digging into the northeast CONUS. An associated cold front
will settle over portions of the forecast area, with model spread
suggesting the frontal passage either Friday or Saturday. Likewise,
have increased chances for thunderstorms Friday night into Saturday
as the boundary sags into the CWA. Overall dynamics are not
impressive as strongest shear remains on the cool side of the
boundary due to the upper trough orientation, so overall severe
threat will be low. Temperatures for the weekend will be several
degrees cooler with the passage of the front and anticipated
convective cloud debris, with highs in the upper 70s to middle 80s.


&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1230 AM CDT SUN AUG 31 2014

Patchy fog is expected mainly across portions of northeast and
eastern MO through sunrise this morning, but is not expected to
significantly reduce visibility at the TAF sites. Otherwise, VFR
conditions are anticipated through much of the forecast period. A few
isolated showers and storms are possible late Sunday evening across
northwest MO, then will become more intense and widespread after 06z.
All TAF sites will likely be impacted by thunderstorms shortly after
the end of the TAF period Sunday night.


&&

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

$$

SHORT TERM...Laflin
LONG TERM...Blair
AVIATION...Laflin






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