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

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000
FXUS63 KEAX 182352
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
652 PM CDT THU AUG 18 2016

.Discussion...
Issued at 333 PM CDT THU AUG 18 2016

An expansive area of surface high pressure across the southeastern
CONUS has produced areas of warm air advection as far north as
eastern Kansas and central Missouri as of Thursday afternoon. A
large CU field has also resulted in this region as depicted on
visible satellite imagery in the midst of southerly surface flow.
These will dissipate after sunset, with mostly clear skies expected
for the overnight period. With persistent warm advection in place,
afternoon highs will climb just above Wednesday`s values, reaching
into the low 90s for most areas. With increasing dew points and
clearing skies overnight, there is the potential for a couple of
hours of patchy fog early Friday morning. Building cloud cover from
the south may minimize this, though areas north of I-70 could still
see periods of fog development Friday morning.

The main focus of this forecast period will reside with tomorrow as
a deepening upper trough currently over southern Canada swings
southeastward across the Northern Plains into Friday afternoon. This
will push a surface cold front through northwest Missouri Friday
evening. Deepening moisture with precipitable water values near two
inches will be more than sufficient to initiate convection along the
front as it crosses in to the local area. Before this feature
arrives, an isolated thunderstorm or two is possible for points south
of the I-70 corridor Friday afternoon in the warm sector of the
approaching storm system. Should storms develop during the afternoon,
the main threats will be in the form of gusty winds and potentially
heavy rainfall. More widespread activity will occur along the
approaching frontal boundary later in the evening. Latest model runs
suggests as slightly delayed arrival of the cold front compared to
previous runs, though still thinking that storms will initiate across
northwest Missouri shortly after sunset. Storms will affect the
Kansas City area late in the evening as the boundary quickly pushes
southeastward with time. Storm mode will assume the form of a
possible MCS and multicellular storms initially given a veering with
height wind profile. With regard to severe potential, the slightly
delayed arrival may be impacted by a more stable atmosphere. Elevated
instability will remain modest, however, and a more southward extend
of the upper trough per the latest model runs suggests 0 to 6 km
shear values near 30 kts, compared to slightly lower forecast values.
Relatively weak lapse rates combined with a stabilizing environment
will limit vertical momentum within storms. The main threat within
these storms will be in the form of strong winds within collapsing
storms and MCS-driven winds, along with locally heavy rainfall. The
progressive nature of the front should inhibit areal flooding, though
localized flash flooding will remain a potential threat. The forcing
along the front will quickly weaken as the front pushes through
central Missouri overnight. Residual storms will taper off through
early to mid Saturday morning, though the severe threat should
quickly dissipate in the early overnight hours.

Post-frontal cloud cover will then scatter out as high pressure
quickly builds into the region Saturday afternoon. The weekend is
shaping up to be rather pleasant with temperatures behind the front
only peaking in the mid to upper 70s for both Saturday and Sunday.
Dry conditions will then continue until the middle of next week
before the next chance of storms will affect the area through the
end of the forecast period.

&&

.Aviation...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 652 PM CDT THU AUG 18 2016

The area will start out with clear skies and VFR conditions
with a southerly winds 5-10kts overnight. The clear skies will allow
the surface to cool down near the cross over point with the dewpoint
in the morning, but with winds staying above 4kts fog should keep
from forming up except near STJ. Cooler air in the low levels over
northern Arkansas and southern Missouri will start to advect into the
region towards sunrise helping to condense the low levels and form an
IFR to MVFR ceiling over the southern portion of the region. At
sunrise the surface temperatures will help enhance the low cloud
deck over the southwest portion of the region for a few hours until
it can burn off. The formation of the cloud deck seems likely, but
the height of this ceiling if somewhat uncertain. Some models have it
forming as low as 300ft while others keep it just under the cold air
advection near 1500ft. The current TAFs have IFR ceilings from 12-14Z
with IFR visibility at STJ lifting into the ceiling during that
timeframe. This stratus deck potential will be monitored and
heights/timing will be adjusted as more data is available to confirm
the timing/heights.

&&

.EAX Watches/Warnings/Advisories...
KS...None.
MO...None.
&&

$$

Discussion...Welsh
Aviation...Barham/MJ



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