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

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FXUS63 KEAX 141727
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1227 PM CDT Sat Oct 14 2017

.Update...
Issued at 1127 AM CDT SAT OCT 14 2017

Have made some adjustments to the forecast for the next 18 to 24
hours. Biggest changes are with cloud trends and resulting
temperatures and surface winds. Satellite imagery showing the
southern third of the forecast area scattering or clearing out
late this morning. This trend should continue to about the MO
river. With less cloud cover, temperatures have warmed much faster
with some areas in the upper 70s and lower 80s. Of note is that
our dewpoints are close to or higher than our normal high
temperatures for this time of year. This anomalously warm and
moist environment is concerning because it will yield greater
instability within a strongly sheared environment. Have also
adjusted surface winds up several kts. Winds will likely have a 10
to 20 degree westward of south motion. This is perhaps a little
less veered then previously expected. The stronger and less veered
surface winds are aiding strong helicity values. Forecast
soundings ahead of the potential storms show 0-1km helicity values
potentially exceeding 300 m^2/s^2. For the line of storms that may
move through the area late this afternoon and early this evening,
given the strong shear, helicity and instability, there is a
distinct risk of tornadoes along with the potential for damaging
winds and hail. To put this day in perspective, while the
synoptic scale features differ some from the March 6th event this
year, many of mesoscale and storm parameters match closely.

&&

.Discussion...
Issued at 248 AM CDT SAT OCT 14 2017

With SE Nebraska in the right entrance region of the UL jet, and
with a surface front enhanced by a LL jet draped right through
the KC metro area early this morning, these two features have been
the focus of developing precip/storms. Moisture is having no
problem continuing to advect into the region with sources
courtesy of both the Gulf of California and GoMex, as evidenced
on WV imagery. As the morning progresses, storm chances will be on
the increase and although these morning storms should be non-
severe, it`ll culminate later this afternoon into a severe
weather threat for much of the forecast area, particularly for
locations east of I-35 and south of U.S. Hwys 136/36 where the
greater instability will lie.

As an upper trough bulldozes its way across the center of the
country today through tonight, it`ll trigger cyclogenesis and give
the stalled aforementioned front a revitalization and the kick
start it needs to continue its progress through MO. Accompanying
this will be an increase in not only surface winds, but 0-6km
shear as well, although the greater magnitude of the latter will
lag behind the front. Regardless, the copious moisture pooling in
(with PWATs well above climatological normals), combining with the
discussed wind shear, and sufficient instability residing within
the warm sector equals storms having the potential to become
severe, with gusty to damaging winds appearing to be the primary
threat, along with hail and a tornadic threat. Model soundings for
this afternoon into this evening depict relatively low LCLs and
rather concerning 0-1km and 0-3km helicity values, which will
warrant keeping a close eye on the mesoscale and near-storm
environment as storms ramp up later today. The expectation is that
storms will congeal into a QLCS for the southern and eastern two-
thirds of the forecast area, quickly exiting late this evening,
with the severe threat diminishing significantly after around
midnight or so.

Behind this system, high pressure will settle into the region by
the start of the new week, and benign weather will dominate
through the remainder of the traditional work week. However, the
next concern will be the low temperatures expected Sunday night -
Monday morning, particularly across northern MO. Although temps
are currently forecast to linger in the upper 30s there, the
closer temps drop toward the freezing mark, the increasing chances
of frost developing, potentially making it the first frost of the
season for some. Therefore, for those with agricultural
interests, overnight Sunday will be the timeframe to watch for
possible frost concerns. Temperatures throughout the remainder of
the week will moderate, slowly creeping back up above normal for
mid-October.

&&

.Aviation...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1227 PM CDT SAT OCT 14 2017

Main aviation issue is the area of rain and storms moving into
northeastern KS and northwestern MO currently. In pockets of
heavier rain there will be temporary visibility reductions.
Otherwise, it looks like the main line of storms will move through
the terminals from about 23Z to 02Z time frame. In the wake of the
storms, with the passage of the cold front, winds will shift to
the northwest and increase with 20kt sustained winds likely, and
possibly stronger. Wind gusts of 30+ kts also look likely through
overnight hours. MVFR stratus behind the front should move out
after sunrise with brisk northwesterly winds decreasing through
the reminder of the late morning hours.

&&

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

$$

Update...CDB
Discussion...lg
Aviation...CDB



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