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

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FXUS63 KEAX 170827
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
327 AM CDT Wed May 17 2017

.Discussion...
Issued at 327 AM CDT WED MAY 17 2017

Complex and potentially potent scenario continues to develop for
the next 12-18 hours as a deep, stacked low pressure system lifts
northward across the region. Ongoing showers and storms will push
northeast through the morning hours, and have generally become a
bit more disorganized the further from the upper-level forcing and
low-level convergence that they travel. Will continue to keep an
eye on this round since elevated instability remains non-
negligible and deep layer shear varies between 40-50 kts, but in
general, widespread severe weather is not expected until the upper
system draws closer this afternoon.

As the system pushes northeast this morning, the upper trough axis
will align with the diffuse dryline/pacific front and swing
through the forecast area. A brief break in cloud cover behind the
current round of storms may be enough to promote very quick, deep
boundary layer mixing and translate the mounting instability to
the surface, allowing surface-based convective initiation to occur
along the boundary. Deep layer shear will be off the charts as the
stacked system passes across the northwest corner of the CWA, so
if convection does fire, there is a strong possibility of those
storms becoming strong to severe. The best forcing/support for
convection will be near the surface low, which will also be the
area where low-level winds may begin to back in response, further
supporting robust, rotating storms. Storm motion will be very
quick, especially as the trough becomes increasingly negatively
tilted and reorients the steering flow to the west southwest
(versus the current south southwest flow early this morning), so
is not difficult to imagine strong wind gusts translating to the
surface in any storm. Tornadic threat is also non-zero in a very
supportive shear profile and without a strong discontinuity in
density behind the boundary to undercut updrafts, but will depend
on whether or not storms can root at the surface.

Behind this second round, clearing skies will promote deep
boundary layer mixing, and the tightening surface pressure
gradient and very strong winds aloft will likely result in
advisory-criteria wind gusts. Timing will depend a bit on how
morning storms/cloud cover play out, but the strongest winds
should occur mainly between 16z-00z, and have drawn up an advisory
mainly along and south of Highway 36 for that time period.

Once the current system departs, a brief break is expected during
the daytime Thursday, and further delays in the arrival of the
next system may keep the evening hours Thursday dry as well.
Another stacked, dynamic system will take a similar path to this
current low track, but surface high pressure over the Great Lakes
region and the brevity of the period between systems may keep the
surface warm front to our south. As a result, convection may be
elevated and the better potential for strong/severe storms could
remain to our south. At least two rounds of convection are
expected with this system; both which will fire along the dryline
in the High Plains and move toward the forecast area as the upper
trough slowly shifts northward. Moderate to heavy rain is possible
but the highest totals may also occur to our south where stronger
convection is expected. This weekend system should exit the area
by Sunday, leaving quieter conditions for the beginning of next
week.

&&

.Aviation...(For the 06Z TAFS through 06Z Wednesday Night)
Issued at 1237 AM CDT WED MAY 17 2017

Main concern for the terminals in the near term will be the
progression of showers and thunderstorms currently lifting
northeast through northern OK and south central KS. If these
storms hold together, they will arrive around 10z, but there
remains some uncertainty in how robust they will remain.
Regardless, that round of convection should dissipate or exit the
area by mid-morning Wednesday, but could see another round form
near or just east of the terminals around 18z Wednesday, which
could last a short period of time before pushing off to the east
and ending storm concerns for the remainder of the period. Winds
will remain out of the S to SSW overnight at around 12 to 15 kts,
still with occasional gusts to 20-25 kts, then will increase to
sustained speeds up to 25 kts and gusts up to 35 kts during the
daylight hours Wednesday. Winds will veer slightly behind the
second round of potentially thunderstorms, but only a few degrees
bringing direction to the SW.


&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for KSZ025-057-060-103>105.

MO...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for MOZ020>025-028>033-037>040-043>046-053-054.

&&

$$

Discussion...Laflin
Aviation...Laflin



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