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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
000
FXUS63 KEAX 171720
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1220 PM CDT Wed May 17 2017

.Update...
Issued at 1212 PM CDT WED MAY 17 2017

An enhanced CU field has developed across eastern Kansas, upstream
of a strong upper-level low centered over southeastern Nebraska.
Rapid clearing across western Missouri through the late morning
has allowed for moderate destabilization underneath a highly
sheared environment. As the parent circulation lifts northeast and
crosses over northwest Missouri, storms will continue to develop
upstream and cross into northwest Missouri through the early
afternoon. While strong to damaging winds are the primary
anticipated hazard, a couple of tornadoes are also possible.
Convection will quickly push through the area by the early
evening. A Tornado Watch is currently in effect for the affected
areas until 7 PM.


&&

.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 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1141 AM CDT WED MAY 17 2017

The main impact for the forecast period will be with persistent
gusty winds through the duration of the afternoon, in addition to
a brief period of thunderstorm activity. Storms are expected to
commence early in the forecast period, though should exit the area
by the mid afternoon hours. The path of the upper level system
should keep the strongest storms north of the terminals, though
cannot rule out strong storms overhead the terminals. Gusts will
taper off this evening, and low level moisture will begin to
return to the area Thursday morning.


&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Wind Advisory until 7 PM CDT this evening for KSZ025-057-060-
     103>105.

MO...Wind Advisory until 7 PM CDT this evening for MOZ020>025-028>033-
     037>040-043>046-053-054.

&&

$$

Update...Welsh
Discussion...Laflin
Aviation...Welsh



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.