Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 172037

Area Forecast Discussion
National Weather Service Topeka KS
337 PM CDT Thu May 17 2018

.SHORT TERM...(This evening through Friday night)
Issued at 335 PM CDT Thu May 17 2018

As of 19Z Thursday afternoon a mid-level low continues to spin
across eastern KS/western MO within the broader eastern CONUS
trough. On the backside of the trough, mid-level ridging continues
to overspread the central Plains. Steep low-level lapse rates
coupled with subtle forcing from the mid-level low has spawned
isolated thunderstorms across east-central KS. Expect activity to
remain southeast of I-35 and diminish near sunset. For tonight, we
turn our attention westward as thunderstorm development is expected
as a lead shortwave and mid-level height falls overspread the High
Plains. Activity is expected to grow upscale in clusters, although a
modest LLJ (~20-30kts) and limited theta-e advection should limit
the eastward progression. For the time being, only have showers and
thunderstorms mention in the north central KS counties after 08Z

Lee cyclone across southeast CO/northeast NM is progged to deepen
throughout the day Friday as a secondary shortwave trough ejects
from the base of the main upper low in the southwestern CONUS. In
conjunction with daytime heating and the shortwave, thunderstorm
development is once again expected along the High Plains Friday
afternoon. A stronger LLJ and increased theta-e advection should
foster upscale growth and MCS maintenance through the overnight
hours with arrival to the western portions of the CWA after 06Z
Saturday morning. Steep mid-level lapse rates are progged to yield
1000-2000 J/kg of MUCAPE. Weakening effective shear (20-30kts)
across eastern KS should limit the severe potential however.

.LONG TERM...(Saturday through Thursday)
Issued at 335 PM CDT Thu May 17 2018

Next, we then turn our attention to Saturday afternoon and evening.
The evolution of convection Friday night/Saturday morning will play
a key role in severity, mode and location of thunderstorms Saturday
afternoon/evening. At this point in time, model consensus continues
to suggest a surface low/warm front/dryline intersection in central
to north central KS with the main upper low remaining west of the
CWA through 00Z Sunday. That being said, weak mid-level height falls
coupled with weakly capped MLCAPE values between 3000-4000 J/kg,
should foster thunderstorm development along the dryline after 21Z
Saturday afternoon. The primary hazards look to be large hail and
damaging winds, some significant, given the strongly buoyant and
modestly sheared environment. A mesoscale-driven tornado threat is
certainly possible, especially on any outflow boundary from Saturday
morning`s convection. Further thunderstorm development is expected
after 00Z as the main upper low ejects across the central Plains.
Stay tuned to subsequent outlooks as confidence is low in boundary
positions and the evolution of Saturday morning`s convection.

The main front will traverse the CWA Saturday night/Sunday morning,
ushering in cooler temperatures with highs Sunday afternoon in the
70s. Shower and thunderstorm chances look to increase by the middle
of next week as another upper low comes ashore in the southwestern
US. Above normal temperatures are also expected with highs returning
to the mid to upper 80s.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 335 PM CDT Thu May 17 2018

VFR conditions are expected through the period. Light east to
southeasterly winds will remain below 10 kts. Any shower and
thunderstorm activity is expected to remain west of the terminals.





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