National Weather Service Raw Text Product

051 
FXUS63 KTOP 072340
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
640 PM CDT Thu Jun 7 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday)
Issued at 335 PM CDT Thu Jun 7 2018

The boundary layer across the region remains characterized by
convectively-processed air, which has been reinforced by an 
influx of theta-e deficits resulting from regenerative cluster-
mode convection across Oklahoma. Air-mass recovery has further 
been inhibited by remnant mid/high-level convective-cloud debris, 
which has also been reinforced by the persistent convection 
farther south. By early afternoon, visible satellite loops 
indicate cloud-thinning across western parts of the forecast 
area, and pockets of clearing have also taken place across parts 
of eastern KS ahead of diffuse MCVs drifting eastward. With 
surface dewpoints in the middle 60s to near 70F, limited surface 
heating is supporting gradual erosion of convective inhibition. 
This is particularly the case across parts of northeast/east- 
central KS displaced east of the primary influx of convectively- 
processed air from Oklahoma. However, weak low-level 
flow/convergence fields across the region suggest that foci for 
ascent supporting any deep convection will remain very subtle. 
This casts considerable doubt regarding prospects for sustained 
convective development for the remainder of the afternoon. 
Nevertheless, sufficient ascent peripheral to the MCVs could 
support some convective development east of a Nemaha to Lyon 
County line through late afternoon. During the evening, a modest 
uptick in isentropic ascent (albeit remaining weak) atop the 
convectively reinforced boundary-layer theta-e deficit may 
facilitate generally isolated shower/thunderstorm 
formation/maintenance farther west that could spread across/enter 
the area through the overnight hours. A conditional strong, to 
perhaps locally severe, thunderstorm risk may accompany this 
activity given suitably steep midlevel lapse rates -- i.e., 
7-8 C/km in the 700-500-mb layer. However, the weak-forcing-for-
ascent pattern, and fairly widespread convective inhibition, 
provide for little confidence regarding the convective risk that 
extends to the severe potential. Moreover, effective bulk shear 
generally at or below 30 kt should tend to mitigate convective 
organization.

For Friday, low-level mass fields will continue to lack any 
salient zones of mass convergence at the synoptic scale beneath 
weak quasi-zonal midlevel flow. Any mesoscale ascent will be 
highly contingent upon the preceding nocturnal convective 
evolution. The low-predictability character of this weakly-forced 
pattern extends to both the convective chances as well as most 
forecast parameters. Building midlevel heights across western 
areas during the day, resulting from low-level warm advection, may
yield heat indices reaching well into the 90s -- potentially 
breaching 100F across north-central KS if the ascent accompanying 
warm advection were insufficient to support regenerative 
convection.

.LONG TERM...(Friday night through Thursday)
Issued at 335 PM CDT Thu Jun 7 2018

For Friday night into this weekend and Monday, a continued pattern 
of low-predictability convective risk will persist as a midlevel 
ridge gradually amplifies over the central Great Plains ahead of a
trough progressing from the Pacific Northwest to the northern
Great Plains. The forecast area will remain displaced well south
of any appreciable midlevel height changes, resulting in little
forcing for vertical motion. Present indications are that -- on
Sunday -- stronger cyclogenesis accompanying the trough (north of
the area) may tend to result in frontolysis for any residual
boundaries across the forecast area while the primary zone of
frontogenesis establishes well to the north. Moreover, with a warm
elevated mixed layer overspreading the area on Sunday, a relative
minimum in convective chances may exist on Sunday -- i.e., most
areas may remain rain-free. Thereafter, the cold front
accompanying the trough is presently forecast to cross the region
on Monday -- perhaps locally reinforcing shower/thunderstorm
chances. While very uncertain, this front may stall, decay, or
advance northward in the vicinity of the CWA through the middle of
next week. Front-related ascent, favorably phased with high
theta-e air on the warm side of this boundary, will support
convective chances into the middle of next week. Until the cold
front crosses the region, increasing low-to-middle-tropospheric
thicknesses and embedded diurnally enhanced vertical mixing will
support very warm temperatures this weekend -- potentially
continuing into Monday ahead of the front. High temperatures will
reach well into the 90s across many locations, with afternoon heat
indices reaching 98-102F ahead of the front in many areas. Some 
cooling trend is expected in the wake of the front by the middle 
of next week, though uncertainty regarding the evolution of the 
front and attendant convection extends to the temperature 
forecast.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 640 PM CDT Thu Jun 7 2018

VFR conditions are expected through the period outside of
convection. Isolated tsra is possible in the 07Z-14Z time period
and have added VCTS to the terminals. Winds becoming south around
10 kts or less by 14Z.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Cohen
LONG TERM...Cohen
AVIATION...53