Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 301116
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
616 AM CDT Sat Aug 30 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 434 AM CDT SAT AUG 30 2014

Quiet weather is forecast through today and much of tonight. Aside
from patches of early morning fog, especially in valleys and low
areas, expect ample sunshine throughout the day with large scale
subsidence across the forecast area from mid morning through the
evening. Afternoon temperatures should warm into the upper 80s to
around 90 given the widespread sun and 850 hPa temps around 20C. May
reach the convective temperature by mid afternoon across the area as
well, but the subsidence aloft will inhibit any showers and dry
weather is to be expected. Mostly clear skies will continue into the
evening but by the early morning hours the surface ridge will push
east of the forecast area with southerly return flow increasing
through sunrise. The south breeze should keep overnight lows in the
middle to upper 60s. Will see moisture advection on the low level
jet across central KS along with increasing isentropic ascent. This
may result in increasing clouds and a few showers or storms into the
highway 81 corridor by around sunrise and have introduced slight
chances after 09Z.

.LONG TERM...(Sunday through Friday)
Issued at 434 AM CDT SAT AUG 30 2014

By Sunday, the focus shifts to the next approaching mid-level trough
that will be progressing eastward across the northern Rockies. This
advancing trough will help to push an area of surface low pressure
into the High Plains and further into the Central Plains Sunday
night into Monday. At this time, the cold front associated with this
system may not move into north central Kansas until early evening,
however embedded shortwaves within the mid-level flow may spawn
isolated to scattered thunderstorm activity over portions of
northern/north central Kansas during the afternoon hours. As the
front approaches the region, expect more widely scattered
thunderstorms to develop along and ahead of the front mid/late
afternoon through the evening and overnight hours. Concern continues
to grow with regards to the potential for strong to severe storms to
develop across much of the forecast area during the late Sunday
afternoon and evening timeframe. 00z model runs show a very notable
increase in the low-level jet (compared to yesterday`s 00z runs),
with a nose of 40-60kts at 850mb entering the region during the
evening. Models continue to suggest decent instability and shear,
along with modest low-level helicity, so there is an increasing
likelihood of supercell thunderstorm development with this activity.
The primary threats will be for large hail and damaging winds,
however cannot completely rule out the potential for an isolated
tornado or two. There also is the potential for locally heavy
rainfall as PWAT values reach upwards of 1.6-1.9 inches.  While many
locations across the forecast area are in need of decent rainfall, a
few locations have received some modest rainfall from the scattered
activity over the last couple of weeks, so those locations will be
more sensitive to this heavy rain potential.

This front should track east of the area by Monday afternoon,
however as the mid-level trough broadens out across much of the
northern U.S., it is expected to orient the front from west to east
and have it become nearly stationary just south of the forecast area
before potentially lifting northward into the region as a warm front
Tuesday into Wednesday. There is still a great deal of model
uncertainty though with the placement and tracking of this lingering
frontal boundary through the middle of next week. Additional
uncertainty lies with the potential for precipitation through the
week as models show several weak embedded shortwaves developing
along the southern edge of this broad trough (that results in fairly
zonal flow across the area), however they don`t seem to be agreeing
with the timing and location of these shortwaves and the scattered
thunderstorms that may develop from them. At this time, the better
chance for precipitation looks to be Monday night into Tuesday from
the lifting warm front, but have decreasing PoPs through mid week
and went dry for much of the latter part of the week due to too much
model uncertainty.

As for temperatures, another mild day is expected Sunday ahead of
the storm system as breezy southerly winds are expected with gusts
of 25-35mph possible. As a result, expect highs to reach into the
low/mid 90s. Slightly cooler conditions expected behind the system
and through the first part of next week with highs dropping into the
80s and low 90s. The temperature forecast for the latter part of the
week is more uncertain due to the discrepancies in how far north a
mid-level ridge will build over the region, but in general expect a
slight warming trend back into the 90s through the end of the week.

&&

.AVIATION...(For the 12Z TAFs through 12Z Sunday Morning)
Issued at 615 AM CDT SAT AUG 30 2014

VFR conditions are likely through the TAF period with light and
variable winds turning out of the southeast this evening. Some
very shallow fog at TOP will dissipate shortly after sunrise.

&&

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

$$

SHORT TERM...Barjenbruch
LONG TERM...Hennecke
AVIATION...Barjenbruch






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