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fxus63 ktop 210443 

Area forecast discussion
National Weather Service Topeka Kansas
1143 PM CDT Fri Sep 20 2019

issued at 334 PM CDT Fri Sep 20 2019

A closed upper low was noted over eastern Idaho on the 20z water
vapor imagery while remnants of Imelda caused showers and
thunderstorms along the Red River valley and Arkansas. Between an upper
ridge to the southeast and the closed low over The Rockies,
southwest flow persisted over the Central Plains. At the surface,
Lee troughing along the Central High plains and ridging over the
southeast continued to favor a southerly surface wind and
dewpoints ranged from the upper 60s to mid 70s from the Central
Plains to the Southern Plains.


..update to aviation forecast discussion...

Short term...(this evening through saturday)
issued at 334 PM CDT Fri Sep 20 2019

Some isentropic lift has aided in the light shower activity
across the forecast area this afternoon. The saturation along this
area of lift is progged to diminish this evening so I do not
expected the rain to continue all night. However height falls are
progged to spread east through the day Saturday. Weak
perturbations within the southwest flow along with increasing q
vector convergence suggests scattered showers and thunderstorms
are probable through the day on Saturday. And this activity may
start as early as sunrise. There continues to be a risk for severe
storms as model show an improving wind profile through the day as
a 500mb jet Max noses into the region. And models prog cape
values of 2000 to 3000 j/kg developing by the afternoon. However
the low clouds may through a wrench into the instability,
especially across northeast and east central Kansas where models hang
onto the stratus for much of the day. Forecast hodographs show
good low level veering of the winds and develop 0- 1km srh of
around 200 m2/s2. Because of this there is some potential for a
tornado or two. However forecast soundings also show a weakness in
the wind profile around 3km that causes an inflection in the
forecast hodograph. This suggests there could be storm
interactions that disrupt updrafts and limit the time a supercell
storm could remain discrete. And by the evening, linear forcing
from the frontal boundary suggests storms may develop into a line.
So the main hazards continue to be large hail and damaging winds
during the afternoon and into Saturday evening.

Temps tonight are expected to only cool off a few degrees as
southerly winds and cloud cover prevent much radiational cooling.
Lows are forecast to be around 70 by Saturday morning. With clouds
expected to linger across the Easter portions of the forecast area,
have lowered saturday's highs into the upper 70s and keep highs in
the lower 80s across north central Kansas where there should be more

Long term...(saturday night through friday)
issued at 334 PM CDT Fri Sep 20 2019

There continues to be better confidence in torrential rainfall
developing Saturday night and Sunday morning. Continued moisture
advection into the frontal boundary with anomalously highs
moisture is expected to favor very high rainfall rates with the
thunderstorms. So have continued the Flash Flood Watch and
expanded it to include Coffey and Anderson counties. Although
models seem to have backed off slightly on quantitative precipitation forecast amounts. Ensemble
plumes from the sref and GFS ensemble show a good clustering of
solutions between 1 and 3 inches for storm totals. Although there
are a few solutions with amounts greater than three inches.
Overall the forecast has widespread 2 to 3 inch amounts and have
kept the 2 to 4 inch wording in the watch. The timing of the front
is a little slower than yesterday in the operational solutions.
So Sunday morning is looking a little wetter. But the front is
progged to eventually push south of Anderson co by the early
evening. So have the forecast with decreasing pops through the
afternoon. Highs Sunday are likely to be cooler with clouds
initially and some modest cold air advection behind the front. The
forecast has in the lower and mid 70s.

A break from the weather is forecast for Monday with shortwave
ridging aloft and surface ridging weakening. There is a little
better consensus among the models with the synoptic pattern for next
week. Unfortunately there remains several opportunities for precip.
So pops remain spread out through the forecast from late Monday
night through Friday. There are indications of a weak wave moving
across the Central Plains on Tuesday though along with some
southerly return flow could bring some storms to the region. Then a
weak frontal boundary is progged to move into central or southern Kansas
on Wednesday. An increasing low level jet into this boundary
Wednesday night could help storms to develop. There is some
variability in the location of this boundary and where the storms
develop so pops are not that high. Then models show energy lifting
out of the southwestern U.S. Thursday night and Friday with a low
pressure system lifting mainly to the northwest of the forecast
area. There are some small pops in for this but the dry slot may
also limit those chances. Temps look to remain fairly close to
seasonal normals through next week with models showing no signs of
strong temp advection. So the model blend has highs generally around
80 and lows in the upper 50s to the mid 60s.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1139 PM CDT Fri Sep 20 2019

For the 06z tafs, MVFR cigs will likely prevail through much of
the overnight hours through Saturday, and cannot rule out some
brief periods of IFR cigs. Isolated showers will be possible into
Saturday morning (primarily near ktop/kfoe). Models have trended a
bit slower with bringing thunderstorms over the tafs, so have
delayed a mention of it until early Saturday evening. Southerly
winds will remain gusty through much of the taf period.


Top watches/warnings/advisories...
Flash Flood Watch from Saturday evening through Sunday afternoon
for ksz010>012-022>024-026-035>040-054>056-058-059.



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