849 
FXUS63 KTOP 071747
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1247 PM CDT Thu Jun 7 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 324 AM CDT Thu Jun 7 2018

07Z water vapor imagery shows an upper ridge over the central plains 
with an upper trough over the west coast. At the surface, an outflow 
boundary has pushed south and west across the forecast area to near 
CNK and EMP. A meso high was centered over the MO river with a 
second meso high over southwest NEB. A surface trough was located 
across the southern high plains from southeast CO through west TX. 

The forecast for today is shaping up to be complex. Just about 
every solution has a different answer for convective trends through 
this morning and any redevelopment later in the day. In the short 
term, think the MCS across western KS will probably hold together 
long enough to move into western sections of the forecast area as 
southerly winds continue to pump moisture north ahead of the outflow 
boundary. Through the rest of the morning, most guidance shows the 
associated MCV propagating east across the area. There are a few 
convective allowing models (CAMs) that linger scattered showers and 
storms into east central KS by the late morning and think it may be 
due to this MCV. The HRRR clearly is behind the curve timing wise, 
but the ARW and NMM support this idea of storms holding together 
into eastern KS. The big unknown is how the storms will evolve as 
they encounter the meso high over northern KS. The expectation is as 
they run into the cooler air to the east they would become more 
elevated and weaken. So I keep some scattered wording through the 
morning with storms moving east, but have POPs gradually diminishing 
thinking storm coverage will lessen as they move east and become 
more elevated. 

For later in the afternoon and tonight, confidence in the forecast 
is not that great. Models suggest there will once again be quite a 
bit of instability (at least 4000 J/kg) developing in an undisturbed 
airmass with temps in the lower 90s and dewpoints holding in the 
upper 60s. However it is not clear that there will be an undisturbed 
airmass as there could be some weak subsidence in the wake of the 
morning convection as well as cooler temps. Additionally there is 
not an obvious forcing mechanism for storm development this 
afternoon. So I only carry some small POPs through the afternoon 
with the expectation the MCS will limit the recovery somewhat. The 
forecast has chance POPs for tonight. The thinking is areas west 
could recover enough for renewed development by this afternoon. 
These storms would likely move across the forecast area through the 
night. The reason for only going with chance POPs is there is no 
consensus among any of the models for timing or location of the 
storms. So think storms tonight may remain scattered in coverage, 
and there simply isn't enough confidence to go with likely POPs. 
Deep layer shear remains marginal this afternoon and tonight, but 
the potential for a very unstable airmass suggests a risk for large 
hail and damaging winds late this afternoon and overnight. 

Highs today are expected to be in the middle 80s to near 90. Cloud 
cover early in the day along with some overturning of the airmass 
should keep highs somewhat cooler than yesterday. Also models show 
some cooling in the 1000-500MB thicknesses and 850MB temps. Lows 
tonight will again depend on coverage of thunderstorms. Given the 
uncertainty have not strayed to far from a model consensus with lows 
in the upper 60s to around 70.

.LONG TERM...(Friday through Wednesday)
Issued at 324 AM CDT Thu Jun 7 2018

Mid-level ridging over the central Plains continues through the 
weekend with multiple pertibations in the flow through this period 
allowing for chances for precipitation.  Models continue to vary on 
spacial coverage of any storms Friday and Friday night with the GFS 
the most robust with precipitation potential. Like previous days, 
ample CAPE will exist Friday although shear appears to be marginal 
near 20-30 knots across northeast Kansas. Soundings indicate a cap 
in place across northeast Kansas Friday afternoon and evening which 
would need to be overcome before storms can develop. Even so, if 
storms do form, steep lapse rates will allow for a any storms to 
become severe with damaging wind gusts and hail the main hazards. 
This pattern continues through the weekend with low-predictability 
storms that would be capable of becoming severe.  For now, models 
hint at very northeastern Kansas and east central Kansas have the 
best chances for precipitation.

A mid-level trough advances across the northwest CONUS Sunday into 
Monday and a frontal boundary moves into northeast Kansas Monday 
afternoon.  There are some chances for precipitation with this 
frontal passage, but the better chances remain north of Kansas at 
this time.  Model solutions diverge towards the end of the 
period making confidence in precipitation chances low after Monday.

As for temperatures, highs look to remain in the 90s from Friday 
through Wednesday.  Heat indicies creep up near 100 degrees Friday 
through the weekend, but temperatures do not look advisory level at 
this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1245 PM CDT Thu Jun 7 2018

Mid/high-level clouds will spread across the region through the
period, though predominantly VFR conditions are expected at the
TAF sites. Isolated to scattered showers and thunderstorms may
develop this afternoon across the area, with additional
showers/storms entering and crossing the region through tonight 
into Friday morning. While localized visibility/ceiling 
restrictions, along with gusty winds, may accompany this 
activity, confidence in these impacts affecting any given TAF 
site is too limited for inclusion in the TAFs at this time.

&&

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

$$

SHORT TERM...Wolters
LONG TERM...Heller
AVIATION...Cohen