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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

FXUS63 KTOP 181139

Area Forecast Discussion
National Weather Service Topeka KS
639 AM CDT Thu Apr 18 2019

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 248 AM CDT Thu Apr 18 2019

Northern stream upper trough is currently centered over the 
western Great Lakes region while the southern stream vort max 
continues to generate several areas of showers and thunderstorms 
from southern Kansas and Missouri into southern Texas. The sfc 
cold front has passed through the CWA with gusty north winds 
behind it this afternoon between 15 and 20 mph sustained. Despite 
the cold air advection in place, decent low level mixing of warmer
air aloft and mostly sunny skies assists temperatures in reaching
the lower and middle 60s this afternoon. Most short term models 
are fairly similar in tracking a piece of energy translating 
through the upper trough as it pushes south and east during the 
late afternoon. While the best forcing resides towards Nebraska, 
chances are increasing for enough forcing to generate scattered 
showers in the afternoon, especially towards central and portions 
of northeast Kansas. With no capping inversion in place and sfc 
cape values between 500 and 750 J/KG, it is conceivable that we 
may see isolated thunderstorms during the mid to late afternoon. 
Given the steep low level lapse rates and decent dry air below 750
mb, localized strong wind gusts would be the main hazards.

Activity wanes after sunset as the upper trough shifts eastward, 
clearing skies this evening. Northerly winds hold around 10 to 15 
mph overnight, keeping temps a bit warmer in the lower 40s. Upper 
30s are anticipated elsewhere with the lighter wind speeds.

.LONG TERM...(Friday through Wednesday)
Issued at 248 AM CDT Thu Apr 18 2019

Friday and Saturday continue to look quiet with upper level
ridging overhead. The lack of large scale forcing and relatively
dry air should keep dry and clear weather over the region. Have 
kept highs on Friday in the middle sixties even though model progs
would suggest highs could be several degrees cooler. Think sunny 
skies should provide enough heating that I didn't want to lower 
the forecast. There is some potential for the lows Saturday 
morning to fall off more than the models show as the surface ridge
axis passes through the forecast area. Clear skies and light winds
should favor radiational cooling and have some of the low lying 
areas falling into the upper 30s as a result. Low level southerly 
return flow develops for Saturday with decent warming progged at 
925MB and 850MB. So highs are expected to reach the upper 70s and 
lower 80s.

For Sunday through Tuesday, models generally show disturbed
weather across the central plains. There still remains differences
among the models as they struggle to handle the synoptic pattern.
Some suggest the pattern splitting while others keep a phased
pattern that slowly progresses east. A lead shortwave is progged
to lift into the central plains Sunday. After that, there is not
much confidence in the model details for Monday through Wednesday,
like the location of an inverted surface trough or axis of higher
moisture. In general with the model consensus showing a slower 
progression to the pattern, will keep some chances for precip 
beginning Sunday afternoon and continuing through Tuesday night.
The GFS shows the better instability for Sunday afternoon and
evening, but the wind fields are progged to be pretty light so
shear parameters do not look that impressive. For Monday and
Tuesday, cooler temps forecast by the models make it difficult to
generate much instability. As for temps, have not strayed much
from a blend of available solutions which puts lows and highs
close to or a little warmer then climatological normals. 


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 626 AM CDT Thu Apr 18 2019

VFR prevails with mid to high clouds gradually dissipating by mid
morning. Current satellite trends show scattered to broken MVFR
stratus dropping southward across far northern Kansas into
northwest MO. Most models hold the denser cloud cover further
north and east of sites, but did include at least few lower 
clouds around through 15Z at KTOP/KFOE. Daytime cumulus 
redevelops in the afternoon with gusty north winds through 00Z 
with speeds from 12 to 16 kts sustained.




LONG TERM...Wolters