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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

FXUS63 KTOP 220800

Area Forecast Discussion
National Weather Service Topeka KS
300 AM CDT Sat Jun 22 2019

.SHORT TERM...(Today and tonight)
Issued at 258 AM CDT Sat Jun 22 2019

07Z water vapor imagery showed an upper low over northeast MT with a 
shortwave digging south towards NV. This kept a southwesterly flow 
over the southern and central plains. At the surface, a weak area of 
low pressure was noted over the TX and OK panhandles. An inverted 
trough stretched from the surface low into northeast KS. 

Models continue to struggle with convection in the short term. But 
isentropic surfaces support the current storms across central KS to 
continue a gradual lift to the north and east. Think the inverted 
surface trough will also aid in the slow propagation of storms. 
After the storms fall apart with later this morning, forecast 
soundings show a stout elevated mixed layer advecting over the 
area. So think without an obvious vort max lifting across the area 
to weaken the cap, a good portion of the day could end up being dry. 
Otherwise a very moist and warm airmass is progged to generate large 
amounts of CAPE by the early afternoon. Deep layer shear is expected 
to be better across north central KS where mid level winds are 
likely to be stronger. But given the magnitude of CAPE over eastern 
KS, severe storms are possible across the entire forecast area 
during the late afternoon and early evening. The biggest source of 
uncertainty is the tendency from the NAM and GFS to scour out the 
low level moisture and reduce the instability overnight. 
Conceptually this does not make a lot of since with the upper trough 
axis progged to remain to the west of the forecast area. So am not 
sure I buy the lack of precip from the models after 06Z. In general 
the weather is going to be dictated more by mesoscale factors so 
confidence is how thunderstorms evolve this evening is on the low 
side. Considered a flash flood watch for the late afternoon and 
overnight hours. But the low confidence in convective trends doesn't 
lend much confidence to a watch at this point. 

Models show the weak surface low over the panhandles lifting into 
north central KS today along the trough axis. This is expected to 
advect the warm sector into eastern KS and help highs warm to around 
90. If temps are able to warm even more, there is some risk for 
reaching heat advisory criteria across parts of east central KS. 
Confidence in this is low given the current convection moving 
towards that area. Lows tonight should remain fairly mild with no 
obvious cold air advection noted in the models. The one caveat would 
be rain cooled air cooling temps, so have lows in the 60s.

.LONG TERM...(Sunday through Friday)
Issued at 258 AM CDT Sat Jun 22 2019

Transitioning into the extended period, more thunderstorms are 
expected Sunday with a typical summer pattern setting up for next 

Thunderstorms are likely to be ongoing across far eastern KS as a 
lead midlevel shortwave trough ejects across the Central Plains. The 
primary hazard with the morning convection is damaging winds. The 
main midlevel trough is progged to eject across the Plains Sunday 
afternoon into Sunday night. Considerable uncertainty remains with 
thunderstorm potential Sunday afternoon as outflow from the morning 
convection is likely to stabilize eastern KS. The main surface 
trough axis is progged to generally bisect the forecast area from 
SSW to NNE. If sufficient destabilization is able to occur Sunday 
afternoon, a favorable environment will be in place along the 
aforementioned surface trough for severe thunderstorms. Large hail 
and damaging winds will be the primary concerns throughout the 
afternoon and evening. 

Otherwise, a typical summer pattern looks to return next week with 
midlevel ridging amplifying through the week. A few LLJ driven 
nocturnal thunderstorms are possible nearly each night although 
these chances a very slight. High temperatures will return to the 
lower 90s with lows in the upper 60s. 

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1212 AM CDT Sat Jun 22 2019

VFR prevails with scattered TSRA expected to develop northward
towards KMHK by 09Z with lesser uncertainty in storms reaching 
KTOP/KFOE overnight. Inserted a VCTS mention for the lesser 
confidence, but otherwise expect activity to clear the terminals 
shortly after sunrise. Low level moisture advection on the nose of
the sfc trough axis results in MVFR stratus in the morning period
before clearing to VFR in the afternoon. Additional TSRA is 
anticipated in the late afternoon and evening time frame. Models 
are still quite uncertain on coverage and timing for precip so 
have just left a VCTS mention at this time.




SHORT TERM...Wolters