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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

                            
000
FXUS63 KTOP 200839
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
339 AM CDT Fri Sep 20 2019

.SHORT TERM...(Today and tonight)
Issued at 339 AM CDT Fri Sep 20 2019

Early this morning an upper level trough was located over the 
western U.S. while a ridge extended across the eastern Plains south 
into the Gulf. Weak embedded waves were moving northeast out of the 
base of the trough and into western Kansas south into eastern New 
Mexico where scattered convection was occurring at 0730Z. Latest 
surface analysis showed an area of 70 degree or higher dew points 
from the Red River south into Texas, while central and eastern 
Kansas had dew points in the 60s. 

For today, remnant PV anomalies will move northeast across the area 
today. Forecast soundings show a weakly sheared environment and 
moderate instability through the day into the early evening hours. 
CAMS continue to develop isolated to scattered convection over parts 
of north central and northeast Kansas today and into tonight as the 
perturbations move northeast, moisture advection increases with the 
increasing low level jet. Have maintained lower end precipitation 
chances through the day and into tonight. Temperatures today will be 
limited in the lower to mid 80s dues to clouds limiting insolation. 

Saturday, a cold front is forecast to extend from northwest Iowa 
into south central Nebraska into southwest Kansas by late afternoon. 
The lead trough is forecast to lift northeast into the northern 
Plains on Saturday which will move the front further south. Airmass 
ahead of the front becomes very unstable and deep layer moisture 
increases across central and eastern Kansas with precipitable water 
increasing to around two inches. Shear will be sufficient for severe 
storms and forecast hodographs and SRH values are favorable enough 
to mention an isolated tornado possibility, especially during the 
early evening hours. 

.LONG TERM...(Saturday through Thursday)
Issued at 339 AM CDT Fri Sep 20 2019

Next main concern will be heavy rainfall potential across much of 
northeast and east central Kansas Saturday night into Sunday 
morning. Forecast soundings show deep moisture profiles. Theta-e 
ridge will lay from southwest to northeast across the area. Forcing 
for ascent will increase as the upper trough moves out into the 
Plains. Also the presence of the entrance region of the upper level 
jet will increase upward vertical motion and upper level divergence. 
Training of storms will lead to locally heavy rainfall with amounts 
of 2 to 4 inches and locally higher possible through mid day Sunday. 
Axis of heaviest rain may shift a bit, but confident enough to issue 
a Flash Flood Watch from Saturday evening into early Sunday 
afternoon.

Looking ahead models differ some with respect to another upper look 
digging into the southwest U. S. early next week and the timing and 
track as it moves out into the plains by the end of the week. SOme 
timing differences also with a lead wave moving through the central 
Plains on Tuesday. Nearly Zonal to southwest flow develops by 
midweek as the upper low then is forecast to move out into the 
Plains. This will keep small chances of precipitation in the 
forecast although there will be periods of dry weather. Temperatures 
will be around seasonal values. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1141 PM CDT Thu Sep 19 2019

For the 06z TAFs, southerly winds will become gusty around 20kts 
late Friday morning through the afternoon hours. Scattered 
showers and storms may develop near the TAF sites by the afternoon
hours and diminish by early evening. Expect cigs to drop to MVFR 
with these storms and remain MVFR (and possibly borderline IFR) 
through the end 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.

&&

$$

SHORT TERM...53
LONG TERM...53
AVIATION...Hennecke