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FXUS63 KTOP 180442

Area Forecast Discussion
National Weather Service Topeka KS
1142 PM CDT Tue Sep 17 2019

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 249 PM CDT Tue Sep 17 2019

As of 19Z Tuesday afternoon, the longwave midlevel pattern remains 
stagnant with ridging across the eastern CONUS and troughing in the 
west. In addition, a negatively tilted shortwave trough was 
translating northeastward through portions of CO, WY, and MT. At the 
surface, lee troughing extended from eastern NM northward the 
western Dakotas. Regional radar reveals scattered showers and storms 
developing across portions of western NE and SD along the 
aforementioned surface trough. The primary concern through the short-
term period is whether showers/storms will reach northern KS by dawn 
Wednesday morning. Short and mid-range guidance continues to diverge 
on the evolution late tonight into Wednesday morning. Current 
thinking is the best potential for rainfall will remain well-north 
of the forecast area -- closer to the aforementioned shortwave 
trough. That being said, WAA near 700 mb could foster sufficient 
ascent for a few storms to develop near the frontal zone across 
southern NE and far northern KS. Confidence is very low for any 
activity in our area and will limit rain chances to slight chance.

By Tuesday afternoon, a few WAA driven showers may continue into the 
afternoon, but like tonight, the potential appears low. Otherwise, 
another warm and humid day is expected with highs in the 90s and 
heat indices up to 100. 

.LONG TERM...(Wednesday night through Tuesday)
Issued at 249 PM CDT Tue Sep 17 2019

Transitioning into the extended period, the overall midlevel pattern 
will undergo little change through the remainder of the week with 
troughing remaining across the western US. As a result, the WAA 
pattern will remain across the region and may result in 
showers/storms, mainly at night Wednesday through Friday. 
Uncomfortable heat and humidity look to continue through the 
remainder of the week with highs in the 80s and 90s and heat indices 
in the 90s to near 100. 

Model solutions continue to diverge with the timing and evolution of 
the western trough Saturday into Sunday. These subtle differences 
will play a major role in the position of the surface front through 
the weekend into early next week. In addition, very rich tropical 
moisture will advect northward into the region as the remnants of the 
tropical system off the TX coast progresses northward. This may set 
the stage for very heavy rainfall along the aforementioned surface 
front Saturday into Sunday. We will have to continue to monitor 
trends through the week as sufficient shear and instability is 
likely to be in-place across the area for a few severe 
thunderstorms. Temperatures by late weekend into next week remain 
quite uncertain as subtle differences in frontal position will play 
a big factor in temperatures Sunday into Monday. GFS has a more 
northern placement of the front, yielding warmer and more humid 
conditions, whereas the ECMWF has cooler and drier conditions with 
the front further south. 


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1142 PM CDT Tue Sep 17 2019

VFR conditions continue. Chances for an isolated elevated shower 
remain but remain very small. Surface winds will not vary 
significantly through the period with diurnal trends of nocturnal 
backing and daytime veering dominating. 



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