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Area Forecast Discussion (AFD)

Issued by Topeka, KS (TOP)

FXUS63 KTOP 242044

Area Forecast Discussion
National Weather Service Topeka KS
344 PM CDT Wed Apr 24 2019

.SHORT TERM...(This evening through Thursday)
Issued at 341 PM CDT Wed Apr 24 2019

Overall, seasonal temperatures continue for the short-term period. 
Areas of patchy fog are possible tonight, especially over east 
central into portions of northeast Kansas, with some showers 
possible mainly north of I-70 around midday.

Currently, an elongated positively tilted trough is extended through 
portions of the forecast area from the mid to upper levels of the 
atmosphere.  This has allowed for cloud cover to be slow to exit the 
region with lingering low to mid cloud cover remaining over east 
central into portions of northeastern Kansas.  Fog from this morning 
was also slow mix out with weak overall winds due to a weak high 
pressure surface ridge in place with the current frontal system off 
to the southeast of the area from the Southern Plains into the Mid 
MS Valley region.  As a result, have left highs depressed slightly 
over east central areas with highs around the middle 70s over north 
central areas.  

Tonight may be somewhat of tricky forecast period considering when 
clouds actually clear the area.  I have patchy fog forecast right 
now overnight into the early morning hours mainly over east central 
areas into portions of northeast Kansas.  The expectation is that 
clouds do eventually clear the area and the surface ridge slides 
slightly further southeast into east central areas.  Most recent 
moisture from yesterday has also fallen over east central areas. 
This leads to some antecedent conditions remaining favorable to the 
formation of fog.  Expecting a relatively shallow saturated layer to 
develop near the surface with radiational cooling and calm winds. 
Therefore, thinking dense fog probably won't form or at least become 
too widespread across the area.  For that reason, have not 
considered a dense fog advisory for overnight at this time.  

Into midday tomorrow, as the upper air pattern transitions to a more 
northwest flow component, a minor shortwave over the northern 
Rockies dives into portions of the Central Plains.  This could bring 
some small chances for isolated morning showers mainly along the Hwy 
36 corridor. Highs tomorrow region the middle 70s. 

.LONG TERM...(Thursday night through Wednesday)
Issued at 341 PM CDT Wed Apr 24 2019

The long range forecast is still marked with uncertainty but some 
clues are coming together that hint to a more active pattern.  

Saturday will see increasing southerly flow over western portions of 
the area as a developing low deepens off the lee of the northern 
Rockies as a Pacifc energy works across the region.  Right now, the 
position and strength of the low focuses the better dynamics over 
Nebraska.  Severe weather with this system doesn't appear to be an 
overly large concern at this time.  However, it may mark the 
beginning of a more wet period.  Overall, the system exits the 
region by Saturday afternoon and then the upper pattern transitions 
to a quasi-zonal flow regime.  More persistent southerly flow 
develops and eventually a Western CONUS trough becoming semi-
permanent through much of next week with southwest flow becoming 
more dominate. 

Although, there is still too much spread in the overall solutions to 
say for sure, it does appear that severe weather either Monday 
afternoon into Tuesday afternoon time frame could become of more
of a concern. Exact hazards still hard to pin down, but the best 
areas of focus could be over east central Kansas once again. 
Perhaps the larger concern into the week -- with several waves of
showers and storms moving across the area -- could become that of
flooding. It does appear that a more moist and deeply saturated 
airmass could set up over the region with continued moisture flux 
into a surface to H85 boundary across the area. Can't rule out 
several inches of rain during this period. But, again, there is a 
good amount of time before this pattern is revealed fully and with
more certainty. Something to consider due to the time of year and
the fact that moisture across the region has not been lacking for
quite some time. 


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1246 PM CDT Wed Apr 24 2019

Earlier fog finally continues to scatter out completely near KMHK
early this afternoon. Overall cloud coverage continues to diminish
across the rest of the area by this evening. Mostly clear
conditions and calmn winds overnight lead to a more confident set
up for fog over portions of the area. Patchy coverage overnight is
thus expected which may include the terminals by early tomorrow
morning until a couple hours after sunrise. Due to some
uncertainty in spatial coverage and the notion that thick dense
fog is not expected, have opted to leave mention of fog out of the
TAFs for now.