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000 
FXUS63 KTOP 181128
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
628 AM CDT Wed Oct 18 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 250 AM CDT Wed Oct 18 2017

Quasi-zonal flow has set up over much of the CONUS with the mean 
Westerlies residing largely over the northern tier near the 
Canadian border. The system of note that will impact the forecast 
area over the next 24 hour period is a fairly low amplitude 
shortwave that has taken on a slight negative tilt as it advances 
into the extreme northern Plains. Surface cold front is being 
pushed into this region as well with a weak lee trough along the 
foothills of the Rockies extending into the TX panhandle. 
Expansive surface high pressure remains centered over the 
southeastern states. 

Overnight low temps remain on track to dip into the upper 40s and 
around 50 in some spots with surface winds not really decoupling. 
So, BL will remain at least partially mixed.  Into the day today, 
pre-frontal trough and weak/highly modified cold front works into 
the area slowly this afternoon as upper trough translates into the 
northern Great Lakes region.  As it does so, mid-level ridge builds 
over the Central Plains. This will cause front to decay and 
undergo frontolysis as it enters the forecast area right around 
the KS/NE border. Therefore, high temps shouldn't be influenced 
greatly by this feature with winds remaining southerly to 
southwesterly. In addition to the wind direction, with mixing 
today only up to about 900-850mb level, have mid to possibly some 
upper 70s going over the area from north to south. Could possibly 
be some ground fog form for Thursday morning but have not 
mentioned in forecast as the moist layer appears to remain very 
shallow. Any concerns likely remain throughout the river valley 
areas. Lows should be a couple degrees cooler with a less well 
mixed BL and thus better radiative cooling. Upper 40s should be 
common.

.LONG TERM...(Thursday through Tuesday)
Issued at 250 AM CDT Wed Oct 18 2017

Relatively good agreement in the extended models with
system/feature timing and overall larger scale pattern. 

Latter part of the week marked by the passage of a mid level 
ridge, keeping conditions dry and on the warm side into Friday. 
Both GFS and EC take the next shortwave trof out of the 
southwestern states and across the Central Plains on Friday, which
spends much of the day bringing moisture back into the column 
before bringing a chance for showers/storms in the overnight hours
into early Saturday. Highs Thursday approach 80 with mid/upper 
70s on Friday, along with breezy conditions as the surface 
gradient tightens. 

Warm temps and moisture advection continue ahead of the larger 
upper trof and frontal boundary, still forecast to sweep across 
the area on Saturday afternoon into the evening hours. Enough 
instability making it this far north to continue mention of strong
to severe storms as this front passes, with storms clearing west
to east by 12z Sunday. Temperatures Saturday hold in the 60s to
low 70s, with slightly cooler highs on Sunday in the 60s.  

Temperatures may bump back north into the low 70s on Monday before
the next push of cooler air moves southward into the Plains states
through Tuesday and take us back to a more seasonal 60s for 
highs. 

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 624 AM CDT Wed Oct 18 2017

VFR conditions persist for the 12Z TAF period. Winds could be a
bit gusty out of the SSW during the daytime hours but weaken as 
the boundary layer decouples near sunset time frame. Ground fog
will be possible near the end of the period, but have not gone
with mention at this time. 

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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