Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 181802
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
102 PM 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 18Z TAFS through 18Z Thursday afternoon)
Issued at 1243 PM CDT Wed Oct 18 2017

Expect VFR conditions at all terminals through the next 24
hours. There may be some moderate low-level windshear at the
terminals as a southwesterly low-level jet strengthens to 30-35
KTS after 6Z and continues to 13Z.

&&

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

$$

SHORT TERM...Drake
LONG TERM...67
AVIATION...Gargan



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