Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 160522

Area Forecast Discussion
National Weather Service Topeka KS
1122 PM CST Mon Jan 15 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 345 PM CST Mon Jan 15 2018

Ample cold advection beneath the western rim of a deep midlevel
cyclone over the upper Great Lakes region continues across the
Great Plains. The influx of an Arctic air mass will continue into
tonight, resulting in sub-zero temperatures and dangerously cold
wind chills. The 850-mb temperature characterizing this air mass
at 12Z for the upstream Aberdeen SD observed sounding around -23C
is well below the 10th percentile per the SPC sounding
climatology. This contextualizes the bitterly cold air mass that
will continue to settle over the area. Moreover, the surface
pressure gradient should remain sufficiently tight to maintain
brisk northwest to north winds facilitating wind chill readings of
15 below to 25 below zero tonight into Tuesday morning. A Wind
Chill Advisory accounts for these conditions -- of which the most
dangerously cold are expected along and north of a line from
Belleville to Holton. Warning-level wind chills may be approached
on a brief/spotty basis, though present indications are that the
marginality of Warning-level conditions should preclude an
upgrade to Wind Chill Warning at this time. While winds speeds
will decrease on Tuesday as the pressure gradient slackens, high
temperatures may not rise much above 10F in many locations.

.LONG TERM...(Tuesday night through Monday)
Issued at 345 PM CST Mon Jan 15 2018

For late this week into the the upcoming weekend, the upper-level
wave pattern over the CONUS will initially de-amplify before
medium-range model guidance indicates mean troughing becoming
established over the western/central states. In response to these
developments, the boundary layer should be warming by mid/late
week while lee troughing becomes established over portions of the
High Plains. Prior to more appreciable erosion of the Arctic air,
enhanced surface-layer winds amid the tightened lee-trough-
flanking pressure gradient could support periods of cold/very cold
wind chills for Tuesday night into Wednesday morning, and again
from Wednesday night into Thursday morning. A Wind Chill Advisory
may become necessary for portions of the region for the Tuesday
night into the Wednesday morning timeframe.

For the second half of the weekend, medium-range model guidance
offers at least modest confidence for an organized deep cyclone
to advance from the central states to the Great Lakes region. A
sufficient influx of moisture ahead of this system will support
precipitation chances Saturday night into Sunday. Given prospects
for appreciable tropospheric warming prior to system passage, and
the potential for a well-defined dry slot to accompany this
system, predictability is presently low regarding precipitation
type, timing, and accumulations.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1120 PM CST Mon Jan 15 2018

VFR conditions are expected to continue at all terminals through
the TAF period. Northwesterly winds have remain sustained between
10 and 15 kts at the Topeka terminals with a few stronger gusts.
This trend should continue into the afternoon hours, before wind
decrease to below 10kts near 20-21Z. Patchy low level cloud cover
is expected to remain scattered and not cause any flight


Wind Chill Advisory until noon CST Tuesday for KSZ008>012-



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