Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 141126

Area Forecast Discussion
National Weather Service Topeka KS
526 AM CST Wed Feb 14 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 335 AM CST Wed Feb 14 2018

A mid-level trough is noted just off the coast of southern
California with southwest flow over most of the southern and
central Plains. Early this morning, dewpoints just south of the
CWA were observed to be increasing indicating the potential for
fog formation. Expect fog to form in the early morning hours in
east central Kansas and generally advect northeastward after
sunrise. RAP/GFS soundings are generally in agreement that this
fog may lift to some low stratus by early morning and clear the
area by early afternoon which is what is reflected in the forecast
(disregarding the NAM that keeps low ceilings across most the
area through late afternoon).

Southwest surface winds this afternoon will aid in warmer
temperatures today with mid-60s still expected near central and
east central Kansas. Further north, near the Kansas/Nebraska
boarder, may only see temperatures reach into the mid to upper 50s
with some lingering snow cover still being reported. Surface low
pressure on the lee side of the Rockies in Colorado begins to move
towards central Kansas tonight, eventually bringing a cold front
through the area Thursday. Lows drop into the mid 30s to low 50s.

.LONG TERM...(Thursday through Tuesday)
Issued at 335 AM CST Wed Feb 14 2018

A mostly dry forecast is on tap for the latter half of the week
and much of the weekend, with 20-40 degree swings in temperatures
during the period.

Upper level blocking low off the California coast breaks down and
phases with a northern stream wave at the start of the period.
Associated H500 height falls attendant to the approaching wave
will allow a residual boundary left in the wake of of a passing
surface cyclone to begin pushing southward. However, model trends
have been slightly slower in the advancement of this strengthening
cold front Thu afternoon and have raised temperatures by 3-4
degrees in the warm sector ahead of the front for Thu. Winds on
Thu night/Fri morning continue to look to be on the stiff side
with a 25-30 ubar/km pressure gradient spreading over the state
coupled with a 6-8 mb/12 hr pressure rise. These winds look to
decrease by sunrise Friday as a 1039 mb Canadian high slides

Temps on Friday still look to struggle to reach the mid 30s for
highs as H850 temps fall by 20-25 degrees C between Thu morning
and Fri midday behind the cold front. However, return southerly
flow sets in late in the day Fri as the high spreads eastward and
the next H300 wave dives across the Rockies. The GFS is the more
bullish solution in the depth of the return flow and strength of
the 290-295 K isentropic upglide Sat morning, and likewise has its
QPF field further north than the EC. However, given the other dry
solutions and the wide spread in the GEFS solutions, kept POPs
confined in the far SE CWA for Sat morning.

A surface weak trough/ridge couplet pass through on Sat/Sat night
and look to bring little more than variable winds. Increasing
southerly flow on the backside of the ridge on Sunday will push
temps back into the 50s to low 60s. However, the next shortwave in
the train dive across the PacNW Sunday/Sunday night and
amplifies, ushering a strong cold front into Kansas. Thermal
profiles do suggest enough instability in the warm sector ahead of
the front to support showers/thunderstorms and have introduced
these elements in the SE CWA Monday afternoon.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 525 AM CST Wed Feb 14 2018

Low visibilities and ceilings currently observed south of
terminals are expected to reach all sites near 13Z. Although
models have been backing off on visibilities slightly, kept
IFR/MVFR restrictions mainly from 13Z through 16-18Z. After
conditions clear, VFR will prevail through the rest of the period.
LLWS looks to be a concern after midnight as the low level jet
sets up over northeast Kansas.




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