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Area forecast discussion
National Weather Service Topeka Kansas
630 PM CDT Wed Oct 18 2017

..update to aviation forecast discussion...

Short term...(this evening through thursday)
issued at 303 PM CDT Wed Oct 18 2017

This afternoon a broad upper level trough was translating eastward
across south central Canada and the northern plains. The weaker
ascent across Kansas was causing some high cirrus to develop. A more
amplified upper level trough will begin to move onshore across the
western US late tonight as a broad downstream upper level ridge
amplifies along the MS River Valley. A weak southern stream upper
level trough across Southern California and northwest Mexico will be kicked
northeast into The Four Corners region.

Tonight, the cirrus clouds should move east of the region. A surface
ridge of high pressure across the northern plains will build south
across NE. Expect clear skies with lows in the mid 40s to lower 50s.

Thursday, a Lee surface trough will deepen through the day across
the Central High plains. The surface pressure gradient will tighten
between the Central Plains Lee trough and surface ridge across the
south central US. South-southeasterly winds will increase through
the afternoon to 10 to 20 miles per hour with some higher gusts. 850mb
temperatures will increase to 18 to 20 deg c, and with deeper
mixing, high temperatures should reach the upper 70s to lower 80s.

Long term...(thursday night through wednesday)
issued at 303 PM CDT Wed Oct 18 2017

On Friday, surface high pressure over the southeastern US will be
retreating eastward with a mid-level trough advancing towards the
central US through the afternoon. A tightening pressure gradient
across the area will not only aid in moisture transport, but also
keep conditions quite gusty Friday afternoon into Saturday. With
clouds building in during the day, highs are expected in the mid-70s
Friday. With the low-level jet overhead Friday night, could see
some showers or storms form during the overnight period.

The main system of the extended period approaches Saturday in the
form of a cold front. Ahead of this front, dewpoints in the low 60s
along with cape between 1000-1500 j/kg are seen. Shear values
indicate the potential for strong to severe storms to form across
the area in the afternoon to evening hours, progressing
southeastward and clearing the area by Sunday morning. All hazards
look possible at this time. Cold air behind the front will kick
temperatures back into the upper 60s by Sunday.

Behind this shortwave, dry conditions are expected to persist
through mid-week. A northwest flow regime sets up from Monday night
Onward aiding in a cool down next week. While highs Monday remain
in the low 70s, Tuesday and Wednesday look to be near the mid-60s.

&&

Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 624 PM CDT Wed Oct 18 2017

VFR prevails as a weak boundary and area of high pressure to the
northwest results in light and variable winds this evening. Low level wind shear
remains marginal this evening around 1400 feet so will continue to
monitor. Saturation near the sfc is not strongly apparent on
forecast soundings at ktop, however the calm winds and weak sfc
inversion should develop shallow MVFR fog aft 09z.

&&

Top watches/warnings/advisories...
none.
&&

$$

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