Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 131747

Area Forecast Discussion
National Weather Service Topeka KS
1147 AM CST Mon Nov 13 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 304 AM CST Mon Nov 13 2017

Early this morning a broad area of low-level stratus was spreading
north, to the east of an Abilene to Hiawatha line. West of this line
skies were mostly clear and areas of dense fog, with visibilities
below one quarter mile to a few hundred feet, have started to
develop and may become more widespread towards sunrise across much
of north central KS and portions of northeast KS. Therefore, the
dense fog advisory has been expanded westward across north central
KS through 8 AM this morning. Areas under the stratus cloud cover
will only see visibilities drop to 3 to 4 miles.

The mid and upper level flow will become more zonal across the
central and southern plains Today into Tonight. A lee surface trough
will deepen across the high plains this afternoon and Tonight. The
resulting pressure gradient at the surface and 850mb will allow for
residual moisture advection northward across OK into southern KS
this afternoon and then across the eastern half of the CWA Tonight.
The resulting isentropic lift at the 290K theta surface will cause
patchy to areas of drizzle to develop this evening and continue
through the night. Cloud cover Today will keep highs in the lower
50s. Overnight lows will only drop into the mid to upper 40s.

.LONG TERM...(Tuesday through Sunday)
Issued at 304 AM CST Mon Nov 13 2017

South to southwest low-level flow persists under a warm and dry
mid-troposphere for more drizzle potential through at least
Tuesday evening. Compared to this past Saturday, models are in
good agreement with the lift being weaker and the moisture not
nearly as deep especially in north central Kansas and a lower PoP
still seems in order with uncertainty in coverage of measurable
precip. Shortwave moving through the northern Plains clips the
local area with a modified Pacific cold front passing in the late
evening and overnight hours. CAPE values still manage to increase
to a few hundred J/kg but realizing this instability still looks
uncertain with the capping not diminishing much. Will maintain a
thunder mention for mainly east central Kansas for the overnight
hours but could easily see only a heavier drizzle materialize in
stronger convergence ahead of the front.

Wednesday finally brings deep subsidence and clearing, but the
next, stronger shortwave enters the Pacific Northwest Thursday,
with another drizzle setup unfolding as dewpoints rise on
southerly winds while the cap is reinforced on westerly mid-level
winds. There continues to be notable timing difference in this
wave and associated cold front passage around midday Friday, with
the ECMWF and Canadian models roughly 12 hours slower than the GFS
and nearly all of its members. Precipitation chances with the wave
and front themselves should be limited at best with the low level
flow still veered, with the primary impact on the front`s timing
being on winds and RH and thus elevated fire weather potential.
Will keep temperatures close to normal for the weekend, but there
are significant difference on how much cold air can make it in by


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1139 AM CST Mon Nov 13 2017

Another busy TAF period ahead with low cigs and low vsby. IFR to
low MVFR cigs are expected to continue through the afternoon
hours. IFR cigs will become prevalent by 00Z at all terminals.
Cigs and vsby will continue to decrease with LIFR conditions near
04Z as drizzle overspreads the terminals. Currently have
prevailing 1SM for vsby between 04Z and 16Z, although brief
periods of lower vsby are possible. Cigs and vsby should begin to
improve near the end of the TAF period.




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