Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 251143

National Weather Service Topeka KS
543 AM CST WED NOV 25 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 334 AM CST WED NOV 25 2015

Ahead of the broad upper low centered over Nevada this morning,
multiple embedded waves were noted downstream through the eastern
Kansas area. Analysis of the sfc to 850 mb layer reveal an increase
saturation through Oklahoma into portions of central KS with the sfc
dewpoints rising into the upper 40s and lower 50s. Forecast
soundings show the enhanced moisture carrying some weak isentropic
lift into the CWA after sunrise today starting out as patchy drizzle
initially. Coverage of drizzle spreads through northeast KS as lift
and saturation increase in the mid levels with the onset of a
stronger embedded shortwave trough to arrive this evening. Despite
the overcast skies and occasional precip, strong warm advection from
the south at 10 to 20 mph will hold highs on the mild side in the
lower 60s.

Rain showers are expected to develop this evening across the area as
the inverted surface trough deepens, bisecting the CWA from
southwest to northeast. Model guidance is fairly well aligned in a
frontal boundary sagging southeast through the CWA overnight, while
the mid level wave approaches from the southwest. The LLJ is
expected to increase after 06Z with a band of enhanced forcing along
the boundary. Precip will generally be light overnight with the
heavier intensity occurring after sunrise Thursday. The good news
though is with the below freezing temps lagging behind the sfc
boundary, all precip remains as rain. Lows tonight will remain
steady, if not rise a few degrees with readings from the lower 40s
in north central KS, to the middle 50s in east central KS.

.LONG TERM...(Thursday through Tuesday)
Issued at 334 AM CST WED NOV 25 2015

Thanksgiving day is still looking messy with widespread rain to
start the day across the area with the heavier amounts across
northeast and east central Kansas. The main concern continues to be
the speed in which the cold air will move southeast across the area
behind the cold front. Models still differ with this and the NAM is
the slowest to drop the temperatures. The ECMWF and GFS are faster
with the GEM the furthest southeast with the freezing line by the
end of the day. Went with a blend of the ECMWF and GFS which offer a
good compromise for the front moving through the area and the
resulting cold air advection behind the front. If the cold air is
faster than anticipated during Thanksgiving afternoon, then ice
amounts will be slightly higher. During the evening hours
temperatures will continue to fall and the area of freezing rain
will shift southeast through the night. Potential still exists for
around 0.25 inch of ice accumulation or less across north central
and northeast Kansas through early Friday morning, while the rest of
the area will likely see a light glaze to around a tenth of an inch
of ice. By Thursday night the focus for heavy rainfall will shift to
the north as the front continues to move southeast. Upper forcing
will continue as energy eject northeast across the Plains from the
western CONUS upper trough. The upper low will be slow to move and
will gradually move east by Tuesday. This sets up a prolonged period
of off and on again precipitation chances. The cold air will still
be in place and does modify through the weekend. Expect periods of
freezing precipitation as well as light rain or drizzle. Areas
across north central Kansas and northeast Kansas will mainly have
the wintry mix while east central Kansas will see a gradual
transition to rain. Will maintain the winter storm watch for north
central and northeast Kansas from Thursday afternoon through early
Friday morning.


.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 535 AM CST WED NOV 25 2015

Drier air at the sfc is gradually being overcome by increasing
moisture from the south...with all guidance lowering cigs to MVFR
between 16 and 18Z today. Gusty winds remain above 12 kts
sustained through period with indications of light drizzle
developing this afternoon. Cigs lower to IFR aft 03Z as rain
showers become widespread. Timing for this switchover may be
adjusted some based on precip bands.


.TOP Watches/Warnings/Advisories...
Winter Storm Watch from Thursday afternoon through late Thursday
night for KSZ008>012-020>024-026-034>039.



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