Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 301135

National Weather Service Topeka KS
535 AM CST MON NOV 30 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 403 AM CST MON NOV 30 2015

The fourth consecutive night of winter weather is well underway, and
once again the extent of weather-related impacts depends heavily on
the minute details of the forecast...leaving very little room for

On the broad scale, the good news is that the strong and persistent
storm system is finally being kicked northeast into the Plains. A
strong upper jet was nosing into western OK and southwest KS with a
swath of strong deep layer vertical motion across the area. The
strongest short wave energy within the broad upper trough was over
central Colorado, and will move into eastern Nebraska by this
afternoon. All of this forcing will keep a swath of moderate
precipitation streaming over the local forecast area through the
morning hours before gradually shifting to the northeast. While this
precipitation is currently all rain, cooling temperatures aloft with
the approach of the main short wave will turn rain over to a brief
period of sleet and then snow through the morning hours...mainly
west of a Morris to Nemaha county line with rain elsewhere.

Looking closer at the important details of the forecast: At 3 AM the
freezing line was diffuse, and while it generally extended from
Morris county to Nemaha county it also seemed to depend on a
specific location`s elevation and other minor details. Naturally,
the heaviest rainfall axis was oriented near the freezing line as
well...with sub-freezing areas having the potential for rather
substantial icing while impacts in the above-freezing air are
minimal. The expectation through mid morning is for the freezing
line to remain essentially stationary with minor fluctuations
possible. The rainfall rates are up to 0.15" per hour or so under
the heavier bands, and any temporary decrease in temperature at a
location could lead to a quick accumulation of ice especially on
trees and power lines and especially in areas that already have ice
on those objects. So confidence in the amount of total additional
ice accumulation is low and the amounts may vary substantially
across small areas...but the potential exists for additional tree
and power line damage mainly in the winter storm warning area.

As previously mentioned, rain will change over to sleet/snow for the
western half of the area. This should begin along the highway 81
corridor by around 6 AM and spread east to near the highway 77
corridor by 9 AM or so. Drier air aloft will also begin to move in
to the area by late morning which will end the bulk of precipitation
but may allow drizzle to continue with the shallow moist layer
persisting. So, the period available for snow to fall is rather
short but given the magnitude of lift with the system and also the
presence of weak convective instability aloft there could at least
be a brief period of moderate to heavy snow. It currently appears
unlikely that any part of the area will get more than 2 inches of
snow, and the best chance for this would likely be in Republic,
Washington, Cloud, and Marshall counties. These areas could just as
easily end up with only a dusting.

Precipitation clears out of the area from southwest to northeast
during the afternoon. Low clouds will hang in for much of the day,
but even clouds should eventually try to clear out from southwest to
northeast overnight. West winds are expected to continue overnight,
and as long as the breeze continues the temperatures should stay in
the 20s. However, if the wind is able to go calm, could see pockets
of colder temperatures and fog.

.LONG TERM...(Tuesday through Sunday)
Issued at 403 AM CST MON NOV 30 2015

By Tuesday morning, both the strong mid-level and surface lows will
have lifted northeast of the forecast area, advancing toward the
Great Lakes region by Tuesday night. Within the mid-level flow,
models show a shortwave trough developing just north of the CWA and
swinging across extreme northeast Kansas late Tuesday afternoon into
Tuesday evening. There isn`t much moisture or available lift over
northeast Kansas with this passing shortwave and expect any
precipitation that develops to stay further north in Nebraska and
Iowa, so have a dry forecast. Surface high pressure will shift into
the area behind this exiting system, helping to bring some welcomed
dry conditions to the region through the remainder of the week and
into early this weekend. This surface high should start shifting
east of the area by the latter part of the week, which will bring
light southwesterly flow into the area and result in high
temperatures moderating from the upper 30s to mid 40s (Tue and Wed)
to the mid 40s to low 50s for Thursday and Friday.  With surface
high pressure anchored over the eastern U.S. by this weekend and
surface low pressure advancing into western Kansas, expect an
increased pressure gradient over the region with breezy southerly
winds supporting continued warm-air advection with weekend highs in
the mid 40s to mid 50s. The next potential chance for some
precipitation may be Sunday/Sunday night as models show another mid-
level trough developing across the western U.S. with a closed-low
developing east of the Four Corners region by Sunday morning.  The
ECMWF shows a much stronger mid-level low and, thus, shows more
available moisture and lift over the area while the GFS keeps the
forecast area predominantly dry.  Have only slight chance PoPs in at
this time, and precipitation would likely be predominantly rain with
a rain/snow mix possible Sunday night.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 528 AM CST MON NOV 30 2015

For the 12z TAFs, ongoing light precipitation today will result in
several hours of LIFR and IFR cig/vis conditions. For the TAF
sites, precipitation should predominately stay in the form of
rain, however there is slight chance for a mix of rain/freezing
rain near KMHK. As this light precipitation gradually exits to the
east this afternoon, cigs/vis will begin to rise to MVFR
conditions by late this afternoon and scattering out enough for
VFR conditions by later this evening. Winds will shift around to
out of the west behind the storm system.


.TOP Watches/Warnings/Advisories...
Winter Storm Warning until noon CST today for KSZ009>011-021>023-

Winter Weather Advisory until noon CST today for KSZ008-020.



SHORT TERM...Barjenbruch
LONG TERM...Hennecke
AVIATION...Hennecke is the U.S. government's official web portal to all federal, state and local government web resources and services.