Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 131717
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1117 AM CST Sat Dec 13 2014

...AVIATION UPDATE...

.SHORT TERM...(Today and Tonight)
Issued at 343 AM CST SAT DEC 13 2014

Weather conditions through tonight will be warm and damp as low
level moisture continues to stream north into the region.

Early Saturday morning, a sharp trough axis extended across Idaho
and Nevada with energy digging into the southern side of the trough
over southern Nevada. This trough will begin to deepen today and
will become a strong closed low by Sunday morning as it crosses the
Rockies. In advance of the system, surface cyclogenesis will occur,
slowly at first, in the lee of the Rockies. This will increase the
southerly low level flow and moisture feed into the region. The
result will be continued periods of drizzle and fog, particularly
this morning and again tonight. The fog is once again not likely to
be particularly dense, but could see dense pockets of fog at times,
mainly tonight. Otherwise, despite widespread cloud cover,
temperatures will be well above normal. Highs in the upper 50s are
likely, with some potential for a few 60 degree readings if the sun
can break through low clouds in a few areas this afternoon.
Widespread sunshine is not likely but the moisture is shallow enough
that a few breaks are possible. Overnight temperatures will not move
much, likely holding in the 50s with continued warm advection and
clouds.

.LONG TERM...(Sunday through Friday)
Issued at 343 AM CST SAT DEC 13 2014

By Sunday, the mid-level trough that is currently situated over the
western U.S. will have progressed eastward over the Rockies with the
mid-level low centered over northern New Mexico. Models show this
low lifting northeastward toward the forecast area through the day
and passing overhead Sunday night into Monday as the associated
surface cold front tracks eastward over the forecast area. Model
soundings show a very shallow moisture layer Sunday morning so
expect some patchy drizzle and fog before the deeper saturation
advects into the area. Several models are showing some elevated
instability as well as some weak surface-based instability Sunday
afternoon into evening, so have kept the mention of isolated
thunder. The best chances for widespread precipitation look to be
during the late Sunday afternoon through Monday morning time frame in
which many locations should receive one-quarter to at least
three-quarters of an inch of rain. Despite the mostly cloudy skies,
the breezy southerly flow ahead of the advancing system will aid in
warm air advection on Sunday with highs reaching near the 60 degree
mark. Models continue to show the cold air lagging well behind this
system with low temperatures Sunday night expected to range from the
upper 40s east to mid/upper 30s west. Temperatures should be
steadily falling through the day on Monday as the cold air finally
advances into the area. While we start losing the deep saturation by
Monday afternoon and evening, there is a chance for some light
precipitation to linger across the area, which could be in the form
of a rain/snow mix as a result of these falling temperatures.
However, any wintry precipitation that develops should be very
short-lived as the system should finally exit the area Monday night.

Dry and cooler conditions are expected Tuesday into Wednesday as
surface high pressure builds in behind the exiting system. High
temperatures should only reach into the mid/upper 30s and possibly
low 40s with low temperatures plunging back into the 20s. During
this time models show another mid-level trough moving onshore to the
west and eventually advancing into the central U.S. by mid to late
week. There are still significant model discrepancies with the
timing and tracking of this system, with the GFS being much more
progressive in bringing the wave and associated precipitation into
the area Wednesday and Wednesday night while the ECMWF lifts
precipitation into the area Thursday through Friday. Have trended
more with the slower ECMWF solution, so have kept a dry forecast for
Wednesday and have increasing PoPs through the end of the week. This
next system should keep the cooler airmass in place over the region
with highs staying in the 30s and lows in the 20s. As a result,
there will be chances for a mix of rain and snow with this system so
we will need to closely monitor this system over the upcoming days
to better fine-tune this potential for wintry precipitation.

&&

.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1117 AM CST SAT DEC 13 2014

Models continue to point towards at best IFR conditions through
the next 24 hours. Still anticipate a slight improvement at FOE
and MHK this afternoon. However by this evening, think LIFR CIGS
will return as low level moisture continues to advect into the
area with models showing weak isentropic upglide. Timing the
changes is most uncertain, and the forecast is a best
approximation based on the RAP and NAM forecast soundings.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...Barjenbruch
LONG TERM...Hennecke
AVIATION...Wolters






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