Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 262330
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
530 PM CST Sat Nov 26 2016

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Sunday)
Issued at 257 PM CST Sat Nov 26 2016

A weak mid-level ridge was in place across the central U.S. this
afternoon, with the CWA wedged between surface high pressure across
the southeastern U.S. and low pressure over the High Plains. This
afternoon a mid-level trough moved into the western U.S., and models
show this trough quickly advancing eastward toward the Rockies
tonight into Sunday.  A decent pressure gradient was in place this
afternoon, will remain in place overnight, and will tighten further
on Sunday to result in a very windy day.  Southerly winds will
remain sustained at 10-15mph as the low-level jet remains centered
over the area.  After midnight, these southerly winds will be
advecting more moisture into the area, with dewpoints rising into
the 40s and cloud cover beginning to overspread the area from south
to north by sunrise.  As a result, the low temperatures may occur
near midnight tonight with temperatures remaining steady or rising
slightly overnight into Sunday morning.

These low clouds will quickly overspread the entire CWA Sunday
morning with the moisture advection pushing dewpoints into the 50s.
The 2 main points of interest for the Sunday forecast are the strong
winds and thunderstorm chances.  Models show the low-level jet
increasing through the day, especially during the afternoon/early
evening hours, with 850mb winds of 50-60kts.  Model soundings show
that the mixing will be shallow, but with such strong winds just off
the surface, expect surface winds to increase to 20-30mph with gusts
of 40-45mph likely.  As a result, conditions will be near Wind
Advisory criteria, so we will need to continue to monitor these
conditions to determine whether a headline will be needed. Although
skies will be overcast through the day, these breezy south winds
will boost high temperatures into the upper 50s to low 60s.

With the advancing trough pushing surface low pressure eastward
toward the area, models show the associated cold front moving into
north central KS by Sunday evening.  However, models continue to
show some scattered warm-air advection precipitation developing
across the CWA late Sunday morning through the afternoon ahead of
the advancing front.  The strong wind profiles will result in around
50kts of 0-6km bulk shear and 35-40+kts of 0-1km bulk shear. Despite
these strong wind profiles, model soundings show a cap remaining in
place through much of the day, so any storms that develop may remain
elevated.  Lapse rates don`t steepen until late afternoon/early
evening, and even then instability looks to be minimal at 250-450
J/kg, at best.  As a result, scattered storms will develop through
the day and cannot rule out the potential for a few isolated strong
to perhaps severe storms.  However, the strong shear in place will
likely limit the sustainability of any stronger storms that develop.

.LONG TERM...(Sunday night through Saturday)
Issued at 257 PM CST Sat Nov 26 2016

Sunday night...expect scattered showers and isolated
thunderstorms to persist through at least 6z as intense lift ahead
of the upper low pivots across the area. Some marginal risk for
severe storms appears possible early given intense wind fields and
expected storm motion AOA 50 mph for any updraft that can sustain
itself. A mild pacific cold front will sweep through early Monday
mainly dry with another warmer than avg day forecast Monday. The
upper system will attempt to tap into modified polar air by later
Tues into Weds when temps will finally reach near or just below
avg with continued CAA and upper troughing aloft through late
week. That said there`s very little snowpack across southern
Canada with any airmass originating there expected to be modified
so temps don`t look unseasonably cold later this week. Conds
should also remain dry for the most part given the very slow
progression of the upper low through the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 530 PM CST Sat Nov 26 2016

VFR conditions are expected through 11Z with a transition quickly
to IFR as low level moisture quickly increases northward. Winds
will increase to around 15kts with gusts to 25 kts by 15Z then
increase to around 21kts with gusts to 32kts around 18Z. MVFR
vsbys with showers expected after 18Z as well as vcts.

&&

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

$$

SHORT TERM...Hennecke
LONG TERM...Omitt
AVIATION...53



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