Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 242319
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
619 PM CDT Wed May 24 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 304 PM CDT Wed May 24 2017

As of early this afternoon, the deep mid- level trough was
centered just east of the CWA, with a weak mid- level ridge
stretching northeastward over the High Plains into the Dakotas.
With the CWA wedged between these two mid-level features, visible
satellite imagery showed scattered cloud cover extending from
Missouri into eastern Kansas, with clear skies in place across the
western half of the state. Weak lift on the back- side of the low
over Missouri resulted in some scattered rain showers developing
across far western Kansas. While the HRRR/RAP show the potential
for a few of these isolated showers to pop up over far eastern
Kansas, dry conditions noted near the surface may result in virga.
As a result, have kept a dry forecast going for the remainder of
this afternoon. Scattered cloud cover combined with northwest
winds resulted in high temperatures staying in the 60s.

Model soundings show the mid-level ridge over the High Plains
advancing eastward tonight into Thursday, with the ridge axis
centered over the region by mid-day Thursday.  This advancing ridge
will help to push surface high pressure over western Kansas across
the CWA tonight, resulting in clearing skies. These clear skies will
support decent radiational cooling with low temperatures plunging
into the mid/upper 40s once again tonight.  The ridge axis should
shift east of the CWA by Thursday evening as a closed mid-level
trough over the Dakotas begins to dig southward into northwestern
Kansas. While models show a couple of embedded shortwaves developing
Thursday afternoon over northwest Kansas and southern Nebraska, any
precipitation associated with these waves looks to remain north and
west of the CWA through the daytime hours.  With surface high
pressure tracking toward the southeastern U.S., the shift to
southerly winds along with mostly sunny skies will result in more
seasonal temperatures with highs in the mid/upper 70s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 304 PM CDT Wed May 24 2017

An unsettled weather pattern is expected to continue through the
weekend while an upper level trough axis remains to the west of
the forecast area. Unfortunately the model progs are rather
subtle with the forcing while keeping steep mid level lapse rates
and decent instability across the area. So confidence in timing
and location of the better chances for precip is a little below
normal. For example, a low amplitude shortwave is progged by most
guidance to move across the central plains Thursday night.
Although some solutions take the energy north across NEB while
others bring it across northern KS. Another subtle wave looks to
move across the area late Friday night and early Saturday. With
this wave models vary from taking the axis of heaviest rainfall
from southern NEB, right across the forecast area and southern
KS. Because of the variation in the model solutions, POPs are
generally in the 30 to 50 percent range. In both cases, models
indicate very steep 700-500MB lapse rates will be over the area
with decent deep layer shear supportive of the potential for
elevated storms with large hail. Models show strong surface based
instability developing for Friday afternoon as well with little
or no convective inhibition. It appears though the upper
subsidence behind the initial wave and a lack of strong low level
convergence prevents storms from forming Friday afternoon.
Concerning the outlook for severe storms on Saturday, this appears
to be highly conditional as nocturnal convection from the
overnight hours Friday may push a warm front further south. The
12Z guidance generally keeps the warm front to the south of
Anderson and Coffey counties are just reaching them. So there are
questions as to how much the boundary layer may recover Saturday
afternoon. Think the greater severe weather potential could be
elevated storms overnight. Things look to dry out for Sunday as a
surface ridge moves through the central plains and the upper
trough axis shears out.

There are some slight chance POPs in the forecast for showers and
storms Monday afternoon and Monday evening. Models show energy
digging down the back side of the upper closed low over WI that
should bring a cold front through the area. There is not expected
to be enough time for strong moisture advection in advance of this
front and as a result the GFS shows only modest instability with
the weak boundary. Additionally the bulk of the dynamics pass to
the northeast of the forecast area. So POPs are only in the slight
chance range for now.

Models develop a low level warm air advection (WAA) pattern by
mid week as the upper closed low and surface ridging continue
moving east. There are some timing differences between the
GFS/ECMWF/GEM with the GFS holding off on the WAA until Wednesday
evening. So there is a signal for POPs late Tuesday and Wednesday
but confidence in the timing could be better.

Temps appear to remain fairly temperate through the forecast
period. The warmest day in the forecast continues to be Friday,
but have trended the forecast cooler with models showing low level
cold air advection through the day. Otherwise highs look to remain
in the 70s with lows holding in the 50s for the first half of next
week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 618 PM CDT Wed May 24 2017

VFR conditions are expected throughout the period. Winds will be
light and variable overnight before prevailing from the south
southeast by early tomorrow morning.

&&

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

$$

SHORT TERM...Hennecke
LONG TERM...Wolters
AVIATION...Heller



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