Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 161748
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1248 PM CDT Sat Sep 16 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 300 AM CDT Sat Sep 16 2017

Isolated thunderstorms were moving northeast across north central
and northeast Kansas this morning, while elevated showers were
developing across east central Kansas at 0730Z. Convection was
developing in an area of deeper moisture convergence and within the
mid level moisture plume extending from southwest Oklahoma across
northeast Kansas. Short term high resolution models have not picked
up on the convection across north central and northeast Kansas early
this morning, but instead focus on convection in the Texas Panhandle
and spread it northeast through the morning hours. Latest surface
analysis had a surface low in northwest Kansas while a cold front
extended from north central Nebraska and into northwest Kansas at
07Z. An upper level trough over Idaho and Montana early this morning
is forecast to move northeast across the northern and central Plains
and into the sunset country of southwest Ontario Canada. The
movement of the cold front and surface low is handled well among
the models today and tonight. The front is forecast to move into
north central Kansas by mid afternoon and by early evening extend
from southeast Nebraska to near Salina then into southwest Kansas.
The front is then forecast to move through northeast and east
central Kansas later this evening and overnight. Main concern for
today will be how much elevated showers, storms and cloud cover may
be present which may affect highs as well as destabilization along
the front later this afternoon. CAMS differ on convection through
the morning hours with the HRRR keeping isolated showers and storms
through mid to late afternoon before firing storms along the cold
front. THe rest of the models hold off convection until late
afternoon and early evening along and behind of the cold front. Have
lowered temperatures a few degrees today and have left small chances
of precipitation through the early afternoon anticipating ululated
convection before forcing along the cold front and the erosion of
the EML over northeast Kansas. Later this afternoon if we are able
to clear out clouds should see the atmosphere destabilize across the
cwa. Forecast soundings suggest around 2000-2500 J/kg of MLCAPE
along with shear of 30-35kts. Strong wind gusts and hail will be be
the main hazards with the stronger storms. Temperatures cool off
tonight behind the front with lows in the lower 50s north central to
the mid 60s southeast.

.LONG TERM...(Sunday through Friday)
Issued at 300 AM CDT Sat Sep 16 2017

Temporary subsidence from the sfc ridge over NE should clear out
precip towards the southeast on Sunday morning. Expect the low cloud
cover to linger throughout the afternoon as the front lifts back
northward during the afternoon and early evening over northeast
Kansas. Model guidance is still quite variable during the afternoon
on the position of the boundary and coverage of precip during the
afternoon, creating a wider span in temperature solutions. The 00Z
NAM appears the much cooler and wetter outlier with both the GFS,
ECMWF, and Canadian being more scattered in nature during the
afternoon. Trended a few degrees lower with guidance resulting in
middle to upper 70s for Sunday. If precip develops earlier in the
day or lingers through the afternoon, temps in the 60s cannot be
ruled out.

Mid level jet streak lifts northeast from the panhandles after 00Z
Monday, veering and increasing h85 winds over the warm front.
Isentropic upglide enhances in this period and feel fairly confident
in more widespread precip based on ingredients and consistency from
guidance. Agreed with the likely pops given late Sunday through
Monday morning. Convection itself appears elevated with effective
shear values around 30 kts in the early evening. Cannot rule a
marginally severe storm capable of small hail and gusty winds.
Activity gradually shifts eastward into Missouri and Iowa on Monday
with a brief break before chances increase once again near the
frontal boundary Monday evening. Dependent on the morning
activity, ample instability with minimal inhibition may be in
place by the afternoon. Shear values increase to near 35 kts,
posing a conditional severe weather risk for the area. Will
continue to monitor in the coming days. A second frontal boundary
is still progged by both the GFS and ECMWF to quickly enter the
CWA Tuesday evening and Wednesday, however coverage of precip is
trending more scarce given the increased subsidence in place.
Uncertainty increases towards late week as a longwave upper trough
deepens across the western conus. Temps and winds are likely to
increase Thursday and Friday with off and on chances for
convection as the upper wave edges closer to the region.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1245 PM CDT Sat Sep 16 2017

VFR conditions are expected to continue through the afternoon
hours. Scattered showers and thunderstorms are expected to
continue in the area through the afternoon. More widespread
showers and storms are expected after 00-03z this evening. The
strongest storms may produce brief VSBY reduction. A cold front
will shift winds to the north this evening. MVFR stratus is also
expected post-frontal. The stratus may begin to scatter near the
end of the period.

&&

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

$$

SHORT TERM...53
LONG TERM...Prieto
AVIATION...Baerg



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