Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 271747
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1247 PM CDT Thu Apr 27 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 343 AM CDT Thu Apr 27 2017

Stratus deck is making its way eastward, leaving clear skies in its
wake. Temperatures at Concordia have fallen to 31, with 34 at
Abilene this hour.  Areas under clouds are still in the 40s, but
with a few more hours before sunrise and clearing moving in quick,
still expect to drop into the 30s with patchy frost still possible
into eastern Kansas this morning. A frost advisory is in effect for
the northern and western counties through 8am.

Period of clear skies and warm air advection should get highs up
into the lower 60s east and upper 50s west before the next round of
clouds and eventually precipitation move in from the southwest later
this afternoon and into the overnight hours.  Not much instability
until after midnight and not much at that, so will carry isolated to
scattered thunder with more widespread rain showers expected, with
best chances for rain between midnight and 7am Friday.  Lows should
hold in the 40s to near 50.

.LONG TERM...(Friday through Wednesday)
Issued at 343 AM CDT Thu Apr 27 2017

On Friday the mid level shortwave providing lift will be over NE
with slightly drier air advecting across the area behind the system.
Therefore the precipitation should come to an end with the exception
of far northern KS where a few showers may linger especially in the
morning. On Friday night the stage will get set for a wet weekend as
a strong mid level low pressure tracks over the Rockies and
eventually ejects out over the plains. Ahead of the low pressure
strong southerly flow will advect moist air from the gulf. Late
Friday night widespread rain should form north of a surface front
located near the I-44 corridor. The low level jet will overrun this
surface front, which will supply moisture and convergence. Moisture
transport vectors will be maximized over southeast KS around the 850
to 700 mb layers. High theta-e air will cause the pwat values to
approach 1.50 inches, which for this time of year is almost record.
The heaviest rainfall should occur during the day Saturday and into
the evening. East central KS will likely see the highest totals
during this time frame due to the lift and quality of moisture that
spreads over this area. Rainfall totals at these locations could
reach 2 inches. Although it does appear that most of the forecast
area will experience rainfall regardless. Instability will be
limited on Saturday with only a few hundred j/kg trying to sneak
into east central KS, so lightning should be isolated.

On Sunday the main low pressure lifts over the area and trowal
precipitation forms as a result. This lift will be maximized
mainly over north central KS although the models are still
wavering around with the exact mid level low track. During the day
Sunday some models are suggesting 1 to 2 inches of liquid at
these locations. Temperatures will be borderline to support snow
especially closer to the surface with a 2 kft deep layer above
freezing. Of course with a system this strong dynamic cooling due
to lift and melting could allow for a change over to snow or rain-
snow mix. This will be more likely across north central KS Sunday
morning and accumulations should stay confined to mainly grassy
surfaces if any.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1240 PM CDT Thu Apr 27 2017

VFR conditions today will gradually deteriorate overnight as our
next weather system approaches from the southwest. Expect CIGS to
fall to IFR levels by sunrise with areas of showers and possibly a
thunderstorm overnight. The rain threat should shift north and
east during the morning on Friday but low CIGs will persist
through the rest of the TAF period.

&&

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

$$

SHORT TERM...67
LONG TERM...Sanders
AVIATION...Skow



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