Area Forecast Discussion
Issued by NWS Topeka, KS

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517
FXUS63 KTOP 211736
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1236 PM CDT Sat Apr 21 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 411 AM CDT Sat Apr 21 2018

As of 09Z Saturday morning an upper level low in eastern CO
continues to generate rain showers across the central Plains. Up to
this point rainfall has been primarily confined to the I-135/Highway
81 corridor. The eastward progression has and will continue to be
slow as dew point depressions are running on the order of 20-30
degrees across the eastern 1/3 of the state. Without the presence of
a strong WAA pattern, saturation will be greatly limited to wet-
bulbing. Thick mid-level cloud cover has limited radiation cooling,
keeping temperatures predominately in the upper 40s to middle 50s.

Rest of today: As the upper low meanders east-southeastward through
the day, expect precipitation to expand eastward. RAP/HRRR forecast
soundings suggest the Highway-75 corridor should see rainfall
reaching surface near sunrise this morning. Little diurnal
temperature recovery is expected through day given the limited
insolation expected. As a result have temperatures in the 50s area-
wide.

Tonight: The upper level low will continue on its east-southeastward
trek across southern KS and OK. While doing so, precipitation will
begin tapering off across north-central KS as large scale ascent
shifts eastward. This trend will continue for the entire area with
precipitation coming to an end from northwest to southeast through
the day Sunday. Weak CAA on the backside of the surface low across
AR will yield slightly cooler temperatures Sunday morning with lows
in the low to mid 40s. As for precipitation totals, it`s no "drought-
buster" by any means, but widespread 0.25 to 0.50" are expected
south of a line from Marysville to Lawrence. Higher totals nearing
0.75 to 1.0" are certainly possible in the far southern counties.

.LONG TERM...(Sunday through Friday)
Issued at 411 AM CDT Sat Apr 21 2018

By Sunday morning, the center of the mid-level low will be located
over Oklahoma and progressing eastward into Arkansas through the
day. Models are in decent agreement in having enough wrap-around
moisture extending into the CWA to keep light rain showers over
portions of northeast and east central KS through the day before
exiting to the east. There are some discrepancies with when this
light precipitation will exit east of the CWA as the GFS/NAM keep
some lingering precipitation into Sunday evening while the
ECMWF/Canadian are more progressive. With low clouds remaining in
place for much of the day over northeast and east central KS, have
kept temperatures a few degrees cooler in these areas with highs
ranging from the upper 50s to low 60s.

Cloud cover will scatter out some on Monday, allowing temperatures
to rise closer to the seasonal normals with highs in the mid/upper
60s.  However, models show the next mid-level trough tracking
eastward into the northern Rockies and progressing into the Northern
Plains by Tuesday. There are still model discrepancies with how
this next system is handled, as both the GFS/Canadian show a
closed-off low developing within the mid-level trough while the
ECMWF keeps an open wave. There are also notable differences in
how far south this closed low or open wave will track across the
central U.S. As a result, confidence remains low for precipitation
chances Tuesday into Wednesday so have only slight to low-end
chance PoPs. Model soundings aren`t showing much in the way of
instability, so expect only scattered rain showers from this
passing system. Temperatures Tuesday and Wednesday will be very
dependent upon the timing/tracking of the associated frontal
passage and any precipitation the develops, so we will need to
continue to monitor model trends with this system. Models show
another mid-level trough developing right behind this exiting
system, with it diving southward from Canada into the Northern and
Central Plains Thursday into Friday. This advancing trough will
help to push another cold front through the area, bringing some
chances for scattered precipitation, but confidence remains low at
this time regarding the timing/tracking/coverage of any
precipitation.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1236 PM CDT Sat Apr 21 2018

Widespread showers persist through the rest of the day and
tonight, gradually ending from NW to SE. Ceilings towards central
Kansas will remain at IFR/MFVR levels, while further NE
conditions lift to VFR levels. MVFR ceilings spread across much
of the area on Sunday morning, though there is some uncertainty in
the coverage of the clouds. Winds remain from the NE at 5 to 10
kts through the period.

&&

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

$$

SHORT TERM...Baerg
LONG TERM...Hennecke
AVIATION...Skow



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