Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 230429
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1129 PM CDT Fri Jun 22 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Saturday)
Issued at 200 PM CDT Fri Jun 22 2018

As of 19Z Friday afternoon, a cutoff upper low was positioned
across the eastern IL/western IN. On the western periphery of the
upper low a low-amplitude ridge axis was overspreading the CWA
ahead the next trough axis in the northern High Plains. At the
surface an area of high pressure was centered in eastern NE with an
expansive stratus field extending south and east from the high
across all of northeast KS. With reduced solar insolation,
temperatures have remained in the upper 60s to mid 70s across the
area. As the surface high exits to the east, a decrease in low-
level cloud cover is expected. An inverted surface trough
extended from northwestern KS, southward towards the surface low
in northeast NM. Water vapor reveals a lead shortwave traversing
portions of the High Plains. As a result, thunderstorms have
developed in portions of northeastern CO. Radar trends suggest
upscale growth into an MCS is ongoing with propagation east-
southward along the theta-e gradient, which extends from northwest
KS, southeastward into central and southeast KS. As far as
precipitation chances go across our area, the best potential for
thunderstorm activity looks to remain south of a line from
Concordia to Garnett. Poor mid-level lapse rates coupled with
effective shear less than 30 kts suggest the severe potential is
relatively low across these areas. As overnight lows go, another
cool summer night is in-store with temperatures in the low 60s.

Transitioning into Saturday, the current forecast is dry across
all of northeast KS during the afternoon and evening hours. The
aforementioned upper trough across the High Plains will slowly
progress into the central Northern Plains with an attendant, weak
surface trough within the Missouri River Valley. Short and mid-
range guidance suggest the majority of precipitation will remain
in northeastern NE and SD, where the favorable ascent is present.
With southerly flow returning to the CWA, a typical summer day is
expected with high in the 80s.

.LONG TERM...(Saturday night through Friday)
Issued at 200 PM CDT Fri Jun 22 2018

Transitioning into the extended period, an upper low will dig
into the central Rockies Saturday night Sunday morning. A
deepening lee cyclone across southeastern CO will increase WAA and
lift a warm front across the CWA by Sunday morning. Some
discrepancy exists amongst guidance with convection that develops
in eastern WY/CO Saturday afternoon. The GFS is the eastern most
solution with storms reaching eastern NE by sunrise Sunday. This
would bring the potential for an OFB to push into portions of
northern KS, which would provide a secondary focal point for
convection Sunday afternoon/evening. Moreover, higher confidence
exists for thunderstorm development across western KS near the
triple point, with upscale growth into an MCS with primary hazards
including large hail and damaging winds. Although an impressive,
veering low-level wind profile could pose a QLCS tornado threat as
well. Not to be lost in the severe potential, the threat for
heavy rainfall resulting into flash-flooding exists as well.
PWATs are progged to range from 1.5 to 2 inches across the area --
which is near the 90th percentile for late June. QPF outputs from
NAM/GFS/ECMWF have widespread 1-2 inch amounts Sunday with
isolated higher amounts.

For Monday and Monday night the surface trough is progged to
remain across the CWA with the upper low remaining across the
central/northern Plains. This scenario would suggest additional
thunderstorm development would be possible if not likely Monday
afternoon and evening. With moderate to high instability coupled
with sufficient effective shear, severe thunderstorms would remain
possible.

Beyond Monday, confidence in thunderstorm potential/location
decreases, although GFS/ECMWF suggest the potential for a complex
of thunderstorms Tuesday evening/night. As temperatures go, a
gradual warmup is expected through the extended with highs
returning to the 90s by Tuesday. Not only does the heat look to
return, but the humidity as well. Heat indices are progged to
reach the low 100s to mid 100s Tuesday through Friday of next
week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1122 PM CDT Fri Jun 22 2018

VFR conditions are expected through the period. With storms
staying south of terminals have taken the mention of VCTS out of
the TAFs for MHK. Soundings show some indication of brief lower
ceilings around sunrise, but confidence is still low so have left
this mention out as a prevailing group. Winds will continue to be
light tomorrow with skies gradually scattering out through the
day.

&&

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

$$

SHORT TERM...Baerg
LONG TERM...Baerg
AVIATION...Heller


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