Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 212044

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

.SHORT TERM...(This evening through Sunday)
Issued at 343 PM CDT Sat Apr 21 2018

Clouds and scattered rain showers are on the docket for the rest
of today and tonight, gradually clearing from NW to SE on Sunday.

Early afternoon water vapor imagery revealed a complex upper
tropospheric cutoff low stretching from western Nebraska to the
Texas Panhandle with the warm/moisture conveyor belt extending
from eastern Texas into south-central South Dakota. This low
pivots over the region tonight and into Sunday while slowly
progressing ESE-- reaching Arkansas by late in the day Sunday. The
mid-level moisture plume has been fighting an influx of dry
easterly flow near the surface throughout the day today. As a
result, QPF values on the eastern flank of the moisture axis have
been underwhelming, with most locations east of Topeka seeing less
than a tenth of an inch. The lack of precipitation in the east
allowed a tight thermal gradient to form with a 10-15 degree temp
spread between Kansas City and Topeka this afternoon. The heaviest
rain fell between Manhattan and Topeka, with many mesonet
stations reporting between 0.5 and 0.7 inches of well-needed rain.

As the low pivots, the axis of heavier precipitation should
likewise wrap around the northern flank of the system and become
more zonally oriented tonight. Given the slow motion of the
cyclone, have kept POPs well into Sunday along and southeast of
the Turnpike. Also lowered highs for Sunday 3-5 degrees below the
21.12Z blended guidance given the steady NNE flow and
stratus/stratocumulus that looks to linger on the backside of the
low throughout all of NE Kansas per GFS/NAM forecast soundings. As
the low gradually pulls away, the chances for showers steadily
decrease, ending early Sunday evening.

.LONG TERM...(Sunday night through Saturday)
Issued at 343 PM CDT Sat Apr 21 2018

Next week will be characterized by near to slightly below normal
temperatures with periodic chances for rain on Tuesday and
possibly Thursday.

The region will find itself under split flow on Monday morning as
the aforementioned upper level cutoff low meanders over the
southeast U.S. Given the continued cyclonic flow in place on
Monday, cannot rule out the chance that clouds linger longer than
currently forecast. Upper level ridging strengthens over the
western CONUS starting on Tuesday and persists through the end of
the week. This places the region under NW flow with a couple of
weak and ill-timed shortwaves propagating through the flow
throughout the week. The first such PV lobe crests the ridge late
Monday and dives across the region on Tuesday. There are some
modest timing differences between the medium range solutions on
the passage of this wave through the Central Plains, with recent
runs now closing off the mid to upper trough and developing a weak
deformation zone on the backside of the low. This may prolong the
threat for rain into Wednesday. Limited moisture return is
anticipated ahead of the system, keeping QPF amounts light and
likely under a few tenths of an inch.

Medium and longer range solutions diverge further on the second
wave for later in the week--which is currently situated south of
the central Aleutian Islands. The GFS/GEM are much more
progressive than the EC, which amplifies and digs the wave further
south than the other solutions. For now, have maintained slight
chance POPs for Thursday, but there is low confidence in the
timing of this precip. Temperatures through the week look to
fluctuate around or slightly below average for this time of year,
but no appreciable airmass changes are in store through mid-week.
As with POPs, the temperature forecast confidence lessens by the
end of the week depending on the evolution of the late week


.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.




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