Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 281949

National Weather Service Kansas City/Pleasant Hill MO
249 PM CDT Fri Apr 28 2017

Issued at 249 PM CDT FRI APR 28 2017

Primary concern with this forecast issuance is the placement and
amounts of highest rainfall this weekend as a very damp, potent
system moves through the region. Rain showers this afternoon have
all but tapered off, leaving a brief period of patchy drizzle then
generally dry conditions for the remainder of the night, before
the next round of rain moves in. Rainfall amounts through this
afternoon are generally around a third of an inch to an inch,
which has saturated the ground and lowered the 6-hr flash flood
guidance to around 3 inches. The lowest FFG amounts are just below
3 inches mainly across central MO and far northwestern portions of
the CWA.

The deep trough currently carving southward into New Mexico will
push east on Saturday, then will deepen and wrap northward as a
cut-off low through Sunday night. The surface low track is
surprisingly consistent among models and their previous runs,
trekking across Oklahoma on Saturday and into west central MO by
Saturday night. The stalled boundary currently sitting over the KC
metro will sink southward this evening as high pressure pushes
down from the north, but will surge back northwestward as the
surface low approaches, settling along a line stretching from
southwestern MO to the STL area Saturday afternoon and evening.
Surface based convection will focus along and just south of the
boundary; however, very high PWATs and deep lift support the
development of elevated convection and substantial precipitation
north of the surface boundary. Despite model agreement on the
placement of large scale features, large discrepancies remain with
the north/south extent and position of the heaviest QPF. Have
stuck with the more southern trend, since surface based convection
will have more instability to work with and should conceptually be
heavier than precipitation to the north, which is also supported
by many of the convection-allowing models. Have expanded the Flash
Flood watch just a shade across central MO, but feel that the main
flood threat for this weekend will be mainly to rivers, outside
the possible isolated flash flood issues across central MO.

After a full day of nearly non-stop rain Saturday and Saturday
night, a dry slot may move through the forecast area Sunday as the
system wraps up, and the surface low lifts northward into north
central MO. Wrap-around precip is expected to slide through
northern MO Sunday night and a few light shallow convective rain
showers are possible on Monday, then precipitation should end with
this system.

Additional rainfall is possible Wednesday and Thursday, but again
the axis of heaviest precipitation looks like it will occur south
of the CWA. Slightly below normal temperatures are expected
through the long-range forecast period with mainly northwest flow
aloft and a more southern position of the upper jet.


.Aviation...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1228 PM CDT FRI APR 28 2017

Lingering rain showers will push out of all terminals prior to
18z, making much of the TAF period dry this evening and tonight.
Ceilings have been a bit jumpy this afternoon but are generally
settling in the middle of the MVFR category on the south side of
the warm front, and near the IFR/MVFR threshold along and north of
the front. This boundary will gradually sink southward during the
evening, bringing sites back to low MVFR and eventually IFR late
this evening. Winds will transition to the northeast as the front
passes, generally at speeds less than 12 kts through Saturday
morning. Rain will push back into the region Saturday morning, and
while the potential for a few embedded thunderstorms was too low
to warrant mention in any of the TAFs, cannot completely rule out
a stray thunderstorm especially at IXD after sunrise Saturday.
Once they begin Saturday morning, rain showers and IFR ceilings
will continue beyond the end of the forecast period.


KS...Flash Flood Watch from 7 PM CDT this evening through Sunday
     evening for KSZ057-060.

MO...Flash Flood Watch from 7 PM CDT this evening through Sunday
     evening for MOZ031>033-038>040-043>046-053-054.



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