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

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683
FXUS63 KEAX 280916
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
416 AM CDT Fri Apr 28 2017

.Discussion...
Issued at 414 AM CDT FRI APR 28 2017

Overall forecast remains on track with the primary change owing to a
potential northward shift to the axis of heaviest rainfall through
the weekend.

Water vapor imagery and high resolution model guidance continues to
suggest isentropic ascent and saturation to generate scattered
showers through the remainder of the early/mid morning hours before
a dry slot ends precipitation from west to east. Highest rainfall
totals will reside along and north of Interstate 70. Should be a
notable break in rainfall this afternoon into the evening hours.

The most immediate concern will be heavy rainfall Saturday morning
into Sunday morning with notable synoptic setup. A slowly-
evolving longwave trough over the Plains states is bringing in a
healthy batch of mid/upper level Pacific moisture and low-level
Gulf moisture. The position of the surface front will help dictate
corridor of the heaviest rainfall over the weekend. Latest
thinking is this boundary will lift north and become quasi-
stationary on Saturday evening. How far north and whether ongoing
convection will limit its northward extent remains highly
uncertain. Confidence is increasing however that where this heavy
band of rain resides will lead to flash flooding concerns and
river flooding as several rounds of moderate to heavy
precipitation trains across the area. Currently, this zone is
expected along a line from Chanute, Kansas to Clinton/Sedalia,
Missouri. It`s worth noting that each subsequent model run has
shifted this corridor further north, with the 06Z NAM now the
farthest northwest approaching the KC Metro area. The takeaway is
that while the exact location of the heaviest rainfall remains
uncertain, the potential exists for a corridor of 3-4 inches of
rain with locally higher amounts to affect the southeast third of
the forecast area, resulting in the potential for flooding rains.
Likewise, a flash flood watch remains in place for these areas,
and future forecasts will closely monitor northwest expansion if
model trends continue.

Wrap-around TROWAL light precipitation is expected on Monday before
precipitation comes to an end Monday evening as the upper low
departs. While slight chances of rain will be possible mid-week,
overall amounts are anticipated to be low. As for temperatures, the
forecast area remains on the cool-side of the surface front/pattern,
resulting in maximum readings below climatological averages.


&&

.Aviation...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1136 PM CDT THU APR 27 2017

Another round of VFR rain showers will move into the area over the
next few hours, followed by another round around sunrise. It
doesn`t look like until late morning that ceilings begin to drop
into the low MVFR range. It seems likely that at some point in the
morning ceilings will be in this range, but exact timing is
uncertain. There is a chance ceilings could fall below 1000ft.
Have left this out for now as it`s not as likely as the MVFR
ceilings occurring. The bulk of the heavy rain looks to fall
after this forecast and this is when it looks more likely for IFR
and LIFR ceilings.


&&

.Hydrology...
Issued at 309 PM CDT THU APR 27 2017

With respect to QPF for this weekend`s system, there is some model
spread and subsequently, uncertainty in just how far north some of
the heaviest rainfall amounts will reach. Given model trends,
current thinking is that the higher rainfall amounts will remain
south of U.S. Hwy 24 but can`t rule out the possibility of
northwest MO and perhaps into portions of the Kansas City metro
area seeing some locally high amounts. Widespread rainfall amounts
tonight through midday Monday look to be in the two to three inch
range with potentially locally higher amounts possible,
particularly in the watch area. Much of this rain will fall on
Saturday into Saturday night, which is the time frame to keep a
close eye on the flooding potential. Antecedent ground conditions
could easily exacerbate the flooding potential. Regarding possible
impacts, while flash flooding is a possibility within the watch
area, this is more of a long-duration event in which area rivers,
creeks, streams, low-water crossings, etc. will feel the brunt of
it all. For those residing near these locations, it is highly
recommended to keep a close eye on river forecasts as the weekend
approaches.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Flash Flood Watch from this evening through Sunday evening for
     KSZ057-060.

MO...Flash Flood Watch from this evening through Sunday evening for
     MOZ039-040-043>046-053-054.

&&

$$

Discussion...Blair
Aviation...CDB
Hydrology...lg



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