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

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FXUS63 KEAX 182326
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
626 PM CDT Sat Aug 18 2018

.Discussion...
Issued at 305 PM CDT SAT AUG 18 2018

Weak ridging prevailing over the region this afternoon in advance
of an upper-level trough diving southeast from the northern
Rockies. Closer to home, surface high pressure extending southwest
from the western Great Lakes is largely controlling the local
weather pattern this afternoon, with latest satellite imagery
depicting a fair amount of fair wx cumulus and smoke from western
North American wildfires over the area. With weak instability
over the region today (MLCAPE values of roughly 1000 J/kg per
latest SPC meso page), cannot totally rule out a pop-up shwr/storm
near the KC metro this afternoon and evening as high-res models
continue to offer a hint, and have introduced an isolated storm
chance through early evening with expected to quickly dissipate
with loss of daytime heating. For the remainder of the night,
dry conditions should prevail with lows Sunday morning falling
into the upper 60s to lower 70s.

Forecast becomes much more interesting on Sunday as aforementioned
upper low over the northern Rockies begins diving southeast across
the northern and central High Plains. As this occurs, fcst models
in excellent agreement that low pressure will develop over the
Red River Vly Sunday morning, with this feature then fcst to
slowly lift northeast before finally passing directly over
northern Missouri during the day on Monday. As has been
highlighted in previous discussions, this incoming feature looks
to be pretty strong for mid-August standards with 500-hPa height
anomalies bordering on 2-3 standard deviations below normal. In
addition to that, strengthening southerly flow in advance of the
feature combined with unimpeded moisture transport along the
western edge of the southeastern U.S. ridge should allow plenty
of moisture advection north into the lwr Missouri Valley with
latest model solutions indicating PWAT values exceeding the 90th
percentile by 00z Monday. These factors combined with increasing
DPVA in advance of the upper low along with strong upper
divergence with the exit region of a cyclonically curved jet
rounding the base of the upper low, should set the stage for
what will hopefully be a prolonged rainfall event beginning late
Sunday afternoon/evening. For now, model instability fcsts look
fairly meager with latest NAM and GFS solutions suggesting MLCAPE
values should remain below 800 J/kg through the duration of the
event. Considering the bulk of rain will likely fall Sunday night
into Monday morning, widespread thunderstorm activity may be hard
to come by, with this factor hopefully suppressing large-scale
flooding concerns due to unsupportive rainfall rates. What does
make for a complicated fcst is the strong dynamical forcing this
feature should have as it moves through, with all indications
point towards a stout dryslot accompanying the feature which
models point to moving through our region Monday morning. This
will likely keep precip totals a little lower than previously
thought, however widespread rains of up to 1" are still possible
given the moisture supply available. By the looks of things, rain
will redevelop over the region later in the day on Monday as main
deformation band moves through the area thunder chances remaining
in the isolated to scattered category as the bulk of instability
should be east of our region by then. Let`s just hope we`re able
to squeeze some beneficial rains out of the system before it
tracks east Monday night into Tuesday morning.

Beyond this, cool high pressure will settle south over the
Nation`s midsection with dry conditions persisting through the
remainder of the week. Temps through Wednesday will only warm into
the lower to middle 80s before a warming trend occurs late week as
sfc high pressure slides off to the east and southerly flow
returns. Rain chances look to increase heading into next weekend
as a frontal boundary approaches from the west by late week.

&&

.Aviation...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 626 PM CDT SAT AUG 18 2018

VFR conditions are expected this evening through much of tomorrow.
As shower and storm chances increase late tomorrow afternoon,
ceilings may start to fall. Have trended to lower VFR with showers
moving in. But there are some indications that ceilings may fall
to MVFR or IFR Sunday evening into the overnight. Winds will be
light through the overnight and then trend to the southeast to
south tomorrow morning around 10 kts.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

Discussion...32
Aviation...CDB


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