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

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000
FXUS63 KEAX 201130
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
630 AM CDT Tue Jun 20 2017

.Discussion...
Issued at 315 AM CDT TUE JUN 20 2017

Northwest flow prevailing over the fcst region this morning as
upper ridging continues to take shape over the western U.S. and a
closed low spins over eastern Canada. Main item of concern today
will focus on a weak backdoor cold front that will begin sliding
south into our fcst area by afternoon as high pressure builds east
across the upper Midwest. As highlighted in recent days, models
continue to show light QPF along this feature during peak heating,
and have maintained a slight chance mention for areas primarily
along and north of Route 50. Overall severe threat appears low as
convection should be kept in check by weak instability /MLCAPE
less than 750 Joules/ despite more supportive wind fields aloft.
As for temperatures, compressed thermal ridging in advance of the
front will lead to a pretty warm day across the area, with upper
80s to lower 90s expected areawide.

Aforementioned front will actually start lifting back north as
as a warm front overnight as upper Midwest high pressure slides
east and leeside low pressure develops over the northern High
Plains. This should lead to a gradual reduction in isolated
shwr/storm activity through the mid to late evening hours with
lows generally falling into the upper 60s to lower 70s.

Fcst from this point forward begins to loose confidence as
attention quickly shifts to our south as tropical storm
development occurs across the western Gulf of Mexico later today.
Closer to home, fcst models in recent days had been showing a
cold front beginning to move through our region Wednesday night
early Thursday as a strong storm system moves through southern
Canada. As highlighted yesterday, signs now beginning to point
towards a sharpening surface ridge extending through the Arklatex
region into west Texas as the tropical system approaches the
coast Wednesday and Wednesday night. Should this feature develop
as advertised, moisture return from the Gulf will be cutoff which
would lead to lower precip probabilities across our area. Latest
QPF model trends appear to be suggesting such a scenario, and PoPs
have decreased slightly Wednesday night and Thursday as a result.
In any event, the tropical system is expected to quickly lift to
the northeast across the Arklatex region Thursday night and Friday
as steering flow increases thanks to a digging northern stream
wave across the Northern Plains. This feature will push the
decaying tropical circulation off to the northeast while also
sending a cold front south across our area on Friday. This should
lead to the best chance for organized precip across our area as
tropical moisture interacts with the southward moving cold front.
Just how far south this front makes it remains in question as the
Canadian and ECMWF show the front hanging up somewhere over/near
our area, while the GFS shows the front clearing our area with dry
conditions returning for much of the weekend as Canadian high
pressure builds over the region. For now, will favor the the
Canadian/ECMWF scenario which shows additional precip chances on
Saturday as another wave dives south and interacts with the
presumed stalled front, while also holding off the cool air
associated with the Canadian high until Sunday. Regardless, the
latter half of next weekend is looking cool for early summer
standard as 850 temps range anywhere between 1-3 standard
deviations below normal.

&&

.Aviation...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 630 AM CDT TUE JUN 20 2017

VFR conditions expected through the fcst period with winds
generally shifting to the west today as high pressure settles to
our south and east. A weak frontal boundary will sag south across
the region late this afternoon, possibly touching off a few shwrs
and maybe a thunderstorm. For now, have offered a VCSH mention as
confidence of impacts at any one specific terminal remains too
low based on its highly isolated nature. Any shwr/storm activity
should clear this evening with winds shifting back to the south as
boundary again lifts north.

&&

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

$$

Discussion...32
Aviation...32



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