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000
FXUS63 KEAX 151117
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
617 AM CDT Wed May 15 2013

.SHORT TERM...(Today through Friday)
Issued at 340 AM CDT WED MAY 15 2013

The main concern in the short-term forecast will be precipitation
chances along and south of a nearly stationary cold front that`s
currently draped just north of the Iowa/Missouri border. This
boundary will drift southward into northern Missouri today, before
lifting back north and becoming diffuse late tonight into early
Thursday. Most model soundings indicate that surface heating should
eliminate most of the capping inversion by early to late afternoon
in the vicinity of the front, possibly allowing thunderstorms to
develop. However, the boundary layer mixing will also deplete some
of the already fairly marginal surface moisture; thus, have kept the
chance of precipitation below 50 percent this afternoon and this
evening. CAPE values in the warm sector are also likely being
overestimated by the NAM and GFS, due to unrealistic surface
moisture content in the models.

An upper low will also eject northeast into the central Plains this
afternoon, lifting into southern Missouri by early evening. A few
thunderstorms may also develop with this feature in an unstable
environment; however, the best lift associated with this upper
feature should remain south of the forecast area. The upper trough
will move eastward on Thursday as the aforementioned surface
boundary over northern Missouri lifts north of the forecast area,
gradually diminishing precipitation chances for our area Thursday
and Thursday night. A shortwave trough currently over southwest
Nevada may skirt the northern edge of the forecast area on Friday;
however, the NAM and EC weaken this feature significantly as it
heads east under a strengthening ridge, so have kept precipitation
chances very low for Friday and Friday night.

Highs today should be a few degrees cooler than yesterday as 850 mb
temperatures decrease and convergence along the boundary weakens;
however, with still decent southwest flow and morning lows in the
upper 60`s or lower 70`s, it will not be difficult to heat into the
mid to upper 80`s by late afternoon. After today, temperatures will
be held down a bit by increasing cloud cover, but should still be a
few degrees above normal with highs in the upper 70`s to lower 80`s
and lows in the 60`s.

.LONG TERM...(Saturday through Tuesday)
Issued at 340 AM CDT WED MAY 15 2013

Saturday-Saturday night: Medium range models in good agreement with
shortwave ridging aloft which will translate east across the Great
Plains and through the CWA by late Saturday night. Lacking any
definable surface feature nearby plus a lack of moist isentropic
ascent this period will be dry generally dry, warm and increasingly
humid. the far northwestern counties may be the exception Saturday
night as the the leading edge of warm air advection on the backside
of the retreating upper ridge moves in.

While there is a known wet bias in the ECMWF/GFS/NAM boundary layer
the progged surface dewpoints may be OK as the southerly winds
through h8 look like they will be tapping into the Gulf of Mexico.

Sunday through Tuesday: This period has the potential to be fairly
active with a threat for severe weather on Sunday and Monday. Have
seen a noticeable improvement in model agreement/timing in the
evolution of the next upper trough. The operational ECMWF and GFS
are more in sync as they both take on a negative tilt to the
eastward advancing upper trough on Sunday. Previously the ECMWF had
been faster in moving the trough eastward but the 00z model run has
slowed down. A modest 30-35kt south-southwesterly low level jet will
advect increasingly unstable air into the region. Scattered mainly
afternoon and evening convection on Sunday looks like a reasonable
expectation as a pre-frontal surface trough interacts with this low
level jet and moderate instability. Marginal 0-6km shear may be
sufficiently strong to support a few severe storms.

By Monday the ECMWF/GFS/GEM all close off an upper low with the
GFS/GEM depicting a very similar location over the Central Plains. A
moderately strong upper level jet will undercut the upper low from
the Southern Rockies through MO/IA and thus provide a conveyor belt
for embedded pieces of energy to stream northeast and through the
forecast area. The ssw low level jet will still be close enough to
continue being a factor in support of scattered convection through
Monday night. The associated frontal boundary...hard to call it a
cold front when the temperatures will still be within the normal
range on Tuesday...is expected to have cleared the CWA and thus put
an end to the rain chances.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 617 AM CDT WED MAY 15 2013

Mainly VFR conditions are expected today across much of the region,
with some cirrus streaming into the area this morning, and scattered
cumulus with bases around 5,000-7,000 ft developing during the
afternoon. There is a chance for thunderstorms this afternoon across
northern Missouri; however, any storms that do develop are expected
to be isolated, and the chance of any storm impacting a TAF site is
low. Winds will remain out of the south this afternoon for most of
the area, except far northern Missouri where winds will be variable
along a nearly stationary cold front.

&&

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

$$

SHORT TERM...Laflin
LONG TERM...MJ
AVIATION...Laflin