853
FXUS63 KEAX 130900
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
400 AM CDT Tue Aug 13 2013
.SHORT TERM...(Today through Thursday)
Issued at 359 AM CDT TUE AUG 13 2013
A modest frontal boundary settled through the region Monday, taking
up residence along the Arkansas border by the early morning hours of
Tuesday. This front made its progress into the Central Plains thanks
to a large trough digging in across the eastern CONUS, which is
simply the down stream result of a persistent blocking ridge
currently in place across western Canada. The resulting meridional
flow has already resulted in a series of pleasant days, with
temperatures ranging a skosh below normal over the past few days.
This trend will only become more pronounced as more cool Canadian air
filters south. This cool pattern should limit afternoon highs to
around 80 degrees from Wednesday through the rest of the work week; a
temperature regime more consistent with early September as opposed to
the middle of August.
However, the dry conditions that will prevail today and Wednesday
may not last through the end of the work week. Models continue to
pick up on a shortwave trough that will undercut the Canadian ridge,
zipping through the Great Basin into the Northern Plains later this
week. Verity of short and medium range models key on this little
feature to bring some storms back to eastern Kansas and northern
Missouri late in the work week as the trough gets picked up in the
still prevailing northwest flow. Model solutions are a little suspect
given the amount of rain they keep forecasting for our region that
does not appear, but consistency in the solutions warrants adding in
POPs for late Thursday night, though the main focus for this activity
is currently forecast for the daylight hours of Friday.
.LONG TERM...(Friday through Monday)
Issued at 359 AM CDT TUE AUG 13 2013
Shortwave ridging will begin to amplify over the intermountain West
during the late week period, while longwave troughing begins to
shift from Quebec/New England into the northern Atlantic. This
evolution will promote a weakness over the eastern Plains early
Friday. 00Z models agree that some shortwave trough will drop in
from the northwest early Friday, but disagree on intensity and
speed. These differences likely arise from variances in upscale
growth of one or more convective systems (MCVs) that will move
across the Plains Thursday night. The GFS remains the most
aggressive, with an intense closed sub 580dm low arriving into NW MO
by 06Z Friday...while NAM/ECMWF suggest a broader, slower moving
system in the same time frame. At this early juncture, it would seem
reasonable that chance POPs are warranted Friday morning with the
passage of this mid level trough.
Thereafter, confidence remains rather high that a favorable position
will exist between a positive tilt ridge to the west and a closed
low to the east through the weekend...with high pressure at the
surface. These features would tend to suggest fair skies, below
normal temperatures and dry conditions will return for Sat-Mon.
Given the upper ridge orientation, it also seems reasonable that
strong Pacific Jet energy arriving early in the week should quickly
flatten the ridge. The intensity and moisture quality of any
upstream Pacific troughing is certainly in question, given the
tendency for the belt of westerlies to be positioned well north this
time of year. Nevertheless, model consensus suggests enough of an
influence to warrant low chance POPs across the western zones for
Tuesday, but would figure that any QPF should be light given its
origin.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1200 AM CDT TUE AUG 13 2013
Primary concern is the patchy fog that is forming across northern and
central MO this evening. Normally fog is not a concern in August.
However, August's weather has been more similar to September and
will treat it that way for this forecast. This means an increase
risk of meaningful fog overnight. Expecting mainly ground fog where
visibilities gyrate between MVFR and LIFR as the fog wafts back and
forth on any puff of wind. Low lying areas will be the primary
resting spot for this fog and the KSTJ terminal fits this profile.
KMCI should be more in line for patchy MVFR fog while KMKC may go fog
free.
Otherwise, fog will dissipate quickly after sunrise. Rest of the
forecast will see VFR conditions and a generous amount of broken high
level cloudiness with light northeast to east winds.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
SHORT TERM...Cutter
LONG TERM...Bookbinder
AVIATION...MJ