AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1158 PM CDT Thu May 23 2013
.SHORT TERM...(This Evening through Saturday Afternoon)
Issued at 409 PM CDT THU MAY 23 2013
Upper pattern is evolving as a deep upper trough pulls further away
while an upper level ridge amplifies and shifts east through the
Plains. Although one usually associates the arrival of an upper
level ridge with minimal precipitation this time it will be
different as a series of shortwaves and increasing isentropic ascent
results in a prolonged period of periodic convection...starting
Friday night. This will result in a change from benign and below
average temperatures on Friday to increasing rain chances, elevated
humidity and slightly above average temperatures by Saturday.
For tonight, surface ridging associated with high pressure over
Saskatchewan and western Ontario extends south through eastern
NE/western IA. This has nudged a weak surface trough out of the CWA
and the resulting subsidence and daytime mixing are finally eroding
the extensive stratocu field from the north and west. These clouds
will likely linger into the early evening and be last to clear from
the east central counties. The rest of the night will be generally
clear and a good candidate for strong radiational cooling.
Mid level cloudiness will increase from west to east on Friday as
warm air advection aloft spreads east. Will keep the CWA dry due to
a continued dry east-southeasterly which maintains a very dry
elevated mixed layer until late in the day. The southerly low level
jet plus increasing instability and isentropic lift will become key
players in the development of scattered convection over KS on Friday
and likely a MCS over IA Friday night which will probably backbuild
into the northern CWA. Both the the 12z NAM and ECMWF mass fields
hint a convective outflow boundary could propagate southwest into
the now southwesterly oriented low level jet. It's also possible new
convection could reform further south over the CWA during the day on
Saturday. There are a number of potential ifs but the general
theme for Saturday is be prepared for scattered convection,
especially in the afternoon as the cap is eroded.
.LONG TERM...(Saturday Evening through Thursday)
Issued at 409 PM CDT THU MAY 23 2013
Forecast for the latter half of the holiday weekend and into the next
week continues to look unsettled. Mid-range operational and ensemble
models continue to advertise the persistence of a blocking pattern
across the United States through the weekend, with some possibility
of the pattern flattening out late next week. However, till the
pattern flattens, the shortwave ridge will reside across the Plains,
continuing to interact with shortwave troughs moving through, and
ejecting from, the trough on the west coast. Severe thunderstorm
activity is not expected to be significant problem. While Gulf
moisture will be available, shear profiles under the ridge will be a
little messy, making it difficult for storms to organize. Have
continued to broad brush in thunderstorms POPs trough these periods.
Otherwise, temperatures under the shortwave ridge will slowly climb
over the weekend, settling above normal early next work week. So,
while hit or miss storms will plague the weekend, at least
temperatures will be pleasant.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1158 PM CDT THU MAY 23 2013
VFR conditions will persist through the forecast period, with clear
skies overnight giving way to scattered midlevel clouds by mid- to
late-morning Friday. A thicker deck of midlevel clouds with bases
around 10 kft will build in during the evening, and a few showers or
isolated thunderstorms will be possible across far northern Missouri
by late Friday evening into the early overnight hours.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
SHORT TERM...MJ
LONG TERM...Cutter
AVIATION...Laflin
