Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
FXUS63 KEAX 050850
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
350 AM CDT SAT SEP 5 2015
Issued at 350 AM CDT SAT SEP 5 2015
Today - Sunday...
Warm moist air continues to flow unimpeded from the Gulf of Mexico
into the region. Diurnal heating will mix out the low-level
inversion resulting in an unstable airmass. However, a lack of any
passing upper system, isentropic ascent and any discernible boundary
will render this potential instability harmless. So, today and
tomorrow will be a repeat of the past week...above average
temperatures and a case of the muggies.
Sunday Night - Thursday...
A very unsettled period which the operational models are having some
trouble delineating timing of each round of convection and when to
end the rain.
The operational models continue to focus on breaking down the upper
ridge which currently lies from the Southern Plains through MO into
the the western Great Lakes. A deep upper level trough now over the
western U.S. will lift northeast and track across the Canadian
Prairies on Monday. Although this system will pass far to the north
the falling heights will be felt this far south pressing a cold
front southward. The primary question is how far south will it get
before it stalls Monday night. There seems to be a consensus that
the boundary will stall over northern MO and become the primary
focus for repeated rounds of diurnally driven convection.
The initial foray into the CWA is expected to occur after midnight
Sunday as convection which formed along the cold front to our north
slides across the CWA. There is also the likelihood of multiple
outflow boundaries generated from earlier convection which will
influence where the afternoon and evening convection will form. So
pinpointing anything this far out is fruitless.
Monday afternoon and evening do pose a minor severe risk for the
northern half of the CWA as there is decent model continuity on the
placement of the front. Afternoon MLCAPES nearing 2500 J/kg plus 25-
30kt 0-6km sheer suggests some support for multicell strong/isolated
severe convection. In addition, with precipitable water values
projected to be in excess of 2 inches or 200 percent of normal.
we`ll need to be aware of the potential for heavy rains and
flooding. More to come as we near this time period. Confidence is
also increasing that higher PoPs will be needed Monday through
Tuesday night due to the presence of the cold front and the
potential for numerous outflow boundaries to act as foci for
GFS/ECMWF and SREF are trending slower in moving the cold front
through waiting for a second shortwave to sweep through. Unsure on
whether or not Thursday will still need PoPs but for now can`t argue
against going with low chance PoPs. In addition, due to the slower
departure of the cold front will hold off on cooling temperatures
down and instead keep them closer to seasonal averages Wednesday and
Much cooler and drier air will eventually force its way southward
and into the region as high pressure builds in. Temperatures will be
more reflective of early Fall as 925mb temperatures fall off a cliff
from 25-28C on Monday to 12-15C by Friday.
.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1219 AM CDT SAT SEP 5 2015
VFR conditions will continue with a pick up in in southerly winds
this afternoon. THese winds should also diminish by very late
afternoon as the boundary layer mixing ceases.