Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
FXUS63 KEAX 012114
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
414 PM CDT Mon Sep 1 2014
.SHORT TERM...(This Evening through Tuesday)
Issued at 412 PM CDT MON SEP 1 2014
Very near term concerns hinge on overcoming a stout cap left from
last nights extensive convection. Visible satellite imagery notes
the thick/flat stratocu deck defining this cap which has spread
across most of the CWA this afternoon. Operational models are having
a hard time dealing with this stable environment and generating
convection across the southern 1/2 of the CWA. Closer look at the
NAM/GFS Bufr soundings, especially the GFS as it has correctly held
onto the cap longer, reveals just how strong the cap is. Short term
Hi-Res models are superior and have trended southward with bulk of
convection and focus on the outflow boundary left by this mornings
decayed convection. For now will pare back PoPs south of the MO
River and focus on far southern counties. Northern half will remain
Otherwise, a weak cold front will drift south through the CWA
overnight, likely stalling over the far southern CWA around sunrise.
Have added fog to the forecast due to near calm winds, clearing
skies across northern MO, very moist boundary layer and a now
climatologically favorable time of year for fog formation.
Weak high pressure tries to build in on Tuesday but probably won`t
have much luck due to the presence of the stalled front. Net effect
is near seasonal temperatures with drier conditions across far
northern MO but remaining humid south of the MO River.
.LONG TERM...(Tuesday Night through Monday)
Issued at 412 PM CDT MON SEP 1 2014
Zonal flow aloft will take root Tuesday through Thursday with falling
pressures building in across the Central Plains late Tuesday and
Wednesday allowing the stalled front to return northward as a warm
front. As the low level jet reforms in response to falling pressures
the isentropic ascent above the warm front should allow scattered
elevated convection to form Tuesday evening and through the night.
Models due pick up on this and the isentropic ascent is quite
prevalent on the 310K surface. Have gone with high end chance PoPs.
Convection will exit the region Wednesday afternoon with dry and
hot conditions returning as an elevated mixed layer spreads in.
The dry weather won`t last long as the medium range models have
remained consistent in dragging a moderately strong cold front
through KS and MO Friday/Friday night. Timing may be a bit of a
problem for high temperatures but convection is pretty certain
during this period. The elevated mixed layer within the pre-frontal
zone should keep the region dry until fropa. Elevated post-frontal
convection likely to break out initially within the surface to h8
layer. A veering low-level jet will keep the convection going
through Friday night.
The weekend is shaping up to be gorgeous as our first true taste of
fall-like weather moves in with high temperatures in the 70s and
overnight lows generally in the 50s.
.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1244 PM CDT MON SEP 1 2014
Weak cold front will slide southeast through northern towards
central MO before stalling this evening. Scattered convection
expected to develop late afternoon from southeast KS through central
MO but should form south of KMCI/KMKC. So, will go with a VFR
forecast until pre-dawn hours. Will introduce MVFR fog then as mid
clouds clear with nearly calm winds and very moist boundary layer.
Late August and September are climatologically favorable period for
fog forming over the region. Latest NAM/GFS Bufr soundings and SREF
visibility prog support adding fog with dense fog possible at KSTJ.
Should mix out fog and any low clouds by mid morning.