Scientific Forecaster Discussion
fxus63 keax 251105
Area forecast discussion
National Weather Service Kansas City/Pleasant Hill MO
605 am CDT Thu may 25 2017
issued at 310 am CDT Thursday may 25 2017
Relative high pressure col moving over the area currently is
resulting in light winds and clear skies. Fog has been patchy at
this point but may increase some in drainage areas like
river/stream valleys before sunset. Otherwise, winds will return
from the south today with highs close to normal in the middle and
upper 70s and no chance for precipitation.
Pattern becomes more interesting to start the Memorial Day weekend.
For Friday, a weak boundary will be in the area as weak high
pressure builds into the area from the north. Several convection
allowing models show storms developing in the vicinity of the
front during the afternoon. With cape values around 2000 j/kg and
shear of 30 to 35 kts, it looks like a few severe storms can't be
ruled out. The threat at this point seems conditional on if the
cap can break.
The better chances for severe storms look to be Saturday but are
contingent on what happens with a mesoscale convective system that models continue to show
tracking into the area. Convection should develop Friday evening in
the High Plains and then track east across Kansas and NE, eventually
moving into MO Saturday morning. Convection later on in the day will
depend on how far this mesoscale convective system pushes a gust front south and gunks up
the environment. Latest model runs vary substantially with this key
aspect though. The GFS and the European model (ecmwf) push a boundary through the
forecast area, pushing the afternoon convection further south.
The NAM, being a little further north with the MCS, has the
boundary in our southern zones and develops a very favorable
environment for severe storms with extreme instability and ample
0-6km shear. Forecast soundings suggest the potential for
supercells with very large hail if the NAM were to verify.
The rest of Memorial Day weekend looks pretty decent with dry
weather expected and high temperatures close to or slightly above
normal. This trend will persist through the rest of the forecast as
the area will be in northwesterly flow aloft. A shortwave trough
moving through the area Tuesday may bring a chance for showers and
storms, but only the GFS shows this. The European model (ecmwf) and the Canadian
remain dry. The northwest flow will allow for high pressure to build
into the area and as a result near normal conditions are expected
through the end of the week.
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 602 am CDT Thursday may 25 2017
Patchy am fog, mainly affecting the stj terminal, will quickly
burn off after sunrise as winds start to increase from the south.
VFR conditions are expected through the rest of the forecast once
the fog lifts. Winds may gust as high as 20 kts this afternoon
and then decrease and back overnight.