Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
FXUS63 KEAX 072335
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
535 PM CST Sat Dec 7 2013
.SHORT TERM...(This Evening through Sunday)
Issued at 341 PM CST SAT DEC 7 2013
Weak shortwave over the Rockies will track into the Plains tonight
and Sunday sending a wave of light snow our way late tonight and
Sunday morning. General model trend has been to back off on snow
amounts slightly, with the higher amounts shifting north of the
MO/IA border in closer proximity to the strong upper level jet.
Still, isentropic lift alone should be enough to produce a broad
area of 0.05" to 0.15" QPF amounts, roughly translating to 1 to 2
inches of snow given liquid/snow ratios around 15:1. Higher end of
this range will be across far northern MO. Given slow snowfall
rates, relatively light wind and the powdery nature of the snow,
impacts should be relatively minimal south of the MO/IA border so a
winter weather advisory will not be issued at this time.
Snowfall will taper off through the late morning and afternoon as
drier air builds down from aloft. However, this drier air may
provide an airmass somewhat favorable for patchy freezing drizzle
Sunday afternoon and evening as a weak low-level trough swings
through. Thermal profiles look borderline between drizzle/flurries,
but regardless of precip type any additional amounts Sunday
afternoon and evening should be very light with little to no snow or
.LONG TERM...(Sunday Night through Saturday)
Issued at 341 PM CST SAT DEC 7 2013
Will still be under the influence of the positive tilted upper trough
to start next week before the upper pattern transitions to northwest
flow. 12z GFS/ECMWF are in very good agreement through the entire
Past couple of runs of NAM/GFS have been generating weak and layered
frontogenesis as a strung out vorticity lobe ejects northeast
through KS and MO Monday/Monday night. Juxtaposition of near
saturated layer with the frontogenesis is mainly south of the CWA
but GFS is far enough north to warrant slight chance PoPs across the
extreme southern counties Monday night. Any snow still on the ground
Monday will limit any warming despite sunshine.
Expect some moderation in temperatures on Tuesday as moderate warm
air advection tries to scour out at least some of the arctic air.
Even with this warming temperatures will only reach the 30s or at
least 10 degrees below average. Another surge of colder air will
force its way into the region on Wednesday with the passage of a dry
cold front. High pressure which follows will quickly move out and
southerly return flow should allow temperatures to climb back into
the 30s for the rest of the forecast period.
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 528 PM CST SAT DEC 7 2013
VFR conditions will persist through the early morning hours of
Sunday. Models continue to indicate a rapid saturation of the
currently very dry low levels of the atmosphere towards daybreak with
an increase in precipitation. Timing of arrival for snow in the KC
and STJ terminals continues to look around 10Z. Depending on the
intensity of the initial snowband, a quick reduction to IFR ceilings
and visibilities will be possible shortly after daybreak.
Intermittent snow showers will persist through the morning, before
snow could taper off to light freezing drizzle for an hour or two at
mid-day. Accumulations of 0.5-1" look possible for the KCI, with
potential for 1.5" of snow towards STJ.
The snow will be a very light snowfall and a 10 knot southeast wind
could lead to slight blowing and drifting of the snowfall.