000
FXUS63 KEAX 301127
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
527 AM CST Fri Jan 30 2015

.SHORT TERM...(Today through Sunday Night)
Issued at 315 AM CST FRI JAN 30 2015

Short-term forecast remains focused on precipitation this weekend
and the subsequent snowfall accumulation potential. Models continue
to become in better agreement, however forecast scenario with
sensitivity to the near-surface warm air continues to make this a
challenging forecast.

Overview: Precipitation is expected to start out as rain or a brief
rain-snow mix with no accumulations on Saturday morning, with rain
the dominant precipitation type during the daylight hours Saturday.
A changeover from rain to snow is expected to gradually occur from
north to south during Saturday evening. That said, areas north of
Interstate 70 are the most likely areas to receive accumulating
snowfall prior to midnight Sunday morning. By Sunday morning, as the
upper system approaches and the strongest warm air advection shifts
to the east in advance of the H85 low, the lowest 2kft should cool,
especially in the presence of precipitation, allowing for the
majority of precipitation to reach the surface as snow. While
heaviest precipitation will be to the east, accumulating snowfall
will remain possible through Sunday afternoon before dry air and
downglide move into the region, ending precipitation from west to
east.

Forecast challenges: Temperature profiles aloft are supportive of
snow the entire duration of the event, yet the sensitivity to simply
a degree or two in the lowest 2kft will make a notable difference to
the forecast precipitation type. Physical concerns that may limit
snowfall accumulations 1) the warm air advection in advance of the
system upon H85 30kt southwesterly winds, 2) the track of the H85 low
pressure, 3) above freezing near-surface layer 1-2kft deep, 4) above
freezing 2m air temperatures present during a large portion of the
precipitation, 5) warm ground temperatures. There is concern how well
models are handling the warm air advection in advance of the system.
For instance, the latest NAM reintroduces a H85 warm layer of +2C
over west central Missouri at 00Z Sun, which is notably warmer than
the previous run. Furthermore, the current forecast track of the H85
low traditionally would not yield widespread heavy snowfall totals
for the majority of the CWA. Couple these challenges with the concern
of at or above freezing surface air temperatures during the initial
snowfall and a warm ground with decreasing precipitation rates on
Sunday, and there are certainly many factors seemingly working
against large snowfall totals compared to what model generated
snowfall accumulation totals would suggest.

Snowfall accumulations: Kept a conservative approach to snowfall
amounts to account for concerns listed above, and potential
melting/compaction. Keep in mind there could also be a notable
discrepancy between snowfall amounts on insulated surfaces (grass)
versus roadways. Highest snowfall amounts are expected to reside in
northeast Missouri, where up to 4-5 inches of snow is possible. Two
inches or more will be possible along/northeast of a line from St
Joesph to Moberly. The KC Metro may be limited to one-half to one
inch of snow. South of Interstate 70, less than one inch of snow is
expected.

Again, it is important to note that although models have seemingly
settled on the timing and position of synoptic features, a small
deviation in this and/or small changes in temperature within the
lowest 2-3kft may spell a significant change in snowfall amounts.
Subsequent forecasts will closely monitor snowfall potential,
especially across the northeast half of the forecast area.

.LONG TERM...(Monday through Thursday)
Issued at 315 AM CST FRI JAN 30 2015

Cold temperatures look to dominate the region as we transition from
the weekend into the work week as the cold Canadian airmass that
should bring snow Sunday continues to slide through the region. In
general, temperatures to start the week will moderate a little for
Tuesday, but ultimately stay around to a little below seasonally
normal values through much of the work week as a broad northwest
prevails pushing more cold air into the Plains States. Other than the
cool temperatures, mid-range models advertise a modest shortwave
trough swinging through northern Plains Wednesday and Wednesday
night. Models are pointing at the potential for some light
precipitation, but given model inconstancy at this point have held
off including in the forecast for now. Lastly, warmer conditions may
return by Friday and next weekend as a western CONUS ridge pushes
east late in the work week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
Issued at 524 AM CST FRI JAN 30 2015

VFR conditions will continue through the majority of the forecast.
Surface winds will become southerly by midday with increasing high-
level clouds. Conditions will deteriorate Saturday morning with MVFR
ceilings and scattered showers entering TAF sites between 08-11Z.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

SHORT TERM...Blair
LONG TERM...Cutter
AVIATION...Blair