Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO
FXUS63 KEAX 041708
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1108 AM CST Tue Mar 4 2014
Issued at 337 AM CST TUE MAR 4 2014
High pressure continues to drift to the east this morning, allowing
surface winds to turn to the south and slow the downward fall of
temperatures. The primary focus in the short term remains focused on
an upper wave passing through the area on Wednesday.
For today, quiet conditions anticipated as upper level clouds
increase through the day. Temperatures will begin a slow rebound
this afternoon as low-level thermal ridge moves overhead. Hard to
account for the direct impacts of snow cover, but latest short term
guidance continues to hint at a run towards 40 in some locations.
Won`t go quite that high, but feel mid-upr 30s could be possible in
areas south of the Missouri river.
By Wednesday, attention turns to a amplifying but transient
mid-level impulse crossing the Central Plains. While mid-level flow
this morning remains nearly zonal in nature, a shortwave currently
initializing over northern California will cross the Rockies late
Tuesday night. This wave is expected to deepen on Wednesday as it
enters the Plains and a 100+ knot upper jet digs into the
southwestern CONUS. Slight differences remain in model guidance with
the favored solutions of the EC/GFS developing the wave southwest of
the CWA. The 00Z NAM was a strong outlier compared to the other
solutions with the wave intensifying over NE Kansas. The 06Z NAM is
more in-line with the remaining guidance. That said, a narrow band of
moisture is expected to pass through the CWA on Wednesday, with cross
sections showing a narrow corridor of strong frontogenesis within the
800:600 mb layer.
Cross sections suggest that as the column saturates, there could be
a brief period of sleet before the column cools sufficiently to
produce solely snow. As previous forecasts discussed, broad
development of stratus is also possible late Tuesday night with weak
lift within the saturated lowest 100mb suggestive of patchy freezing
drizzle or fog. Feel the area with the highest potential of this
activity would be extreme NE KS and NW Missouri. As far as QPF and
wintry accumulations are concerned, model discrepancies with the
intensity of the wave, associated lift, and speed of top-down
saturation continue to pose forecast issues. The consensus of the
ECMWF/GFS/GEM which pull the wave further south and are more delayed
in column saturation would suggest amounts around 0.05". Meanwhile the
discounted NAM with a more intense solution and stronger
frontogenesis would indicate about 3X those amounts. That said,
current forecast continue to suggest upward of a half inch of snow
as the band of frontogenesis passes through Wednesday afternoon.
Should a stronger band of precip form, temperatures are expected to fall
under that band down near or below the freezing mark.
Thursday-Friday: Shortwave ridging will move into the region for
Thursday and temperatures with a southerly wind will rebound into
the 40s. Friday`s forecast continues to remain problematic.
Southwesterly low level flow will transport quite a bit of low level
moisture northeast by Friday morning ahead of a frontal boundary
sinking towards the region. Wouldn`t rule out a bit of fog/drizzle
along this boundary in the morning hours. Otherwise, depending on
cloud cover, temperatures will try to climb into the 50s further
Next weekend: Model guidance continues to indicate the frontal
boundary will sink through the area Friday night. Wouldn`t be
surprised to see drizzle, light rain, or even light snow as this
narrow corridor of low-level moisture moves through. The good news
is that after a cooler Saturday, temperatures will begin to climb on
Sunday and exceed normal levels by Monday.
.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1101 AM CST TUE MAR 4 2014
VFR conditions are expected through much of the forecast until late
tomorrow morning when lower, MVFR ceilings work south into the area.
There is potential for some minor fog tonight as winds diminish. This
probability is enhanced by the melting of the sleet/snow cover with
temperatures warming into the 30s and the higher sun angle. For now
have reduced visibilities to around 4 miles late tonight. Light snow
looks possible late in the forecast as a band slides south through
the area. Forecast soundings suggest more of a showery type nature to
the snow with some low-level instability noted. This could mean
several quick bursts of snow at the terminals with conditions,
particularly visibility, worse than forecast. But the overall trend
will be for minor visibility restrictions due to the light snow. The
most likely timing for this will be late Wednesday morning through
early in the afternoon.