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Area forecast discussion...updated 
National Weather Service Springfield MO
1205 PM CST Sat Dec 27 2014

..updated aviation section...

issued at 1205 am CST Sat Dec 27 2014

Addition, minor revisions to the forecast made for this afternoon.
Not much has changed from this morning's update other than include
a risk for the development of small bands of moderate snow. One
such band developed over the Tulsa, OK area over the past few
hours producing an inch of snow and a light accumulation of snow
on bridges/overpasses. Latest RUC/hrrr runs continue to hint at
this possibility in our area this afternoon. And with the
elongated shear zone still present in the mid levels overhead, a
few mesoscale bands of moderate snow are plausible.

Temperatures continue to hover right around the freezing mark, so
it will require heavier snowfall rates (moderate snow, 1/2sm vis
in observations) to support sustained snowfall accumulation. To
this point, the "best" accumulation has been in grassy areas near
the MO/Kansas state line in Cherokee/Crawford counties in Kansas and
Jasper/Newton counties in Missouri. Will continue to monitor
development of mesoscale snow bands in Oklahoma over the next few
hours and alter expectations accordingly.

Dry air in the 850/700 mb layer continues a slow southeastward
progression and light snow has not been mentioned in the metars at
Parsons, Chanute and Fort Scott, Kansas over the past few hours.
The observation at Pittsburg, Kansas has seen light snow come and go
over the past hour, so a slow southeast progression of the dry
air in the mid levels will continue, likely reaching the I-44
corridor by late this afternoon based on trends from the RUC/hrrr.

Precipitation will gradually end this evening across the area.
Will need to watch for black ice potential as temperatures fall
into the 20s. Any residual moisture on area bridges and overpasses
will have the potential to freeze.

Update issued at 940 am CST Sat Dec 27 2014

Forecast updated to account for thermodynamic and radar trends.

Deeper cold air has come in quickly and allowed for a mix/change
over to snow across the west/northwest half of the area (or so).
Most persistent area of light snow has been across southeastern
Kansas where a dusting of accumulation has been observed on grassy
areas. Air temperatures are holding in the low/mid 30s. Looking at
area obs and after making a few calls, Road temperatures are a bit
warmer (upper 30s in southeastern Kansas, warmer on the MO side).
Since snow showers will be on again/off again in nature, it does
not appear that we will receive persistent enough precipitation
rates to overcome relatively warm ground temperatures. As a
result, any snow accumulation will be on grassy areas and light
(a dusting).

Timing the ending of the snow is proving somewhat tricky. Looking
at the 12z ktop sounding, there is a wedge of dry air in the
low/mid levels working southeastward (850-700mb layer). This is
already entering the northwestern portion of the outlook area and
meshes up nicely with surface observations in Kansas/Oklahoma. At
this hour, light snow reports are becoming more sporadic at kfsk
(fort scott) with rising cloud bases, which supports the idea of
tracking these mid level dewpoint depressions. As a result, have
followed this for timing the end of precipitation.

Across the eastern portion of the outlook area, the cold front has
exited east and temperatures will slowly, but steadily drop
through the day. Will look at the forecast for this evening
shortly to see if there is need to introduce a brief period of
light snow before ending around midnight.


Short term...(today and tonight)

Light rain was increasing in coverage over eastern Oklahoma this
morning, which will shift into southeast Kansas and the Missouri

We followed the hi-res arw with our precipitation and pop forecast
through today and tonight. This solution suggests placing light
rain further northwest by 12z, and translating an axis of light
rain eastward across southern Missouri with time.

We think the areal coverage of measurable rain will be high,
however, rainfall amounts will be low. Many locations will only
experience measurements less than one tenth of an inch.

Light rain should linger across south central Missouri this
evening and tonight, eventually exiting the entire region by
Sunday morning.

Long term...(sunday through friday)

A cooler air mass will have spread across southern Missouri by
Sunday bringing temperatures down into the 20s to start the day.
High pressure will be shifting directly overhead causing winds
to become light and variable under sunny skies.

An extended period of dry weather is expected heading into the
upcoming work week. Fast zonal flow will occur over most of the
nation's mid section as northerly winds persist at the surface.
This pattern will keep moisture at Bay, bringing dry weather.

These northerly winds will also allow some polar air to move into
the Ozarks. Temperatures will plummet by Tuesday and Wednesday
with highs only in the 20s and lows in the teens.

Rain chances finally increase by Thursday night and Friday as a
storm system slowly approach from the west. Thermal fields will be
border line rain or snow for precipitation type. Therefore we have
a rain or snow worded in our forecast for Thursday night and
beyond. Details regarding precipitation type late next week should
be better understood in time.


Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1205 am CST Sat Dec 27 2014

Challenging forecast as cold air continues to move into the region
while drier air lags a bit. A narrow band of precipitation
continues to affect jln and at times sgf. This will gradually
shift east with -sn ending at jln by mid afternoon and -rasn
changing to -sn this afternoon before ending by dark.
Precipitation at Branson will likely be -ra initially, with some
-sn mixing from mid afternoon Onward. Overall, IFR/low end MVFR
has been common, though brief periods of LIFR are possible where
small scale bands of heavier precipitation develop. Given these
being so small in scale, have not mentioned LIFR in the tafs at
this time. Models continue to indicate an orderly exit of this
system tonight. Stratus will exit from west to east with lingering
cirrus possible.


Sgf watches/warnings/advisories...


short term...Cramer
long term...Cramer

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