Area Forecast Discussion
Issued by NWS Springfield, MO

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FXUS63 KSGF 030541

Area Forecast Discussion
National Weather Service Springfield MO
1141 PM CST Fri Dec 2 2016

.SHORT TERM...(This evening through Saturday Night)
Issued at 256 PM CST Fri Dec 2 2016

As advertised for several days now, the upper trough is in the
process of closing over across the Desert Southwest this
afternoon. As the low closes off, some slight upper level ridging
down stream will build across our area through Saturday.

The remaining impulse (or what`s left) is forecast to spread
eastward through the day on Saturday. Ahead of this feature,
moisture will being to stream northward from the Gulf of Mexico.
Lift from the upper disturbance and perhaps some slight isentropic
upglide from frontal boundary south of the region will cause rainfall
chances to increase from south to north. Initially, the
atmospheric column will be quite dry. This will likely lead to
sleet mixing in with rain initially, at least until we can fully
moisten the boundary layer. This should be nothing more than some
conversational sleet pellets.

.LONG TERM...(Sunday through Friday)
Issued at 256 PM CST Fri Dec 2 2016

The upper level disturbance quickly slides eastward over the Ohio
River Valley by Sunday evening. Rainfall should quickly come to
end from west to east through the day on Sunday. The upper level
low pressure will begin to slide eastward along the Rio Grande
Valley through early next week.

By Monday afternoon, the ULL begins to open into a wave before
continuing on to the north and east. As it opens, a surface low
will begin to form around the mouth of the Sabine River. The
surface low should track from the TX/LA border north and east
toward western Kentucky by 12z Tuesday. Synoptically speaking, we
are in the ideal location for snowfall, however, given the lack of
a decent snowpack, the north/northeast flow will be moderated
keeping thermals warm enough for all liquid.

Finally, our first true Arctic air mass of the season is forecast
make an appearance by Wednesday and especially into Thursday and
Friday. Raw ECMWF values for Thursday keep us into the lower and
middle 20s. Given this trend, we have dropped lows for Thursday a
decent amount, however, we are still warmer than the ECM for now.
This will likely need to be adjusted with later forecasts.

The certainty of an Arctic plunge is above average, however, we
are concerned about differences among the globals regarding a
weather disturbance along with the Arctic front. ECMWF and GEM both
have some light snow shower activity along or just behind the
frontal boundary. The GFS is dry, but again does agree that Arctic
air will spill into the region. Did keep some mention of rain/snow
showers for this time, but again confidence is very low at given
the differences among the globals.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1126 PM CST Fri Dec 2 2016

Ceilings will continue to gradually build downward from around 10
kft to around 4 kft through late tonight and Saturday with
increasing moisture spreading northeastward ahead of the southwest
U.S. cutoff low. The swath of light rain currently over northeast
OK will have some drier air in the lower levels to saturate but
will carry at least vicinity showers for all areas by late morning
or early afternoon.

Late in the forecast period will carry MVFR ceilings/visibility
and predominant showers as extra lift from northern stream
shortwave trough approaches the region. For now will keep
precipitation all liquid as forecast thermal profiles are expected
to be too warm for frozen precipitation near the airports.




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