Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Norman OK
950 PM CST Sat Dec 20 2014
only minor updates to the forecast this evening. The primary
change is to remove the mention of dense fog in the west this
evening. It is not completely out of the question to see some very
isolated areas of dense fog overnight... but the trends in the
high- resolution model output are to be less aggressive with the
dense fog formation in our forecast area and generally confine the
dense fog to higher elevations /such as the Wichita Mountains or
some of the higher elevations of Roger Mills and Ellis counties/.
Will continue to mention general fog and drizzle overnight.
Previous discussion... /issued 548 PM CST Sat Dec 20 2014/
aviation discussion for the 00z tafs is below.
have low confidence in the tafs.
Overall...think worsening conditions will occur at all sites
through 18z...though exactly when and how bad conditions will
get remain very uncertain. All sites will be MVFR or lower by
06z. Widespread IFR and lower conditions may develop across the
area...mainly after 12z. Chances of conditions dropping below
Airport minimums remain low. Improving conditions may occur west
of kavk-klaw-ksps after 18z.
Patches/areas of -dz will develop after 09z...mainly east of
Previous discussion... /issued 308 PM CST Sat Dec 20 2014/
moisture bounded by strong inversion is not expected to go
anywhere until cold front surges in late Monday. Mixing on higher
terrain has progressed into western Oklahoma and adjacent parts of
northern Texas...but this is not expected to make it very far east
this evening. Backing/increasing flow ahead of incoming shortwave
expected to allow stratus and fog to redevelop tonight. With the
clearing across far western/northwest Oklahoma this
evening...could see temperatures fall well down into the 30s before
higher dewpoints begin to surge northward. This could lead to a
fair amount of dense fog late tonight and will mention this in the
grids. Fog expected elsewhere...but not as dense. Patchy drizzle
also expected overnight and Sunday morning as trough approaches.
Cannot rule out some light showers as well but will not mention in
In association with the mentioned cold front...deep and very cold
trough will evolve over the Southern Plains and points east late
Monday through Tuesday. Models are coming into better agreement
with development of Post-frontal precipitation. Based solely on
thickness forecasts and historical 700 mb-500 mb thermal thresholds...one
might expect snow across western/southern Oklahoma on Tuesday.
However...with lower level deterministic forecasts and forecast
soundings...lower levels appears to stay too warm for too long for
anything more than a possible rain/snow mix before ending near the
Red River. This scenario will be monitored but at this time no
mention of snow in latest forecast issuance.
Cool down will not last long as southwest flow commences late
Wednesday into Christmas day ahead of next weather system. Another
cold front still expected Christmas night and Friday. This frontal passage
appears to be dry and will bring temperatures down closer to
average into next weekend.
Preliminary point temps/pops...
Oklahoma City OK 39 50 42 57 / 10 10 10 10
Hobart OK 38 53 38 57 / 10 10 10 0
Wichita Falls Texas 39 55 41 63 / 10 10 10 0
gage OK 34 53 36 55 / 10 10 10 10
Ponca City OK 37 49 43 54 / 10 10 10 20
Durant OK 41 52 45 59 / 10 10 10 10