Winter Weather Discussion 2009-7-5

Winter Weather Discussion for December 23-24, 2009.
Valid: 12/23/2009.

Highlights:

– Winter Storm Watch for central, north-central, and northeast
Oklahoma. Snow accumulations of 3-5 inches in Oklahoma City northward
to Ponca City is likely with 4-8 inches in eastern Oklahoma.

– Severe thunderstorms are possible in eastern Oklahoma later today.
Primary threats are large hail and damage winds, however an isolated
tornado cannot be ruled-out.

– Winter Weather Advisory is posted for west-central, northwest, and
parts of southwest Oklahoma tonight into Thursday. Light freezing
drizzle is likely tonight changing to snow early Thursday. Snow
accumulations of 1-3 inches will be likely.

– Bitterly cold temperatures are expected behind this system,
especially areas that receive snowfall. Temperatures may not get much
above freezing beyond the weekend in many areas.

Discussion:

12z guidance seems to have converged on a solution of moving the upper
system through north Texas and then ejecting it northeast through
eastern OK/western AR. This puts a large part of Oklahoma in the
favorable deformation zone for heavy snow fall. The NAM continues to
ingest dry air at 700mb behind a lead shortwave trof and therefore
reduces overall QPF across the central/eastern parts of the state. I
find this suspicious given the copious amounts of moisture and
placement of the 700mb low. As such, I'm going with the consensus of
the model runs and keeping snow accumulations in eastern Oklahoma.
I'll take the hit if it doesn't happen, I'm tired of the forecast
variations.

Travel problems are likely due to the typical diurnal min in traffic
early in the morning and start of precipitation in the 3-5am timeframe
Thursday morning. Snow will develop east during the day and should be
ending in central Oklahoma during the late afternoon hours. The most
likely time for heavy snow will be during the morning hours. The
heavy snow threat will shift east and persist a little longer in
eastern Oklahoma through late Thursday. Flurries may continue on
Friday, but the heavy snow threat will have ended.

Temperatures will be bitterly cold Thursday through at least Sunday,
especially in areas of snow accumulations. Another storm system
approaches the region on Tuesday and this system looks to have
sufficient moisture to produce snow. Quick look at 00z ECMWF yields
this may be more of a southern Oklahoma/north Texas event. However,
as we have seen with the current system, forecast tracks will likely
change.

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About Putnam Reiter

Putnam has been storm chasing since 1990 and is a co-founder of Hook-Echo.com. For his day job, Putnam works in emergency management for information technology.
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