Winter Weather Discussion 2010-1-4

Winter Weather Discussion for January 27-29, 2010.
Valid: 2010-01-27

*Significant Winter Storm to Impact Oklahoma*
*Preparations should be rushed to completion*

Highlights:

– Significant winter storm to impact Oklahoma, this is a Particularly
Dangerous Situation with the likelihood of life threatening amounts of
freezing rain, sleet, and snow.

– Winter Storm Warning for much of Oklahoma, north of a line from
Lawton to Muskogee. Excessive snowfall is expected in northwest
Oklahoma and the panhandle with 8-12 inches total accumulations
likely. Along the I-44 corridor, a cold rain will start off Thursday
and turn to freezing rain during the midday hours. A quick transition
to sleet and eventually snow will occur by Friday morning. Total ice
accumulations may exceed one inch in some areas with sleet of 2-3
inches and snow 3-5 inches.

– Winter Storm Watch for much of south-central and southeast Oklahoma.
In southeast Oklahoma a cold rain is likely much of the day Thursday
changing to freezing rain and sleet during the overnight hours. The
event should end with snow.

– Timing of this event is particularly problematic in Oklahoma City,
since the general public will venture out Thursday morning only to be
caught in the transition to freezing rain during the late morning
hours. This may lead to widespread wrecks, stranded motorists, and
difficulty for emergency vehicles to move around. A situation similar
to December 24th is quite possible.

– Strong winds will occur with this system and after it leaves late
Friday. This will likely aggravate the situation and widespread power
outages are becoming a likely result.

– The forecast continues to call for a high-end event across much of
Oklahoma. Additionally, after the system passes, temperatures will
plunge into the single digits and teens. This will create a
life-threatening situation for those unable to move to warm shelters.

Discussion;

12z NAM has indicated warmer surface temperatures, which would delay
the switch over to freezing rain in parts of Oklahoma. It does some
rather weird things with the precipitation types later in the
forecast. The 12z GFS remained consistent with prior runs on the
temperature profile and for now I will stick with the GFS. At this
point I will err on the GFS side of the forecast and take the hit if
we end up with just a cold rain. Model QPF fields have fluctuated
here and there the past few runs and I really think that is about
normal. They are still getting a handle on the upper low and
especially the 700mb dry slot. Changes in QPF across the state are
likely until the upper system is well sampled by the upper air
network. Since the upper system will be over Mexico through tomorrow
morning, we may have to wait a few more model runs.

It is important to note that the models remain in unusual agreement
regarding the placement and trajectory of this system. While the NAM
has shown some changes in the surface temperatures, this doesn't
appear to alter the potential at this point.

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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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