Winter Weather Discussion 2010-1-3

Winter Weather Discussion for January 27-29, 2010.
Valid: 01/26/2010

*Significant Winter Storm to Impact Oklahoma*
*Prepare now for this winter storm*

Highlights:

– Winter Storm Watch for all of Oklahoma except McCurtain County.
General timing is late Wednesday through Friday. Excessive snow is
likely for Northwest Oklahoma into the panhandle of 8 to 12 inches.
In the I-44 corridor, rain will turn to freezing rain around midday
Thursday and then to sleet late Thursday, eventually snow into late
Friday. Total amounts are still questionable, but there appears
potential for significant accumulations of ice greater than one inch.
In southeast Oklahoma, rain will turn to freezing rain late Thursday
and eventually sleet/snow on Friday. As with central sections, there
appears potential for significant amounts of ice.

– This is a high-end impact event with significant travel problems
likely across a large part of Oklahoma by late Thursday. Stranded
motorists are likely on major interstates and secondary roads. Timing
of this event is critical since the traveling public will not see any
adverse weather Thursday morning, only to be caught in it by Thursday
afternoon. This is a very similar situation timing wise to December
24th.

– Sporadic power outages are likely and there is increasing potential
of widespread power problems, lasting several days. Initially, ice
coated power lines will cause problems and then be complicated by very
strong winds on Friday and Saturday as the upper system departs the
region.

– Wind chills will be quite low on Friday with surface temperatures
dropping into the single digits to teens Friday thru Sunday. This may
create a life-threatening situation for those without power.

– Current watch product will likely be upgraded to warnings Wednesday morning.

Discussion:

18z NAM continues in good agreement with prior runs. There is an
interesting change in the placement of the upper system with this run
and one I'm not jumping on right now. It develops a closed low in the
northeast section of the trof by Thursday, resulting in a more
pronounced dryslot. Not sure this is going to be an issue and
honestly has very little impact on the overall forecast. The end
result is that model data remains consistent among all three major
guidance systems for the upcoming event Thursday/Friday.

I have to note that I have concerns regarding the amount of warm/moist
air in Texas. Dewpoints in the 50-55F will be in southern Oklahoma
and should work against the incoming Canadian air. Snow cover is
lacking across Kansas and there may be potential for the airmass to
modify. However, expected timing and quick movement of the airmass
should really limit this potential. The end result is that a firm
grasp on precipitation type won't occur until Thursday. There is a
fine line (about 1 degree C) between a cold rain and a big mess. I
will not ignore the available model guidance and as such continue to
forecast frozen/freezing precipitation for Oklahoma. I will also note
that none of the models have backed-off on the winter weather forecast
for Thursday/Friday. The consistency and agreement among the models
is quite unusual.

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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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