Winter Weather Discussion – 2009-1-2

Severe Weather Discussion for January 26 – 28, 2009.
Valid: 01/25/2009.

Highlights:

– Winter Storm Watch remains unchanged from earlier issuance.
Warnings are likely by Monday morning for parts of the watch area.

– Impacts for the majority of the watch area will be to travel with
some isolated power outages. Widespread moderate travel impacts are
likely with isolated areas of high impacts. There still appears to be
an area of east-central Oklahoma, maybe Cherokee/Adair Counties that
could experience moderate impacts to critical infrastructure,
including power facilities.

– The event is expected to end midday Wednesday.

– An incident has been created in WebEOC for the ice storm, please log
into 2009026 – Ice Storm.

Discussion:

Little change in the model forecasts for the next few days. NAM
continues to be low on the QPF with the GFS in the middle and ECMWF
high. For now the GFS is the best route as it has been rather
consistent in the storm total QPF. The 18z run did increase amounts
somewhat in eastern Oklahoma, but I'm going to wait and see if this
continues the next few runs.

Recent model runs also show some potential for change over to sleet as
the 850mb low moves into Texas and backs the flow aloft. This would
mean that some of the expected freezing rain amounts would instead be
sleet, obviously a positive relative to power lines. However,
confidence in the timing is still low and for now I'm sticking with
mainly a freezing rain event.

Freezing drizzle should start by Monday morning across much of the
watch area. At this time, the morning rush area for both Oklahoma
City and Tulsa look decent. However, as the day progresses road
conditions will deteriorate. The evening rush hour for both cities is
likely to be rough as freezing rain continues in earnest across the
area. Monday night will see freezing rain continue with potential for
thunder freezing rain as models BUFKIT plots show elevated
instability. Tulsa is likely to see a more prolonged period of this
condition. Models rarely forecast QPF well in these events and always
under-do the QPF forecast. As such, any area that experiences
prolonged thunder may see a rapid accumulation of ice. This will have
to be closely monitored on Monday and may result in rapid changes in
the forecast.

Models are pretty insistent that the precip will decrease by Tuesday
afternoon. For now, I'm keeping the event through Wednesday morning
and will reduce later if necessary.

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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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