Weekly Severe Weather Discussion

Severe Weather Discussion for February 22 – 28, 2010.
Valid: 02/21/2010.

Highlights:

– Slight chance of snow for southwest and south-central Oklahoma on Tuesday.

– Rain is possible on Thursday with a chance of snow Thursday night.

– Rain is possible on Sunday.

– Temperatures will be near 40F tomorrow, mid 40s Tuesday-Wednesday,
upper 40s Thursday, low 40s Friday, upper 40s Saturday-Sunday.

Probabilities:

– Severe Thunderstorms in Oklahoma: < 5%
– Storm Chase: < 5%
– Winter Precip; 20%

Discussion:

Active week ahead as the atmospheric pattern remains amplified.
Models are in decent agreement through the week. Impacts are expected
to be on the low-end with the first two systems in Oklahoma, more
significant impacts are likely Tuesday in Texas. The last one may
have more significant impacts, but really a tough call seven days out.

Shortwave trof currently moving over the state will translate
northeast and merge with the larger medium wavelength trof over the
northern U.S. Another southern stream shortwave trof will move
eastward towards the region from the downstream side of the eastern
Pacific Omega Block. This system will track across central Texas,
with limited impacts for Oklahoma. GFS/NAM indicate the atmospheric
profile will be cold enough for snow across much of central Texas.
NAM shows 4-6 inches in this area with the GFS a little less. FTW has
issued a winter storm watch for areas south of I-20 and this looks
good. Temperatures will be near 30F, so not sure how much will stick.
Either way, snow looks likely for central Texas northward to
southern Oklahoma. In Oklahoma, amounts should be less than an inch.

This southern stream shortwave trof moves east and merges with a large
eastern U.S. closed low. The southern latitude movement of this
system causes a deep intrusion of dry air into the Gulf. The air
invading the Gulf appears to be a Pacific/Canadian mix but still
pushes 60F dewpoints to Yucatan and western Cuba. Southern stream
ridging shifts east as the next shortwave trof moves into the region.
This one will be a little farther north, bringing impacts to Oklahoma.
GFS shows mainly snow for the state, but not so sure this is the
best path to go. As such, I'll go with low-end snow probabilities and
put POPs in the forecast. If something more significant develops, it
can be handled with special discussions. Although I must admit that
it appears very easy to generate snow this year.

Upper system moves east and may deamplify as it moves into confluent
flow with the eastern U.S. closed low. Looking west, weak shortwave
ridging will give way to a southwest U.S. closed low by next Sunday.
ECMWF is the preferred model showing a rather powerful low moving
eastward early Sunday morning. Shortwave ridging in the Gulf will
shift eastward with some recovery implied by Sunday. However, surface
pressure will likely remain in the 1016mb level near Houston with
recirculated Canadian air likely into at least portions of the area.
Despite this, some 60F dewpoints appear possible moving into south
Texas. This upper system will likely bring an impressive amount of
WAA across the region and without cold air being in-place, I'm not
sure we're in for snow, at least in this forecast cycle. Snow would
seem a greater possibility as the upper system departs, but that is
for next week. It certainly does have potential to be a weather maker
across the U.S. the 28th into early March.

Temperatures remain on the low-end of climatology for late winter.
With only four days at or above normal for February, I see no reason
why it will change this week. There have also been no tornado reports
for the month of February. This may change with the plethora of
systems this week. However, a more likely change may be seen with the
system around March 1st. I can't wait to see how the NASCAR race goes
off in Vegas next Sunday.

I didn't get too far away from the models through Friday, I did go my
own direction next weekend.

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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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