Weekly Severe Weather Discussion

Severe Weather Discussion for March 15 – 21, 2010.
Valid: 03/14/2010.

Highlights:

– Thunderstorms are possible on Friday, with some potential for severe
thunderstorms. Slight chance of snow in the panhandle late Friday
into early Saturday.

– Spring begins on Saturday.

– Temperatures will be in the upper 50s Monday, mid 50s Tuesday, near
60F Wednesday, mid 60s Thursday – Friday, upper 50s Saturday, and low
60s Sunday.

Probabilities:

– Severe Thunderstorms in Oklahoma: 10%
– Storm Chase: 5%
– Winter Precip: 5%

Discussion:

Seemingly endless parade of southern stream systems will continue this
week, along with the associated Gulf intrusions. The first will occur
on Monday-Tuesday as the closed low over the four-corners moves
southeast and then turns east over south Texas. The system will
translate east into the eastern U.S. as another, weaker, shortwave
trof drops southward along the east side of the southern stream ridge.
These systems will move east by the end of the week as another
shortwave trof develops in the southern jet. GFS/ECMWF are similar in
the overall pattern for this week.

In general sensible weather impacts will remain low with the first two
systems as there will be little surface moisture for them to utilize.
Cloud cover and some virga seems the most likely impacts Monday and
Wednesday.

More noticeable impacts are possible on Friday as a shortwave trof
digs southeast into the region. The position and movement of the trof
is not optimal for severe weather due to the rather meager moisture
return. However, the GFS has consistently shown modified moisture
return into the state by late Friday. Additionally, GFS creates some
narrow instability across western Oklahoma Friday afternoon with the
upper system approaching this area. Given the above, a low confidence
forecast for severe thunderstorms seems prudent. At this time,
widespread severe thunderstorms are not expected, but POPS are
inserted for general thunderstorms and for isolated severe. Track of
upper system and cold surface high moving southward may correlate for
snow in the panhandle. At this time, amounts would be low, but I'm
going to insert POPs for it anyway.

Beyond this week, GFS flip-flops make the longer-term forecast
difficult. ECMWF out to 240 hours indicates another southwest U.S.
around the 23rd. Current track of the system on the 19th indicates a
Gulf intrusion, but maybe not as significant as the prior plethora of
systems. As such, a severe threat may develop around the 23rd. The
GFS has shown this off/on for the past several days. However, the 12z
run today was about the only one to hint at it, the 18z run was a
throw-away. The GFS is seemingly important since dewpoint progs are
provided out to 384 hours (not that one should ever use it that far
out).

I used the NAM/GFS blend through Friday on temperatures and went well
above the GFS next weekend. While I agree the incoming surface high
will be cold, there should not be a lot of clouds to hold the
temperature down. As such, for late March, I'd expect to reach the 50s.

—————————————————————-
This message was sent using IMP, the Internet Messaging Program.

Facebooktwittergoogle_plusredditpinterestlinkedinmailby feather

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.
This entry was posted in Severe Weather. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *