Severe Weather Discussion for April 1 – 7, 2013

Severe Weather Discussion for April 1 – 7, 2013.
Issued:  03/31/2013.
Highlights:
–  Severe thunderstorms are possible on Sunday across western and central Oklahoma.
–  Showers and thunderstorms are likely Monday afternoon through Thursday across much of the state.  It won’t rain the entire time, but beneficial rainfall appears possible.
–  Officially – 2 tornadoes in January, 0 in February, and 1 in March.
–  Temperatures will be in the mid 60s Monday, mid 40s Tuesday-Wednesday, upper 50s Thursday, upper 60s Friday, mid 70s Saturday-Sunday.
Probabilities:
–  Severe Thunderstorms in Oklahoma:  35%
–  Storm Chase:  25%
Discussion:
Large trof  will develop over the eastern U.S. by Monday and translating offshore by Thursday.  Northwest flow will dominate the region much of the week, but even with that a few shortwave trofs will provide ample opportunity for rain.  The developing eastern U.S. trof will drive a strong cold front through Oklahoma late Monday, setting up a cool few days across the region.  The cold dome will result in isentropic lift across the region as the shortwave trofs pass near the region.  18z NAM/GFS start rain chances late Monday and continue them through Thursday.  General idea is for a large area of showers with embedded thunderstorms.  Severe potential looks low if not nil.
Rain will translate eastward out of the area as cold surface high shifts.  ECMWF shows a shortwave trof passing over Kansas but believe moisture will be limited and as such no pops expected.  Depending on how this evolves, there could be an enhanced wildfire threat but given expected rain could certainly be mitigated.
Attention then turns to developing western U.S. longwave trof.  GFS and ECMWF have been very consistent regarding the evolution of this system into the western U.S. by Monday 04/08.  There are obvious differences but the main trend is the same.  Difficult part for this forecast is another D7-8 severe weather threat.  Given time of year, climatology would certainly point to enhanced severe weather potential.  I have gone with higher-end slight risk chances for Sunday.  Additionally, there seems to be decent, dare I say it? (Dare, Dare), chase potential next Sunday.  500mb flow strengthens across the region while surface dewpoints in the low 60s return to much of the state.  18z GFS shifted around some with the 700mb/850mb reducing the overall threat but that is certainly model noise this far out. There will be minimal 500mb support as the main trof will be just off the California coast.  However, 35-45kt 500mb flow could contain a small shortwave trof or some other perturbation to initiate convection.
Longwave trof becomes established across the western U.S. by Monday 4/8 and deep layer moisture flows into the region.  Models offer a variety of solutions for this day but potential is certainly there for a medium-end event.  By Tuesday it appears  that the flow becomes unidirectional and could mitigate another threat.  Additionally, time of year does not favor a three day event.  Either way, Monday and Tuesday are beyond the scope of this forecast.  Will certainly monitor and initiate special discussions if necessary.
Temperatures look cold Tuesday-Wednesday, warming through the remainder of the week.  Took a GFS and EC blend, which seemed close anyway.
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